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# Design of belt drives

Question asked by zaveri in #Coffee Room on Jan 18, 2013
zaveri · Jan 18, 2013
Rank A3 - PRO
From my design course, i learnt how to design a belt drive connecting only two pulleys. (a driver with a driven).

now i want to know the procedure, for designing a flat belt connecting more than 2 pulleys. (a driver pulley with 2 or more driven pulleys). Posted in: #Coffee Room
CE Designer · Jan 18, 2013
Input speed/Output speed = (Db/Da)*(Dd/Dc)*(Df/De)......etc.

where D = diameter of the pulleys
the terms in the brackets are just a ratio of the driven pulley diameter to the driver pulley diameter
Ramani Aswath · Jan 19, 2013
Rank A1 - PRO
Unless there is a substantial angle of contact between the pulley and the belt power transmitted will be reduced.The total power of the drive pulley has to be the sum of power drawn by all the pulleys in the circuit plus a little more to take care of inertia of the connected loads.

Each driven pulley will run at a speed = RPM(Drive Pulley) x (dia.D.P/dia (driven pulley)).
If you are cascading pairs of pulleys, what CE Dsigner has posted above applies.
zaveri · Jan 19, 2013
Rank A3 - PRO
In my case i have to couple a motor to a couple of alternators using belt and pulley.

I have not decided the pulley diameters yet.

all three machines in this case are going to be fixed rigidly to a support, and the centre distances between the shafts will be constant(which even i don't know yet).

Now what i want to know is that provided the given data:

maximum power, torque and speed of motor.

speed of rotation of each driven machine shaft, and the torque to be provided to it.

the centre distances between the machine shafts.

Now how do i determine this:

the length of the belt connecting all these machines

the number of plies of the belt. (the pulley diameters can always be varied as per requirement).
CE Designer · Jan 21, 2013
Well pulley sizes are dictated by the the final speed you require and the speed the speed of the motor. Your space limitations of the setup will dictate the center distances of the pulleys.
Once you have both pulley sizes and center distances you can find your belt. Belts are standard. You can refer to a supplier or to a data sheet.
Use this calculator to help.
There are also different types of belts to consider for special applications. You have flat belts, v-belts, cogged v-belts, timing belts etc.
Depending on the operating characteristics such as speed and torque transfer you need to select the ideal type of belt.
CE Designer · Jan 21, 2013
zaveri
zaveri · Jan 21, 2013
Rank A3 - PRO
CE Designer

Thanks a lot dude.

I will post the schematic diagram soon. As of now i am interested only in flat belts.

the calculator link which you have provided is usefull, but then is there anyway by which i can calculate for a system consisting of more than two pulleys.
CE Designer · Jan 21, 2013