Stihl RM2 modifications

[JeffHK454]

Can the Stihl RM2 style chain be modified for better cutting speed?

Before I started frequenting this site I had little (no!) knowledge of what chains did what and how well they did it.

It seems that I have several RM2 chains in very good to new shape that I don't use because they just don't cut like a RS chain.

I didn't know if those "kickback straps" could be shortened up to give the chain a better "bite"?

Thanks, Jeff

 

[SWE#Kipp]

Cant you just grind down the triple-humped tie straps ????
If the depth gauge is same as on the RM it should work i think ,,,
if its worth the effort is another question ,,,,

/Kristoffer

 

[Kneejerk Bombas]

You can grind away at your chain all you want. It takes time and you need to be careful not to cut into tie straps or other critical chassis parts.
I'd just use them as they are, keep them as emergency back-up chain, or sell them on eBay.

 

[Kneejerk Bombas]

Cant you just grind down the triple-humped tie straps ????
/Kristoffer

The bumpers are on top of the drivelink, not the tie strap.

 

[JeffHK454]

Putting aside the amount of work it would take to remove the triple-humped part of the kickback link , would I end up with a better performing chain?

I was considering making a grinding fixture so that it can be done on a hand feed dry grinder. This method I could take the exact amount off each link with no danger of hitting any other part of the chain. It would take less than 30 seconds a link , roughly.

Jeff

 

[Kneejerk Bombas]

Putting aside the amount of work it would take to remove the triple-humped part of the kickback link , would I end up with a better performing chain? Jeff

Yes, you should.
There are a few issues. First is the ability to plunge cut or cut with the tip buried, those bumpers slow these cuts a lot. Next is spun weight, a lighter chain accelerates faster and has less centrifugal drag at the tip and sprocket. A third factor is chip clearance. After a chip is cut it needs to park somewhere until it is thrown out of the kerf. Any space you make in the "chip channel" will help with clearing chips.
If you want to learn more about grinding away extra metal on chains, read the thread, "Will the real logger please stand up". It's a long but interesting thread with tons of theoretical information on chains.

 

[Kneejerk Bombas]

The bumpers are there to reduce kick-back, so removing them will disable this safety feature.

 

[SWE#Kipp]

the bumper text was ripped from stihl.com ,, i have never used or seen one of those chains ,,,, but you are probably right ,,,

/Kristoffer

 

[JeffHK454]

Thanks Mike, for your info. I will have to be more aware of the potential for kickback with a modified RM2.

I have a beat 029 with a 20" RS that out cuts my new 440 with 25" RM2 . That just don't seem right!

The 440 has less than 3 hours on it so it's still tight and the 029 has ALOT of time on it but still it's a 029!

I put a RS on my MS 440 today , man what a big improvement!

How would a half-skip work in frozen hardwoods?

Jeff

 

[Kneejerk Bombas]

The full complement chain will cut faster untill you get to wood about 28" or so (assuming your bar is that long) then the skip will cut just as well or even better.
What happens is in big wood, the chips clog up the "chip channel" and pile up on the cutters so they stop cutting and just drag chips out. By removing cutters, less chips are made and there's more room for them in the channel.
What I do on my 24" bars is put a bigger sprocket on and run skip. This increases the chain speed and complements the skip chain. It's probably still not as fast as non-skip chain, but it sure save on sharpening time. Most of the trees we work are in residential settings, so we dull the chain a lot.
The 440 should kick a$$ on that 029, if not, somethings not right. Have you open up the exaust and retuned the carburator yet? Once that's done try an 8 tooth sprocket.

 

[Crofter]

Jeffhk454;

I think Mikes advice is right on. I have trouble leaving well enough alone too. I did just what you are thinking about. You could not grind them off that quickly without heat affecting (possibly softening, maybe hardening to brittle) the area of the drive link right above the rivet hole. Ask Ehp what it is like to wear a saw chain for a garter belt!
I freehand ground a few with the angle grinder and it is slow if you want to be careful not to nick anything you shouldn't. I switched to filing and that was better. Still something like half an hour for a 16 inch chain and I have a chain clamp you can really lay into. I cannot remember exactly what the gain was, but I think around 3 seconds on a 8 inch cut with a wild thing. Seems to me the rakers do not have the same front contour as a non bumper link chain and by removing the material from the bumper link you get a chain that is then even more kickback vicious than a regular chain.
I think that wild thing is now sporting a square filed chain and it might win the owner the odd case of beer if he can find an unsuspecting vicim!

 

[JeffHK454]

I run a 25" bar on my 440, and I will tell you I did dull the heII out of the RM2 that was on it trying to cut a frozen Mulberry. It also has a "Walker copy" muff. and the carb's been tuned. It runs strong but with that chain it's making small chips and dust not a rooster tail. My 029 runs great for what it is , little more compression than stock and my first and only port job on a saw. The 029 also had a new RS chain ! I bought the 029 for $90 (no chain or bar) just to try my hand at port work and if I screwed it up then it was no big loss.

I think that a handicapped 440 against a turned up 029 is a closer fight than I had first thought!

I think the chain has as much to do with saw performance as the motor!

Jeff

 

[Kneejerk Bombas]

When you compare two saws, use the same bar and chain, they are the same bolting pattern from an 029 to an 044, I think. Otherwise your results will be skewed.
Also, cutting frozen wood is slightly harder on a saw chain, but you're not going to dull it just cutting up one frozen tree, unless you hit the ground or something in the tree. It only takes an instant of contact with the ground, and the chain is dull. Sometimes, you don't even realize you did it, other than the saw starts to cut lousy.

 

[JeffHK454]

Crofter , I agree with the damage possibilities from too much heat to the kickback links 100%. I had planed on using whats called a Air Knife in my grinding process. It's an alu. bar with a special contoured grove that generates near freezing temp air using the shops compressed air! I use it at work when grinding thin heat treated tool steel.

Sorry I can't describe it better but what it does is keep small, hard metal parts cool or even cold when grinding.


Jeff

 

[JeffHK454]

Mike , I did not say it was a fair fight

Hit the ground , man I'm lucky if I don't hit my self or my truck!

Thanks for the info guys.

Jeff

 

[DanManofStihl]

I grind down the triple humps and they cut great after that. I like the Rm chain better then the Rs the Rm seems to stay sharper longer when I am cutting drity nasty logs.

 

[Locoweed]

Jeff, those air coolers are Hilsch Tubes.

Here is a link to the theory http://www.exair.com/vortextube/vt_theory.htm

And some products http://www.exair.com/vortextube/vt_frmain.htm

 

[JeffHK454]

Thanks Mr Weed for the linky, it does a better job of describing than I did!

Jeff

 

[Crofter]

Thanks very much re the vortex tube. I have had problems with grinding heat affecting teeth to the point of being unable to hand file after. That even when trying to be very careful and taking small bites as Jokers refers to. What is a source for that item?

 

[Locoweed]

Do a froogle search for vortex tube and you will find they are fairly expensive. Do a google search on hilsch tube and you will find several links on how to build your own.