Point Of No Return???

[rahtreelimbs]

With all the chat about modded saws and chain speed I was wondering if there is a point that you can turn a chain too fast and start to lose it's cutting ability?

 

[Stumper]

I don't know if there is a point where the chain doesn't cut well but there IS a point where it is hard to keep on the bar.

 

[Marky Mark]

Let's see here's a 500cc look at that chain rolling.

 

[stihltech]

stuffed up

I know the chain willfill up with chips and cut slower. I did that at Grizzley's. I keep thinking a skip chain might help, but I always get told I am wrong, Except by my Stihl rep who has done a bit of stocksaw racing in his day. Sorry Chris, I just wonder.

 

[Stumper]

A local racer (who wins some) insists that skip is better because of a chip clearing advantage.

 

[ehp]

There is always a point where you are geared to high, it does not matter how much power you have, and it takes power to turn a chain at a faster speed, there will be a point that you are lossing to much power just to turn the chain instead of cutting the wood and as far as chain speed everything has it max load it can handle so if you get the chain going to fast yes it can break , mostly just with bike saws, every year they seem to be geared bigger to cut faster,
stihl tech , Chris is correct

 

[heviarti]

see this link for info on what oregon says about skip chains

there is talk on this very subject there..

 

[mikey]

Keeping the chain on the bar with severe speed could be a problem.How bout that Predator for chain speed?I think safety is a concern with the chain traveling at warp speed.Large pitch heavy chain could do some real damage .

 

[heviarti]

remember, a chain is really pretty tough.. roller chains (such as on a motorcycle have gone *really* fast. 280some miles an houor in the case of tsubaki roller chain setting a landspeed record with some two-sportster-motor powered thing..

 

[Lawn Masters]

I'd think that after a certain point its slightly harder to keep a chain lubricated correctly. I think a really high output oiler would be required, otherewise the chain would stretch and wear like a bench grinder was used on it, and it would break pretty quick.

This concept makes some sense right? I dont know that I'm right for sure though.

 

[stihltech]

lube

I think the chain lube is not that big of an issue. The saw is warmed up before the cut, lubing the chain. The actual cut may only last 3 seconds(or in my case, 7 to 10). Also, the chain is designed as sharp as possible, which in itself cuts down friction.
I would say it requires less lube than normal wood cutting.

 

[Marky Mark]

I will let you guys know what it's like to run that 500 next month.
There's stil time to get a ticket.

 

[glens]

Rich,

During some of my tests, I've noted a marked decrease in cutting ability as the chain approaches the speed of sound, or approximately 750mph. (about 26,500 rpm with a 30-pin &frac12;" sprocket) &nbsp; Near as I can tell, the shock wave builds up in front of the cutter and interferes with direct contact with the wood fiber (which, under such pressure, bends out of the way?).&nbsp; But the cutter itself is not harmed by operating in that manner.&nbsp; It isn't until approaching the speed of light (about 26,500 rpm with a 26,723,440-pin &frac12" sprocket, or using the same 30-pin driver, approx. 23,605,705,354 rpm; and oiling <i>does</i> become an issue, Wayne!) that the cutter itself starts to be detrimentally affected.

Glen

 

[ehp]

Glens sorry cannot quite swallow that one , but if you got a saw with a 30 tooth gear 1/2 pitch and will turn 26000 rpm's , i would really like to see it if you donot mind, boy when you got those guys to make that bar for the 30 tooth gear they must of asked some questions because that sucker would be real deep

 

[glens]

Glad I could entertain you, Ed!&nbsp; I thought especially you would appreciate that one.

Glen

 

[stihltech]

wow

Nice one Glen, but if the chain breaks there could be a danger to low flying aircraft.

 

[sedanman]

Actually if the chain broke a light speed, it would be a danger to orbiting satellites!

 

[Crofter]

Glen, you are more than a little handy with math. Do you think it is the pure strain of the centrifugal force trying to bring the chain into a circle that exceeds its tensile strength or is it that the force lifts the chain out of the groove and any external side force derails it straddling and splayed over the side rail where it is fractured by bending and or impact? We know they break but why. Where does the salmon belly bars etc. contribute?

 

[glens]

Actually, if the chain broke at light speed it could cause a rift in the space/time continuum if Scotty wasn't there to oversee the re-materialization.

Frank, I don't think that mere centrifugal force is enough to bust a (healthy?) chain.&nbsp; The side force you speak of is more along the lines of what I think would be the major contributor.&nbsp; I think it's important to remember that in comparison to a chain-driven vehicle (wasn't that brought up earlier?) the chain is of a different type (huge factor) and that load occurs at the end-points of the loop (major factor).&nbsp; With saw chain, the load points are the drive sprocket and along the "free" run leading to it (on a down cut; throws are much rarer on the up cut, right?).&nbsp; On the down cut, virtually all of the chain slack is on the top run of the bar and centrifugal force wants to send the chain into orbit just about the time it's snatched over the nose, so it's got the greatest distance from full guidance there and would be greatly susceptible to side forces as you describe.

Back when Doug B. did his write-up about running the Predator (the attached image is dated Mar 21 2003) I'd played with suggesting a different bar shape, but never got around to it.&nbsp; It would be expensive and the bar would not (necessarily) be symmetrical, effectively increasing expense, but the bar would stand a much better chance of fully guiding the chain if it were shaped to "fill in the gap" along the top approach to the nose, though I don't know how much initial tension would be required to match the centrifugal force generated during operation.&nbsp; At any rate, I feel full guidance would contribute greatly toward safe and sure operation, especially when side forces to the upper forward loop are encountered.

Being "handy" with the math is greatly helped by my trusty HP48 calculator with built-in handling of units such as length, speed, mass, etc.

Glen

 

[Crofter]

Lots of air space between bar and chain there. EHP mentioned falling cookies derailing and busting chain. I have hit them and sent them flying and thot it cute. Come to think of it, having that chain wrapped around your leg or back around your trigger hand might not be so cute.
I think we should get Sedanman to fire up his belly bar and we take turns tossing cookies to see if we can derail him to judge its merits.
.