Getting serious about lo-pro

[LumberJeff]

lo-pro vs 3/8

the way i understood from other threads on this site is; lo-pro is.365 pitch and 3/8 is .375 pitch. correct me if I am wrong. please


:newbie:

 

[mtngun]

the way i understood from other threads on this site is; lo-pro is.365 pitch and 3/8 is .375 pitch. correct me if I am wrong. please

Lo-pro seems to be 0.365" - 0.366".

3/8 seems to be 0.367" - 0.368". Perhaps 0.001" - 0.002" longer than lo-pro, not a true 0.375".

 

[Brmorgan]

All of which are right out the window anyway after the first board is cut with a new chain and it starts to stretch.

 

[ray benson]

the way i understood from other threads on this site is; lo-pro is.365 pitch and 3/8 is .375 pitch. correct me if I am wrong. please


:newbie:

Check a 100' roll of each. They will have the same number of drive links.
Pitch is the same.

 

[mtngun]

The 3/8" x 0.063" times were 151 seconds and 146 seconds in that order. Average = 148.5 or 0.64 inches per second.

The lo-pro times were 137, 139, and 137 in that order. Average = 137.7 or 0.69 inches per second.

Since doing that test with the lame 066BB, the saw was fitted with a dubious OEM jug and a pop-up piston. The jug also had my first ever port job, with all its imperfections. The rings never sealed well, and compression was stuck around 120 - 125 psi despite the pop-up. Plus, there was evidence that the plating was continuing to flake off the jug (the plating had been damaged by sawdust in a previous incident). I decided to abandon that top end, but wanted to do a speed test before moving on.

Another 12.5" cant, ponderosa pine, possibly from the same tree.

Same 2 chains as before except, while last time the chains were fresh out of the box, this time they had been sharpened to factory specs.

3/8 x 0.063 Woodland Pro milling chain -- 0.565 inch/sec first pass, 0.49 inch/sec 2nd pass. Revs began at 10,500 but gradually dropped off to 9,100 by the end of the second pass.

lo-pro x 0.050 Woodland Pro milling chain -- 0.73 inch/sec first pass. Revs began at 11,000, then settled into 10,000. During the last foot of cutting the saw seemed to lose power and I had to baby it to maintain 9000 rpms.

When the saw lost power, I worried another chunk of plating had flaked off, and I didn't want to risk damaging the bottom end, so I didn't do a second pass with lo-pro as originally planned.

Today the low pro was 29% faster than the 3/8.

Hard to say how the OEM top end compared, speed-wise, to the lame BB. The OEM beat the BB with lo-pro, but the BB beat the OEM with 3/8. Could be due to chain sharpness, or to variations in the wood. I really NEED a dyno.

 

[mtngun]

Another day, another 066 top end, same 12.5 pine cant.

This is the popped & ported 066BB, which has lots of freeport, plus the rings refused to seal well. 128 psi last time I checked.

I had previously tuned it by ear to 13,500 rpm, where it was still blubbering. It didn't clean up until 14,000+.

3/8 lo-pro, 1st pass 0.76 inch/sec. It seemed happy running at 10,400 rpm. I had decided to skip wedging the kerf to save a few seconds. But, about six feet into the log, it balked and would barely run. I let it idle for a couple of seconds, then tried it again, and it took off. Not sure what happened -- partial siezure ? the 2 big knots at that spot ? or the bar being pinched in the kerf, since the kerf had not been wedged ?

I was a little paranoid about the engine overheating, so I retuned to 12,000 rpm WOT.

3/8 lo-pro, 2nd pass 0.76 inch/sec. This time it wanted to run around 9500 rpm. Funny how the cut time ended up exactly the same ? Perhaps the rich tuning allowed it to take a bigger bite ?

This time I wedged the kerf at the start end of the log. Yet, the engine still balked about six feet into the cut. Once again, I let it idle for a couple of seconds, and then it was willing to resume cutting.

I had planned to do a comparison test with 3/8 chain, but decided against it because of the mysterious stalling problem.

Despite the engine problems, the 0.76 inch/sec speed is the 066's best to date.

 

[820wards]

Another possible way of putting this to good use when doing long days in the field is to start out with aggressive rakers and run a 7 pin sprocket. Then after touching up the cutters 3-4 times swap to an 8 pin sprocket.

This saves the hassle of doing the rakers in the field.

Bob,

i have been using a 7 x .404 and just got a 8 x .404 to try on the next wood I mill. I also have my rakers set at .045" because of the torque in my 820 motor. Do you know what percent of chain speed I can expect from switching to the 8 x .404?

jerry-

 

[BobL]

Bob,

i have been using a 7 x .404 and just got a 8 x .404 to try on the next wood I mill. I also have my rakers set at .045" because of the torque in my 820 motor. Do you know what percent of chain speed I can expect from switching to the 8 x .404?

jerry-

8/7 or 1/7 = 14% more, it's not a lot but it's better than nothing.

 

[mtngun]

Some good news and some bad news for lo-pro fans.

A new speed test, with the new-style Bailey's 066 BB kit. Squish was set to 0.023", otherwise, the kit is unaltered. Saw was tuned to 13,000 RPM WOT at the beginning of the test. 7 pin rim. The usual 12.5" wide pine cant.

Two passes were made with Woodland Pro lo-profile milling chain, then two passes were made with WP 3/8 milling chain.

lo-pro x 0.050" 1st pass 0.79 in/sec, 2nd pass 0.83 in/sec, average 0.81 in/sec. The saw seemed happiest pulling 10,000 - 10,400 RPM. A virgin chain was used for today's test as will be explained later.

3/8 x 0.063" 1st pass 0.56 in/sec, 2nd pass 0.67 in/sec, average 0.62 in/sec. Saw seemed happiest pulling 9100 - 10,000 RPM. The chain was nearly new, having only been used for this series of speed tests.

Here is a summary of all the milling speed tests I have done so far, ordered fastest to slowest:

Lo-pro
0.81 in/sec new "as-is" BB
0.76 in/sec wood ported 2008 vintage BB with chattered bore
0.73 in sec wood ported OEM with damaged bore
0.69 in/sec "as-is" 2008 vintage BB with chattered bore
0.75 in/sec average for all tests

3/8" x 0.063"
0.64 in/sec "as-is" 2008 vintage BB with chattered bore
0.62 in/sec new "as-is" BB
0.53 in/sec wood ported OEM with damaged bore
0.60 in/sec average for all tests

On average, the lo-pro is 25% faster than 3/8", at least on this peaky 90cc saw. A torky saw might give completely different results.

But, I ran into a problem. I had noticed the lo-pro chain was an extremely snug fit in the bar. At first, I assumed it was because the bar was brand new and not broken in yet. However, it seemed to get worse with each use, instead of getting better. So..... I examined the drive links very carefully. A micrometer confirmed the worst -- the drive sprocket is hammering the drive links and peening the edge. The drive links on this chain -- which has only been used for these speed tests -- now measure 0.057"- 0.061". I'm going to have to painstakingly dress each drive link before this chain can be used again. :bang:

With the typical worn and sloppy bar groove, you might not notice the peening problem, but my new Stihl bar doesn't like it one bit.

Now that I have data showing that lo-pro is 25% faster, I can justify buying the expensive special spur sprocket. Hopefully, that will solve the peening problem.

I'm also going to look into the possibility of turning down 0.404" rims to fit lo-pro. I'll have to fabricate a mandrel to hold the rims while they are being turned in the lathe, so that project may take a few months.

 

[DRB]

Thanks for the continued tests. We need to get lo pro figured out. Thanks for taking one for the team before I get around to trying it out.

Is the lo pro kerf smaller than regular 3/8 ripping chain?

 

[mtngun]

Is the lo pro kerf smaller than regular 3/8 ripping chain?

Yes.

 

[Brmorgan]

My low-pro cuts about 9/32" kerf. Very narrow.

 

[mtngun]

Just checked the drive links on the virgin lo-pro chain used in yesterday's speed test. They are peened to 0.060", after only being run for 4 minutes ! ! !

I won't run lo-pro again until I have a more appropriate drive sprocket.

It will be interesting to see if the peening goes away with a better fitting sprocket.

 

[Andrew96]

At any one time I'd assume there would be 3-4 tangs engaged taking the full power of the saw. That might just be the point at which the drive tang is overloaded...producing the peened edge. Maybe it's just the amount of power through the drive tangs more than the ill fitting sprocket. I'm sure I'm not the only one interested to see once you get the proper one sorted.

 

[mtngun]

At any one time I'd assume there would be 3-4 tangs engaged taking the full power of the saw.

I think I posted a pic of a cut-away sprocket, several pages back, showing that only 2 tangs engaged the sprocket (versus 3 tangs engage when the chain fits propertly).

It doesn't sound like a big deal, but I guess it is.

I'm pretty sure I can turn down a 404 sprocket to the correct diameter for lo-pro, just got to figure out a mandrel to hold the sprocket in the lathe.

I think if we get the drive link problem sorted out, it'll be smooth sailing after that. Smooth, 25% FASTER sailing.

 

[BobL]

Just checked the drive links on the virgin lo-pro chain used in yesterday's speed test. They are peened to 0.060", after only being run for 4 minutes ! ! !

I won't run lo-pro again until I have a more appropriate drive sprocket.

It will be interesting to see if the peening goes away with a better fitting sprocket.

I don't understand what you mean by peened to 0.060. Do you mean the links have been thinned from 063 to 060?

 

[Brmorgan]

I think he means the front of the drivers are starting to mushroom from being forced against the drive pin of the sprocket. I've noticed it on all my chains but have never really paid much attention to it. Next time I'm up top at the shop I'll take a pic of the older low-pro chain that has two seasons of cutting on it. I have no idea what it looks like though.

I'm a little lost on the logic of using a .404 sprocket though... Please explain?

To turn it down, could you chuck an old clutch drum by spreading the jaws outward to grab the inside of the drum (just like the clutch would) and install the rim on the splines with some way of keeping it tight? It might not be dead accurate but it's not like you're turning a piston or something.

 

[mtngun]

I don't understand what you mean by peened to 0.060. Do you mean the links have been thinned from 063 to 060?

It's an 0.050" gage chain. The drive sprocket has hammered the edge of the drive links and caused them to bulge.

 

[mtngun]

I'm a little lost on the logic of using a .404 sprocket though... Please explain?

The unproven theory is that all rim sprockets are basically the same except for OD. The OD of a 3/8 x 7 is too small for lo-pro. The OD of a 404 x 7 is too big for lo-pro.

But, if I had a way to chuck the 404 rim in the lathe, I could turn it down to fit lo-pro.

Just a theory, and it may not work.

I've thought about using an old clutch rim as a starting point for the lathe mandrel, but bear in mind that the rim is hardened tool steel and very, very tough to cut on a lathe. The mandrel must have an iron grip on the rim.

I will probably have to make a mandrel from scratch, and heat treat it.

 

[Andrew96]

Well two tangs engaging might explain it. To turn down that 404, you might choose to spin it and grind (either on your lathe or somewhere else) as I doubt you'll be able to hold it properly with and iron grip. Any sandwich arrangement mandrel will hold it accurately enough to grind it.