Blade speed

[postville]

Read an interesting article in the Cooks flyer on blade speed and sawdust size. They mention don't run over 5000 fps or you will not be able to make coarse dust that will stay in the gullet. Makes sense.
How do you set the rpm on a LT40 with a Kohler 25?
Bob

[POSTON WIDEHEAD]

Are you saying 5000 feet per second?   say_what

[5quarter]

hehe...if my saw was running at 5000feet per second, the least of my worries would be the size of the chips! can't answer your question but the article was very informative. tim Cook knows his stuff.

[Brucer]

Blade speed should be around 5000 FPM (feet per minute).

5000 FPS (feet per second) is about 3500 miles per hour, or about 5 times the speed of sound. I just finished reading an article about the USAF's "waverider" hypersonic jet that is supposed to travel around that speed :D.

[Magicman]

My WM operator's manual tells me the sawing RPM speed to adjust the engine to.  I figure that they have the proper blade speed worked out from there.

I have a tachometer that I hold against the rear engine shaft to determine that proper engine speed.

[drobertson]

I would agree,  I would either go to the  manual, or give the wmz techs a call. You may need to pick up a tach as well.

[postville]

10/4 -feet per minute.
How do you adjust the engine speed?

[bandmiller2]

Band speed is important but not critical,you have a considerable range.What Cooks say on dust is true.When my bandmill was run with the 2 cyl. Wisconsin I had too high a surface feet per minute,but didn't know it.After converting to the 15 hp Baldor three phase motor I slowed the band down and got better performance courser dust and the teeth stayed sharper longer.It would also give you longer band life, fewer flex cycles.Alot has to do with available power,as more power allows you to feed fast enough to take a good bite. Frank C.

[ely]

i would say all the commercial made mills are designed to run at or near the numbers that tim talks about in his article. one way you get a saw to move outside this area is when you start changing the drive pulleys and/ or the band wheel dia.
i dont know where it is but someplace, i have seen a formula that lets you figure your surface feet per minute on the saw, by punching in all the different pully sizes and engine rpm etc..

its the same principle on all mills, you want to feed the blade into the log at the optimum speed to cut the fastest... and its all relative to the sharpness of the band. if you are haveing to slow down in the cut then your band is sawing the same wood for no reason.

[CooksSaw]

Here's one formula for figuring feet per minute on your band blade:

Example: 
1) First figure feet per revolution:  3.14 (pi) x 26 (bandwheel diam in inches) = 81 ÷ 12 (1 ft.) = 6.80 ft. per revolution
2) Second figure pulley ratios: 16 (drive pulley) ÷ 3.83 (engine pulley) = 4.18
3)Lastly:  3400 (engine rpm) ÷ 4.18 (pulley ratio) = 815 rpm x 6.80 (ft. per revolution) = 5,544 ft per min. band blade speed

Hope that helps.
James

[tyb525]

Too slow, the cut becomes rough and each tooth on the band becomes stressed, leading to premature cracks in the gullet.

Too fast, the blade gets hot easier and loses tension resulting in a wavy cut. Also will load the engine down easier due to the higher ratio to get the higher band speed.

Fast band speed is not a bad thing as long as your motor can keep up with it and keep the feed rate high enough to utilize the band speed.


Funny, I just saw a post from a long-time member that said just the opposite, band speed needs to be at least 5000 FPM.

[Solomon]

Thanks for the lesson James.  I'm going to memorize that.  Pete.

[CooksSaw]

Funny, I just saw a post from a long-time member that said just the opposite, band speed needs to be at least 5000 FPM.

5,000-5,500 is a happy medium for most sawmills out there. We have customers set up running up to 6,500 ft. per min. for specific purposes but this is typically not ideal for the average sawmill setup.
There is no set in stone number as there are so many variables that differentiate one mill setup from another. But a safe setup is going to be 5K-5,500 for most people.

James

[drobertson]

I would like some owners of the engine in question to write in. Magicman has a valid point, Unless there have been changes in the drive pulley  and enging pulley, the only question is how fast to set the rpm's on this engine.  Going back to the ole give it a listen while tweaking the throttle can go along way if a tach is unavailable. Then get a bonified sharp blade and a reasonable size log and make some test cuts.  Poor man poor ways has worked for me.  A tach would be the best senario,

[Magicman]

How do you adjust the engine speed? 

I hate to give a short answer, but my owners manual told me how to adjust the speed on my engine.