iDRY Vacuum Kilns

Sponsors:

Power source, pulleys, ratios, rpm, etc......

Started by joegeds, January 20, 2016, 09:30:20 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

joegeds

I'm just beginning to think about the process of building a sawmill.  Obviously, the first item to consider is the power.  I'm wondering what HP (or cc) engine is optimal?  What is the lowest HP one could use?  Also, I have seen some of the homemade mills on here with two pulleys (one on the engine, one on the bandsaw wheel), and I have seen several with 3 different sized pulleys changing the ratio and rpm.  What is the optimal set-up?  Do some guys use 3 pulleys because they don't have the correct size lying around?  It seems to me that two would be best.  Any help would be great.  TIA
Ghosts crowd the young childs' fragile, egg shell mind........

dustyhat

I have three sets of double pulleys , but would like only two . just the way my configuration worked out. motor size just depends on what you want to do. i have seen them with eight hp. and up. you will always want more no matter what you put on.

Brucer

Key points:

-You only want to power the drive wheel that is pulling the blade through the cut.
-You will want your blade to travel at about 5000 feet per minute (no less) to ensure that the blade won't wander in the cut.
-You will want your engine running at the speed that provides the maximum torque.
-More torque is better. That means (in order of preference) electric, diesel, and gas.
-Remember, the more torque you have to deal with, the bigger your drive components will have to be.
-I know a couple of guys with 12 HP gas mills and they cut nice lumber, but not as fast as my 28 HP gas engine. The guys with 35 - 60 HP diesels cut way faster than I do.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

schmism

here are some recommendations from cooks

QuoteHere are some guidelines: 8 hp max speed 3,500 fpm, 12 hp max speed 4,000 fpm, 16 to 18 hp max speed 4,500 fpm, 25 hp max speed 5,000 fpm, 30 hp and above max speed 5,500 fpm.

https://www.cookssaw.com/index.php/increase-portable-sawmill-profits-a-production/how-fast-should-a-bandwheel-turn

I suggest you spend some time over there as he covers several good topics when it comes to best practices you might want to follow when building yours.


If you dont understand why the bandspeeds increase as the hp goes up its like this.    As a tooth makes the cut, the material it removes (sawdust) has to be "stored" while the band is in the log.  This is the function of the gullet on the band.   If you fill up the gullet the blade performance dramatically decreases.   The quicker you feed into a log,  the more material per tooth you have to remove.  You can do things like use fewer teeth,  allowing a larger gullet,  but there is a ratio of the size of the "tooth profile" to the remaining blade.   (eg large gullets require large bands)  if you make that ratio to small (as in many regrinds) your bands will eventually become to week and break.
so the easiest thing to do is to increase band speed so more teeth make it through the cut in any given period of time.   Why dont you just run fast band speeds on low hp mills.  you could, but each tooth takes a given amount of hp.    HP/tooth is a closely tracked item in production mills.

TLDR,  stick with cooks recommendations for band speeds to hp for good saw performance.
039 Stihl 010AV  NH TC33D FEL, with toys

joegeds

Quote from: Brucer on January 20, 2016, 10:44:48 PM
Key points:

-You will want your blade to travel at about 5000 feet per minute (no less) to ensure that the blade won't wander in the cut.
-You will want your engine running at the speed that provides the maximum torque.


OK, I did not know these two things.  Now about the pulleys - is there any advantage to having more than just 2 pulleys - one one the motor shaft, and one on the drive wheel?  In other words, if my mill is such that my blade is going 5000 ft/min, at max torque of the engine, with just two pulleys, I'm good, right?
Ghosts crowd the young childs' fragile, egg shell mind........

Magicman

Welcome to the Forestry Forum, joegeds.  I wish you the best with your sawmill build, and that was a very nice Clinton re-build.   :)
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

It's Weird being the Same Age as Old People

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

Kbeitz

The had part of not using a jack shaft that takes another set of pulleys is getting the engine up next to
the Bandsaw wheel. Sometime you cant do this because the shaft turns the wrong way. So you need to
turn the engine around and that puts the engine output shaft a long way away from your bandsaw wheel.
And from the little bit of experience that i have I think you will need a double grove pulley. One grove just
slips to much. It take a lot of power to pull a band saw blade through a log. On my mill I'm using a 13hp
Honda and one belt just would not take that kind of HP. Also using a jack shaft will let you have a place
later to install and alternator or hydraulic pump if you would ever want one. You could make a really long
shaft from your band saw wheel and drive it from the back.
Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

Kbeitz

Collector and builder of many things.
Love machine shop work
and Wood work shop work
And now a saw mill work

Den-Den

Quote from: Brucer on January 20, 2016, 10:44:48 PM
-You will want your blade to travel at about 5000 feet per minute (no less) to ensure that the blade won't wander in the cut.
-You will want your engine running at the speed that provides the maximum torque.

I disagree with the above statements.
schmism's post explains it well

As for minimum power; consider that years ago, logs were ripped by two men using a pit saw.  Two strong men = less than ONE horsepower.  The pit saw traveled very slowly by band-mill standards but was capable of straight cuts.
As to pulley configuration, this can only be designed correctly AFTER the engine RPM, HP and band speed are chosen.  A minimum pulley size will be needed to prevent the belt slipping on the engine pulley.  If you can get the needed ratio with this size pulley and a large pulley on the drive wheel shaft - good.  In some cases a jack shaft is needed.  An additional benefit to a jack shaft is that it makes it easier to change the band speed after building the mill (just change a pulley and a belt or two).  If you started with a minimum size pulley on the engine; cannot put a smaller one on for slower speed.
You may think that you can or may think you can't; either way, you are right.

Ox

An example for you to put away for later use if you want:  I have a homemade mill based on a Linn Lumber 1900.  13hp Predator, 3.7" centrifugal clutch on engine bought from Surplus Center, running a Gates B belt to a 14" driven pulley turning a 19" band wheel which is a pulley with a tight fitting belt for the tire.  Idle side is the same wheel.  At 3600 engine RPM the FPS is somewhere around 4500, I can't remember exactly and doing math gives me headaches.  No slippage ever with that single belt not being drum tight, but snug.  Loose enough that I know I'm not taking out bearings from too much tension.  More engine power would be fantastic but I'm satisfied with the 13hp.  If I had 20hp or more on there, I'd probably have to change to 2 belts.  I was able to max out my mill (within an inch) cutting 2.5" black cherry slabs but it was slow.  In normal tree sizes, up to around 20" or so it works just fine and make perfect lumber when we measure "perfect" in the rough cut lumber way.  Hopefully all this will help someone someday as to what will work with very little limitation.
K.I.S.S. - Keep It Simple Stupid
Use it up, wear it out, make it do or do without
1989 GMC 3500 4x4 diesel dump and plow truck, 1964 Oliver 1600 Industrial with Parsons loader and backhoe, 1986 Zetor 5211, Cat's Claw sharpener, single tooth setter, homemade Linn Lumber 1900 style mill, old tools

Thank You Sponsors!