Impeller rotation?

Discussion in 'Lawn Mowing' started by Procutlawn, Sep 7, 2004.

  1. Procutlawn

    Procutlawn LawnSite Member
    Posts: 21

    I am building a loader from scratch from a Trac vac 860. I am using the housing from the 860 and am getting an impeller made from a fab shop. My question is, as if you were facing the front of the housing, where the intake goes in, which way does the impeller need to rotate to make it blow out the top? Do you need an engine that the shaft rotates clock wise?

    Thanks :blob3:
     
  2. mbricker

    mbricker LawnSite Senior Member
    Posts: 505

    You are walking on very dangerous ground. Do you have confidence that your fab shop can produce an impeller that will stay together despite the centrifugal forces of almost 4000 rpm, while being impacted with not just leaves/clippings, but assorted other junk of varying hardness/mass? Can you say "grenade?"

    As far as your question about rotation, many impellers I've seen had straight vanes, and would function well rotating either way. For a straight vane impeller, it's the housing that determines the direction of discharge. Look at your housing from the intake side--where is the discharge? If it is coming off the left side the motor rotation needs to be clockwise as you face it. If discharge comes off the right side, rotation needs to be ccw.

    All this is assuming you are talking about a direct drive--that is, the impeller mounted directly on the end of a motor crankshaft.

    Question--why not use the trac-vac impeller?
     
  3. Procutlawn

    Procutlawn LawnSite Member
    Posts: 21

    The shop in town here makes impeller's for silage blowers that blow silage up into silos, some are 2 foot big...they have expirience to say the least, they make them the same exact way trac-vac billy goat would, but for a heck of a lot cheaper.

    My thought was....say the exhaust is on the right, facing the intake, that means it would have to rotate counter clockwise. Now if it rotated clockwise instead of counter, would'nt it suck in thru the exhaust and exhaust thru the intake? Or is rotation not a factor with straight bladed impellers?
     
  4. mbricker

    mbricker LawnSite Senior Member
    Posts: 505

    I can't say what a trac vac impeller housing looks like, but the housings I am familiar with, have the intake right in the center of the housing--you are looking right in at the hub of the impeller. So think of the path of the material being blown. It is a spiral, from the center outward to the exhaust (discharge). The material, and air, being propelled thru the housing are actually hurled from the center outward by centrifugal force. So it can't reverse and come out the intake if the rotation is wrong for the housing. Still assuming the intake is at the hub.

    What would happen is the material would still find its way out the discharge, since it is hurled to outside of the spiral by the centrifugal force. But with the discharge pointing the wrong way and not matching the rotation, the flow would be very turbulent and the blower would be pretty inefficient--using a lot of horsepower to overcome the turbulence rather than moving material.

    Most small horizontal shaft gas engines rotate counterclockwise (as you face the shaft end). However, engines made to be coupled directly to a pump are available which rotate clockwise. So whichever way your housing is built, you should be able to get a motor to run it.
     

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