Replies

1. 
   RickW | May 05, 2008 05:32am | #1

   The Old Woodworking Machines forum has several online calculators, including a pulley size/RPM calculator.Here's the link-http://www.owwm.com/math/default.aspx.

   Rick W

2. 
   BruceS | May 05, 2008 05:36am | #2

   VD = vd  if memory serves me correctly.  You will have to do the math.  Velocity in rpm's times large pully diameter =  velocity in rpm's times small pully diameter.  No need for any books or graphs/charts.

   In your case the big D will be the unknown, the big V will the 700 RPM, little v will be motor speed, little d will be motor pully diameter.

   Good grief,  It's been 35+ years since I took the exam for my Engineers license, and now I loose my glasses all the time ;-) 

   Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

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   Edited 5/4/2008 10:43 pm ET by BruceS

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   Edited 5/4/2008 10:44 pm ET by BruceS

   
   

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   Edited 5/4/2008 10:49 pm ET by BruceS

3. 
   QCInspector | May 05, 2008 06:21am | #3

   http://www.csgnetwork.com/pulleybeltcalc.html

1. 
   BruceS | May 05, 2008 05:10pm | #6

   Thats a slick calculator.  Way back when!  I had to push a pencil.Work Safe,  Count to 10 when your done for the day !!

   Bruce S. 

    

4. 
   Don01 | May 05, 2008 07:10am | #4

   I know your pain. My bandsaw manual was confused, the mfrs. rep could not help me. Out came the calipers and my pencil.

   A nice collection of calculators
   http://www.owwm.com/math/default.aspx

   This site also can supply info on a nice range of old machinery.

   Don

1. 
   polarsea1 | May 05, 2008 09:24am | #5

   The ratios of the diameters of the pulleys are proportional, in other words a two inch pulley will drive a four inch pulley at half it's (the two inch) speed or vice versa. 

   A ten inch pulley has twice the circumference of a five, etc.

5. 
   [email protected] | May 05, 2008 07:37pm | #7

   What you are concerned with is the ratio of the circumferences of the pulleys. 

   Since the equation fro circumference is Pi X d, for both pulleys, the Pi drops out, and all you need is the ratio of the pulley diameters.

   If the motor turns at 3450-rpm, then to get 700 rpm on the wheel, the drive pulleys need a ratio of 3450/700.  Which is 4.929, or roughly 5.  So, the pulley on the motor needs to be 1/5 the diameter of the one on the wheel. 

   For a 1725-rpm motor, the ratio would be 1725/700, or 2.46.  Which is roughly 2.5, so the motor pulley needs to be 0.4 the diameter of the one on the wheel.

6. 
   musashi | May 06, 2008 05:03am | #8

   Thank you all for the help.  The calculators were quite helpful, and with the various explanations that people gave I was actually able to understand what was going on! ;-)

   I remember something like this from my bicycling days many years ago.  X number of teeth on the front chainring combined with X number of teeth on the freewheel was the equivalent of pedaling a direct drive wheel of Y diameter.... something like that.

   I figured the machinery equivalent to this couldn't be all too difficult.

    

   Thanks again,

   Alex

   Outside of a dog, a book is a man's best friend. Inside of a dog, it's too dark to read.
   -Groucho Marx
1. 
   Don01 | May 06, 2008 07:04am | #9

   Alex,Don't forget that your target blade speed is expressed in surface feet per minute.
   This is dictated by the blade manufacturer along with tension.This link provides some useful information, also a good source for bladeshttp://www.woodworkershaven.com/timber_importan.htmlDon