Re: (EASY????) Servo Motor Shaft Modification

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>
wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "John Stevenson"

<john@s...>

> >
> > Conversion was very easy.
> > I stripped it down, removed the front bearing and built the shaft
> up with weld then machined this back
> > down to 16mm to suit the pulley that's going on it.
> > Bearings are 17mm so anything under that isn't a problem. I also
> took the oppertunity to extend the
> > shaft by weld by 1/2" or so.
> > I scrapped the original pressed steel front mounting and turned a
> new 5/8" thick alloy plate up to
> > carry the bearing, two thru bolts and 4 tapped holes to match up
> with the bridgy.
>
>
> John Stevenson said "Conversion was very easy".
>
> John. What in the world would have been a difficult conversion?

Whew, for a while their, I thought I was looking for a free lunch.


I took a treadmill motor and found the main shaft to have a 17 mm
(0.669" ) shaft that was 0.9 inches long as measured from the edge of
the bearing flange to the shoulder.

To put the thing in the lathe, I had to put a steadyrest on the 17mm
section and center drill the shaft. the 17mm surface got scraped
from the steadyrest as it was so darn soft.

I turned it down to 1/2" as that was all I needed. I didn't need to
replace the motor end, although that would not be too hard to do on
the drive end.

I am mounting it on the large flange that is wleded to the body, and
not the motor end. the motor end appears to be too weak of a
mounting place all around. the motor is held together by 2 bolts,
but the end is not keyed or anyother way of transfering the torque to
the end.


As for welding, WHY ?

the shaft is 17mm to start. it would be easy to make an end that has
a 5/8 bearing, or 16mm bearing it the shaft itself was scored.

Although.... the 7/8 long section that is available for a drive gear
is close to too short. There was another section that was smakker
than 1/2 (I didn't record the dia) tha extended another 1.3 inches,
or it does now after I turned it down to 0.375". If one wanted to
make the shaft the full 5/8 (or whatever) for 2 inches, then one
would need to either build it up with a weld or some such.

If that is the case, then one is welding almost 2" from the end of
the armature core. Fast welding and cooling between would keep the
heat down on the core.

Like my mod, I don't think he had to touch the rear of the motor.

Again, it is a soft shaft, but the rear plastic housing has the
brushes and needle roller bearings, so it could be used as is.

Additional comments.

My motors did not have a rear shaft for encoder and to add one
required drilling thru the rear plastic housing that enclosed the
roller bearing. this is a potential dust entrance point and should
be addressed with a shaft seal.

The magnets are mounted so that only two bolts could be used to mount
the front to the rear, but the motor housing is so thick it would be
easy to just make an external sleeve/mount if there was room inside
the machine for it.

Triple check the dimentions for your project. Brandon had picked up
a couple motors and found the shaft was almost a half inch shorter
than listed and the motor was almost too long to fit in the knee.

Dave