Getting serious about lo-pro

[BobL]

Lopro chain pics

I just measured the driver link thicknesses on my 050 chain.
My setup is
a Stock 441 with 25" 050 GB bar.
Chain is GB R50S (Carlton N1C)
Standard 3/8 sprocket.
Chain has been used to cut up trailer load of firewood, and then used to mill about 2 dozen small slabs. There was a fair bit more stretching at the start than regular 3/8 chain.

Firstly comparing brand new chain (new drive link thicknesses are between 0.0480 and 0.0490") with the used chain.

There is evidence of some small amount of peening of the edges of the used drive links, maybe a bit like Brads. These drive links thicknesses range from 0.0505 to 0.0485 so the peening is minimal, maybe as the peening is generated it is being ground away by the bar groove.

This is about the most peening on any single drive link (this one was 0.0505").

About half of the links look reasonably clean like this (0.0485 to 0.0495")

Sprocket shows significant wear but it has also seen a fair bit of service with a pair of standard 3/8 chains (ie not a good idea). I'll keep using this sprocket with this chain but when I make up the next loop I will start with a brand new sprocket.

Using a used sprocket also might explain some of the tie wear.

Here's how it wraps around the sprocket.

Overall it looks like a bit more wear than I am used to for 3/8 chain but not sufficient to stop me using this combo at this stage.

 

[mtngun]

Thanks for the wonderful close-up pics, Bob. I wish I could take pics like that.

What I am looking at is how the drive links index on the spokes (or since we can't see the spokes, how they index in the ports). The gap between the port and the drive link changes as the lo-pro wraps around the 3/8 rim, since it does not fit well.

The net result is that one or two links carry all the load, instead of spreading the load equally over 3 or 4 links.

Here's my lo-pro on a 3/8 rim. Same pattern with the increasing gap.

Now here's one of the modded 404 rims with lo-pro, and the gap between the port and the drive link is 100% consistent, as it should be.

So why did my drive links peen like crazy, while your drive links seem unaffected ? A fair question. More CC ? Longer bar ? Different brand chain ?

All I know for sure is that I had serious peening on a virgin chain after only 4 minutes run time, and the modded rim seems to have eliminated the problem.

Thanks for the data. It's confusing, but that's real life.

 

[mtngun]

cermet

Tried the cermet bits tonight.

But the bits chipped or eroded. I tried it several times with different speeds and feeds, was able to lessen the damage, but was not able to completely eliminate the damage.

Eventually the rim diameter came out right, by that time I had smoked all the cutting edges on this particular bit.

The bit was $5, the rim was $5, so not counting my time, I've got $10 invested in the rim. Since I personally require only one rim a year, I can live with paying $10 for a rim (vs. $50+ for the Logosol spur). However, it's not a production worthy process that I could use to make rims for other people.

 

[BobL]

Good work mtngun. Hope it works out for you.

 

[Brmorgan]

So why did my drive links peen like crazy, while your drive links seem unaffected ? A fair question. More CC ? Longer bar ? Different brand chain ?

All I know for sure is that I had serious peening on a virgin chain after only 4 minutes run time, and the modded rim seems to have eliminated the problem.

Thanks for the data. It's confusing, but that's real life.

Buddy you gotta take it easy on those virgins...

 

[srcarr52]

Machine Ideas

Tried the cermet bits tonight.
But the bits chipped or eroded. I tried it several times with different speeds and feeds, was able to lessen the damage, but was not able to completely eliminate the damage.

Just a few suggestions for mass production because it sounds like you're approaching the final answer to LP chain milling at a reasonable price.

Check your cutter height on your lathe. If the cutter is too low you'll chip the really hard inserts more often. I've always set the cutter slightly above the rotation center of the part. This keeps the tip of the cutter in compression and is less likely to chip off.

You can always rough the piece in with a grinder on the lathe and then finish with the cutter. This will save you on the cost of inserts.

Check with you local engine machine shop. They can chuck your already made mandrel in a crank grinder and take the material off in a couple of seconds. If they don't have a crank grinder an older Sioux style valve grinder has an X-Y table and can be used to grind down the outside diameter. But you'll have to turn down your mandrel to fit in the chuck.

 

[mtngun]

I'm not going to pursue the modification of 404 rims any further, unless I acquire new equipment.

It was never seen as a for-profit venture, merely an opportunity to help my fellow CSM'ers, if I had a practical means to do so.

For my own use, a rim will last me a year, and I can live with destroying a $5 insert to make that rim. It's just that it's not a production worthy way to make the modified rims available to other people.

 

[mtngun]

New problem. As discussed in an earlier post, the sprocket teeth on my 3/8 x 0.050" Stihl bar were ground back to create a perfect fit with lo-pro. At the time, there was about 1/32" clearance between the side links and the modded bar nose, and it was working perfectly.

Lately the nose has been getting extremely hot. At first, I thought the bar bolt was pinching the sprocket bearing, but that issue was addressed, and now it is obvious that there is no longer any clearance between the side links and the nose.

I don't know what caused the 1/32" clearance to disappear. I'll investigate and report back.

 

[mtngun]

A close up of the modded nose sprocket, showing severely deformed teeth.

Also, note the sides of the nose are spread apart more than they should be.

The damaged nose sprocket does not spin freely. No doubt the bulged teeth are dragging inside the sprocket.

I don't understand what caused the damage to the teeth, or what caused the sides to spread apart, but I understand this isn't going to work.

Later, I'll tear the sprocket apart and do an autopsy.

Until I have a solution, I have to put this nose sprocket out of service.

 

[mtngun]

Inside of nose sprocket revealed ! ! !

At last, we get to peek inside a sprocket nose tip. It's basically a very skinny roller bearing. The only moving parts are the itty bitty rollers and the sprocket itself. The 1" diameter disc in the center is solid and does not move. As long as our CSM bolts and clamps stay inside that 1" disc, we don't need to worry about pinching the moving parts.

Close up of the damage. Teeth are hammered, side of nose (that thing in the top half of the pic) is deeply grooved.

Simulation of how lo-pro was riding on the damaged sprocket. For this pic, I set the side links right against the tip, similar to a hard nose, because that's how the chain was riding the last time I used it. As you can see, the drive links are not meshing with the sprocket teeth. That explains how the teeth got hammered.

Simulation of how lo-pro was riding on the modded tip before the damage occurred. For this pic, I left a slight gap between the side links and the tip. The drive links mesh pretty well. There is no obvious problem here.

Simulation of how regular 3/8 meshes with the sprocket. Slight gap between side links and tip, and mesh looks good.

The autopsy results tell us that the sprocket bearing was NOT pinched, as originally believed.

So what went wrong ?

Remember that in the beginning, I ground off the tips of the sprocket teeth to let the chain move closer to the sprocket and be supported by the drive links. The mod looked great and worked great -- for a while.

However, the tips of the teeth no longer speared the chain, like a normal sprocket nose. Without that spearing action, the chain was free to slide off the sprocket. Sure, the drive links were confined by the two sides of the tip, but those sides are pretty flexible, plus the drive links wore deeply into one side. The flexing and wear allowed the chain to slide deeper into the nose, which in turn screwed up the mesh and caused sprocket damage. Everything that happened, made everything else worse.

My current theory is that the root cause of the problem was a lack of side to side support for the chain, because the chain wasn't being speared by the modded sprocket tips.

In the future, I will not grind the sprocket teeth back. I may narrow them a bit, but it seems to be important that they "spear" the chain.

I've never had a chance to closely examine a proper lo-pro nose sprocket, so I don't know how they differ from a 3/8 sprocket.

 

[Philbert]

Great photos. This makes about 10 times I wish that I could rep you! (Somebody help me out here!)

I will use these in future chain saw classes.

Thanks.

Philbert

 

[BobL]

Real good work mtngun - I agree with your diagnosis 100%.

Now that you have that puppy apart what about turning up an annulus that turns the left overs into a roller nose. Flip the outside plates so the wear is on the outside. Don't worry about reriveting, it's going back onto a mill anyways - I'd just use some high tensile 6 mm allen bolts.

If you don't feel like doing it - you might might to send the bits to me and I will have a go - have to wait till august though till I get back to Oz.

 

[mtngun]

BobL, I gave the roller nose project serious thought, and decided I could buy a Logosol picco bar for less than what I would spend trying to make a roller nose, so if you want the old tip, you are welcome to it.

The Stihl 3/8 replacement tip arrived today. Once again, the Stihl tip did not fit the lo-pro chain, not even close. For some reason, the sprocket teeth were unable to "spear" the lo-pro links.

The Stihl sprocket teeth are around 0.059" thick.

The space inside the links on Carlton 3/8" x 0.050" chain is 0.065"+ wide, plenty wide enough for the sprocket teeth.

The space inside Carlton lo-pro links is around 0.055" - 0.056" wide, NOT wide enough for the sprocket teeth.

Using a safe-edge file, I filed the exposed portion of the sprocket teeth until they were about 0.052" thick. Now the teeth can "spear" the links. You can't see it in the pic, but the drive links are not meshing perfectly with the sprocket. I dunno if that is going to be a problem, but I don't have any better ideas at the moment, so I will try running it like this.

 

[billstuewe]

Mtngun, all my tips raise the chain obove the bar like in your picture and give me no problem. Try milling with it.

 

[huskyhank]

Mtngun, all my tips raise the chain obove the bar like in your picture and give me no problem. Try milling with it.

Yes, that's how its supposed to be as far as I know.

Tried to rep you, mtngun, for all this good work but it won't let me.

 

[BobL]

Here's my 050 tip

 

[mtngun]

BobL, that looks like a decent fit. Thanks for the info. I'm guessing the sprocket teeth on your GB tip are much thinner than the sprocket on my Stihl tips ?

I measured the sprocket thickness of some other brands:

-- 0.056" on a lightly used German Carlton 3/8"

-- 0.058" on an extremely worn Windsor 3/8"

-- 0.064" on a moderately worn Windsor 3/8"

All of those are too thick to "spear" lo-pro, unless modded.

It's been a long, bumpy road, but we are making progress at understanding lo-pro.

 

[BobL]

BobL, that looks like a decent fit. Thanks for the info. I'm guessing the sprocket teeth on your GB tip is much thinner than the sprocket on my Stihl tips ?

I guess so - I'd measure mine except I'm on the other side of the planet - closer to PNW than home.

It's been a long, bumpy road, but we are making progress at understanding lo-pro.

Mostly thanks to your determined efforts!

 

[glennschumann]

Creating a source for a picco rim sprocket...

I asked Grande Dog if they could source a picco replacement tip, and a picco rim sprocket for the larger saws, and add it to their product line... here is what he said...

http://www.arboristsite.com/showthread.php?t=140007

Thought it might have helped to ask...

 

[glennschumann]

Would it be possible to get a picco bar tip and transfer just the sprocket and bearings to a regular tip (remove and replace the rivets)/ Is there a picco sprocket that is large enough to fit in a regular tip?

Just a thought