Is a lightened flywheel overrated? (I think so)

[BRENT in 10-uh-C]

One of the things I always heard growing up in the Model-A hobby was that we wanted a lightened flywheel in our Model-A. Especially if we were going to "tour" with it! The "he said/she said" reasoning that has been associated with this advice seemed plausible to me for years until a few months ago I started analyzing the "what & why" this was needed. A few explanations I have always heard that come to mind are;

#1: The extra weight of the stock-weight flywheel is not good on the rear main bearing as it causes the babbitt to wear faster.

#2: The extra weight of the flywheel makes shifting take longer.

#3: The heavier flywheel makes the engine accelerate much slower.

#4: The roads are different now and we don't need the heavy flywheel like they did back then.

#5: (Add your reason here...)



So this really begs the question n my mind is a lightened flywheel actually better? Well I guess my mindset now after trying a few things on a current project is that it could be, however more than likely it is a "band-aide" to cover up another fault. Let's explore my thoughts and then I would like to hear yours.

Thinking about #1, there is a 3 inch long bearing back there that most engineers would agree is way over-engineered for the task. Just how much extra wear do you suppose 12 pounds of spinning weight makes over the life of the bearing? In other words, exactly how many miles do we suspect the babbitt's life will be shortened? Now granted if someone has a sub-standard babbitt job, then maybe less weight can mask this issue. Maybe the issue is with a flywheel that is 20+/- grams out of balance that is wiping out the babbitt? Yes, a lighter flywheel might prolong the bearing life in this instance but why not correct the root problem?

In considering the number 2 reason, I have heard this but have also found that many drivers actually operate their vehicle with a mindset that defies Henry's original intent of operation. Now granted many Model-A engines must be operated in such a manner to overcome their mechanical deficiencies of low torque or less low-end power but again, choosing to use a lighter flywheel to band-aide those problems such as a worn camshaft or a cam that has the name "Touring" attached to it is in my opinion, doing it for the wrong reason.

One other thought to add, using 600wt transmission oil greatly improves shift quality by slowing the turning gears during clutch operation too however many owners choose not to use the heavier lube for various reasons.

I think many items listed in explanation #2 apply to the reason #3 also. My experiences are that with a stock flywheel and an 'in-specification' original cam (--or one of Bill Stipe's IB330), the acceleration is quite satisfactory due to driving within the engine's torque band. Couple that with a high-compression head and the combination makes a Model-A quite suitable for 95 percent of the traffic flow we typically encounter.

Number 4 is one I have pondered for many years and I have come to realize that it is all in the driver's operational mindset. Over the past decade I have had the privelege of training many Model-A owners on how to drive their newly restored vehicle. The common factor I see out of the majority of these first-time operators is they want to drive it like a sports car by slipping the clutch to take off, making high RPM shifts, and go-kart type steering maneuvers. I show them how the vehicle will effortlessly move away from a stop with the engine idling just by smoothly releasing the clutch pedal. Again, the inertia of the heavier flywheel is a plus. Next the driver typically wants to accelerate to 30mph before attempting to make a low to intermediate gear change. Once they realize that they can accelerate much faster by making their 1st to 2nd gear change at 10mph and using the torque of their engine to propel them, they are usually amazed. They are even more impressed when a 90 degree turn can be made while the transmission remains in high gear. Equally amazing to the veteran hobbyist who drive a Model-A with a 3.54 rear end ratio and negociate the same 90 degree turn without the need for downshifting. Adding to that amazement is when they learn that engine has a stock weight flywheel. Some might even be appauled to hear we are using stock weight flywheels w/ heavier counterweighted crankshafts!!

So my point in this lengthy rant is can someone give me a satisfactory reason why we really should be using a lightened flywheel other than to mask or cover-up some other mechancial deficiency?

.

[marc hildebrant]

Does the stock flywheel help to dampen out the 4 cylinder "vibration" at certain speeds ?

Could that be why Ford used a heavy flywheel vs a balanced crank ?

Marc

[John Stone]

Brent, I agree with you 100%. I like the heavy flywheel until I have to lift one but that is only temporary.

One member of our club says the lightened flywheel is good because when hitting a railroad track, the crankshaft does not flex as bad and cause the center main to go out. (I say the crank is probably not ground on a center line)

Another one say he likes the V8 pressure plate because it is easier on the left leg. He is a machinist and actually turns the flywheels down.

[Patrick L.]

I've wondered the same things without having any experience with them,, so I'm happy to see this.. I like that heavy ole flywheel,, You take off without throttle as you mentioned or come to a 'rolling' stop and just stick the lever into 2nd and let the clutch out.. While I think I would 'upgrade' the engine someday I find the tired out motor has plenty of power for me.. I happen to be one that prefers low engine speeds over high engine speeds in these motors,, I don't believe in the low RPM 'hard on the babbitt' theory.. I'm also glad to hear that someone has used 'weighted ' cranks without cutting the flywheel without ill effects..

[Ron/IA]

Brent - I have the original flywheel in my Fordor, and prefer it. The Fordor is a heavier car than other A's, but I really don't notice any advantages of a lighter flywheel versus the original. I have driven A's with the lighter flywheel.

As for the lighter foot pressure using the V8 clutch, I have been using a shortened clutch arm for a couple years now, and while it is not quite as light as the V8 clutch; to me there isn't much difference. I also have driven A's using the V8 clutch.

I think with anything, there pros and cons; but in this case Henry put a lot of thought and design in the Model A. When you change one thing, it can affect another. For instance; changing the rear end ratio from 3.78 to 3.54 makes a noticeable affect. Yes, you will have higher top speed at lower engine RPM, but you will notice the car doesn't climb steep hills as well.

Finally, I agree with your comments.
Thanks, Ron/IA

[RockHillWill]

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I had tried the lightened flywheel on the first Pick up that I restored, thinking that it would be getter suited for a left leg that got 'damaged' in a pit road incident in Atlanta in '85 or '86. I was unable to tell any difference in the clutch pedal pressure that what was in my stock Tudor. I actually tore that (fine point) pickup apart, because I could not get it to idle down 'extra slow'. After I got the heavy flywheel put back in it, I could tell a noticeable lowering of the idle RPM and was not able to see any difference in the clutch pedal pressure required.

I have no 'scientific' input on this issue, just offering some input!

BTW, I went ahead and put the heavy flywheel in for the Panel Truck. From my racing background, I have usually been inclined to find a 'better way' on whatever I am doing, but an old-time Model A guy has FINALLY got me believing that ol' Henry got it right the first time. My problems and road troubles have all but dissapeared since I have reverted to using original parts.

Just a thought.

[RockHillWill]

Agreed there Vince! I had installed the lightened flywheel on what I thought was 'expert' advice, and neglected to do any real thinking at the time.

That thinking may also have been tainted with my racing experience that made us convert to the small diameter, multiple disc clutch, and that was its effects on braking and acceleration, especially on the road courses and small tracks.

It took me a long time in racing to finally learn, that if you continue only using and/or copying other peoples ideas, the best you are going to run is second!

BTW Vince , I love your Avatar

[MikeK]

I guess (and I do mean guess!) it depends on where you want the crank to break. The traditional place is for the rear to snap off. Any piece of metal can only take X number of stresses before fracture. That number is a function of the degree of flex and the number of cycles. An 80 year old crank is already way towards that point. Adding throw counters and reducing the flywheel weight changes the dynamics of the shock waves, or flexes. You now have less at the rear flange and higher stress in other places. (Here a front dynamic element would be nice.)

As a result, you will get more remaining run time on an already 80 year old crank than would remain with the heavier wheel in place. Simply, you are gambling that your chances of crank failure will be reduced. Now, if you can find a NOS crank (keep dreaming) with zero flexes, you'll gain almost no confidence against failure unless you live another 80 years. It would be someone else's problem.

OK, now let's look at a NEW crank. Not NOS without counterweights, a new Scat, Crane, Burlington, etc. with counterweights. None (Well, maybe a $3K custom) is 100% countered for each throw. That crank will STILL always be doing a harmonics dance back and forth along it's length while running. ANY inertial dynamic introduced at either end will make the stresses unequal along the length. Now remember X number of stresses before fracture, that number a function of the degree of flex and the number of cycles. For maximum life of an I-4 flat crank, on each external end of the crank you need a dynamic(inertial) mass equivalent of sq.root of 2 (1.414) times the inertia of the adjacent crank element (throw). Nobody runs a front flywheel (solid damper) that big, and nobody has a rear flywheel that small. The best compromise is a rear flywheel as light as you can get. Of course, even with a heavy stock fly-anchor at the back, the average street A will never approach that cumulative X stress point within that owner's use time if you have a NEW crank to start. The only thing that owner will get is a marginally quicker acceleration.

Now, another consideration- If you reduce the inertial damping (actually, you are reducing the energy conservation of the shock wave) by lightening the flywheel, that shock wave continues down the drivetrain! No flywheel on the back would be like taking a #3 pneumatic rivet gun to the tranny teeth!

Everything is a compromise. Henry made his, based on NOS parts and then- conditions. There probably is no definitive right or wrong, it is only what you want to happen, or how you wish to prioritize and distribute probabilities of failure at various points in the entire system.

[Pete]

Originally Posted by MikeK

I guess (and I do mean guess!) it depends on where you want the crank to break. The traditional place is for the rear to snap off. Any piece of metal can only take X number of stresses before fracture. That number is a function of the degree of flex and the number of cycles. An 80 year old crank is already way towards that point. Adding throw counters and reducing the flywheel weight changes the dynamics of the shock waves, or flexes. You now have less at the rear flange and higher stress in other places. (Here a front dynamic element would be nice.)

As a result, you will get more remaining run time on an already 80 year old crank than would remain with the heavier wheel in place. Simply, you are gambling that your chances of crank failure will be reduced. Now, if you can find a NOS crank (keep dreaming) with zero flexes, you'll gain almost no confidence against failure unless you live another 80 years. It would be someone else's problem.

OK, now let's look at a NEW crank. Not NOS without counterweights, a new Scat, Crane, Burlington, etc. with counterweights. None (Well, maybe a $3K custom) is 100% countered for each throw. That crank will STILL always be doing a harmonics dance back and forth along it's length while running. ANY inertial dynamic introduced at either end will make the stresses unequal along the length. Now remember X number of stresses before fracture, that number a function of the degree of flex and the number of cycles. For maximum life of an I-4 flat crank, on each external end of the crank you need a dynamic(inertial) mass equivalent of sq.root of 2 (1.414) times the inertia of the adjacent crank element (throw). Nobody runs a front flywheel (solid damper) that big, and nobody has a rear flywheel that small. The best compromise is a rear flywheel as light as you can get. Of course, even with a heavy stock fly-anchor at the back, the average street A will never approach that cumulative X stress point within that owner's use time if you have a NEW crank to start. The only thing that owner will get is a marginally quicker acceleration.

Now, another consideration- If you reduce the inertial damping (actually, you are reducing the energy conservation of the shock wave) by lightening the flywheel, that shock wave continues down the drivetrain! No flywheel on the back would be like taking a #3 pneumatic rivet gun to the tranny teeth!

Everything is a compromise. Henry made his, based on NOS parts and then- conditions. There probably is no definitive right or wrong, it is only what you want to happen, or how you wish to prioritize and distribute probabilities of failure at various points in the entire system.

Right on on all that...
I have had very good success using a 11 lb aluminum flywheel with an aluminum clutch cover and a 12 lb big block Chev. front damper.
This is about as close to equal weight on each end of the crank as is practical.. It torsional vibration you are reducing.
We spin these engines 6000 and have never broken a crank.

[Purdy Swoft]

This time I've got to agree with Vince. I've got model A's both ways and would prefer lighter flywheels in all of them. I run a model B flywheel in my roadster and it out performs the ones with stock heavy model A flywheels. I get faster acceleration, easier gear shifts and less weight has got to be easier on the main bearings. I run other mods like higher compression, two B carbs, warmed up ignition, free flowing exhaust and a Stipe ground cam. My engine is low milage and runs the original Ford balanced rotating assy. It idles good and will chick ah lunk with the spark retarded after a slight warm up. Its got wonderful low end torque. I can let it idle and pop my foot off the clutch pedal and it will take off without choking down. We've never needed to ride the clutch when taking off. I have good hill climbing ability and its got power much like a modern vehicle. This is my experience.

[BILL WILLIAMSON]

No, I didn't go away,
Question: Is "lugging" REALLY hard on the babbitt, or is this just poppycock? Parade modes are "lugging!" "Yep, I tore up my babbitt in that LOOOOOONG parade!" These old low compression engines with a "boat anchor" flywheels are suited for "lugging!" REAL lugging would be at 10 MPH in high gear on a steep mountain grade and would surely be tough on many internal pieces!! We eliminate REAL "lugging" by GRABBIN' second gear, or low, if necessary. I think poor workmanship causes MANY babbitt failures. Bill W.

[ctlikon0712]

This is a subject that I have thought allot about also. I have tossed around most of the pro's and con's mentioned minus Mike K's dissertation... wow Mike that is an interesting point and read.
I learned a long time ago on Rochester Quadrajets that if a company puts many hours and even years of engineering into a product, that you’ll usually get more out of using the design as intended than throwing a "Holley" on it to make it faster. That is unless you plan on spending years and allot of money on research. I plan on leaving my car's engine alone except for a maybe a higher compression head. My car is a woody and heavier than most.

[Mike V. Florida]

I would think that if one were to add weight by adding weights to the crank one should also remove that weight from the fly wheel to get the net weight about the same?

[Patrick L.]

I learned a long time ago on Rochester Quadrajets that if a company puts many hours and even years of engineering into a product, that you’ll usually get more out of using the design as intended than throwing a "Holley" on it to make it faster...end quote..
Hehehe,, personally i've always been a Carter man..

[ericr]

does anyone know if cars of similar horsepower, weight, etc. (Chevrolet, Dodge Brothers, etc.) had similar flywheels?

[BRENT in 10-uh-C]

Originally Posted by Purdy Swoft

This time I've got to agree with Vince. I've got model A's both ways and would prefer lighter flywheels in all of them. I run a model B flywheel in my roadster and it out performs the ones with stock heavy model A flywheels. I get faster acceleration, easier gear shifts and less weight has got to be easier on the main bearings. I run other mods like higher compression, two B carbs, warmed up ignition, free flowing exhaust and a Stipe ground cam. My engine is low milage and runs the original Ford balanced rotating assy. It idles good and will chick ah lunk with the spark retarded after a slight warm up. Its got wonderful low end torque. I can let it idle and pop my foot off the clutch pedal and it will take off without choking down. We've never needed to ride the clutch when taking off. I have good hill climbing ability and its got power much like a modern vehicle. This is my experience.

You experience is worth noting and I definitely value it however I cannot help but ponder some folks comments as it relates to actual experience in lieu of what seems believable. Theory has always been a good guide however sometimes it seems misleading. My point with what I highlighted in red is definitely not meant to be critical but instead is to point out something that many others seemingly say too. We all tend to say that it is easier on bearings but I want to know by just how much is it easier on them? I want someone to say with certainty that there is XX percent of additional longevity with the lighter flywheel. Not hypothetical or probability.

Next, exactly how much faster is the engine acceleration with the lighter flywheel? If 0-50mph in a 100% stock engine is 25 seconds, are we saying that it would be more like 23 seconds with the lighter weight flywheel --or 15 seconds with the lighter flywheel? Again, please no assumptions or theories wanted because my unscientific tests shows it to be neglible when both vehicles are driven in the same manner ...much like Mike has suggested above.


One or two other points about Mike's great commentary. If we are truly worried about how many harmonic cycles each component of our Model-A has left, then maybe we should be messin' with different cars or leave them parked in the garage! Even should we choose to run a lighter flywheel to possibly eliminate breakage or failure, at what point do we start worrying about cycle failures of rear axle shafts, or spindles, or steering components?

.

[ursus]

I have heard a few others say that the smoothest running engine of this lineage was the Model B engine with pressed on counterweights. These weights were added on to the earlier uncounterweighted Model B crankshafts when such engines were returned to Ford for rebuilding. Ford reassembled these with the stock flywheel, thus making the assembly heavier than the stock counterweighted assembly. Ford must have thought this was OK.

[1930artdeco]

O.k. here is my 1.5 cents worth. This is just my thinking here and my interpretation of physics

#1: If you hang a 65# flywheel on any bearing I would think it would tend to wear faster, even if the bearing is 3" long. Now if you hang a 20# flywheel it should not wear as fast. This is assuming that the crank is flexing a bit as it is fairly long and there are only two other bearings supporting it.

#2: The lighter the flywheel should let the engine spool up faster as it does not have to impart as much energy to move a 20# flywheel (or whatever weight you have) vs. a 65# flywheel. Whether that translates into faster acceleration is what needs to be timed.

This is all just H.S. physics and logic talking here and I can be totally dead wrong. I do not have any facts to back this up, just my logic. I lightened my FW by about 12#'s which is the weight of the counterweights. This would take some weight off of the rear bearing and keep the total weight the same. "I think" the engine spools up a bit faster and she might accelerate a bit faster. But, I think the long stroke of the engine tends to limit how fast she will spool up.

Mike

[40 Deluxe]

Another factor to consider when worrying about that "heavy" original flywheel beating up on that poor defenseless rear main:
How much pressure (or "weight") does the rear main see when #4 fires? A lot more than the weight of the flywheel!! Peak cylinder pressure at light loads is about 300 PSI, and piston area is about 10.7 sq. in. So we have a force of over 3,000 pounds pushing on that Babbit bearing! Even having just 50# or so of compression puts almost 600 pounds of pressure on the rear main before the cyl fires.
I really doubt the rear main notices whether a few pounds have disappeared from the flywheel!

[MikeK]

[QUOTE=BRENT in 10-uh-C;536079]. . . at what point do we start worrying about cycle failures of rear axle shafts, or spindles, or steering components?

We shouldn't beyond reasonable prudence. Life is too short. As we all know, there are two groups of vehicle owners- the users and the possession collectors. I know people with 4x4's that pull the sheets over their head and stay home when it snows an inch or two.

[Marco Tahtaras]

Originally Posted by MikeK

I guess (and I do mean guess!) it depends on where you want the crank to break. The traditional place is for the rear to snap off.

I'm sure there are examples to the contrary, but the ONLY broken cranks I've seen were improperly reground. I still have a Burlington crank on the shelf for a future project however.

[SteveB31]

It has always been my understanding that we remove the weight off the flywheel BECAUSE we add the weights on the crankshaft to counter balance the crankshaft (like Ford did on the later B motors). Therefore, we still have the SAME amount of total weight (crankshaft + weights + flywheel) like Ford did (they reduced the flywheel weight when they added weight to the crankshaft).

Your thoughts?

[denis4x4]

I buy SteveB31's idea that the weight is still the same, just rearranged. Too, my car with the lightened flywheel and a counterweighted crank is probably 400 to 500 pounds lighter than a stock Model A.

[Mike V. Florida]

I think this thread is great!! We have various opinions alot of facts, and not a single one is personal. As a matter of fact I see where the posters are going out of their ways to see that nothing posted is personal in nature!

[Kohnke Rebabbitting]

Mass does Matter, the rear main on a Model A has always be a strong point with Factory Babbitt, of the three bearings, except where the Babbitt has been replaced by incompetence.

The rear bearing is not the one that catches the most wear, it is the center Bearing, and the crank Bows from the heavy weight of the flywheel.

Just about every crank that has had a lot of miles will measure out about the same wear, on both ends, and the center will measure about 3 times more from the crank running bowed.

Get rid of the weight, and get rid of some of the wear.

[Purdy Swoft]

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Originally Posted by ursus

I have heard a few others say that the smoothest running engine of this lineage was the Model B engine with pressed on counterweights. These weights were added on to the earlier uncounterweighted Model B crankshafts when such engines were returned to Ford for rebuilding. Ford reassembled these with the stock flywheel, thus making the assembly heavier than the stock counterweighted assembly. Ford must have thought this was OK.

The original flywheel that was used with the first year model B engines with uncounterweighted crankshafts were not the same as model A flywheels. All of the model B flywheels were lighter than model A flywheels as far as I know. I have one of the flywheels that was used with the early B engine on my roadster. I didn't record the weights at the time but the clean B flywheel without the ring gear was 20 lbs. lighter than the flywheel that I removed from my A . I meant to re weigh the B flywheel after I installed the new ring gear . In my exitement To get the engine together I forgot . The ring gear probably weighs around 4 lbs. . If this is the case my flywheel would be around 16 lbs lighter than a model A flywheel . The engines in two of my cars have similar mods, same head, cam and both run dual up draft B carbs. One has a B flywheel and the other has a stock model A flywheel. The one with the B flywheel has better throttle response and accelerates faster than any model A that I have ever driven. The gears shift smoother than any model A that I have ever driven. I am convinced that if a flywheel is properly lightened and balanced, low and mid range performance will increase. A hevier flywheel may actually have a higher top end speed. I'm more concerned with low and mid range power than cruising at 65-70 mph. I've had the A flywheel car up to 75 mph going up hill picking up speed. I still prefer the lighter flywheel.

[tbirdtbird]

Alas, no one chimed in on the part where you teach modern drivers how to drive the darned thing. Today's drivers have no clue about what a long-stroke motor is and all the low end torque that gives them. Don't need to rev to 4K each shift and have a 6-speed box to get somewhere. Those extra gears are needed because the low end torque of a modern motor does not exist

[eagle]

As I see it, the trouble with the "quicker spool up" theory is that few pounds less of spinning mass is going to make the mass of my whole car speed up faster? Don't buy it, although maybe with the car not in gear... I also agree with the description Brent gave of driving. "Shift early, not often" Thats my theory. Some people nearly blow their gaskets over the "lugging" issue. I've heard people say " I'm not grinding the gears, thats just a little clicking on the way in" Yeah right, shift early and no more "clicking".

[BILL WILLIAMSON]

Originally Posted by tbirdtbird

Alas, no one chimed in on the part where you teach modern drivers how to drive the darned thing. Today's drivers have no clue about what a long-stroke motor is and all the low end torque that gives them. Don't need to rev to 4K each shift and have a 6-speed box to get somewhere. Those extra gears are needed because the low end torque of a modern motor does not exist

Tbird,
Excellent thoughts! It's so easy to get caught up in faster & quicker is better & if we do this mod & that mod, our engines will last better than Ford designed it. Is some of our "engineering"? better than Ford's? With proper driving & good maintenance, a Model A, in stock form, will deliver MANY miles of good service.
I sold my '30 coupe that would run 80 MPH with all stock drive train & 19" wheels, it WAS fun. Now back to my bone stock '29 coupe for a new experience in driving it as Ford intended. It has sufficient power & speed for city & country driving, with the exception of freeway trips. I'll endure the typical buzzing/vibrating, etc, just to keep it as it was designed. I cheated a little, It has 16" wheels & a dandy Zip-A-Rak telescoping luggage rack! Bill W.

[John LaVoy]

When I was working on my first Model A restoration for a tour car I located a machine shop in Southern California. The shop was owned and operated by a man named Kong. He did land speed runs in a drop tank racer in the late 1940s. I had him add counter weights to my model A crank. He said that I needed to lighten the flywheel to assist with acceleration and that you should remove at least as much weight as you added to the crank. He cut my fly wheel to 34 pounds. I figure he must know what he is talking about regarding the reduction in weight of the flywheel since he had been racing on the salt with Model A and V-8 flat heads and setting many records.

It so happens his car was on display with my new Roadster Pickup in the Ford booth at the recent SEMA show. The drop tank racer has his name painted on the side of the car. I thought it was something since the crank used in the pickup was one of the cranks I had him do in 1964, I had a couple done and never used one until now.

[PC/SR]

Interesting thread. My pal Jerry and I used to drive the fire and logging roads of Northern California in his A coupe before either of us had a drivers license. That stock flywheel was great for doing 3, 4, 5 mph over ruts and all. That coupe even had a 4 speed transmission. Man, we could idle over those ruts.
50 years later I could not drive my speedster with a lightened flywheel on those kinds of roads, but I do like it on FAST hill climbs.
I doubt that in ordinary driving anyone but an experienced driver could tell the difference between a lightened and regular flywheel.
High school physics, as ArtDeco noted, and experience confirms, that you will "store" more energy in a heavy flywheel and that will make a difference in the rpm drop, or rise, between a 15 and a 20 mph shift point, but you will hardly notice it. Except that is one of the reasons you do not need to double clutch to shift up but do to shift down.
Shifting early, not often, at low rpm, is permissible, even desirable, in an A not so much because of flywheel weight, but because the stock camshaft profile produces low end torque and a high volumetric efficiency at low rpm, and that has little to do with flywheel weight except that it maintains rpm at the shift point, whatever it might be. You cannot efficiently shift to 2nd at 10 mph with a so called touring cam, no matter what the flywheel weight. Nor can you idle comfortably to 400 rpm with a 35 lb flywheel.
Whether a lightened flywheel is "overrated" depends on your use. If you drive steady speed, or ordinary tour and club driving at whatever speed, the stock flywheel is fine, no matter what speed equipment you have.
If you want to race, really push it, get a lightened wheel.

[gwhite]

Originally Posted by John LaVoy

When I was working on my first Model A restoration for a tour car I located a machine shop in Southern California. The shop was owned and operated by a man named Kong. He did land speed runs in a drop tank racer in the late 1940s. I had him add counter weights to my model A crank. He said that I needed to lighten the flywheel to assist with acceleration and that you should remove at least as much weight as you added to the crank. He cut my fly wheel to 34 pounds. I figure he must know what he is talking about regarding the reduction in weight of the flywheel since he had been racing on the salt with Model A and V-8 flat heads and setting many records.

It so happens his car was on display with my new Roadster Pickup in the Ford booth at the recent SEMA show. The drop tank racer has his name painted on the side of the car. I thought it was something since the crank used in the pickup was one of the cranks I had him do in 1964, I had a couple done and never used one until now.

Charles "Kong" Jackson?!?!? Wow!

[MikeK]

Originally Posted by gwhite

Charles "Kong" Jackson?!?!? Wow!

Lotsa A and early V8 speed stuff marked KONG out there. Here's a thread from our twisted sister, the HAMB. Scroll down to post #37. KONG

Interesting how this thread is progressing, now through testimonials. All BRENT's fault, posting intelligent questions!

[Jim/GA]

Originally Posted by SteveB31

It has always been my understanding that we remove the weight off the flywheel BECAUSE we add the weights on the crankshaft to counter balance the crankshaft (like Ford did on the later B motors). Therefore, we still have the SAME amount of total weight (crankshaft + weights + flywheel) like Ford did (they reduced the flywheel weight when they added weight to the crankshaft).

Your thoughts?

When it comes to rotational inertia of a rotating system (also known as moment of inertia), not all mass added or removed from the system is the same. It also depends on the SQUARE of the distance that mass is from the center of rotation.

Here is a simple example:

1 lb. of mass that is removed 10" from the center of rotation (1*10*10=100 lb-sq.in.) is equivalent to 4 lbs. of mass added to a point 5" from the center of rotation (4*5*5=100 lb-sq.in.) to maintain the same total rotational inertia of the system.

So, to remove as many pounds from the flywheel as you add to the crank in counterweights is probably over correcting by quite a bit, because the counterweights added are probably closer to the crankshaft main bearing centers than the weight you removed from the flywheel. You need to keep track of where you are removing and adding the weight.

This is classical mechanics.

[Marco Tahtaras]

Originally Posted by Jim/TX

When it comes to rotational inertia of a rotating system (also known as moment of inertia), not all mass added or removed from the system is the same. It also depends on the SQUARE of the distance that mass is from the center of rotation.

Here is a simple example:

1 lb. of mass that is removed 10" from the center of rotation (1*10*10=100 lb-sq.in.) is equivalent to 4 lbs. of mass added to a point 5" from the center of rotation (4*5*5=100 lb-sq.in.) to maintain the same total rotational inertia of the system.

So, to remove as many pounds from the flywheel as you add to the crank in counterweights is probably over correcting by quite a bit, because the counterweights added are probably closer to the crankshaft main bearing centers than the weight you removed from the flywheel. You need to keep track of where you are removing and adding the weight.

This is classical mechanics.

I was going to comment similarly but you beat me to it! Several folks have mentioned "total weight" without regard to the distance of that weight from the axis.

[Patrick L.]

How much is actually usually added to a 'weighted' crank ?? It seems I've always heard and read that about 20# 'must' be removed from the wheel when the crank is ' weighted' .. Physics is physics and 'arm' [length] is everything isn't it ?? My girlfriends have always said that anyway..

[Pete]

Originally Posted by MikeK

Lotsa A and early V8 speed stuff marked KONG out there. Here's a thread from our twisted sister, the HAMB. Scroll down to post #37. KONG

Interesting how this thread is progressing, now through testimonials. All BRENT's fault, posting intelligent questions!

Thanks for the link Mike. Brought back a lot of memories.
I talked to Kong at Bonneville several times and had one of his 2 coil ignitions on one of my engines. That was probably the finest battery ignition there ever was for a flathead.

[Paul from Maine]

I agree with you on every point. However, I would like to point out that in #4 you mention upshifting from 1st to 2nd at ten mph. Try shifting from 1st to 2nd at ten feet, not ten mph. No need to to double clutch, no need to wait for gears to slow down in the tranny, no gear grinding, an instant shift, and quick get away because of that 60 plus pound flywheel! Got that technique from a late twenties issue of Popular Science. I was skeptical until I tried it myself. The article also recommended shifting from second to high as soon as possible without lugging the engine. Again no need to to double clutch, no need to wait for gears to slow down in the tranny, no gear grinding, an instant shift, and quick get away because of that 60 plus pound flywheel! Let the criticism and naysaying begin!

[dumb person]

Another thread was discussing replacing the rear main bearing in the car. That reminded me of this thread. If you removed the rear main bearing would the weight stress the gearbox input shaft and bow the crank down a little until the bearing was replaced?

[Craig Lewis]

Originally Posted by Patrick L.

How much is actually usually added to a 'weighted' crank ?? It seems I've always heard and read that about 20# 'must' be removed from the wheel when the crank is ' weighted' .. Physics is physics and 'arm' [length] is everything isn't it ?? My girlfriends have always said that anyway..

I utilized patterns from one of the Restorer series of books & cut these crank weights from 5/8 plate steel.
After grinding and dressing to fit the crank, the 4 together weighed 11 pounds just before welding them on.
The machinist who balanced everything commented what very little metal had to be ground from the 4 lugs to bring it into balance... so I'd guess 10-11 pounds is about the average.
It seems I had 30 lbs cut from the flywheel (haven't got my notes handy)
I still haven't run it, but now you guys got me worried cuz I hope it doesn't lose that distinctive low Model A idle with the light flywheel!

[Milton]

"Thinking about #1, there is a 3 inch long bearing back there that most engineers would agree is way over-engineered for the task."

Now why would they do that? Why is it that every babbitt A that I have disassembled shows main wear the most at the rear?

#2: True, however, how fast must one shift? Not enough compression to slow the motor down before the car rolls to a stop? Est-ce que tu comprends speedshift?

#3: True again, but then the rotational momentum is diminished. I dislocated a friends neck once by spinning the tires in dirt and when the tires hit the pavement he was looking at the roof. Takes a lot to beat an A off the line, but after that it's all over.

#4: That's one that I never heard before.

#5: I'm with MikeK and the reduction of torsional vibration.

And most of all the light wheel allows my Stipe IB350 to announce itself very well at an idle.

[Pete]

Originally Posted by Craig Lewis

I utilized patterns from one of the Restorer series of books & cut these crank weights from 5/8 plate steel.
After grinding and dressing to fit the crank, the 4 together weighed 11 pounds just before welding them on.
The machinist who balanced everything commented what very little metal had to be ground from the 4 lugs to bring it into balance... so I'd guess 10-11 pounds is about the average.
It seems I had 30 lbs cut from the flywheel (haven't got my notes handy)
I still haven't run it, but now you guys got me worried cuz I hope it doesn't lose that distinctive low Model A idle with the light flywheel!

I hate to be a wet blanket but the guy that did your welding should go back to welding school.

[Craig Lewis]

Originally Posted by Pete

I hate to be a wet blanket but the guy that did your welding should go back to welding school.

Oh really? It was tig welded at a reputable welding shop because I didn't have the equipment at that time. I migged the weights in place, then it was all preheated in an oven, tigged while hot & placed back into the oven to cool overnight.
You're entitled to your opinion Pete, although several people have commented to the contrary.

[RockHillWill]

My opinion is that is a VERY nice approach.

The more I learn about MIG welding and the effect that the rapid cooling has on the neighboring material the less I like it.

The alignment clamps are a nice touch. I know some that do not use them.

Nice work!

[Special Coupe Frank]

I think Herm made a good point ( as usual ), about the center main and crank flex.

If counter-weights are added to the stock crank or a weighted crank is used, the flywheel should probably be lightened accordingly to keep the entire assembly at stock weight.

And to borrow a statement from Steam heating guru Dan Hollohan, "the dead men knew what they were doing" in terms of design and engineering.

And there was at least one autombolie that employed a flywheel at both ends of the crank: the Rickenbacker.

SC Frank

[Jim/GA]

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Originally Posted by Craig Lewis

It seems I had 30 lbs cut from the flywheel (haven't got my notes handy). I still haven't run it, but now you guys got me worried cuz I hope it doesn't lose that distinctive low Model A idle with the light flywheel!

It might.

Put the engine together with these weights and the lightened flywheel and run it on a test stand. See how you like it. Before getting it all buttoned up, if you don't like it, you can get a different flywheel and try again.

A new tight engine isn't going to idle as nicely as it will after it wears in and loosens up, so run it on the stand for a while, then decide how you like the idle.

[BRENT in 10-uh-C]

Originally Posted by Special Coupe Frank

I think Herm made a good point ( as usual ), about the center main and crank flex.

If counter-weights are added to the stock crank or a weighted crank is used, the flywheel should probably be lightened accordingly to keep the entire assembly at stock weight.

And to borrow a statement from Steam heating guru Dan Hollohan, "the dead men knew what they were doing" in terms of design and engineering.

And there was at least one autombolie that employed a flywheel at both ends of the crank: the Rickenbacker.

SC Frank

Why?? Again, this is counter to what I suggested.

Also, just how much does the crankshaft bend with a 40 lb flywheel vs. a 62 lb flywheel? I have not measured it so it is only speculative however by my thoughts, it is very marginal as compared to the flex the crankshaft will see with a higher compression head and its increased cylinder explosions.

[Pete]

Originally Posted by Craig Lewis

Oh really? It was tig welded at a reputable welding shop because I didn't have the equipment at that time. I migged the weights in place, then it was all preheated in an oven, tigged while hot & placed back into the oven to cool overnight.
You're entitled to your opinion Pete, although several people have commented to the contrary.

Your method was good and you will most likely never have any problems with them, BUT, the welding itself looks like an amateur did it.
I was a welding inspector in the aircraft industry at one time and I know what good welding looks like. Besides inconsistancies, you have undercut.
Another thing that is bad is mixing 2 different kinds of welding. Mig and tig, even if it is just tack welds. Mig wire is far different from tig filler rod in most cases. When you have to tig weld over mig tacks it can cause a hard spot that may become a stress riser.
By the way, there was a thread on tig welding on the HAMB awhile back and you can go there and see what good welding looks like.

[MikeK]

OK, time to throw a wrench in the works-

Brent's initial post asked "#5: (Add your reason here...)"

This fits #5: Reaction couple.

All rotating assemblies are gyroscopes. The crank and flywheel are BIG ones.
Any movement of the vehicle like turning or going up and down on the suspension will induce a counter torque along the axis of the flywheel. That means a bending force between the the flywheel and crank. Where? At the rear flange! What "takes" (holds up) that load? The rear bearing.* A hard bounce or turn at 3000 rpm may give you a torque equivalent to a 1000 lb dead weight on the end of the crank. That force may be up, down, left, right. Bye Bye rear bearing. Cyclic stress on the flange. Less flywheel weight = less force, so . . .



OK, what about reaction couple from the heavy spinning counterweighted (or -un) crank???
Since the crank has a bearing at each end, the force is applied to the block ends, not the external flywheel flange.

NOTES:
* Load at the center main bearing will be much, much less, as a lever arm is involved. Distance from center to rear main contact center is one long arm of a torque lever. The other lever has a much shorter length, the CG of the fly to the rear bearing contact point. Crank deflection (a Young's modulus function) will determine how much off-axis twisting the journals do within the bearings.

My personal analysis of all this- You can run the engine wide open on a dyno for 80 years with any weight flywheel or crank. Near zero stress on the rear flange and rear bearing. If you DRIVE the vehicle, wear and cyclic fatigue damage accumulate in those two places. Drive like grandma, little to worry about. Drive like Pete, you had better cut down the rotational elements or else!

[Pete]

I love it.

[Chris in CT]

OK,OK I was going to try to stay out of this, but I just can't help myself! I'd like you to think about the word, "damping" and throw the balance weight out the window for a moment. That 63 # flywheel was put there to "damp" the impulses from the cylinders as they fired. The 63# flywheel also allowed the driver to "set it and forget it" as far as the timing advance lever was concerned, since at the lower compression of the stock engine the revolving flywheel would easily overcome timing inconsistencies.
What happens with the so-called "counterbalanced" crankshaft is that each of the slings (counterweights) "damps" the combustion impulses right under the subject cylinders, rather than at the end of a long, twisty, spindly piece of forged steel. Once you have effected that "equalization" of combustion impulses, it is no longer necessary to have 63# of cast iron at one end of the engine - in fact, it is counter-productive because it will continue to cause the crankshaft to twist with each impulse where with a lightened flywheel that twist will be proportionately reduced.

The only way to actually prove this to our scientifically-minded brethren is to perform a Fourier Analysis on the rotating assembly, a complicated process requiring a lot of time and equipment.

Oh, incidently, have those of you who have removed 20# or so from your flywheel noticed that the engine is much more sensitive to the position of the ignition advance lever than it was when the flywheel was full weight? I have. So much so that I am tempted to go out and get a centrufigal dizzy! When I go for a drive, it keeps me quite busy trimming the thing. Happy Motoring, Guys!
Chris

------------------

www.burlingtoncrankshaft.com

[Tom Wesenberg]

Whoa! Now my head is spinning!

Good thing it's hollow so there's less rotational mass, otherwise it would fall off!

[BRENT in 10-uh-C]

Originally Posted by Chris in CT

OK,OK I was going to try to stay out of this, but I just can't help myself! I'd like you to think about the word, "damping" and throw the balance weight out the window for a moment. That 63 # flywheel was put there to "damp" the impulses from the cylinders as they fired. The 63# flywheel also allowed the driver to "set it and forget it" as far as the timing advance lever was concerned, since at the lower compression of the stock engine the revolving flywheel would easily overcome timing inconsistencies.
What happens with the so-called "counterbalanced" crankshaft is that each of the slings (counterweights) "damps" the combustion impulses right under the subject cylinders, rather than at the end of a long, twisty, spindly piece of forged steel. Once you have effected that "equalization" of combustion impulses, it is no longer necessary to have 63# of cast iron at one end of the engine - in fact, it is counter-productive because it will continue to cause the crankshaft to twist with each impulse where with a lightened flywheel that twist will be proportionately reduced.

The only way to actually prove this to our scientifically-minded brethren is to perform a Fourier Analysis on the rotating assembly, a complicated process requiring a lot of time and equipment.

Oh, incidently, have those of you who have removed 20# or so from your flywheel noticed that the engine is much more sensitive to the position of the ignition advance lever than it was when the flywheel was full weight? I have. So much so that I am tempted to go out and get a centrufigal dizzy! When I go for a drive, it keeps me quite busy trimming the thing. Happy Motoring, Guys!
Chris

------------------

www.burlingtoncrankshaft.com

Yeah, me too Pete!

Hey Christopher, I'm glad you jumped in!! Thanx!! So using a Burlington crank as the baseline, what do you feel is the optimum weight for the flywheel/PP assembly on your crank using a 5.5/5.9 head and a Stipe cam that makes good torque in the low range??

[Allanw]

Originally Posted by Tom Wesenberg

Whoa! Now my head is spinning!

Good thing it's hollow so there's less rotational mass, otherwise it would fall off!

Haha!

[Vic in E-TN]

Very interesting reading from Mike K especially. I have a couple of counterweighted cranks and lightened flywheels and I like the performance. I have mostly high compression heads. There are too many variables to make a definitive assessment.

Think about this for a minute. If you want your engine to last as long as possible you should put the best shocks on your car. They will reduce body movement and reduce the resulting stresses on the crank/bearings.

Vic

[MikeK]

He He, now I'm loving it too. I used to make engineering students pee their pants by chalking "Fourier" on the board. Applied to physical materials harmonic analysis problems, you'll need to decide what transforms are applicable. I vote for using eigenfunctions as delineators. LINK

Sometimes in engineering you hit the theoretical wall, and just need to do hard physical operational testing if you want answers. In lieu of setting it all up on a test stand (or cleaning up all the puke after the above lecture) I offer the following alternative calculator. I believe this will give the answers Brent seeks.

[BRENT in 10-uh-C]

An OUIJA board!! Come one, ...come all as we gather around the table...

[dumb person]

If i was not dumb i would be able to do those calculations...

[BILL WILLIAMSON]

Originally Posted by Tom Wesenberg

Whoa! Now my head is spinning!

Good thing it's hollow so there's less rotational mass, otherwise it would fall off!

Tom,
Don't forget the sinus, (sniff!) cavities, without these green caves, we could only see our lint filled belly buttons, I pluralized it in case you have 2, on the positive side, you would NEVER stain your buckskin loafers, or burn out your eyeballs watchin' that "one of a kind" sunset at the beach, provided you live on the LEFT coast! You folks on the RIGHT coast don't know what you been missin'! Bill W.

[Pete]

"I vote for using eigenfunctions as delineators." LINK

Ya know, now that you mention that stuff, I actually remember about 20% of it....lol

[Phred]

One of the better discussions on the forum that I have read in quite a while. Lots of reasoned opinions and no name calling.

Well done and thank you.

[larrys40]

Brent, excellent topic... Here's my quick 2cents worth. I've driven and used both in my persnal engines and quite frankly I can't tell much difference, except that a stock flywheel definately enables the car to idle much more smoothly than one that is lightened. I think that was the intent of Ford to help give the engine it's smoothness, motion, and torque ( maybe I'm relating this wrong but then maybe not).

All things created equal in rebuilding engines it is no surprise that all engines do not run exactly the same. I always tell my customers these are like kids... as much as you want them to be the same they are not. As far as breaking crankshafts I don't think that's much of an issue with Model A Cranks.... after messing around with these for 35 years I've not personally heard of anyone I know or otherwise who "broke" a crank. There's lots of factors of that including metallurgy, abuse...etc

As I said... personally I can't tell a difference but I do think that the smoother running Model A, idler and otherwise will have the stock flywheel. Again, just my 2 cents worth. Isn't this a great hobby! so many great cars, so many great people!
Thx.
Larry S.

[RockHillWill]

Hey Mike K; I LOVE it! Nice work.

Vic: You are an astute thinker!

Chris: I agree with you.

Great thread.

[Chris in CT]

Originally Posted by BRENT in 10-uh-C

Yeah, me too Pete!

Hey Christopher, I'm glad you jumped in!! Thanx!! So using a Burlington crank as the baseline, what do you feel is the optimum weight for the flywheel/PP assembly on your crank using a 5.5/5.9 head and a Stipe cam that makes good torque in the low range??

Hi Brent,
This is getting pretty funny. Eigen functions, huh? That Ouija board is looking pretty good right now. Again, if we were to perform a Fourier Analysis on the rotating assembly, we could come up with an ideal weight for the flywheel/pressure plate assembly. My guess, based entirely on Ouija board consultations would be somewhere between 30 and 36 lbs as an ideal weight for an I-4 of 200 cubic inches and three mainbearings. My own flywheel is 40lbs stand-alone, but the next time I have the engine apart I think I'll try to get it to 36 w/ pressure plate. I have a single channel Fast Fourier Analyser, but you really need a two channel unit to do the necessary calculations... By the way, is your Ouija board single or dual channel?

Happy Thanksgiving to all cranks everywhere - balanced and unbalanced!

[Rowdy]

Now another thought. If a person chooses to lighten a flywheel some will depend on where the weight is removed the most, outboard or inboard next to the crank flange. Just some thoughts about inertia in this whole debate. Rod

[Jim/GA]

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Originally Posted by Rowdy

Now another thought. If a person chooses to lighten a flywheel some will depend on where the weight is removed the most, outboard or inboard next to the crank flange. Just some thoughts about inertia in this whole debate. Rod

I agree. See post #35.

[MikeK]

Originally Posted by Chris in CT

. . . I have a single channel Fast Fourier Analyser, but you really need a two channel unit to do the necessary calculations... By the way, is your Ouija board single or dual channel?

Single channel:

Dual channel:


If you have a single channel fast fourrier transform (FFT) device you could still do independent acceleration analysis at different axis points and get a very good data set for good 'ol pencil and paper 3-axis graphing. It would take a while (forget 'fast').

Of course, there will always be 968 1/2 variables unaccounted for in any specific engine build, so perhaps Brent's "Come one, come all.." statement is valid. A multi channel Ouija may be the way to go.

[Jim Huseby]

I have more layman's questions concerning the energy the flywheel must store and release. At firing impulse on a stock A, the crankshaft flexes torsionally from the energy imparted at the journal and must then "snap back" (and vibrate somewhat torsionally). When it snaps back (primary return pulse), it tries to impart more spin to the flywheel and it also tries to push the rod and piston backwards. Am I right so far? This un-even rotation of the rotating mass (it was already uneven because of uneven rod angularity during each rotation, pressure cycling, etc.) results in another character in the vibration signature. What is the duration of the primary pulse/return pulse? The point in crankshaft angularity when the return pulse will occur increases as rpm rises and will not only change the vibration signature, but will also change the magnitude and timing of the pulses in relationship to the crank's natural frequency. (Harmonics implied.) One of many new thoughts to me, as already stated in this thread, is that the counterweight's mass performs another important function in addition to "counterweighting". (You can't completely counterweight a mass that is part unevenly-reciprocating and part rotating with a purely rotating mass.) That other important function is to reduce crank flex.
It seems to me that the vibration signature would be different for any point it could be measured along the length of the crankshaft. This thread has moved my "theoretical wall" either past my present view or I am against the wall.

[Pete]

Originally Posted by Jim Huseby

I have more layman's questions concerning the energy the flywheel must store and release. At firing impulse on a stock A, the crankshaft flexes torsionally from the energy imparted at the journal and must then "snap back" (and vibrate somewhat torsionally). When it snaps back (primary return pulse), it tries to impart more spin to the flywheel and it also tries to push the rod and piston backwards. Am I right so far? This un-even rotation of the rotating mass (it was already uneven because of uneven rod angularity during each rotation, pressure cycling, etc.) results in another character in the vibration signature. What is the duration of the primary pulse/return pulse? The point in crankshaft angularity when the return pulse will occur increases as rpm rises and will not only change the vibration signature, but will also change the magnitude and timing of the pulses in relationship to the crank's natural frequency. (Harmonics implied.) One of many new thoughts to me, as already stated in this thread, is that the counterweight's mass performs another important function in addition to "counterweighting". (You can't completely counterweight a mass that is part unevenly-reciprocating and part rotating with a purely rotating mass.) That other important function is to reduce crank flex.
It seems to me that the vibration signature would be different for any point it could be measured along the length of the crankshaft. This thread has moved my "theoretical wall" either past my present view or I am against the wall.

A good point Jim. If you take the reverse impulse moment and apply Chlomondely's grillage coefficient you will see that the forward strake force is cancelled and the engine will run like a top.

[MikeK]

Originally Posted by Pete

A good point Jim. If you take the reverse impulse moment and apply Chlomondely's grillage coefficient you will see that the forward strake force is cancelled and the engine will run like a top.

[Jim/GA]

Originally Posted by Pete

A good point Jim. If you take the reverse impulse moment and apply Chlomondely's grillage coefficient you will see that the forward strake force is cancelled and the engine will run like a top.

Which is a key component of Rockwell International's "Turbo Encabulator".

See technical video here:

https://www.youtube.com/watch?v=oIS5n9Oyzsc

It all makes perfect sense (classical mechanics).

[Pete]

Originally Posted by Jim/TX

Which is a key component of Rockwell International's "Turbo Entabulator".

See technical video here:

https://www.youtube.com/watch?v=oIS5n9Oyzsc

It all makes perfect sense (classical mechanics).

Reading the original article is still a ROFLMAO experience.
I first saw it in 1946.
http://www.adl.com/uploads/tx_extprism/1995_q1_29.pdf

[Jim Huseby]

Well Pete, you got me. I googled Chlomondelly's grillage and got more good info. 'Next time you're in my neighborhood we can go to Chlomon's Delli and Grille. My CCPU may sound smoother after that.

[daren007]

I have read this before and I do not who first said it but here it is.


If you are in a hurry you are driving the wrong car.

[goodcar]

Originally Posted by MikeK

He He, now I'm loving it too. I used to make engineering students pee their pants by chalking "Fourier" on the board. Applied to physical materials harmonic analysis problems, you'll need to decide what transforms are applicable. I vote for using eigenfunctions as delineators. LINK

Sometimes in engineering you hit the theoretical wall, and just need to do hard physical operational testing if you want answers. In lieu of setting it all up on a test stand (or cleaning up all the puke after the above lecture) I offer the following alternative calculator. I believe this will give the answers Brent seeks.

Very amusing, my kind of teacher. Had one applied calculus class in my electronics tech school education. Got really good grades but never had a clue as far as really understanding it. Now almost 72 but back then had a good memory and knew if I got a certain type of problem I knew what the answer should look like. Had I gone on to more advanced math I would have flunked. Nice pictures and explanations Mike, you're obviously very smart but I really appreciate your humor and cut the crap conclusion. Drive and enjoy the Model A. There are numerous aspects to this hobby, something for everyone.

[dave11]

A lightened flywheel does affect the idle condition. A stock model a with a heavy flywheel will idle down to 3 - 400 RPM.
The same engine with a lightened flywheel will idle quite slow but not as smooth.
Important to some folks / not so much to others


Dave

[johnneilson]

Very good thread here, lots of correct information.
The one thing, and I may have just breezed by it, is the intended use of the motor combination. The lightened flywheel will be most noticed in the acceleration of the car. Usually this is in conjunction with multiple modifications to increase performance of vehicle. I have been told many things about flywheels, including that a Model A will not run without one.

Keep up the good work, all of this is to be considered in the world of the Model A/B.

Also, if the original Turbo Encabulator article surfaces, I would like to send to some youngsters at work, just to see their reactions.........

John

[1930marie]

Originally Posted by BRENT in 10-uh-C

One of the things I always heard growing up in the Model-A hobby was that we wanted a lightened flywheel in our Model-A. Especially if we were going to "tour" with it! The "he said/she said" reasoning that has been associated with this advice seemed plausible to me for years until a few months ago I started analyzing the "what & why" this was needed. A few explanations I have always heard that come to mind are;

#1: The extra weight of the stock-weight flywheel is not good on the rear main bearing as it causes the babbitt to wear faster.

#2: The extra weight of the flywheel makes shifting take longer.

#3: The heavier flywheel makes the engine accelerate much slower.

#4: The roads are different now and we don't need the heavy flywheel like they did back then.

#5: (Add your reason here...)



So this really begs the question n my mind is a lightened flywheel actually better? Well I guess my mindset now after trying a few things on a current project is that it could be, however more than likely it is a "band-aide" to cover up another fault. Let's explore my thoughts and then I would like to hear yours.

Thinking about #1, there is a 3 inch long bearing back there that most engineers would agree is way over-engineered for the task. Just how much extra wear do you suppose 12 pounds of spinning weight makes over the life of the bearing? In other words, exactly how many miles do we suspect the babbitt's life will be shortened? Now granted if someone has a sub-standard babbitt job, then maybe less weight can mask this issue. Maybe the issue is with a flywheel that is 20+/- grams out of balance that is wiping out the babbitt? Yes, a lighter flywheel might prolong the bearing life in this instance but why not correct the root problem?

In considering the number 2 reason, I have heard this but have also found that many drivers actually operate their vehicle with a mindset that defies Henry's original intent of operation. Now granted many Model-A engines must be operated in such a manner to overcome their mechanical deficiencies of low torque or less low-end power but again, choosing to use a lighter flywheel to band-aide those problems such as a worn camshaft or a cam that has the name "Touring" attached to it is in my opinion, doing it for the wrong reason.

One other thought to add, using 600wt transmission oil greatly improves shift quality by slowing the turning gears during clutch operation too however many owners choose not to use the heavier lube for various reasons.

I think many items listed in explanation #2 apply to the reason #3 also. My experiences are that with a stock flywheel and an 'in-specification' original cam (--or one of Bill Stipe's IB330), the acceleration is quite satisfactory due to driving within the engine's torque band. Couple that with a high-compression head and the combination makes a Model-A quite suitable for 95 percent of the traffic flow we typically encounter.

Number 4 is one I have pondered for many years and I have come to realize that it is all in the driver's operational mindset. Over the past decade I have had the privelege of training many Model-A owners on how to drive their newly restored vehicle. The common factor I see out of the majority of these first-time operators is they want to drive it like a sports car by slipping the clutch to take off, making high RPM shifts, and go-kart type steering maneuvers. I show them how the vehicle will effortlessly move away from a stop with the engine idling just by smoothly releasing the clutch pedal. Again, the inertia of the heavier flywheel is a plus. Next the driver typically wants to accelerate to 30mph before attempting to make a low to intermediate gear change. Once they realize that they can accelerate much faster by making their 1st to 2nd gear change at 10mph and using the torque of their engine to propel them, they are usually amazed. They are even more impressed when a 90 degree turn can be made while the transmission remains in high gear. Equally amazing to the veteran hobbyist who drive a Model-A with a 3.54 rear end ratio and negociate the same 90 degree turn without the need for downshifting. Adding to that amazement is when they learn that engine has a stock weight flywheel. Some might even be appauled to hear we are using stock weight flywheels w/ heavier counterweighted crankshafts!!

So my point in this lengthy rant is can someone give me a satisfactory reason why we really should be using a lightened flywheel other than to mask or cover-up some other mechancial deficiency?

.

The M.E.'s and the mechanical experienced expressed my anticipated response and makes sense mathmatically. A lightened flywheel coupled with a "damper" and balanced crank I believe offers an advantage IF you have a concern for higher RPM's or sustained 55-65 mph of operation. A rebuilt stock motor just went back in my car because that's what I grew uo with and I know I'm going to get another 40-50k out of it. By the way, what does a damper look like installed? I have not seen that one yet. Its all fun stuff. I enjoy seeing the many ideas we come up with to keep our cars on the road.

[Pete]

Originally Posted by 1930marie

The M.E.'s and the mechanical experienced expressed my anticipated response and makes sense mathmatically. A lightened flywheel coupled with a "damper" and balanced crank I believe offers an advantage IF you have a concern for higher RPM's or sustained 55-65 mph of operation. A rebuilt stock motor just went back in my car because that's what I grew uo with and I know I'm going to get another 40-50k out of it. By the way, what does a damper look like installed? I have not seen that one yet. Its all fun stuff. I enjoy seeing the many ideas we come up with to keep our cars on the road.

If an engine is out of balance, it is out of balance at all rpm from one to infinity, not just at 55-65 mph.
You feel the vibration at resonance or harmonics of resonance but the vibration is there at all other rpm's, just to a lessor degree.
Even if you only did parade driving at idle, an engine would benefit from balancing and last longer.

I have a pic of a 12 lb. big block Chev damper installed on a B race engine but can't post it. Probably because the website certificate has not been renewed.

[Pete]

Originally Posted by johnneilson

Very good thread here, lots of correct information.
The one thing, and I may have just breezed by it, is the intended use of the motor combination. The lightened flywheel will be most noticed in the acceleration of the car. Usually this is in conjunction with multiple modifications to increase performance of vehicle. I have been told many things about flywheels, including that a Model A will not run without one.

Yea, the dimwit that came up with that one must have never seen a race car.

Keep up the good work, all of this is to be considered in the world of the Model A/B.

Also, if the original Turbo Encabulator article surfaces, I would like to send to some youngsters at work, just to see their reactions.........

I have a copy of the original article published in the Washington Engineer in 1949.

John

Pete

[Mike V. Florida]

Glad to see that the opinions still hold after 5 years.

[Y-Blockhead]

Some of these old threads are confusing to read at times as they were written back when Ryan allowed people to remove their own post.

So some of the comments here are responses to posts that are no longer there...

[JayJay]

Originally Posted by Y-Blockhead

Some of these old threads are confusing to read at times as they were written back when Ryan allowed people to remove their own post.

So some of the comments here are responses to posts that are no longer there...

Point taken, Y-B. I suggested that OP (another thread) read this as I think Brent made some excellent points. And ten years later continues to do so...

[Jim Brierley]

It depends on what you will be doing with, or how you drive your 'A'. If you are going to do any kind of racing, it would be stupid to not lighten your flywheel. For normal driving, do as you like.

[Pete]

Originally Posted by johnneilson

Also, if the original Turbo Encabulator article surfaces, I would like to send to some youngsters at work, just to see their reactions.........John

Old thread but, John, in case you didn't get a copy of the T-E, here it is again for posterity and young fokes that haven't seen it.



The Turbo-Encabulator in Industry.

For a number of years now, work has been proceeding to bring perfection to the crudely conceived idea of a machine that would not only supply inverse reactive current for use in unilateral phase detractors, but would also be capable of automatically synchronizing cardinal grammeters. Such a machine is the "turbo-encabulator." Basically, the only new principle involved is that instead of power being generated by the relative motion of conductors and fluxes, it is produced by the medial interaction of magneto-reluctance and capacitive directance.
The original machine had a base plate of prefabulated amulite, surmounted by a malleable logarithmic casing in such a way that the two spurving bearings were in direct line with the pentametric fan. The latter consisted simply of six hydrocoptic marzelvanes, so fitted to the ambifacient lunar waneshaft that side fumbling was effectively prevented. The main winding was of the normal lotus-0-delta type placed in panendermic semiboiloid slots in the stator, every seventh conductor being connected by a nonreversible tremie pipe to the differential gridlespring on the "up" end of the grammeters.
Forty-one manestically spaced grouting brushes were arranged to feed into the rotor slipstream a mixture of high S-value phenylhydrobenzamine and 5% remanative tetryliodohexamine. Both of these liquids have specific pericosities given by P=2.5Cn6.7 where n is the diathetical evolute of retrograde temperature phase disposition and C is Chlomondeley's annular grillage coefficient. Initially, n was measured with the aid of metaploar refractive pilfrometer (for a description of this ingenious instrument, see Reference 1), but up to the present, nothing has been found to equal the transcendental hopper dadoscope (2).
Electrical engineers will appreciate the difficulty of nubing together a regurgitative purwell and a supramitive wennelsprock. Indeed, this proved to be a stumbling block to further development until, in 1942, it was found that the use of anhydrous nangling pins enabled a kryptonastic boiling shim to the tankered.
The early attempts to construct a sufficiently robust spiral decommutator failed largely because of a lack of appreciation of the large quasi-piestic stresses in the gremlin studs; the latter were specially designed to hold the roffit bars to the spamshaft. When, however, it was discovered that wending could be prevented by a simple addition to the living sockets, almost perfect running was secured.
The operating point is maintained as near as possible to the h.f. rem peak by constantly fromaging the bitumogenous spandrels. This is a distinct advance on the standard nivel-sheave in that no dramcock oil is required after the phase detractors have been remissed.
Undoubtedly, the turbo-encabulator has now reached a very high level of technical development. It has been successfully used for operating nofer trunnions. In addition, whenever a barescent skor motion is required, it may be employed in conjunction with a drawn reciprocating dingle arm to reduce sinusoidal depleneration.
References
1. Rumpelvestein, L.E., Z. Elektro-technistatisch-Donnerblitz vii.
2. Oriceddubg of the Peruvian Academy of Skatological Sciences, June 1914.
For more than 50 years the Arthur D. Little Industrial Bulletin has endeavored to interpret scientific information in terms that the lay person could understand. "The Turbo-encabulator in Industry" is the contribution of J.H. Quick, graduate member of the Institution of Electrical Engineers in London, England, and was first published in the Institution's Students' Quarterly Journal vol 15 no. 58 p. 22 in December 1944. Also published in The Washington Engineer 1949.

[ThosD]

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With a 60 lb flywheel, non synchronous transmission and a well worn model A, I find waiting for the engine rpm to drop so I can complete a double clutch upshift to be painfully long; slowing down, losing momentum and frustrating drivers following me. Things to do this year: engine rebuild, lightened flywheel and F150 3+ 1 trans.
I think the reason many on this forum do not see a need for a lighter FW is because the stock A engine does not rev very high during a typical drive to the ice cream parlor. By design, the heavy FW allows the 4 banger to idle around 500rpm or less (better for shifting the non synchro trans) and it stores energy to keep the engine and car moving in slow and loaded conditions. The A's 200 cubic inch engine design is typical for engines built in the 20s and 30s. My A's stable mate is a 2 liter sports car that red lines above 8k rpm. I installed a lightened fly wheel in the small car and noticed the engine responding quicker to changes in throttle. Rev matched, double clutched downshifts are a breeze. The down side is that 1st gear starts require a little more finesse in coordinating gas application and clutch release. The high strung little engine would stall if I set the idle at 500 rpm.

[Jim Brierley]

Some of you now have spinning heads, mine just HURTS!!!

[Dodge]

Lightened flywheel to offset the couterweighted crank.

And to each his own, its like in the Model T World cast iron piston motors lug down better
and aluminum piston motors rev quicker.

It depends on how your going to drive it.

[Ian Crawford]

I can't seehow a lighter flywheel will have any effect on the main bearings. If you take that the flywheel weight is about 63lbs and that on an original engine with a 4.2 c/r the cylinder pressure is about 75PSI. The stock bore is 3.875 so the piston area is 11.80 sq/in which would give us a force of about 884lbs directly on the closest main bearings. That is without the engine even firing. I really don't see that if the flywheel weight is 38lbs or 63lbs would make any noticeable difference. The ballance of the flywheel/clutch assy. will however have a dramatic effect as the out of ballance effect increases by its speed (RPM).