May 082013

This page is a continuation of How to Design a Flat Belt Drive [Step-by-step Tutorial] – Page 2.

Step 4 – Finding the Belt Velocity (V m/s):

Maximum velocity of belt (V) can be found out using the following equation:

V~=~{{pi dN_1}/60}~m/s


d → Diameter of the smaller (driving) pulley in m

N1 → Speed of the driving pulley in rpm

Step 5 – Selection of Belt:

There are two types of belts from which you can select from. They are:

  1. Dunlop “HI – SPEED” 878 g duck belting – Used in light and medium duty applications with high belt velocity.
  2. Dunlop “FORT” 949 g duck belting – Used in heavy duty applications with medium belt speeds.

For design power < 20 kW and belt velocity > 16 m/s, select Dunlop “HI – SPEED” 878 g duck belting.

For design power > 20 kW and belt velocity < 16 m/s, select Dunlop “FORT” 949 g duck belting.

Note: If you are using PSG design data book, refer page no. 7.52 (May 2012 reprint) for selecting the right flat belt.

Step 6 – Determination of number of plies:

The number of plies can be determined using the maximum belt velocity and the minimum pulley diameter from the following table.

Table (iv) – Determination of number of plies using maximum belt velocity and minimum pulley diameter

No. of plies Maximum belt velocity in m/s
10 15 20 25 30
3 90 100 112 140 180
4 140 160 180 200 250
5 200 224 250 315 355
6 250 315 355 400 450
8 450 500 560 630 710

In the above table, the values given in italics are the values of minimum pulley diameter in mm.

Note: If you are using PSG design data book, refer page no. 7.52 (May 2012 reprint) for the above table.

For the next step (i.e., Finding Load Rating at V m/s) go to next page.

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  • Varadha Yamunan

    Good one :) Helped me pretty well.. Thank you

    • Surjeet S

      You are welcome… Get fresh content from by liking us on facebook and subscribing to our e-mail newsletter :)
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  • pradeep patil

    While designing belt drive set the centre height of both pulley shall be same?
    what is effect on power transmission if their is height difference?

    • Surjeet S

      The heights of the pulley centers from ground depend on the height difference between the driving and driven shafts. They may or may not be the same. If there is a height difference, the centre to centre distance (between the pulleys) increases. This will have a direct impact on the arc of contact and the design power we calculate.

      • Sarungbam Romen Singh

        Hello Surjeet,
        In the Book “Design of Machine elements” by VB Bhandhari, the arc of contact factor, Fd is multiplied with the rated power while as per the formula you’ve referred here, the said factor divides the rated power.
        [Corrected Power= {(load correction factor x rated power) x arc of contact factor}]
        Please clear me this confusion I m having with.
        I am just an Electrical Engg. Student working on the flat belt drives.
        Thanking you in anticipation.

  • Ron Verduguez

    can you give the references of the equations that you used on this design? thank you…

    • Surjeet S

      These equations can be found in any standard design databook. In India, we normally follow PSG Design Databook

      • Ron Verduguez

        thank you…

  • Dineshraj Srinivasan

    can you give design calculation for the v-belt drives ?

  • Hem Shailabh

    Hi! Can you tell me why the product of coefficient of friction and angle of wrap is minimized when designing open belt drives for certain maximum stress? Please reply asap. @Surjeet_S:disqus I am yet to start studying DME, i asked this from my knowledge of Kinematics-OM. Thanks

  • Eng Medson Naftal

    Thanks i understand well