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  • Timing belt damage issue

    Discussion in 'The main mechanical design forum' started by kevin136, Nov 19, 2011.

    1. Steve6br

      Steve6br Member

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      Pulley / belt profile

      Just a thought. Have you checked that the tooth profile on the belt and the pulleys are the same? Mixing tooth width / pitch or shapes that are not correctly matched will quickly destroy a belt.....
       
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    3. viveknarang15

      viveknarang15 New Member

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      Beside the factors mentioned above, the temperature also effects a lot. If the temperature rises then the life / effeciency of the belt will also decrease.
       
    4. Engmatnyc

      Engmatnyc New Member

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      A generic timing belts rule is to keep your minimum pulley diameter 8 times bigger than the belt pitch.
      If you have a belt tensioner this could introduce fatigue effect loading on the back of the belt. Make sure the tensioner is not too close to the idler pulley. Its diameter should be at least 80% of the smallest pulley diameter.
      Let us know

      Gianluca
       
    5. kevin136

      kevin136 Well-Known Member

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      Hallo friends,
      Sorry for reply late.
      Thanks Vic,yep we have to keep the transmit ratio.Now we have Changed the material Al6061 into Al x2011(T8),which should be harder and strong enough,I think.
      You are right,Steven.We did confirm pulley supplier with the profile of pulley and belt.Supplier checked and will polish the details such as surface,fillet,tooth width,etc.
      Hi Engmatny,it don't have tensioner." minimum pulley diameter 8 times bigger than the belt pitch",is that necessary? Would you please explain it more details? May be that would be a problem.

      Thanks all your guys.
      Kevin
       
    6. vic.blackall

      vic.blackall Well-Known Member

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      Kevin136, The point that I was trying to make was that if the smaller pulley is too small, and therefore has too few teeth in contact with the belt for the power being transmitted, then the loading on each tooth would be higher than the teeth are designed to carry. What Engmatny is saying, as a rule of thumb, is that if the tooth pitch is say, 10mm then 8 x 10 = 80mm Pitch Circle Diameter for the smaller pulley. This is more applicable to the minimum recommended pulley size that a belt of that pitch should go down to, to prevent over bending of the belt. This also applies to any tensioner diameter that might be used to run on the back of the belt. The smaller pulley should be the starting point, and therefore, should be sized to give sufficient teeth in contact to transmit the load required.
       
    7. kevin136

      kevin136 Well-Known Member

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      Hi Vic,
      You are right.
      If the pitch circle is too small,that each tooth has to bearing too much loading.
      Now situation is the pitch circle diameter of small pulley is 13.37mm,pitch 2mm,working speed 5k rpm,torque, 0.2Nm.That means too small.However,we can’t change the transmit ratio and too big according to the small space.
      Thanks for your kindly detailed explanation!

       
    8. vic.blackall

      vic.blackall Well-Known Member

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      What is the ratio? Could you put a tensioner on the back of the belt, close to the small pulley, to increase the angle of wrap around the small pulley?
       
    9. kevin136

      kevin136 Well-Known Member

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      These two pulleys are S2M with 30 teeth and 21 teeth,central distance according to calculation is 75.453-75.535.
      Someone said that it would be better to loose a little bit.
       
    10. Erich

      Erich Well-Known Member

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      Could we have some more information about the design and the requirements?

      Belt width?
      Reinforcing cord material? Polyester, kevlar, glass fiber, steel?
      Center distance adjustable or fixed?
      Material of base that references the two shafts?
      Temp range for operation?
      Temp rise during full load test?
       

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