[Stoves] Calculating the RPM

[Kevin]

Dear Frank

1: Box shape and diameter are VERY important.  At "critical speed", for a given combination of rotational speed and container diameter, centrifugal force will hold the pellets stationary against the container wall, and there will be zero tumbling and pellet wear. A machine running at say 95% critical speed will create very little abrasion, but a machine running at say 60% of critical Speed will create a great deal of abrasion effect, because of the cascading action.

2: Do you want to turn the drum/container/box for a fixed time, OR a fixed number of revolutions?

3: One could calculate the required HP, but the simplest and least costly thing is to try the 1/3 HP motor, and if it does not overheat after say 4 consecutive tests, it is good for the job. If it does overheat, then you have proven that you need a bigger motor.

Best wishes,

Kevin
  ----- Original Message ----- 
  From: Frank Shields 
  To: 'Discussion of biomass cooking stoves' 
  Sent: Tuesday, February 12, 2013 2:30 PM
  Subject: [Stoves] Calculating the RPM


  Greetings Stovers,

   

  Building equipment for determining the hardness of pellets and biochar I need something to turn a 9 kg box at a speed of 60 RPM +/-  1.

  I have a 1/3rd HP motor that is rated at 1725 RPM

  Fitted with a 2" pulley attached to the motor and going to an 8" pulley gives me a shaft turning 431 RPM

  Then another 2" pulley going to an 8" pulley on another shaft gives me 108 RPM

  I plan to adjust the 108 down to 60 using a voltage regulator. 

   

   

  Is this a good plan? 

  And is there another factor I need to include for the weight of the box I am turning?

   

  Thanks

   

  Frank

   

   

  Frank Shields

  Control Laboratories, Inc.

  42 Hangar Way

  Watsonville, CA  95076

  (831) 724-5422 tel

  (831) 724-3188 fax

  www.controllabs.com

   

   



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