I need help from all of you sawmill experts. :'( For the first time this past Sat., I ran my portable sawmill that I have been building for the past year and a half. Everything worked very well, but when I would hit a knot, it seemed that the engine governor wanted to hesitate before engaging and keeping the speed up. The blade is a simonds 13' 2" .042 7/8 like used on a woodmizer. This is a brand new twin cylinder 18 hp. Vangard Briggs and Stratton engine. Also, I was cutting cyprus which was about 9 inches in diam. Was it simply that I was going to fast? The engine rpm was 3300 and the blade was traveling at 4500fpm. When I slowed to about 3000rpm, it seemed better. Max. rpm on the engine is 3600. :'(
Pappa Dave,
The only time I have run into problems like you describe is when I advanced the head of the mill too fast. The engine would bog too far for the governor to respond. (your blade rising in the cut will cause bogging also --look to set/alignment and speed if this is the case)
It could be that you are expecting too much from your 18 horse engine and need to slow down some. Nine inch cypress should cut like butter though and not offer too much resistance. Of course, if the sap wood has dried then even small logs become difficult to saw and your blades will suffer too.
Just a note to look for: I have had condensation in the fuel tank and minute amounts of water get into the engine fuel bowl and cause me to think that the governor is failing. The gasoline will float on the water in the bowl until you move the mill enough to cause it to slosh and then the engine will pick it up and sound like it is bogging. Cleaning the float bowl may help stop your problem and is one of those "inexpensive" fixes.
If you haven't put a sediment bowl on your fuel line then you should. Put it between the fuel tank and your fuel filter and it will save you a lot of grief and make your filter last a lo-ong time. NAPA sells them if you can't find them anywhere else.
They are the little glass bowls that used to be put on all gasoline engines before the engineers decided that filters were cheaper and better. :D
yeah, the little glass bowls! I had that on my (ancient!) Allis Clamers CA- tractor was as old as I am.. you could SEE what was causing the problem. My International has a metal bowl, and you don't get the visual- but it does let you drain it. I will admit tho, if you dropped and smashed the glass bowl you were SOL til you got a new one :( lw
when i cut knotty material i kind of hold back on the saw head to momentarily reduce feed rate as i enter the knot, i also do this as i enter the log. this seems to reduce the wavyness that will occur as my blade dulls. the only time my onan 24 bogs is when my feed rate is way to high.
Most saws all basically run the same. With circle mills, you should almost stop before you enter the log. You never hit the saw with the log moving too fast. This will cause the log to dive in or out. I imagine the same can be said for band mills.
If sawing too fast, the gullets will fill with sawdust. The dust then runs down the side of the saw and pushes the saw out. It can also heat the saw.
But, in a circle mill we have the benefits of gravity. With those band mills, if your band gullets can't get rid of all the dust, it will build up, until you lower your feed and your band can take it away.
All saws are designed to rip a log, not cross cut it. With knots, you are crosscutting the limb. Your saw is cutting 2 different directions at the same time. Big knots have a tendency to push the saw out of the cut. That's why you have to alter your feed speed.
Thanks Ron:
I think I need to slow down on the feed rate. Also, I was thinking about putting some brass as a rub plate on the bottom side of the blade at the guides to keep the blade from diving. Any ideas? ::)