8 pin rims

[woodworkingboy]

I have an old 242 xp that I like to use for limbing. At stock specs, I believe that it is one of the higher rpm saws comparatively at 15,500, but I've modded it to where i can dial it in up to 17000 rpms for working. If my calculations are correct, that works out to over 7000 feet per minute chain speed. It doesn't throw the chain with any frequency. Just saying....

 

[squisher]

Jay if that post is directed to me either I'm misunderstanding you or you're misunderstanding me. I didn't say it throws the chain more with an 8 pin. I said that when the chain does throw that a eight pin rim is going to throw it harder than a seven pin. Sometimes I went for what seemed like ages and ages without ever throwing a chain. Other times it might happen twice in the same day.

 

[squisher]

Who here has perfect chain tension the entire time a new chain breaks(stretches)in? If you do kudos to you for stopping to adjust your chain constantly. For most I think, you slap it on kinda tight and wait until it seems kinda loose to adjust it up again.

 

[MasterBlaster]

Aren't Stihl shains pre-stretched?

 

[cory]

Who here has perfect chain tension the entire time a new chain breaks(stretches)in? If you do kudos to you for stopping to adjust your chain constantly. For most I think, you slap it on kinda tight and wait until it seems kinda loose to adjust it up again.

 

[squisher]

Aren't Stihl shains pre-stretched?

I'd say if they are they failed miserably at it. Stihl chain is all I've run in recent memory.

 

[woodworkingboy]

Not directed at you, Squish, I've been waiting for years for the opportunity to show off and say that I have a work saw operating at 17000 rpms. I'm pretty good about attention to chain tension, such that I've been known to snatch up someone else's saw to adjust. Like saws call my name sometimes.

 

[squisher]

Well Jay. I am impressed. You know I love a modded saw myself.

 

[woodworkingboy]

Yep, and the way you've described it, a real good one.

 

[Magnus]

Saws today has less power stored in weight, less power in low rpm and lower torque so it is harder for them to hold higher loads than older saws.
Instead they have higher rpms and acceleration so chain speed is still around 20-21m/sek even though they have 7 pin.

The Jonsered 400 series had 8pin. Fine thinning/limbing saws!
500series could have either 7 or 8.

 

[Magnus]

Has anyone personally been issued by a thrown chain or actually know someone who has? Any time I've thrown a chain it ALWAYS comes off the drive and just slaps me, maybe all worry for no reality?

When Oregon introduced X series chain There was a lot of bar tip thrown chains as the cut out in drive link was not there so it tried to ride up on sprocket in bar.
I got a bunch of that chain, but returned all of it.
I threw chain a couple times when first testing that bloody thing.

I get customers here every week that throw chain in bar sprocket for various reasons.

Broken chains have increased the last years as many don't know how to run chain grinders but get them cheep enough to don't bother learning.

 

[Magnus]

I have an old 242 xp that I like to use for limbing. At stock specs, I believe that it is one of the higher rpm saws comparatively at 15,500, but I've modded it to where i can dial it in up to 17000 rpms for working. If my calculations are correct, that works out to over 7000 feet per minute chain speed. It doesn't throw the chain with any frequency. Just saying....

This is hard to believe if it has original ignition as the ignition is not capable of delivering sparks faster than 15 000rpm according to SEM (manufacturer of the ignitions)

 

[woodworkingboy]

Don't believe it, Magnus, and I'm sure not interested in arguing about it, but you can come over some day and I'll loan you my saw if it is still operational, and my good tachometer. Then you can find your post and delete it. The Husky issued spec on a stock 242xp is 15,500rpm, by the way, and my saw before being modified, certainly showed that. Perhaps bring your own tach.

 

[Magnus]

Thats OK, I won't ague it either then. Is it blue or black ignition?

I got some lists from SEM a while back that raised these questions. Since no one really care about top rpm it is of little importance.
It is the speed in wood, under load with said hp output that is interesting. I ran a lot of 242's.. I have 4-5 versions here.
Setting saws after performance is a lot better than after a rpm someone guessed would be optimal.

 

[SouthSoundTree-]

Stihl is much more 'prestretched' than Oregon.

I run Stihl.

State Parks runs Oregon. Easier to file after hitting some many nails in camp ground trees.

I have two small cuts in the gusset of my Arborwear pants from a thrown chain. Way close enough.

 

[woodworkingboy]

No reason to be negative about rpms, Magnus, it's just more information. They are something to look at when doing mods, along with other factors where changes get introduced. As you say, in the wood when cutting is what is important, but it makes sense to know the combination of details to learn what works for improvements and what doesn't. Also there is what you are going to be using the saw for when considering the revs.

What I think of as general guidelines for work mods is likely going to increase the max rpms, translating to chain speed, out of the cut tells you if that has been achieved. Emphasis may vary, and that may not be the setting where you want to run the saw, or it may be. The discussion was about chain speed, why I mentioned rpms, not talking about the saws functionality with them, though it is quite good with the 242xp running very fast. I thought it would be interesting to see how a saw designed to run at a higher rpm when stock would take to a mod.

 

[Magnus]

I like Jonsereds thesis better with low rpm and bigger rim to get same chainspeed.
There is a lot of negative stuff that comes along with high rpms. Easily avoided with a bigger rim.

Reason that most don't increase chain speed in transmission is that the engines are lighted and running lean = can't handle it.

There is a limit in rpms that is set by the gas flows in and out. It needs time to expand and burn out.

The faster you want gases in the harder it is to control fuel amount in it.
The faster you want gases out the more is not burnt.

 

[Al Smith]

My big old torquers came with 8 pin .404 rims, McCulloch 125 and Homelite 2100S .Fact an 8 pin was the only option offered for the Homey. They don't bog down even with a 48" bar like in my avatar picture.

In 3/8" pitch I have a Husqvarna 2100 CD with an 8 pin that wears a 32" inch bar, it doesn't bog down .On occasion I use an 8 pin on a souped up Stihl 038 mag but only on 20".I could run a 32" but it seems to do better with a 7 pin .