Subject: Grinding Again

From: [email-masked] (Ken Knaell)
Date: 5 Dec 1996 19:06:43 -0500

Speaking of grinding, well we were once...

Does anyone know if the pulsating torque from a single phase
motor could contribute to the "dishing" that I and at least
one otherr person have had with their surface grinding.
A three phase motor would be much better in this respect and
I am considering buying one and re connecting my motor/rotary-
phase-convertor back up to test this hypothesis.  If you have
1/2 horsepower coming out in 1 horsepower bursts at 50% duty
cycle it seems it could make belts vibrate (mine do) and all
other kinds of nasty things happen.  Seems like nothing is
simple once you grow up.

Ken,
Bethesda, MD

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From: "Steven O. Smith" <[email-masked]>
Date: Fri, 6 Dec 1996 17:24:37 GMT

> other kinds of nasty things happen.  Seems like nothing is

I don't think so Ken (I could be wrong). It seems like there are lots of
sources of vibration far easier to come across than anything from the
single phase motor. Do the belts vibrate at 60 Hz? if not, it's not the
motor.

I don't have any dishing trouble with my 1 HP, 10" or my 1/4 HP 6"
grinders. Both are single phase.

-- 
Steven O. Smith
[email-masked]

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From: [email-masked]
Date: 10 Dec 1996 02:38:14 GMT

In article <[email-masked]>,
[email-masked] writes:

>compressor in the shop kicked on, the welder worked great.  When it quit,
>the welder went back to sputtering?  Any Ideas?
>
>

Leave an air line open so the compressor runs all the time. <g>

Peter

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From: [email-masked] (Fitch R. Williams)
Date: Tue, 10 Dec 1996 05:46:35 GMT

[email-masked] (Reckless) wrote:

>Frank Perdicaro <[email-masked]> wrote:
>>I've seen loose grounds do all sorts of odd things, including
>>the result (more power) you are seeing.

>>In the past, wicked and long discussions have been written about
>>the 'impossibility' of some of the results of bad grounds.  Most
>>of writers have been ignorant and offensive, and I do not want to 
>>have another round of than.

>>Spend long time checking your ground conditions.

>>Ground problems I've seen include 'start elevator blow up computer',
>>'turn on printer, blow up power strip', 'start washing machine, blow
>>light bulb', 'plug in printer, it lights on fire',  'sun comes up, 
>>circuits go off', and the list is much longer than this.

>>I suspect that you are driving the 3phase with a converter, and that
>>converter is on the 'other' side of a center-tapped circuit.  With 
>>high load on the other side, the ground is moved, giving more voltage
>>to the welder.

>OK, from what I understand of Cecil's setup, he has a substantial shop
>with 3-phase power.  I don't believe his problem is a ground problem
>per se, but more likely a loose phase connection between the power
>panel and the transformer.  Loose neutrals do this in single-phase
>circuits.  If the welder is single-phase (most MIG units are unless
>they're really big), its connected to only 2 of the three phases, and
>one of those has the loose connection.  When the compressor goes
>online it acts as a rotary converter and stabilizes the loose phase,
>but when it shuts off the voltage on that phase drops, hence the
>symptoms he describes.

>My suggestion: check the grounds (for safety reasons, of course), and
>pay extra special attention to all the hot leads and any neutrals.
>Check the voltage at the breaker panel when welding and at the welder
>outlet.  I suspect that both will be low when welding.  If so, the
>problem is outside somewhere between the panel and the transformer(s).
>If the supply lines are aluminum, they have a tendency to get loose
>with time.  Make sure everything is tight.  The power company may need
>to be called if the problem is not in your equipment/building.

>I had a similar problem at the last house I lived in.  The neutral
>connection was loose at the pole transformer, and after I tightened
>all the connections in the breaker panel (without changing the
>problem), Edison was called and they replaced a crimp on the neutral
>wire.  Solid power once again.

>Check it out and be careful
>-Reckless

I had written almost exactly that, then yours showed up on
my screen.  I second the be careful part - leave anything on
the hot side of the main breakers for the power company.
Aluminum wire cold flows and can lose contact pressure, most
of the power company wiring to the main panel is aluminum.

One question - do you experience this behavior on other
single phase equipment?  If so, is it  wired to the same
single phase?

Fitch

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From: [email-masked] (Reckless)
Date: Tue, 10 Dec 1996 00:44:20 GMT

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From: [email-masked] (Fitch R. Williams)
Date: Mon, 09 Dec 1996 14:17:04 GMT

>Bethesda, MD

I havn't done the math, but I suspect that the inertia of
the grinding wheel will even out the pulses from the motor.
In any event, it would only amount to a very small
percentage change in the surface speed of the wheel.  I've
seen some expensive grinders that had longish flat belt
drives to isolate the motor vibration from the grinding
spindle - I don't remember the manufacturers name, although
for some reason I think it had a French sound to it.  

I'd suggest  a careful check of the balancing of the
rotating mass.  By careful I mean to get both ends in
balance.  If it is only balanced around the centerline, but
the counterbalancing masses are at opposite ends of the
shaft, you can get a rocking vibration displacement on each
end.

Fitch

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From: Frank Perdicaro <[email-masked]>
Date: 9 Dec 1996 22:37:27 GMT

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From: [email-masked]
Date: 9 Dec 1996 20:03:31 GMT

In article <[email-masked]>, [email-masked] (Fitch R.

>>A three phase motor would be much better in this respect and

I was using a single phase Mig welder this weekend and it seemed to be
underpowered (Millermatic 35 with spool gun)  When the 3 phase 10 hp
compressor in the shop kicked on, the welder worked great.  When it quit,
the welder went back to sputtering?  Any Ideas?

Cecil in OK

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From: [email-masked]
Date: 11 Dec 1996 05:54:21 GMT

>the welder went back to sputtering?  Any Ideas?

  It sounds to me like the wireing to the welder outlet is not heavy
enough and is causing a voltage drop. The compressor may have boosted the
voltage to the outlet. 

 Just a guess but you might try hooking a volt meter to the outlet while
running the welder and see.

   Wayne Cook

Quality is like buying oats,
        if you want nice, clean, fresh oats you must pay a fair price.

However, 
        if you can be satisfied with oats that have already been through
the horse...
                          
That comes a little cheaper...