How to Design a Timing Belt

At Fenner Precision, we are dedicated to being the leading manufacturer of precision urethane belts. This short overview will assist you in the design of timing belts for your application, please contact us if you require any assistance.For unique applications, technical support is available from our knowledgeable engineering and sales staff.

Step 1

Determine the peak torque for your drive. This is usually the motor starting torque, but may also be any unusual momentary or shock loads which may occur during normal operation.

Step 2

Determine the largest pulley diameters that can be utilised, considering the space limitations and drive ratio of your system. This helps to increase the torque capacity of the drive and extends the service life of the belt.

Step 3

Select the belt tooth profile (contact us for advice if required). If the peak drive torque is at the upper limits of torque transmission capability for the selected profile, consider using the next higher torque rated profile. Find the corresponding pitch for the selected profile, this value will be needed to calculate the number of belt teeth required.

Step 4

Calculate the teeth in mesh (T.I.M.) (contact us for the formula if required), also bare in mind the teeth in mesh factor. Divide the peak torque (from Step 1) by the T.I.M. factor to determine the design torque.

IMPORTANT: Check the belt pitch again to make sure this adjustment in torque has not moved your application outside the limits of the desired pitch for the pulleys you chose.

Step 5

Calculate the belt pitch length based on the design center distance of your drive.

Step 6

Divide the belt pitch length by the tooth pitch selected and round the result to the nearest whole number. This is the number of teeth on the belt for your application. Adjust the nominal center distance of your drive design to match the belt. 

Step 7

Calculate the effective tension (Te) on the drive using the pitch radius and design torque of the smallest loaded pulley in the system.

Step 8

Select the strength factor for your application and divide the effective tension from step 7 by the strength factor to determine the required break strength for the belt design. (b) Multiply by 2 to represent a double span break. Consult the break strength table (contact us to obtain the table) to determine the required reinforcement type and belt width. The value listed in the table must be greater than the design break strength.

Step 9

Select a belt width that is capable of handling the design torque with the selected pulley size. Note: This belt width may be different from the width selected in step 8. The belt width required for the system will be the wider of the two.


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