The Ford Barn

BRENT in 10-uh-C · 10-18-2023, 12:25 PM

Quote:

Originally Posted by JayJay

Looks like something you might see on a hit-and-miss engine...

Quote:

Originally Posted by johnneilson

It doesn’t

J

I tend to agree with y'all, however there was a time in the past here on Fordbarn where this Model-A engine rebuilder was praised for his ingenuity in doing this. At the time, I did not have a crankshaft balancer in my shop to be able to verify the effectiveness. Now some years later, what I believe I know about this kinda makes me hesitant to believe it really was of any benefit of masking torsional flex. Maybe other rebuilders can figure out the logic??

nkaminar · 10-18-2023, 12:49 PM

Brent, Most Model A engines will not need the dampener on the front because of the way they are driven. If you are going to push the engine and get near critical rpm's then you take the chance of a broken crankshaft. Model T's break their crankshafts often because of the torsional stress. There is nothing wrong with putting a dampener on the front of the crankshaft and it will definitely reduce the torsional stress in the crankshaft, that are present at all rpm's. It is not a balancer, which is a different animal. It is a dampener which is like a shock absorber for the torsional vibrations. Below is a link for a white paper that goes into all the details. If you or anyone else has questions about the paper, I will try to answer them.

https://www.fordbarn.com/forum/attac...0&d=1611503312

Added: There is some evidence that adding a torsional dampener will increase the life of the main bearings.

Jim Brierley · 10-18-2023, 02:32 PM

Cranks break their flange off because of something called nodulation, the minute flexing of the crank caused by each power stroke. When #1 or 2 fire, the front half of the crank bends one way, when #3 or 4 fire, it bends the other way. Sounds dorky but it happens. I've seen broken cranks in a Model A/compressor, and its certainly not from excess power.

I can't believe that Kelly's damper in the flywheel actually does anything. The damper needs to be at the other end of the crank.

Pete · 10-18-2023, 03:10 PM

Quote:

Originally Posted by johnneilson

It doesn’t J

It doesn't.

Pete · 10-18-2023, 03:14 PM

If you want to know if a dampener is working, it should feel warm after running at freeway speed for a few miles.

Some of the early developed lead shot filled ones on race engines got so hot the lead melted.

nkaminar · 10-18-2023, 03:20 PM

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Brent, Regarding the picture you posted of the flywheel with the added dampener. I assume that is a rubber coupling for the inertial ring. That is not the right place for a dampener. The biggest torsional deflection is at the front. Read the white paper (link in post # 22). If anything it will add flywheel inertia and reduce the torsional vibration felt by the driver in that way. It may reduce the vibration through damping but would have to be tuned to a very low frequency.

10-18-2023, 12:49 PM	#22
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 4,031	Re: Lightened flywheel Brent, Most Model A engines will not need the dampener on the front because of the way they are driven. If you are going to push the engine and get near critical rpm's then you take the chance of a broken crankshaft. Model T's break their crankshafts often because of the torsional stress. There is nothing wrong with putting a dampener on the front of the crankshaft and it will definitely reduce the torsional stress in the crankshaft, that are present at all rpm's. It is not a balancer, which is a different animal. It is a dampener which is like a shock absorber for the torsional vibrations. Below is a link for a white paper that goes into all the details. If you or anyone else has questions about the paper, I will try to answer them. https://www.fordbarn.com/forum/attac...0&d=1611503312 Added: There is some evidence that adding a torsional dampener will increase the life of the main bearings. __________________ 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; 10-18-2023 at 01:36 PM.

10-18-2023, 02:32 PM	#23
Jim Brierley Senior Member Join Date: Jun 2010 Location: Temecula, CA Posts: 4,110	Re: Lightened flywheel Cranks break their flange off because of something called nodulation, the minute flexing of the crank caused by each power stroke. When #1 or 2 fire, the front half of the crank bends one way, when #3 or 4 fire, it bends the other way. Sounds dorky but it happens. I've seen broken cranks in a Model A/compressor, and its certainly not from excess power. I can't believe that Kelly's damper in the flywheel actually does anything. The damper needs to be at the other end of the crank.

10-18-2023, 03:14 PM	#25
Pete BANNED Join Date: May 2010 Location: Wa. Posts: 5,423	Re: Lightened flywheel If you want to know if a dampener is working, it should feel warm after running at freeway speed for a few miles. Some of the early developed lead shot filled ones on race engines got so hot the lead melted.

10-18-2023, 03:20 PM	#26
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 4,031	Re: Lightened flywheel Sponsored Links (Register now to hide all advertisements) Brent, Regarding the picture you posted of the flywheel with the added dampener. I assume that is a rubber coupling for the inertial ring. That is not the right place for a dampener. The biggest torsional deflection is at the front. Read the white paper (link in post # 22). If anything it will add flywheel inertia and reduce the torsional vibration felt by the driver in that way. It may reduce the vibration through damping but would have to be tuned to a very low frequency. __________________ 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; 10-18-2023 at 06:39 PM.