Chain Saw Math

[Philbert]

I thought chainsaws could only divide. . . .

Spacemule . . .

One DIVIDES the logs into pieces so that the number of cords of firewood MULTIPLIES;

One DIVIDES one's time on A.S, so that the number of chainsaws one owns MULTIPLIES;

One DIVIDES the bar-and-chain oil containers from the two-stroke oil containers so that the useful life of the chainsaw MULTIPLIES;

. . . one is the same as the other grasshopper. . .

(Philbert)

 

[Erick]

So then how is the number of drive links on the chain affected by the gravitational pull of the earth? If the chain spins fast enough through the earth’s magnetic field will it create enough energy to power my house... or maybe some lights at least, so I can cut at night?? Will the chain spin backwards if I cut wood in the southern hemisphere???? :dunno:


J/K Nut, good job this has been discussed before and there are calculators out there for this very thing.

So for you saw grinders out there how many times do the rings go past the exhaust port at say 15,000 RPM….. now how wide/square do you wanna make that port.

 

[Philbert]

So then how is the number of drive links on the chain affected by the gravitational pull of the earth? If the chain spins fast enough through the earth’s magnetic field will it create enough energy to power my house...

I dunno. Might be some wind power in there. . .

Philbert

 

[Erick]

I dunno. Might be some wind power in there. . .

Philbert

:blush: oops sorry...... shouldn't have eaten that bean soup.

 

[slowp]

Be sure to calculate the coefficient of friction, which would be affected by the rate of dispensed bar oil. Also the type of wood one is dividing.

 

[wigglesworth]

Here is some more useless......I mean interesting info

http://www.madsens1.com/saw facts.htm

 

[BobL]

If the chain spins fast enough through the earth’s magnetic field will it create enough energy to power my house... or maybe some lights at least, so I can cut at night??

Nope - completely wrong setup to generate anything. To generate a voltage across its length a conductor has to move thru a magnetic field such that the conductor length cuts magnetic field lines. Spinning a loop of wire or chain parallel to a magnetic field (ie CS pointing sorth-south) cuts no magnetic field lines hence creates no voltage. Spinning perpendicular to the field it only creates a voltage across the thickness of the wire or chain which is small and as you only have one loop and the earth's magnetic field is small the total possible voltage is very small AND sitting on a bar that is itself a conductor means the whole thing is shorted out anyway.

To generate anything substantial
- the bar would have to be an insulator (or chain insulated)
- the bar itself would have to rotate along its major axis like a big drill bit
- you would need hundreds of chains on the bar
- chain could not be a closed loop

I find this graph useful to show newbies.

 

[BobL]

Spacemule . . .

one DIVIDES the logs into pieces so that the number of cords of firewood MULTIPLIES;

Ones DIVIDES one's time on A.S, so that the number of chainsaws one owns MULTIPLIES;

One DIVIDES the bar-and-chain oil containers from the two-stroke oil containers so that the useful life of the chainsaw MULTIPLIES;

. . . one is the same as the other grasshopper. . .

(Philbert)

AND one can always Divide by Multiplying by its inverse.

 

[BobL]

if your chain touches a rock for just one second, every tooth on that loop will have hit the rock 20 times[/B].
If the chain touches the rock for only a split second, each tooth might only have hit the rock 10 times.

Calc is 100% correct, but given these numbers I am always surprised at how relatively little damage occurs when real chains hit real objects. For example I have cut through many nails when milling and they never seem to affect more than 3 or 4 consecutive cutters in a major way and maybe 3 or 4 more randomly staggered cutters following thereafter were get extra dull. I cut through a 1/2" coach bolt last year and only about 12 cutters all up were affected. My guess is that these cutters were the ones that take the brunt of the hit and the rest follow in their wake so to speak.

One time I didn't quite tighten up a 3/8 tensile steel bolt on my mill and the bar gradually moved so the chain was able to slowly make contact with the bolt and it cut half way through the bolt before I noticed, hey this thing is cutting a bit slow. I guess I was lucky it did not slip big time!

I realize that these situations are different to hitting something like a really hard rock but nevertheless I am surprised that the chain damage is not greater than it is

 

[Philbert]

Calc is 100% correct, but given these numbers I am always surprised at how relatively little damage occurs when real chains hit real objects.

Me too. I often see just a few messed up teeth on a chain that has hit something and maybe some dulling on the rest. Chain must bounce on contact? That might be able to explain it for hitting a small rock, but not for cutting through a 1/2" bolt.

Philbert

 

[Philbert]

Back to School . . .

4) How does a saw cut through big trees when only taking those little 'bites' and making those small chips?

Back to our example: a full comp, 70 drive link chain, would normally have 35 cutters. 35 cutters X 20 cuts per second each = 700 'bites'/chips per second!
They start to add up.

Philbert

 

[brian22]

This is very interesting and impressive.

 

[fearofpavement]

Good informative post. Garners respect for the tools we use and have appreciation for.

 

[Philbert]

Bump!

(for the topic, and also for @spacemule)

Philbert

 

[Franny K]

"Please let me know if these are correct,"
Phil, There are 1640 drive links per 100 foot of 3/8 chain. It is ok to call it 3/8 but using 0.375 has been noted really deserves a correction multiple times on here. The title has to do with math. Maybe this was not realized 11 years ago.

Perhaps for those in fragile sedimentary rocks it is common to damage all the cutters in an incident, Here in hard metamorphic rocks it is often that the whole bar must be deflected and 3 cutters or so are mangled. Then there are the times really half of the cutters, those on one side of the bar escape damage.

 

[Wood Doctor]

Not on a modern saw. Older saws had gear boxes. Current ones are direct drive. The faster speed on troutfisher's post would mean less torque.

Philber

Exactly. I recall watching the chains going around on the old McCullochs. You could see teeth as they went by. Some said Marilyn Monroe could blink her eyes fast enough to strobe stop them.

 

[Huskybill]

Like gps recalculating? What’s the feet per minute of the chain with different diameter rims. I know the chain is flying.

.325” 8 pin, 9 pin rims.
3/8” 8 pin, 9 pin rims
404” 8 pin, 9 pin rims I’m tempted to try a 10 pin rim on the shorter bars.

I ran 325-8, 3/8”-8, 404-8, in the woods cutting hardwoods.

7 pin rims are too slow.

 

[Huskybill]

"Please let me know if these are correct,"
Phil, There are 1640 drive links per 100 foot of 3/8 chain. It is ok to call it 3/8 but using 0.375 has been noted really deserves a correction multiple times on here. The title has to do with math. Maybe this was not realized 11 years ago.

Perhaps for those in fragile sedimentary rocks it is common to damage all the cutters in an incident, Here in hard metamorphic rocks it is often that the whole bar must be deflected and 3 cutters or so are mangled. Then there are the times really half of the cutters, those on one side of the bar escape damage.

Your right chances are one side of the chain gets damaged very quickly.

 

[Philbert]

Like gps recalculating? What’s the feet per minute of the chain with different diameter rims. I know the chain is flying.

.325” 8 pin, 9 pin rims.
3/8” 8 pin, 9 pin rims
404” 8 pin, 9 pin rims I’m tempted to try a 10 pin rim on the shorter bars

Go back to the first couple of posts and substitute those values. It's simple arithmetic.

Philbert

 

[rd35]

Well.....I guess my thinking was wrong. I thought that "whirring" sound when I revved up my saw what the chain cutters breaking the sound barrier.....guess it was just a lack of proper lubrication on the bar!!!