Re: Building an RSG

• To: tesla-at-pupman-dot-com
• Subject: Re: Building an RSG
• From: Alan Sharp <AlanSharp-at-compuserve-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Mon, 06 Sep 1999 10:36:32 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Ritchie

>The grinder sounds ideal if there is little endfloat in the shaft.
>It should make mounting the Tufnol disk a bit easier,  and 1/2 hp
>is more than enough torque !

Very little float on the shaft, and mounting the disc shouldn't be a
problem, someone has already done this, using the washers that 
come with the grinding wheels.

>If you leave the motor un-modified it will run asynchronously around
>2900 rpm.  A higher break rate will be needed to avoid problems with
>surging and resonant rise as the firing point is constantly moving
>along the supply waveform.  Above 200BPS this problem dissapears
>very quickly.  I would still recommend modifying the motor, even if
>it meant I had to hire another grinder to do the grinding !

Yes I was planning to use at least 195bps.

>I don't know if you can control the speed of the motor in the grinder
>using a Variac.  If it is a universal motor (with brushes,  and a
>wound rotor, etc.)  then you will be able to control it OK.  The
>3000rpm rating sounds like an induction motor to me,  and this might
>not change speed smoothly if you decrease its supply voltage.
>Have you tried this with the motor under load ?

I tried to remove the end covers - took out all the screws but the covers
wouldn't come off - they would barely turn, my guess is that the end covers
and bearings are mounted on grooves in the shaft. I suspect that a
universal
motor would have better access for ventilation, changing the brushes etc?

If I could get into it - I would probably come up to Newcastle for the day
and let you grind the flats!

Thanks,

Alan Sharp (UK)

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