|
Is a lightened flywheel overrated? (I think so) 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? . |
Re: Is a lightened flywheel overrated? (I think so) 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 |
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) 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..
|
Re: Is a lightened flywheel overrated? (I think so) 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 |
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) 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 |
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) Quote:
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. |
Re: Is a lightened flywheel overrated? (I think so) 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.
|
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) 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?
|
Re: Is a lightened flywheel overrated? (I think so) 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.. |
Re: Is a lightened flywheel overrated? (I think so) does anyone know if cars of similar horsepower, weight, etc. (Chevrolet, Dodge Brothers, etc.) had similar flywheels?
|
Re: Is a lightened flywheel overrated? (I think so) Quote:
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? :rolleyes: . |
Re: Is a lightened flywheel overrated? (I think so) 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.
|
Re: Is a lightened flywheel overrated? (I think so) 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 |
Re: Is a lightened flywheel overrated? (I think so) 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! |
Re: Is a lightened flywheel overrated? (I think so) [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? :rolleyes:
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. |
Re: Is a lightened flywheel overrated? (I think so) Quote:
|
Re: Is a lightened flywheel overrated? (I think so) 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? |
Re: Is a lightened flywheel overrated? (I think so) 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.
|
Re: Is a lightened flywheel overrated? (I think so) 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!
|
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) Quote:
|
Re: Is a lightened flywheel overrated? (I think so) 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
|
Re: Is a lightened flywheel overrated? (I think so) 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".
|
Re: Is a lightened flywheel overrated? (I think so) Quote:
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. |
Re: Is a lightened flywheel overrated? (I think so) 1 Attachment(s)
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. |
Re: Is a lightened flywheel overrated? (I think so) 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. |
Re: Is a lightened flywheel overrated? (I think so) Quote:
|
Re: Is a lightened flywheel overrated? (I think so) Quote:
Interesting how this thread is progressing, now through testimonials. All BRENT's fault, posting intelligent questions!:) |
Re: Is a lightened flywheel overrated? (I think so) Quote:
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. |
Re: Is a lightened flywheel overrated? (I think so) Quote:
|
Re: Is a lightened flywheel overrated? (I think so) 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..
|
Re: Is a lightened flywheel overrated? (I think so) Quote:
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. |
Re: Is a lightened flywheel overrated? (I think so) 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!
|
Re: Is a lightened flywheel overrated? (I think so) 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?
|
Re: Is a lightened flywheel overrated? (I think so) 2 Attachment(s)
Quote:
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! |
| All times are GMT -5. The time now is 10:47 PM. |
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.