On Wednesday 11 April 2018 04:32:05 jeremy youngs wrote:

> Does it have to be a servo ?? 1800 in lb nema 34 steppers are
> inexpensive and your speed needs are not great , it's possible a
> stepper and a kelling drive would get you there . But again more input
> needed.
> Gene , I know of a bunch of 700 ozin SLO-Syn but they are syncronous
> at 72 rpm, how would one drive them ? My only experience with slosyn
> is a couple small ones I purchased ten years ago , aren't they
> essentially a bldc without hall sensors?

Enough of a resemblance that if the coils are brought out right, you can 
drive them with most any old 2 phase stepper driver.

But probably even slower than a 60hz frequency drive, most are for 120 
volt line power.  A 40 volt supplied m542 does not have the cajones to 
drive a slow-syn with "usable torque"

And I believe that same comment would apply to the 3 phase stepper 
drivers too. I've begun to see some of those for sale, even considered 
one for the lathes Z but couldn't find a driver for the bigger ones.  
That AC powered stepper 8 amp that sells for about $160, seems to have 
some pretty advanced current mapping, at no speed is it resonant. I'm 
using that driver on the G0704's Z, and it can run, direct drive, 
from .001" minute on up to about 140 ipm, lifting the head, and making 
less noise than the N23 sized 470's on the xy table. The dm860h that 
came with that kit, was all done at 27 ipm driving a N34-1600 oz/in. 
Noisy as all get out. Its on the Sheldon Lathes Z now, running faster, 
but you can still hear it across the street with the garage door closed.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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