# Torque calculations

1. Jul 29, 2012

### karl8695

Hi all,

I have a peristaltic pump that i need to rotate at 26 rev/min. The gear arrangement attached to the pump is calculated at 13.1:1 therefore I am assuming an input speed of 340rev/min is required to produce a reduction in speed to the desired output of 26 rev/min.

Gear A (1st driver) - 12 teeth
Gear B (1st driven) - 43 teeth
Gear C (2nd driver) - 9 teeth
Gear D (2nd driven) - 33 teeth

My problem is that I need to know what Force is required to turn my pump and thus the the force required by my drive unit, a 'power spring' to transmit the desired force. I do not have any measuring devices other that a spring scale graduated in Kg. I did however determine the force required to rortate the input shaft, albeit not at the correct speed which came out at an average of 1.8 Kg over 10 tests. I did this by tying a thread around the input shaft to the gear arrangement and then attaching the other end to the spring scale and simply pulling and recording the max pull in Kg over 10 seperate attempts.

Can I determine the torque (power) i need from my power spring to turn my pump at a constant speed of 26 rev/min?

2. Jul 29, 2012

### huntoon

Some random thoughts:

If the ratio of your gears is 13.1:1 I would have thought the other way. That you only need 2rpm input to get 26 rpm from the pump.

I think to measure the torque you should offer the pitch of the gears or the pitch circle diameter/radius of the gears.

Input torque on the gears should be (torque of pump)/13.1

I think you need to provide the displacement of the pump.

pump torque = ((pressure * displacement)/2pi)* efficiency

eg: pressure = 240 bar
displacement = 55cc
eff = 0.95

T= 200Nm

3. Jul 31, 2012

### karl8695

No, the pump definatley works with a geared reduction so 340 rev/min input speed.
Displacement of the pump = 0.3Litres/min
Pressure = 0.1 bar
Efficience is unknown

4. Oct 11, 2012

### ankurimnu

Hey dont know whom to ask but i have a question......
I am using a gear box and its center distances are 70,90 and 120...its a three stage reduction gear box.... i want a total gearbox ratio of 40.....how should i select the modules i have to use in each 3 stages for getting proper ratio ???