Thread: Stock Appearing Race Saws

Maybe the fact that the original flywheel is balanced at almost 30k RPM and that someone spent the $ to balance the crankshaft.

Have you seen a machine that will quantifiably balance a chainsaw crank, flywheel, and clutch at the same time?

How much parasitic loss is possible by an engine that is out of balance?

Fred

Suppose too, you could put snow tires on a ferarri and then have them carefully balanced for maximum performance.

Originally Posted by timberwolf

Suppose too, you could put snow tires on a ferarri and then have them carefully balanced for maximum performance.

I figure snow tires on this Ferrari would be faster than drag slicks on a pinto.


Fred

But not as fast as a ferarri with the propper tires.

If a fly wheel was balanced once it can be balanced again after a good bit of the crank breaking weight and HP robbing fins have been removed from it.

Apparently Marcel and Harry agreed about it. I'm not going to second guess people who have had that much sucess.

I've built saws both ways and tested saws with both flywheels. Never really noticed much difference except the temp of the engine.

Do it your way ................

Fred

so...

As far as the pin holing goes.... the major benefit I want is better strutural integrity. The guys who are good at it use them for balancing also.


I assume they get the crank in place, and drill through the metals that are pressed together in the 3 piece crank. So lets say they put a 1/8 drill bit through there, then warmed up the crank and used the same size diameter pin into the hole for a tight fit. It really sounds like it would tighten up the crank for the high speeds this saw turns.

So do you have any pics of marcel saws? Or do you have any marcel saws now?


Thanks for the pics




Buck

Fred I haven't proved it but I've stated before it just makes sense to me like this. if you block off the intake side of a vacuum pump it actually unloads it self as it is no longer flowing and the work being done is lower. I have measure the decrease in current flow in fan motors and pumps because of this.

so if we want to prove it out how much energy does it take to spin that fan at even 13k? Come on Brian whip up a calc to figure it out.

I want to through out another idea, what kind of heat is being generated in the magnets while being energize 217 Hz?
Are there any ill effects to the gauss of the magnet with the generated heat and no cooling fins? Less ignition maybe but how much does it degrade if at all and will it cause any loss of performance?

Originally Posted by buck futter

I assume they get the crank in place, and drill through the metals that are pressed together in the 3 piece crank. So lets say they put a 1/8 drill bit through there, then warmed up the crank and used the same size diameter pin into the hole for a tight fit. It really sounds like it would tighten up the crank for the high speeds this say turns.

SOunds like a good idea, but that's not what was done. It was just through the bells.

So do you have any pics of marcel saws? Or do you have any marcel saws now?


Thanks for the pics

No pics and none of Marcel's saws.

Fred

Well I guess you can't win em all.

Maybe I'll guess the next one up.

Fred what do you have right now on the project table?

drum roll please..............

bowtie?

I bought this nice old saw and the old guy said he was to old to use this old saw and he couldn't get it started and he hadn't started it since the mid 90's.
So you know what I'm thinking a new fuel filter and fuel hose and I have this sweet looking saw. Then one thing leads to another and we start talking mix ratios and he mention how he put the saw away with amsoil in it. We its the only thing I can think of that would cause this type of damage.

I did look at an 066 fly wheel and calculated the exposed portion of each as it protrudes past the fin before it. Then calculated the force on it going 250 MPH and it was substantial. 1/2 a HP at stock WOT RPM and closer to 1 hp at full RPM. It's a crude way of estimating the drag, but I'm confident it's in the ball park.

Also tested it on a 372, lightened flywheel with all fins removed it gained 400 or 500 RPM WOT and cut times improved close to 5%.

I strongly suspect that air cooling is all but irrelevent in a 5 second race. Air cooling does not work until there is a temperature difference, so as long as the outside of the jug is cool it is doing nothing but blowing air about. Real life demonstration of this is welding or grinding. You can grap a chunk of steel with bare hand a couple inches from a weld and run a bead on it without getting burnt, you can grab a iron bar and push it against the grinding wheel until the edge is glowing, as long as you don't hold it too long the heat won't have time to travel through it to reach your hand.

The thermal conductivity of aluminium is 3-4 times higher than iron or steel, but still it is going to thak time for the fins to get any heat from the engine.

I have been making heads with cooling fins, but think I will be dropping that idea, looks nice, but for a short race they don't do much.

If it's the fins working against atmosphere that robs HP, then why not have them spin in a vacuum? Have seen this suggested before, (duct tape the starter intake grille). Anyone ever try it?

Originally Posted by Danger Dan

If it's the fins working against atmosphere that robs HP, then why not have them spin in a vacuum? Have seen this suggested before, (duct tape the starter intake grille). Anyone ever try it?

As BF mentioned, restricting the intake on a centrfugal air pump drops the load on it but will not reduce it as much as taking the fins off entirely.

I see the old debate about crankcase volume relation to output is still alive. If it were so simple that smaller is always faster period, it would have been settled long ago. What some winning saw builders of the past did is not conclusive evidence except that they were doing more right things than the competitors then with the engines available. Cut times have been dropping steadily in recent years, though that is not entirely engine related.