Tony Smith wrote:

> Largish stepper motors can be had fairly cheaply.  At the RPM you're
> after they'd work nicely.  Downside is you need to make drivers for
> them.  Not hard, but a bit of a nuisance and pushes the cost up
> somewhat.  The simplest driver is for unipolar motor (6 wire) and is 4
> fets and a bit of logic.  

I've trouble finding a stepper motor that can produce 50 Nm (7000+ ozf.in).
The biggest I found have a holding torque of 40 Nm (5700 ozf.in), which is
a bit more than what we have now (as stall torque).
http://www.anaheimautomation.com/hightorque.htm

Are there stronger stepper motors?

How does the holding torque of a stepper motor relate to the stall torque
of a DC motor? One site says that "dynamic torque" is about 70% of holding
torque. Is "dynamic torque" what I have available to move something? (I
know that the available torque goes down with speed, but since I'm working
at around 1 rot/s, it seems that is very slow for a typical stepper motor
and it develops its maximum torque.)


> I'm sure James would be happy with orders for a few hundred LiniSteppers

Probably :)  However, it seems that the circuit as-is won't be able to
handle the currents I suppose will be necessary for 40...50 Nm torque.

Thanks,
Gerhard

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