Now here comes the Woodland Pro lo-pro ripping chain, again brand spanking new. The Stihl bar was also new and the chain was a tight fit in the bar, with noticeable drag. A new rim sprocket was used, too. Break-in consisted of running the chain at part throttle for a couple of minutes before beginning the cut.
After cutting two boards, the lo-pro had stretched and needed to be tightened.
5 boards plus an odd sized leftover. The boards have nice character, but they are too punky and have too many checks to be suitable for furniture. I think I'll use them for closet shelving. The odd sized leftover will even get used as a backer for "no trespassing" signs. The saw dust will get used to clean up oil spills in the shop. I don't like to waste natural resources.
I suppose you want to know the results ?
With the 3/8" chain, the saw was running in its powerband, at 8500 - 9500 rpm. Even if I pushed it hard, it wouldn't drop below 8500. Compare that to my last trip to the woods where the saw was struggling to maintain 8500 in a doug fir and would bog unless fed oh-so-slowly.
In other words, the 12.5" pine cant was not much of a challenge for the saw, and that's a problem for this test, because lo-pro shines in situations where the saw is underpowered with 3/8 chain. Oh, well.
With the lo-pro chain, the saw started out running 10,000 - 10,500 rpm. Cool, that's exactly the rpm I had hoped to attain with lo-pro chain.
However, by the second cut the rpms had dropped, and by the 3rd cut it would only hold 9200 with a modest push. Either the chain had dulled quickly, or else the saw was getting tired (or hot). I didn't let it cool off between passes except for the few minutes it took to get set up for the next pass.
For each cut, I paused a single time to install one wedge, which took 2 - 5 seconds depending on how many times I dropped the wedge.
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.
Note that both the first and the last lo-pro cuts were 137 seconds, even though it had lost 1000 rpms. How is that, you ask ? Because on the first pass, I did not have a good feel for the optimal feed rate. Practice makes perfect.
Ditto for the 0.063" chain, where the 2nd pass was faster than the first.
The lo-pro cutting speed was 7.8% faster than the 0.063" chain, on average.
I was expecting at least 10% faster, so I'm a little disappointed. However, something happened to slow the speed down quite a bit part way through the lo-pro test -- it could have been the saw, it could have been the chain dulled quickly, it could have been knots (the lo-pro boards did have more and bigger knots), it could have been ice (the log had been sitting out in the weather for 2 years and parts of it was wet and frozen). And so forth.
However, for all its imperfections, this is as fair a speed comparison as I'll ever be able to do, so I have to accept the results. :agree2:
The next step in this saga is just to continue running the lo-pro and see how it holds up. Will it continue to stretch or will it stabilize? Will it continue to dull quickly? Will it's speed advantage be more pronounced in bigger wood?
The difference in the height of the side links does affect the way lo-pro fits a rim sprocket (dunno about how lo-pro fits on a 3/8 SPUR sprocket). The drive forces will be carried by only 2 drive links instead of the usual 3. That's more stress per tooth.
