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  • Rotary brush design.

    Discussion in 'The main mechanical design forum' started by Dang Hung, Nov 16, 2021.

    1. Dang Hung

      Dang Hung New Member

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      Hello, I'm designing a rotary brush based on the idea of Gerotto The bull excavator robot. There are 2 brushes, each weighs 16kg with outside diameter 320mm, the inside diameter is 170mm. I want to attach the brush to the electric motor so I intend to make a bushing inside the tube and mount the brush directly on the motor shaft. The problem is the motor shaft diameter is only 19mm, although the loading force is still in the range but may I ask, does the idea of mounting something directly on motor shaft a good design. I'm concerned that if the brush hit something the motor shaft will break. Anyone have experience in designing mechanical part please help me.
       

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    3. Erich

      Erich Well-Known Member

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      You can design in a shear pin, that will break when a jam occurs.
      You can also install an overload clutch. This device stops transmitting torque when a set torque is exceeded. Usually they can be reset once the jam is cleared.
      One solution is cheap, one solution is quick to reset.
      Your choice.
       
    4. s.weinberg

      s.weinberg Well-Known Member EngineeringClicks Expert

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      Erich basically said it, but another option that might bridge the gap is a tolerance ring. This is basically a thin piece of sheet metal that is formed into radial waves and goes between your shaft and bushing. I've never personally used one as torque overload protection, but they're nifty little things, are advertised for this use and the theory seems sound.
      Not as cheap as a shear pin, not as robust as a proper clutch, but might be a happy medium, depending on application. Relatively cheap, and should automatically reset once you've gone below your slip torque limit
       
    5. Dana

      Dana Well-Known Member

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      Unless it's spinning really fast so rotor inertia is an issue and the brush hits a sudden hard stop, it's not likely the motor torque is sufficient to break the shaft; it'd stall the motor first . As far as external loads are concerned, the motor manufacturer usually provides information on the allowable radial and axial loads applied to the motor shaft
       
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