--
Help would be greatly appreciated with a sequence of diagnostic steps in the
correct order please.......

1 HP 1440 rpm Crompton Parkinson on my lathe, belt driven - suddenly stopped
or rather failed to start.

With belt removed, she starts and runs sweetly, with belt on just a mains hum.

Regards to all, Sam

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NoviceWithSparks
fired this volley in news:74715$507c99aa$43de0cc0$14334
@news.flashnewsgroups.com:

--

Listen for the centrifugal switch clicking in and out as the motor spins
up and down with no load. If it does, it's at least functioning, and the
likelihood of the contacts not "making" are small, unless there's some
mechanical chad in there keeping them apart. Which is, not terribly
likely, but possible if you've been turning plastics or such.

If the switch seems to be functioning, you can check it's continuity
across the contacts, or just assume it is.

It sounds to me like an almost completely open start-cap. Replacing it
with anything even nearly close will give you a quick verification.
Visual on an open or dried out cap will usually show a bulge at the top
cap, maybe a puncture in the rubber relief valve, and maybe some
corrosion; signs of electrolyte leaking out.

LLoyd

On Mon, 15 Oct 2012 23:18:02 +0000, NoviceWithSparks
wrote:

--
Help would be greatly appreciated with a sequence of diagnostic steps in the
correct order please.......

1 HP 1440 rpm Crompton Parkinson on my lathe, belt driven - suddenly stopped
or rather failed to start.

With belt removed, she starts and runs sweetly, with belt on just a mains hum.

Regards to all, Sam
Greetings Sam,
Almost without a doubt the cap. A motor with a centrifugal switch
needs to have the start winding energized so that there is a preferred
direction for the rotor to turn. I suppose the contacts to the start
winding could be making such poor contact that hardly any current
flows resulting in low torque but I doubt that. A weak cap on the
other hand could provide enough torque to start the motor only
unloaded but not enough when the motor is loaded. Another problem may
be the run winding. It may not be up to snuff and can only run
unloaded. Bad insulation in the windings can cause shorts between the
windings. This will result in lower torque and more heat. If the motor
runs unloaded for a few minutes does it get real hot? If not then
suspect the start cap.
Eric

I echo the "weak cap" explanation.

If the switch was not closed at 0 RPM, the motor would just hum.
The fact that it starts unloaded clinches it.



--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

*After receiving your prompt help Guys and Gals?, I've tried the following:*

1. Laid my hands on a good multimeter with capacitance - The all steel cased
start capacitor is labelled: TCC 75uF 275 V - testing it with the meter
gives 82.5 uF which sounds within range - Could it be defective despite this
result? Are there any other tests to be done on it?


2. Ran the motor for 15 minutes unloaded as you suggested- Case became
comfortably hand warm - no signs of any excessive heating.


3. Connected a test lamp across the terminals where the start cap normally
goes - the lamp is alight on startup and goes out, consistently, as the
motor reaches full speed - Can I take it that this proves the centrifugal
switch is good?

Any further advices gratefully received as the compatible start cap from Brook
Crompton Motors is £28 by the time it drops through my letterbox and as you
can imagine I don't want to make a Boo Boo!

Regards to all, Sam


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NoviceWithSparks wrote:

*After receiving your prompt help Guys and Gals?, I've tried the following:*

1. Laid my hands on a good multimeter with capacitance - The all steel cased
start capacitor is labelled: TCC 75uF 275 V - testing it with the meter
gives 82.5 uF which sounds within range - Could it be defective despite this
result? Are there any other tests to be done on it?


ESR. You can have a poor connection insde the capacitor, yet still
read close to the stated capacitance.


2. Ran the motor for 15 minutes unloaded as you suggested- Case became
comfortably hand warm - no signs of any excessive heating.

3. Connected a test lamp across the terminals where the start cap normally
goes - the lamp is alight on startup and goes out, consistently, as the
motor reaches full speed - Can I take it that this proves the centrifugal
switch is good?

Any further advices gratefully received as the compatible start cap from Brook
Crompton Motors is £28 by the time it drops through my letterbox and as you
can imagine I don't want to make a Boo Boo!

On Tue, 16 Oct 2012 20:18:01 +0000, NoviceWithSparks
wrote:

*After receiving your prompt help Guys and Gals?, I've tried the following:*

1. Laid my hands on a good multimeter with capacitance - The all steel cased
start capacitor is labelled: TCC 75uF 275 V - testing it with the meter
gives 82.5 uF which sounds within range - Could it be defective despite this
result? Are there any other tests to be done on it?


2. Ran the motor for 15 minutes unloaded as you suggested- Case became
comfortably hand warm - no signs of any excessive heating.


3. Connected a test lamp across the terminals where the start cap normally
goes - the lamp is alight on startup and goes out, consistently, as the
motor reaches full speed - Can I take it that this proves the centrifugal
switch is good?

Any further advices gratefully received as the compatible start cap from Brook
Crompton Motors is £28 by the time it drops through my letterbox and as you
can imagine I don't want to make a Boo Boo!

Regards to all, Sam
I can't give an opinion on your meter but I can about other things. I
think your starting circuit is probably good. I think the run windings
are probably good. The cap I don't know. But you don't need a starting
cap from Crompton. I can't imagine it's any type of special cap. Do
you have another motor that uses a start cap rated for the same
voltage and at least as many uF as the cap in question? Just
substitute the cap from another motor for the one in the Crompton
motor. The last starting cap I bought was about two years ago and it
cost me about $5.00 US. I know things are more expensive out your way
but I'm sure you can get a new starting cap from someplace that sells
motor repair parts for lots less than what Crompton wants. Try this
link: http://www.hi-wire.co.uk/acatalog/Mo...apacitors.html
About 1/6 of the Crompton price. But then there's VAT and shipping and
who knows what else.
Eric

wrote in message
...
On Tue, 16 Oct 2012 20:18:01 +0000, NoviceWithSparks
wrote:

2. Ran the motor for 15 minutes unloaded as you suggested- Case
became
comfortably hand warm - no signs of any excessive heating.

Is the pulley loose on the motor shaft?

It's very likely that you need a new start capacitor.. a split-phase motor
will operate just fine without a start capacitor (cap terminals bypassed),
but the capacitor increases the starting torque for a s-p motor with a load
applied.
I'm not suggesting you run a lathe without the start cap, you definitely
need it for this application.

The 75uF value may be too low a value for a 1 HP motor (that value is
typically found in a 1/4 HP motor).. it may have been substituted by someone
else, a previous owner maybe.

Most test meters don't offer worthwhile indications/readings for
capacitors.. there are numerous possible capacitor faults which a general
purpose DMM won't be able to check for.

You should be able to locate a new motor start cap without too much effort
depending upon sources near you (AC only, not a DC type) of a higher value
(up to about 500uF for 1 HP, the actual values vary somewhat widely from the
actual marked values). Many Ebag sellers offer motor caps.

While you're waiting for the cap to arrive it may be very worthwhile to pull
out the motor, open the case and do a routine inspection, particularly the
centrifugal start switch contacts and general internal cleanliness of the
motor, lubricating the bearings if possible.

--
WB
..........


"NoviceWithSparks" wrote
in message roups.com...
--
Help would be greatly appreciated with a sequence of diagnostic steps in
the
correct order please.......
1 HP 1440 rpm Crompton Parkinson on my lathe, belt driven - suddenly
stopped
or rather failed to start.

With belt removed, she starts and runs sweetly, with belt on just a mains
hum.

Regards to all, Sam
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Pulley is absolutely tight on the shaft - Have ordered a start cap as
recommended - will post the results......

Regards and thanks to all, Sam

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Inscribed thus:

On Tue, 16 Oct 2012 20:18:01 +0000, NoviceWithSparks
wrote:

*After receiving your prompt help Guys and Gals?, I've tried the
following:*

1. Laid my hands on a good multimeter with capacitance - The all
steel cased
start capacitor is labelled: TCC 75uF 275 V - testing it with the
meter gives 82.5 uF which sounds within range - Could it be defective
despite this result? Are there any other tests to be done on it?


2. Ran the motor for 15 minutes unloaded as you suggested- Case
became comfortably hand warm - no signs of any excessive heating.


3. Connected a test lamp across the terminals where the start cap
normally goes - the lamp is alight on startup and goes out,
consistently, as the motor reaches full speed - Can I take it that
this proves the centrifugal switch is good?

Any further advices gratefully received as the compatible start cap
from Brook Crompton Motors is £28 by the time it drops through my
letterbox and as you can imagine I don't want to make a Boo Boo!

Regards to all, Sam
I can't give an opinion on your meter but I can about other things. I
think your starting circuit is probably good. I think the run windings
are probably good. The cap I don't know. But you don't need a starting
cap from Crompton. I can't imagine it's any type of special cap. Do
you have another motor that uses a start cap rated for the same
voltage and at least as many uF as the cap in question? Just
substitute the cap from another motor for the one in the Crompton
motor. The last starting cap I bought was about two years ago and it
cost me about $5.00 US. I know things are more expensive out your way
but I'm sure you can get a new starting cap from someplace that sells
motor repair parts for lots less than what Crompton wants. Try this
link: http://www.hi-wire.co.uk/acatalog/Mo...apacitors.html
About 1/6 of the Crompton price. But then there's VAT and shipping and
who knows what else.
Eric

If its any help I've recently bought a 63uf 250v motor start cap from
them. It cost me £6.00 less a few pence. I cut the threaded bit off
to fit it inside the original metal shroud screwed to the motor
housing.

--
Best Regards:
Baron.

On 10/15/2012 19:18, NoviceWithSparks wrote:



Gearbox locked? Can you turn the chuck by hand, and does the motor turn
when turning chuck by hand?

--
Steve Walker
(remove brain when replying)