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Belt Speed Questions

Discussion in 'Grinders' started by Hyde_me, Jul 22, 2015.

  1. Hyde_me

    Hyde_me New Member

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    If my motor rpm is 1750 and i add a 3 inch drive pulley to it, what is the speed of the pulley said to be? Is the 3 inch pulley going at 1750. I need to know the initial speed for my calculations for crown pulley setup when I make the small wheel attachment that Dancom has on his site.

    I have 2 step pulleys with 5 steps going from 3 inch down to 1 inch. If I invert them in relation to each other like the belt grinders for sale on Beaumont Metal Works website it would give me 5 speeds.

    If the belt is around the 3 inch pulley rotating at 1750 rpm going to 1 inch pulley that would give me a rpm of 5250. If the belt was on the 1 inch pulley rotating at 1750 going to a 3 inch pulley the the speed would be 583 rpm. Then the pulley attached on 1 end of a shaft rotating at 583 and turning a 4 inch wheel on the belt grinder going to the small wheel attachment of 2 inches would give the speed at the attachment of around 1166 rpm.

    It would be within a reasonable speed range for the small bearings I think. Any thoughts?
     
  2. dancom

    dancom Dust Maker

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    The speed of the small wheels is important to reduce wear in the bearings and extend their lives. Stay under 10,000 RPM and you'll be fine.
    I think that's what you are asking.

    Yes, the 1750 is the RPM no matter what size wheel you stick on it, it's still 1750 RPM. Size of wheel relates to surface feet measurements.
    RPM * (diameter * pi) /12 = SFM

    Excel is your friend. ;-)

    Dan
     
  3. Hyde_me

    Hyde_me New Member

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    So a 4 inch drive wheel @ 1750 to a 1 inch small wheel would give me 7000 rpm and the larger wheels would be less. So I should have no problems with the speeds then. Thanks!
     
  4. Icho-

    Icho- Staff Member

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    A 1" or a 10 inch drive wheel will both be the same rpm but the 10 " drive wheel will move the belt a lot faster because the 10" has a larger circumference. So by changing the drive wheel diameter you change sfm but not rpm.
     
  5. dancom

    dancom Dust Maker

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    Hyde,

    The bearings I used were rated for 20,000 RPM. I'd never run them at that though. If you have a little 1/2" roller that is the one that's going to be closest to the speed limit. You'll be at RPMs x 8 with that little guy. I use a 4" wheel but run my drive slower at say 50% or less to keep the revs on the attachment slower.

    The nice thing about referencing surface feet/minute is that it is dictated by the drive wheel and constant no matter what size of attachment: 10" wheel or 2" wheel the SFM is the same. This is great when you know the speed ranges suitable for different abrasives. You can adjust your speed to suite the belt and not worry about wheel size.

    Good luck! Let us know how it works out.

    Dan
     

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