Re: ON/OFF/Brake lever does not wsork on the Clausing

In article <Q7-dnTX7jOPmx-fVnZ2dnUVZ_oPinZ2d@xxxxxxxxxxxx>,
Ignoramus13075 <ignoramus13075@xxxxxxxxxxxxxxxxxxxx> wrote:

On 2008-07-13, Joseph Gwinn <joegwinn@xxxxxxxxxxx> wrote:
In article <cI-dnRC8aNvFY-TVnZ2dnUVZ_oTinZ2d@xxxxxxxxxxxx>,
Ignoramus13075 <ignoramus13075@xxxxxxxxxxxxxxxxxxxx> wrote:

Big, detailed pictures are here:

http://igor.chudov.com/projects/Clausing-Colchester-13-36-Master-Lathe/08-O
n-O
ff-Switch/

The ON/OFF/BRAKE lever on the lathe is not working. The way I
understand it should work, is that in the rightmost (clockwise)
position it should act as a brake, and if lifted up and turned
counterclockwise, it should turn the lathe on. However, it does not do
a good job and the lathe is always on regardless of the position of
this lever. I can still turn the lathe off by manipulating the little
lever in front of it (REV2/REV1/OFF/FWD1/FWD2) and switching from
forward to neutral, but I feel that it is wrong and is a safety issue
as the lathe sometimes needs to be turned off and braked instantly
with one hand.

On the back of the lathe, the big lever is connected to a steel
bar. (the top one) This steel bar has a oblong hole for the brake
engagement. <B>However, the screw for the brake falls out of this
oblong hole</B>. The bar still engages the brake by acting on the
side of the nut, however it does not feel right.

The switch that should turn the lathe on and off, seems to be operated
by the lower bar. The last photo shows that this bar should be
permanently pulled up by a spring (see spring mounting pins) but the
spring is missing. I believe that with the spring, the feel of the
ON/OFF/BRAKE lever would be different and it would "click" as the
dimples on these two bars engage and disengage.

HOWEVER, and this is the crux of the problem, the limit switch that
should be operated by the lower bar, does NOT open or close any
contacts on the lines that lead into it from the main motor starter.

I have a feeling that someone messed with this and bungled this issue.
Has anyone seen anything similar?

Was it powered from a VFD before? VFDs do not like their motor load
switched, and are likely to emit magic smoke if one does this. So,
people bypass the switch.

It was never wired for a VFD, that's for sure.

One theory shot to hell.


In my lathe, I pulled all AC wiring out of the switch, instead having
the motor wired directly to the VFD 3-phase output. The switch is
instead wired to the VFD 24-volt control inputs, and tells the VFD what
to do. The switch works as it always did, with one exception - if one
is spinning at full speed with a big chuck and (using the switch) tells
the VFD to stop, it may instead trip because the motor is overrunning
the VFD. There is no harm in this, but it is a nuisance.

I think that a quick stop is a big safety advantage.

I also added an external braking resistor to the VFD, which helped a
lot, but I can still trip it.

You may opt for a lower resistance and higher watt rating.

Yes, up to some limit.


One odd thing to look for: As received, the green wire in the cord was
not connected to the machine frame, instead flopping around in the 4"
square box, probably because there was no convenient ground screw. No
attempt had been made to attach it to anything. I discovered this when
I noticed that I was getting a tickle when I touched the machine frame.
The tickle is due to leakage in the motor, and is quite common in old
motors, especially if they are dirty. Changed the 4" square box for a
modern one with grounding screw, and finished the job. No more tickle.

But still leakage, right?

Oh, yes. It's harmless unless it gets large. The 5914 measured ~100
volts to ground using a DMM (with 10 Mohm input resistance), so the
leakage was something like 10 microamps. A layer of dirt can easily
achieve this.

One always grounds the frame of a washing machine because they always
have a little leakage from the motor as well. And sometimes a lot of
leakage, if the washer leaks water onto the motor.

When I was maybe 16, the widow next door, a friend of my Mother, was
getting shocks from her washing machine, and Mother sent me over to fix
it. The ground wire was missing, and probably was never installed.
When the machine was new, no problem. But it grew on you. I made and
installed a ground wire, and no more shocks.


You also want that ground to work so if the motor shorts the VFD will
trip, rather than putting 240 volts on the machine frame.

Interesting. I think that the limit switches operated by this lever,
are not working right.

I would not be surprised. Does the manual say much about how this is
supposed to work? On my 5914, there is a mechanical clutch and brake
that does work, but I never use because it always trips the 3 HP VFD,
which is a little small for a 2 HP motor with lots of spinning mass.

Joe Gwinn
.

Relevant Pages

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