Lightened flywheel
- Thread starter jtucker
- Start date
Smokedtires
Senior Member
How does a lightened flywheel affect MPG? I understand the ability to spin rpms quicker, but I would think the heavier flywheel would carry rpms longer saving gas on a touring engine. As I prepare to have new bearings installed in my engine, this is also a consideration.
You might want to look at this discussion from a few years ago. Raises some very good questions.
updraught
Well-known member
The flywheel stores and releases energy. When you take off with a light flywheel you will save on gas, but need more going up the next hill as you haven't stored much energy when taking off. In stop start conditions with a heavy flywheel you will probably waste the stored energy each time you stop.
Pete
BANNED
Most any general machine shop can lighten one for you.
If you do that, you should have the flywheel/clutch and disc balanced, each separately and then the flywheel and clutch cover as an assembly.
BRENT in 10-uh-C
Well-known member
Dave is in Minnesota and looks like he is pretty close to you. He has experience with what you are looking for. Maybe give him a call?
http://www.durableperformance.net/about.html
nkaminar
Well-known member
Flywheel weight (rotational inertia) is more complicated than initially perceived. The crankshaft has rotational vibration at all speeds, more at some speeds called critical rpm. The Ford engineers were either pretty lucky or pretty smart in that the flywheel inertia was just enough to cancel out the rotational vibration of the crankshaft so that it was not felt by the driver.
There is a spot along the length of the crankshaft where there is no rotational vibration, called a node point. With the original flywheel that point is the flywheel. With a lightened flywheel the node point moves forward so that now the flywheel is experiencing rotational vibration. The driver can feel this in the steering wheel when driving a car with a lightened flywheel. More so at lower rpm.
The addition of counterbalancing weights complicates this and changes where the node point is and how much rotation vibration is felt in the lightened flywheel.
The rotational vibration causes stress in the crankshaft and will lead to breakage under certain conditions. The addition of a vibration (rotational) dampener at the front of the crankshaft will reduce the rotational stress in the crankshaft.
There is a spot along the length of the crankshaft where there is no rotational vibration, called a node point. With the original flywheel that point is the flywheel. With a lightened flywheel the node point moves forward so that now the flywheel is experiencing rotational vibration. The driver can feel this in the steering wheel when driving a car with a lightened flywheel. More so at lower rpm.
The addition of counterbalancing weights complicates this and changes where the node point is and how much rotation vibration is felt in the lightened flywheel.
The rotational vibration causes stress in the crankshaft and will lead to breakage under certain conditions. The addition of a vibration (rotational) dampener at the front of the crankshaft will reduce the rotational stress in the crankshaft.
Pete
BANNED
Flathead B circle track engine with 12 lb. big block Chev damper. NO flywheel or clutch. (in/out rear end) Less felt vibration than a stock A/B engine.
6500 rpm twice a lap. 168 hp at 5800 rpm.
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Pete
BANNED
Dan Price flathead, modified to 14 to 1.
Pete
BANNED
I never checked it. It idled at about 2000.
That engine is in some museum now and I don't know what one.
ModelA29
Well-known member
I picked up a trick B engine a couple weeks ago. Aluminum flywheel and homemade dampner (not sure if that's right since there is no rubber in it). It's got a cross drilled "C" (yeah I know - no such thing) crank.
I'm always reminded of lessons from a friend while building race cars. Make it light - every pound you take out is a pound you don't have to accelerate or stop.
I'm always reminded of lessons from a friend while building race cars. Make it light - every pound you take out is a pound you don't have to accelerate or stop.
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nkaminar
Well-known member
29, That is an interesting engine. The "dampener" looks like a flywheel more than a dampener. Putting flywheels at each end of the crankshaft will change things and I am not sure how things will change. Usually the most extreme twisting is at the front.
Dampeners have two ways of dampening the torsional vibration. One is through the rubber connection to a heavy disk and the other is through some sort of friction connection. The rubber connection actually wears out after a while because of the constant flexing. Dampeners are designed for each engine using computer simulation and testing. It is not something that an average gear head can do.
Dampeners have two ways of dampening the torsional vibration. One is through the rubber connection to a heavy disk and the other is through some sort of friction connection. The rubber connection actually wears out after a while because of the constant flexing. Dampeners are designed for each engine using computer simulation and testing. It is not something that an average gear head can do.
BRENT in 10-uh-C
Well-known member
Y'all really want to discuss the effectiveness of a balancer on a Model-A/B engine, explain how this one works??
Looks like something you might see on a hit-and-miss engine...Y'all really want to discuss the effectiveness of a balancer on a Model-A/B engine, explain how this one works??
johnneilson
Well-known member
It doesn’t
J
J