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ENGINE RPM PULLEY SIZE YIKES!!

Started by flip, April 11, 2005, 10:40:15 AM

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flip

I bought a Kohler Magnum 16HP engine to run my blade on my home built mill.  A friend of mine is giving me a 4" pulley centrifugal clutch to use.  My question is....The engine is governed at 2850 rpm max and I have a 4" drive pulley and 19" band wheels.  What size driven pulley do I need to get my needed 4500 spfm???  Math is definitely NOT my forte. 
Thanks,
Flip :P
Timberking B-20, Hydraulics make me board quick

MemphisLogger

Scott Banbury, Urban logger since 2002--Custom Woodworker since 1990. Running a Woodmizer LT-30, a flock of Huskies and a herd of Toy 4x4s Midtown Logging and Lumber Company at www.scottbanbury.com

flip

Thanks!  Looks like I'm going to need a 11" driven pulley. :)
Timberking B-20, Hydraulics make me board quick

Jeff

As a reminder, there are plenty of other calcs, including those built by Don_P in the forum toolbox. You can get there by clicking the forum extras link that looks like this:



Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Kirk_Allen

Flip,
Double check your math. I came up with 12.5: Driven pully on the calculator and that gives you 4536 sfpm.  An 11" gives you 5155 sfpm.

flip

I'm starting off with Lennox blades.  I just ASS U ME D that the acceptable range would be between 4500-5100 spfm.  I think I will go with a smaller pulley just to compensate for less than 100% efficiency in the engine.  Good idea?  What'cha guys think?
Flip
Timberking B-20, Hydraulics make me board quick

Fla._Deadheader


  Might want to check the power curve on the engine. Our Honda 24HP reaches peak power at 3450. I open 'er wide open, then cut back a bit. That's where I set the ratio at.
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

samdland

THE FORMULA TO FIND S.F.P.M. IS: MOTOR R.P.M. X MOTOR PULLEY DIAMETER ÷ DRIVEN PULLEY DIAMETER X BAND SAW WHEEL DIAMETER X 3.1416 ÷ 12 = S.F.P.M.

flip

Soooo, it's better to run at peak torque even if that is not the peake RPMs and adjust driven wheel to get the SPFMs up? 
Flip
Timberking B-20, Hydraulics make me board quick

Larry

I thought of this thread today while reading the latest catalog from Cook's sawmill.  Stephen Cook had a little article about band speed.  He was saying 4 to 5,000 fpm on lower horsepower mills.  Higher horsepower gets speeds in the 5,500 to 6,000 fpm range.

Thought I would check there web site to seen if the article was online...it wasn't... but I found a very similar article that Tim Cook wrote.  Looks to me like Tim believes in running slightly slower speeds than his brother.  Maybe a little food for thought.

BTW...they got all kind of cool stuff for the home builder. :)

http://www.cookssaw.com/Articles/bandsawturn.php
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Fla._Deadheader

  I ain't no Engineer, but, works for us.

 Most narrow bandblades run 5500 or so. Shoot for that and you can't go wrong, whatever speed you run.  ;D ;D

  Guess Larry just shot my theory all to crap.  ::) ::) Thanks, Larry ;D :D :D :D :D
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

jrokusek

Quote from: Larry on April 11, 2005, 04:25:05 PM

http://www.cookssaw.com/Articles/bandsawturn.php

Fla._Deadheader beat me to it - but that's a bit different than what Suffolk Machine recommends (bottom of page):  http://www.suffolkmachine.com/did_you_know.asp

I wonder if this is something like the Ford vs. Chevy debate?  The "mine is better than yours" sort of thing?

Fla._Deadheader


  I'm not trashin Suffolk. They were trying their best to help us, when we started buildin our mill. Just couldn't get their blades to run well.

  The instant we changed to Munks Blades, we went to sawin. Haven't looked back since. Ask Swede about them Munks. ;) ;)
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

jrokusek

Where can I get these blades.........because I need all the help I can get!   :D

Fla._Deadheader


  Look to the left of the page.  "Menominee Saw" sells 'em.  ;) ;)
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

GF

When you measure the pully do you go by the outside diameter or the inside diameter?

pigman

The ouside of the pulley if the right width belt is used.
Things turn out best for people who make the best of how things turn out.

RoadKill

I checked some handbooks that I thought used a slightly different method and found that the manufacturers use a method that ends up with an "effective diameter" that is slightly smaller than the actual sheave od.  It matters most if one of the sheaves is small, like 4".  I think it is because the belt is actually resting on the sides, so the diameter at contact is somewhere in the groove.  Check handboods from belt and pulley makers for tables that give effective diameters.

Yah, born in da UP, but 20 yeahs heah neah Baahstin.

jrokusek

Now that you mention it....the pulley I'm looking at seems to state the "working diameter" based on the belt width you use.  Check the following:  http://www.surpluscenter.com/item.asp?UID=2005041311215063&item=1-BK160-H&catname=powerTrans

Jim

pigman

Quote from: RoadKill on April 13, 2005, 11:35:05 AM
I checked some handbooks that I thought used a slightly different method and found that the manufacturers use a method that ends up with an "effective diameter" that is slightly smaller than the actual sheave od.  It matters most if one of the sheaves is small, like 4".  I think it is because the belt is actually resting on the sides, so the diameter at contact is somewhere in the groove.  Check handboods from belt and pulley makers for tables that give effective diameters.


That was what I ment to say. but I didn't say it. ;)
The diameter will be the diameter of the outside of the belt if wrapped around the pulley. Now I am confusing myself. smiley_sweat_drop
Things turn out best for people who make the best of how things turn out.

wiam

What is the working diameter of this one? :D :D



For some reason the belt fell off when this happened.  I replaced it with cast iron. ;D

Will

pigman

The pulley looks fine.  ;) Must have been a bad belt. ;D
By the way, how did the cast iron belt work. I would think cast iron would be a little stiff for a belt. :P
Things turn out best for people who make the best of how things turn out.

Fla._Deadheader


  When we first rigged up the mill, I bought cast pulleys. The 4" engine pulley separated one day. Just spun the outside lip right off ???  Good old CHEENA Crap.  That's when we went to the 5V style STEEL pulley. That one bites. No slip at all.  ;D
All truth passes through three stages:
   First, it is ridiculed;
   Second, it is violently opposed; and
   Third, it is accepted as self-evident.

-- Arthur Schopenhauer (1788-1860)

wiam

Pigman I knew that was coming right after I posted. ::)

Will

D._Frederick

Wiam,

That pulley looks like a dye-cast pot metal one, they were not ment for anything above a fractional hp motor.

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