Lightened Flywheel
 

I mostly see lightened flywheels used with counterweighted cranks. Are they only useful only together, or will they work well with a stock crank? If you had to choose from a 33# or 42# flywheel, what would be the best choice and what would be the advantages of either? I would think the 33# would get the nod.

Re: Lightened Flywheel
 

I thought you had already asked this same question a few months ago. If not, I apologize but here is a thread ( Is a lightened flywheel overrated? (I think so) )I posted a few years ago about the topic.

To answer your question specifically, they work well with stock crankshafts too. I would go with the 42# flywheel, ...and my reasoning is discussed in the link I posted.

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Re: Lightened Flywheel
 

We had a flywheel lightened at a machine shop once and cannot tell the difference. from a stock flywheel. Stock crankshaft. No better and no worse.

Re: Lightened Flywheel
 

Brent, I am sure glad your memory and searching ability is better than mine. I thought I had asked this before but couldn't find it! Thanks!

Re: Lightened Flywheel
 

I did not search for it, and was only working off of memory that you had asked something about it. The link I posted is the one I started several years ago.

Re: Lightened Flywheel
 

Impressed! I can't remember what I had for supper yesterday!

Re: Lightened Flywheel
 

Engines are beyond dumb, and well into stupid, the crank doesn't know or care what is behind it. I'd go with the 33 lbs. The lighter weight will accelerate and de-celertate quicker, and make quicker shifts possible. Do the math! It will not add horsepower.

Re: Lightened Flywheel
 

Must be another myth or old wives tale, but, I've always heard that at least 12# needs to be removed when using a counter weighted crank.

Re: Lightened Flywheel
 

Dang, that's impressive. Especially with 9000+ posts and going strong.

Re: Lightened Flywheel
 

My '29 roadster has a stock engine with a lightened (weight?) flywheel. It helps with engaging/disengaging a Borg-Warner overdrive.;)


Bob-A:D

Re: Lightened Flywheel
 

Brent,
We may have discussed this before so sorry if it is a repeat. For the rest, it may be of interest.

When using a lightened flywheel, I have had the experience of the "naturally occurring harmonic vibration" change rpm range.

A few years back, while doing some component testing for my touring car, I discovered the following: On an engine with a counter-weighted and balanced crankshaft, using an extremely lightened flywheel caused the vibration to present itself between 50 and 54 mph with a standard ratio rear end. Normally I see this vibration between 42 and 46 mph. Having the vibration show at 50 - 54 mph could not be worse for driving average roads with a touring engine.

The solution was to install a heavier flywheel, about 10#, and the harmonic vibration dropped back to between 46 - 49 mph which is much more drive-able. I believe if a standard weight flywheel were to be installed, the range would have dropped into the normal range of 42 - 46 mph. All the flywheels and matched pressure plates were balanced.

We even tried Ron Kelly's method of modifying a SB Chevy front harmonic balancer and mount it to the inside of a lightened flywheel. It actually worked the best in narrowing the vibration range. Voodoo or fuzzy logic I know but it was hard to argue with good results.
Good Day!

Re: Lightened Flywheel
 

I'm pretty confident that all Mr. Kelley's balancer did was add weight to the center of the flywheel. The flywheel mass (-of any weight) cancels any affect of the flywheel mounted balancer when they are both mounted onto the same flange. If it were mounted onto the opposite end of the crankshaft where it could dampen the torsional pulsations of the crank, then it would do a lot of good.

Re: Lightened Flywheel
 

Thanks for that observation Brent, It was my understanding that a harmonic dampener is most effective at the front end of the crankshaft? Having seen a a flywheel mounted dampener, not only did it look complicated, but one also has to remove the motor to fit it. Whereas the Harmonic dampener pulley is so much easier to fit, and in my experience, very effective.

Re: Lightened Flywheel
 

While I'm no expert in this area, it seems to me that a heavy flywheel will cause greater torsional stresses in the crankshaft due to its inertia. For that reason, I have gone with a lightened one at the back and one of those Murray Horne (From NZ) harmonic balancers on the front. I have no reason to regret that.

Re: Lightened Flywheel
 

I had to look for it awhile but this is a VERY good explanation of what torsional vibration is and how it is dealt with. The pics don’t show because it is a very old post but maybe MikeK can be persuaded to re-post it.

It is from 2-24-13. Post #32

Re: Lightened Flywheel
 

50lb B flywheel, stock A crank,Murray's balancer..no more 'harmonic' rpm..smooth all the way..

Re: Lightened Flywheel
 

During A engine development all the engineers involved with the work identified the torsional vibration,Harold Hicks had the temerity to bring it up to Mr Ford,who was a proponent of the heavy flywheel compensating for the issue..the engineers finally 'won' in '32,a mechanical advance distributor,larger crankshaft journals and later a counterbalancing addressed the issue..
Benson Ford research center oral histories..right from the horses mouth..

Re: Lightened Flywheel
 

Brent,
I agree, it added weight and that was key in lowering the range of vibration. The same happend when a flywheel of approximate equal weight, that was solid...no balancer added, was tried.
The difference between the two was the range of vibration was much tighter and less in intensity to almost not noticeable. The mounted balancer appears to take the edge off the torsional pulse, when a cylinder fires or the maximum pressure is reached on the compression stroke. I now run that version of flywheel in my Phaeton.

I tested these varying flywheels with the engine on the dyno. By varying the load at the rpm the vibration was most evident, the vibration could be intensified and clearly observed. The battery of tests taught me how to better build and tune an engine. Again...some say fuzzy logic but the dyno and results don't lie.

I have tried one of Murray Horne's combination front pulley/dampers. It also helps lessen the observed harmonic slightly. I need to complete more tests on his product when I have time. Available time seems in short supply of late.
Hope you and family are doing well...Good Day!

Re: Lightened Flywheel
 

This is all interesting. I enjoy the conversation.

What I have learned is that I can put my flywheel money into a new cam and will get more usable benefit.

Re: Lightened Flywheel
 

When you try to accelerate the flywheel will suck the energy created by the cam and release it when you decelerate.