Quote Originally Posted by dickieto View Post
hi robin
looks like i will need to go back to school,maths was never my strongest subject
i was thinking more along the lines of a 40mm pulley!!!.and driving the stepper with a reduction to the shaft.would this work or would the stepper be running to fast when the ganty is moving at high speed
as you have said i am just a beginner and speed,torque,force applied etc are all new to me.
i was thinking of making a prototype using chains and sprockets (my works got plenty)just to try out the theory,measuring pull needed to turn drive shaft with spring scales!!
thanks for your input
Tom
Tom,

See the inline answer I gave to Robin's questions. He is quite right, there is the 'suck it and see' approach or the 'model and calculate' approach (and then usually an element of suck it and see!) - with something this complex its worth spending some time getting a basic appreciation of the numbers to try and see if things look reasonable...

If you want a more detailed description of the torque/forces/etc to help you understand the number just ask...

A 40mm PCD dia pulley is approx 120mm circumference (24 tooth). Therefore 1 rev moves 120mm. Set 1 rev = 1200steps then 1 step = 0.1mm. At 10m/min rapid the pulley turns at 10,000/120 = 83.33rpm, geared down 3:1 (12teeth/36teeth) the motor turns three times as fast = 3 x 83.33 = 250rpm, in 1/2step mode this is 250/60 * 400 = 1667 steps/sec which is no problem.