czar800
ArboristSite Guru
That was copied and pasted this is along the line of my original thought.
In most things I bow to the Masters superior knowledge but in this case a saw with a heavier flywheel will only hold a higher rpm for the fraction of a second that it takes to use up the extra stored energy. After that both saws will be equal.
However in all other respects you are invariably right.
OldJack.. My friend has a JD D, I've had a B.. from what I remember the manifold is only about 8" longer on from the right cylinder... that's a VERY short delay in exhaust pulse compared to the delay between firing cylinders... I think it's more likely they sound like they're firing evenly because the exhaust pulse is pretty slow and they're close enough together anyhow they sound like 1 long pulse.
The reason I can't agree with it in theory (correct me if I'm wrong) is that it doesn't matter if the mass is moving in a straight line or in a circle, the speed it's moving at is all that matters... so a wheel half the size still have the same linear speed (thus stored energy) as the larger one given the same vehicle speed... I just don't see how this adds up when talking physics, so I'll just say don't believe everything you read on the internet.
A lighter flywheel allows the engine to spool up quicker.....a good thing in a cold start race maybe.
A heavier flywheel will help the engine maintain rpm in the cut.
Depending on what you want, determines whether or not you would prefer a lighter, or heavier flywheel.
That's not what I was implying, if it sounded that way... I was saying an equal mass at half the radius, and equal *linear* velocity would have the same energy.. but looking at the formulas it doesn't seem to be the case, and I've been out of physics class too long to be able to understand the 'why'Assuming I understand your point…
The change in stored energy is squared by the change in diameter but only doubled by the change in rpm, one is logarithmic and the other linear.
So when the wheel is twice the diameter and half the speed, the larger diameter results in a fourfold increase in stored energy but the corresponding lower rpm only decreases it by half.
If we did not change the weight or weight distribution, and we reduced a wheel and tire diameter by half but drove the same speed, nothing would change. It would be a major change that just broke even. Moving the weight closer to the rotation center reduced stored energy, but the increased RPM to maintain the same speed increased stored energy the same amount. One cancelled the other, and stored energy did not change!
So reduced weight in the flywheel would be beneficial for a limbing saw then?
Exactly ,it effects power distribution , throttle control , traction control or planting of the power and transmission shiftiness. I see no benefits of lightening chainsaw flywheel where it spends most of it’s time at WOT.l know a motocross bike has a lighter flywheel than an enduro bike............if that explains anything. Flywheel wieght is definately a tuning aid for OEM's in the bike world. Adding or reducing wieght won't change HP.....but it will change how its delivered.
When I think of flywheels and the weight of a flywheel. I always recall going to the steam shows and seeing relatively low horsepower steam tractors belt pulley outworking modern much higher Hp tractors PTOs.
torque does the work, not hp
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