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02-04-2021, 08:41 PM | #1 |
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Lightened Flywheel?
What is the recommended weight for a lightened Model A flywheel?
What is the weight of a stock A flywheel?
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Alan 1929 Special Coupe 1941 Pick-Up 1955 Victoria |
02-04-2021, 08:48 PM | #2 |
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Re: Lightened Flywheel?
Stock flywheel is 63
I've got mine down to 37 What's a perfect weight? I guess that would depend on engine and what would work best for your application Sent from my iPhone using Tapatalk |
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02-04-2021, 10:27 PM | #3 |
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Re: Lightened Flywheel?
I run a stock b flywheel with a stock a crank...b fly is 53lbs
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02-05-2021, 08:03 AM | #4 |
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Re: Lightened Flywheel?
I have a v8 clutch and the flywheel is about 35 lbs.
I am not saying that is the best, it is just what I have. |
02-05-2021, 08:26 AM | #5 | |
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Re: Lightened Flywheel?
Quote:
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02-05-2021, 08:59 AM | #6 |
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Re: Lightened Flywheel?
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Using a lightened flywheel is a matter of personal preference. How fast do you want to accelerate from a stop light? A lightened flywheel wont make any difference in how fast you can pull a hill. It will add more torsional vibration that will feed into the transmission and that I believe I can sense.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
02-05-2021, 08:59 AM | #7 |
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Re: Lightened Flywheel?
I reduced the rotating group weight by 10 lbs with the B flywheel,added about 4 with the harmonic balancer. A flywheel stores kinetic energy and by virtue of its mass dampens impulse.
In my opinion it has to do with your vision of the car.I want the mass to aide driveability,smoother operation. Although I basically double the power output of the engine through modification I don't race.My goal is a long distance touring car with reliability,I dont need a jack rabbit off the line,but want the smooth pulling power.In traffic the kinetic energy stored yields smoother clutch operation and smooth acceleration. |
02-05-2021, 09:16 AM | #8 |
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Re: Lightened Flywheel?
Whats important is building the engine for what you plan to do with it. I know folks who invest thousands to build an engine capable of racing and drive it like a touring car.
Another thing to consider is vendors run a business and sell items for profit. Its not fully in their interest to be sure a modification they sell fits your needs. Social media forums is an area where you need to filter based on your goals for the car. Often trends become established based not on need,but on a group justifying the money they spent. |
02-05-2021, 11:52 AM | #9 |
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Re: Lightened Flywheel?
I do know that lightening the flywheel will change the torsional response of the drive line. The natural frequency will increase. But where the weight is removed is also important. I would want a technical reason, experience or expected positive changes that will result from lightening the flywheel alone. It would seem that counterweighting the crankshaft would be better in terms of vibration that occurs at about 42 mph. But again, before I would make this change, I would want to know what it gets me....vibration free engine, improved bearing life...what?
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02-05-2021, 10:06 PM | #10 |
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Re: Lightened Flywheel?
With no flywheel, when you put pedal to the metal (or wood) the energy goes to the back wheels to make you go.
With a flywheel some, or a lot, depending on weight, gets stored for later. This saved energy transfers to the wheels when you try to slow down or are slowed down, whether you like it or not. |
02-05-2021, 10:55 PM | #11 |
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Re: Lightened Flywheel?
I'm not sure that all will be able to relate to this answer, but where the weight is in relation to the outer diameter of the flywheel, actually does affect the speed and performance.
Look at a figure skater and watch as they begin to make a spin in their vertical axis; their arms are stretched out, and as they bring their arms in closer to the center line / axis of their body, their speed dramatically increases to a point of disbelief ! The weight never changed, just its location in the rotation. Without destroying the structure and strength of the flywheel, removing the weight from the outer diameter from both sides, should help in the acceleration of the motor. I'm sure your rear main bearing will thank you for the gesture too. |
02-06-2021, 12:13 AM | #12 |
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Re: Lightened Flywheel?
OK, What is the weight of a standard flywheel with pressure plate and ring gear attached?. Mine comes in at about 70 pounds.
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02-06-2021, 08:16 AM | #13 |
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Re: Lightened Flywheel?
I'm no expert, but Les Andrews says "The stock flywheel weighs 63 lbs. 4 oz. Do not drop it. Keep feet clear when lifting the flywheel into place. Feet do not mesh well with the flywheel ring gear." I can verify that this is true. Don't ask me how I know.
Marty |
02-06-2021, 11:30 AM | #14 |
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Re: Lightened Flywheel?
Many thanks to all who responded!
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Alan 1929 Special Coupe 1941 Pick-Up 1955 Victoria |
02-11-2021, 11:48 PM | #15 |
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Re: Lightened Flywheel?
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02-12-2021, 10:05 AM | #16 | |
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Re: Lightened Flywheel?
Quote:
Terry |
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02-12-2021, 01:39 PM | #17 |
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Re: Lightened Flywheel?
I have heard that one of the rationales for removing the perimeter of the back of the flywheel (thereby lightening it) was to allow the three-finger V8 clutch to fit. Is there truth in that, or will the V8 clutch fit within the depression in the stock flywheel? If not, how much do you need to increase the diameter of the depression to make it fit?
The thread that Brent mentions in #5 is a very interesting read. Lots of opinions, most well-supported. I'm coming up on building a touring engine with 6.0 head, and I'm leaning more towards lightening only as much as I need to for a V8 clutch to fit. I'm not so interested in speed of spin-up as I am in a smooth low speed idle and maintaining inertia while climbing. JayJay
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JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan Last edited by JayJay; 02-12-2021 at 04:52 PM. |
02-12-2021, 02:17 PM | #18 |
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Re: Lightened Flywheel?
This like discussing oil. It never seems to end.
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02-12-2021, 02:31 PM | #19 |
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Re: Lightened Flywheel?
With my lack of knowledge of engines my question is what is accomplished by lightening the flywheel? Is it done in a machine shop ? Thanks in advance !
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02-12-2021, 04:47 PM | #20 |
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Re: Lightened Flywheel?
yes it is a machine shop that will do the flywheel.
With a lightened flywheel the car spools up much faster because it isn't trying to move an additional 35 lbs. Take offs at a light are much quicker. On my car I have the lightened flywheel along with a V8 clutch. The v8 clutch makes it way easier to depress the clutch. |
02-12-2021, 05:04 PM | #21 |
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Re: Lightened Flywheel?
IMO, this all boils down to how you will use the car. If it is around town, a lighter flywheel is probably better, especially if you drive it like a modern car and it sounds like a lot of you do. All the talk of spooling up faster etc indicates to me that you want to drive it like a sports car. That is not what they were made for
I do a lot of long distance touring on open roads so I stick with a heavier flywheel in that car. In another, which I use for all sorts of things and is more often in traffic, I lightened the flywheel. Horse for courses! Idle is much better with a heavy one and once up to speed, it makes NO difference, in fact, I feel it smooths things out, even at 50mph. Down shifts are easier but up shifts take a little longer - so what! Drive it like Henry intended, changing up early, drive steady and a heavy flywheel is better. Drive like a modern car and a lighter one suits better. IMO, It takes self discipline to drive the way they did in the day when you're tangling it with modern traffic.
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02-12-2021, 07:36 PM | #22 |
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Re: Lightened Flywheel?
A lot of disatisfication with vibrating model A/B engines can be attributed to NOT balancing the flywheel assembly after lightening.
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02-12-2021, 08:02 PM | #23 |
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Re: Lightened Flywheel?
Here is the math. So if you reduce the diameter by half and keep the mass the same you reduce the inertial to one-fourth. If you also remove weight by machining off the outside diameter you will reduce the inertia even more, to 1/16 if my calculations are correct. The weight of a lightened flywheel is taken off of the outermost radius so the effect is more than what you would expect by just comparing the weights.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. Last edited by nkaminar; 02-12-2021 at 08:27 PM. |
02-12-2021, 08:29 PM | #24 |
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Re: Lightened Flywheel?
For the disk, the mass is proportional to the area. The area of the original disk is pi X R squared. If you reduce the diameter of the disk by machining it to half the diameter, the area is pi X (R/2) squared or 1/4 of the original. So the inertia of the machined disk is 1/4 x 1/4 or 1/16 of the original.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
02-13-2021, 05:26 AM | #25 |
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Re: Lightened Flywheel?
A senior project in mechanical engineering school for us was to design a flywheel for a Gyrobus. The challenge was that if the shape was the traditional thick rim style, the stresses were too high and it would fly apart. After computer iterations, it came out as a thin rim, tapering to a thick hub. From the link, you can see the real ones weren't much faster that a Model A, but a lot heavier.
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02-13-2021, 07:54 PM | #26 |
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Re: Lightened Flywheel?
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If a stock flywheel blows up and takes your legs off, you can sue the manufacturer. If a modified one blows up, you don't have a leg to stand on. |
02-13-2021, 08:19 PM | #27 |
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Re: Lightened Flywheel?
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I'm part of the only ever generation with an analogue childhood and a digital adulthood. Last edited by Synchro909; 02-16-2021 at 02:32 AM. |
02-13-2021, 09:22 PM | #28 |
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Re: Lightened Flywheel?
As I recall, 30 lbs off of mine.
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02-13-2021, 11:22 PM | #29 |
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Re: Lightened Flywheel?
Not sure I can answer the OP’s question, but with my recent installation of a rebuilt engine, I also installed a machined-down flywheel and V8 clutch/pressure plate. The flywheel still feels very heavy to me, but obviously is lighter than a stock A flywheel. The V8 clutch is very smooth.
Jim |
02-16-2021, 02:30 AM | #30 | |
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Re: Lightened Flywheel?
Quote:
Yeah, you convinced me ! I’m a believer in Murphys Law ! Think I’ll stick with STIPES aluminum flywheel !! |
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02-16-2021, 06:57 AM | #31 |
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Re: Lightened Flywheel?
The forces on a flywheel at 2000 revs are not going to be anywhere near 8000 revs.
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02-16-2021, 07:37 AM | #32 |
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Re: Lightened Flywheel?
So at 8,000 rpm my Fordor with the present gearing and in high gear and overdrive would be going 220 mph. Guess I'll head for the salt flats.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
02-16-2021, 07:53 AM | #33 |
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Re: Lightened Flywheel?
this discussion is often brought up on the early 1 and 2 cylinder cars- where the weight of the flywheel is really meaningful.
with a 4 cylinder engine- not so much. |
02-16-2021, 12:28 PM | #34 |
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Re: Lightened Flywheel?
To Pete's point, lightened stock flywheels are verboten in SCTA competition.
I have been looking at some of the "lightened" flywheels and noticed that some have material removed from a inside. While this will reduce the weight, it does not address the MOI calculation. I have been working on some FEA analysis of this and the hub strength. Preliminary MOI shows that there can be as much as 35% reduction in MOI by removing weight off of the OD vs the ID. This in itself will reduce the amount of hub stress too. Still a ton of work to do on this, computer time is limited, J
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