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Sawmill build engine question.

Started by spottedog, February 07, 2021, 09:06:38 AM

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spottedog

Hi to all I an new here. I am building a mill using 19inch surplus center pulleys and pillow block bearings. I have a 3 inch driven pulley and 14 inch drive pulley. It will have a carriage about 36 inches wide. I have a 16hp vanguard I intended to use but after reading here am wondering if I should go bigger. I have looked at a 18hp vanguard and kohler by the specs the kohler is about 20 pounds heavier. Wondered if anyone was using either and had a preference one over the other.

Patrick NC

Welcome to the forum. I don't have any answers for you other than get all the horsepower you can. I'm sure there are lots of folks on here that can help you more than I can. 
Norwood HD36, Husky 372xp xtorq, 550xp mk2 , 460 rancher, Kubota l2501, Case 1845 skid steer,

Joe Hillmann

Surplus center wheels have small center holes.  That means small shafts and bearings.  So you will have to keep the pressure on your band a bit lower so you dont break shafts and bearings.  

With low band tension you cant cut very fast without wondering.  So, 16 hp should have more power than your blade can handle and still cut straight.

 I have a 14 hp mill with rubber tires for band wheels that can only handle light blade tension.  I would guess I have milled 2000 or so logs and maybe 5 or 6 of them allowed me to cut at a speed fast enough that the power of the engine wasn't enough.  But on those all I did was slow down the cut a bit.

spottedog

How big of shaft should I use? I bought 1 1/2 shaft and bushings to fit the pulleys. Linn lumber uses 1 7/16 shaft for there mills so I figured 1 1/2 would be all right. Maybe the stuff they use is different material to take the pressure.

Joe Hillmann

2" is often recommended.  The problem is a band wheel with a 2 inch hole, a 2 inch shaft and 2 inch bearings probably costs $500.    Whereas the same same set up with a 1.5" shaft through surplus center is probably closer to $100.

As long as you don't over tension the blade what you have will be fin.  About 8ish years ago there were 2 or 3 different threads of people who built mills with 1.5" shafts that either kept wearing out bearings or eventually broke/bent the shaft.

If you are building a hobby mill I would go with what you have.  If you are building something you  plan to cut really wide slabs on(+24" cuts all the time) or something you plan to run fast to get lots of production out of then maybe you should consider bigger shafts.

One cheap, middle of the road option may be to buy the wheels with 1.5" center holes from surplus center but use a 2 inch shaft that you have only the last couple inches turned down to fit your wheel holes.  That way you can use bigger bearings and shafts but the much lower cost wheels.

The mill I have is way under built.  Money was tight when I built it and if I were to help someone else build a mill I would have tons of things that I would tell them is wrong with my mill.  But if I were to build it again to day knowing all the things that is wrong with it I would build it the same way I did because it was cheap and built with what I had.(the only place I probably wouldn't cheap out is on the blade guides.

JoshNZ

I built my mill and used 1.5" shafts from memory. Turned from 4140 and I've got taper lock type bearings in the pulleys. It works fine I can run enough tension that the pillows get hot and I've never noticed shafts bending or tracking changing.

As mentioned if I were going to build another I'd go to 2" shafts and the larger type bearings to handle those days you wanna run a butt load of tension.

spottedog

Thanks for the input. Glad to know it will work although not ideal. I will use what I have for now its not going to be a production mill just for my own use. I was looking at the cooks blade guides, but didn't want to spend that much. I think I am going to buy the wheels and make the rest. 

ajsawyer


JRWoodchuck

I used surplus center 19" pulleys with 1 1/2" bushings and am pleased with how they work. Definitely get the bushing style pulleys not the bored pulleys they don't handle a sawmill very well. 
Home built bandsaw mill still trying find the owners manual!

JRWoodchuck

Forgot to answer your question haven't used any of those motors but never heard anyone complain about having more power. 
Home built bandsaw mill still trying find the owners manual!

ajsawyer

Quote from: Joe Hillmann on February 07, 2021, 05:38:38 PM
"About 8ish years ago there were 2 or 3 different threads of people who built mills with 1.5" shafts that either kept wearing out bearings or eventually broke/bent the shaft."

FYI 1018 steel can withstand a 42,000 psi load with infinite fatigue life. Given a cross-sectional area of 1.77 square inches(1.5" diameter shaft), that translates to more than 74,000 lbs of force, over many cycles, needed to deform the shaft through fatigue.

A 1.5"x.042" blade has a cross sectional area of .063 square inches. For a saw with 1.5" diameter 1018 main driveshafts to reach the limit load (42ksi), a 1.5"x.042" blade would have to be under 74,000lbs/(2x.063)=587,300 psi of tension.

I suspect the broken/bent shafts were made of chineseium...

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