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Old Jul 25, 2007, 02:47 PM
Registered User
Joined Oct 2006
46 Posts
Electric motor problem

I have a small drilling machine driven by a 1/4 HP induction motor (British) sometimes it fails to start and just hums, if I switch off and try again normally it runs. This happens not on a regular basis, sometimes it goes for days OK then plays up. Is there some sort of maintenance needed? David
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Old Jul 25, 2007, 03:43 PM
John Stevenson
Guest
n/a Posts
Re: Electric motor problem

On Wed, 25 Jul 2007 14:47:15 -0500, stereotype
<stereotype.2uansn@rcgroups.com> wrote:

>
>I have a small drilling machine driven by a 1/4 HP induction motor
>(British) sometimes it fails to start and just hums, if I switch off
>and try again normally it runs. This happens not on a regular basis,
>sometimes it goes for days OK then plays up. Is there some sort of
>maintenance needed? David


What tune does it hum ?

Old Jul 25, 2007, 03:45 PM
dave sanderson
Guest
n/a Posts
Re: Electric motor problem

On 25 Jul, 20:47, stereotype <stereotype.2ua...@rcgroups.com> wrote:
> I have a small drilling machine driven by a 1/4 HP induction motor
> (British) sometimes it fails to start and just hums, if I switch off
> and try again normally it runs. This happens not on a regular basis,
> sometimes it goes for days OK then plays up. Is there some sort of
> maintenance needed? David
>


sounds like the start /run cap is on its way out. when its not working
if you spin it up by hand does it run?
new caps are quite cheap.

of course I could be wrong, no doubt someone more knowledgeable will
be along shortly.

Dave

Old Jul 25, 2007, 04:25 PM
ChrisQuayle
Guest
n/a Posts
Re: Electric motor problem

stereotype wrote:
> I have a small drilling machine driven by a 1/4 HP induction motor
> (British) sometimes it fails to start and just hums, if I switch off
> and try again normally it runs. This happens not on a regular basis,
> sometimes it goes for days OK then plays up. Is there some sort of
> maintenance needed? David
>
>


Check all the wiring for continuity and tight connections first,
especially the leads that go into the motor terminals. They can
sometimes work loose on older motors. As someone else said, after that,
it's most likely the start capacitor, or it's wiring...

Chris
Old Jul 25, 2007, 10:56 PM
Don Young
Guest
n/a Posts
Re: Electric motor problem


"stereotype" <stereotype.2uansn@rcgroups.com> wrote in message
news:stereotype.2uansn@rcgroups.com...
>
> I have a small drilling machine driven by a 1/4 HP induction motor
> (British) sometimes it fails to start and just hums, if I switch off
> and try again normally it runs. This happens not on a regular basis,
> sometimes it goes for days OK then plays up. Is there some sort of
> maintenance needed? David
>
>
> --
> stereotype
> ------------------------------------------------------------------------
> stereotype's Profile: http://www.rcgroups.com/forums/member.php?u=119209
> View this thread: http://www.rcgroups.com/forums/showthread.php?t=718458
>

If it has a centrifugal starting switch (you can hear a click when it starts
and again when it is nearly stopped) the switch contacts and the mechanism
to operate it can be in need of cleaning. This usually requires disassembly
of the motor. No lubrication is normally used.

Don Young, USA


Old Jul 26, 2007, 06:09 AM
MikeH_QB
Guest
n/a Posts
Re: Electric motor problem

On 25 Jul, 20:47, stereotype <stereotype.2ua...@rcgroups.com> wrote:
> I have a small drilling machine driven by a 1/4 HP induction motor
> (British) sometimes it fails to start and just hums, if I switch off
> and try again normally it runs. This happens not on a regular basis,
> sometimes it goes for days OK then plays up. Is there some sort of
> maintenance needed? David
>
> --
> stereotype
> ------------------------------------------------------------------------
> stereotype's Profile:http://www.rcgroups.com/forums/member.php?u=119209
> View this thread:http://www.rcgroups.com/forums/showthread.php?t=718458


Pretty sure it the cap that's getting old & 'leaky'. Hasn't failed
altogether as it would never start or possibly blow mains fuse. They
just get a bit worn out sometimes. Your cheapest and quickest option
is to replace the cap, they don't cost much and are (normally)
external so dead easy to get access to & replace. Tip - just be
careful fiddling with any connections if you have recently attempted
to start it, as the cap may hold a nasty residual charge which might
make your hair stand on end, eyes light up and teeth rattle a bit!

Mike

Old Jul 26, 2007, 12:40 PM
David Powell
Guest
n/a Posts
Re: Electric motor problem

In article <vhdfa350t18719r9nnm80r98vlv2b2ccg7@4ax.com>,
John Stevenson <john@stevenson-engineers.co.uk> in
uk.rec.models.engineering wrote:

>On Wed, 25 Jul 2007 14:47:15 -0500, stereotype
><stereotype.2uansn@rcgroups.com> wrote:
>
>>
>>I have a small drilling machine driven by a 1/4 HP induction motor
>>(British) sometimes it fails to start and just hums, if I switch off
>>and try again normally it runs. This happens not on a regular basis,
>>sometimes it goes for days OK then plays up. Is there some sort of
>>maintenance needed? David

>
>What tune does it hum ?


Anything, it doesn't know the words, so it has to hum.

Regards,

David P.

Old Jul 26, 2007, 02:21 PM
Registered User
Joined Oct 2006
46 Posts
Quote:
Originally Posted by Don Young
"stereotype" <stereotype.2uansn@rcgroups.com> wrote in message
news:stereotype.2uansn@rcgroups.com...
>
> I have a small drilling machine driven by a 1/4 HP induction motor
> (British) sometimes it fails to start and just hums, if I switch off
> and try again normally it runs. This happens not on a regular basis,
> sometimes it goes for days OK then plays up. Is there some sort of
> maintenance needed? David
>
>
> --
> stereotype
> ------------------------------------------------------------------------
> stereotype's Profile: http://www.rcgroups.com/forums/member.php?u=119209
> View this thread: http://www.rcgroups.com/forums/showthread.php?t=718458
>

If it has a centrifugal starting switch (you can hear a click when it starts
and again when it is nearly stopped) the switch contacts and the mechanism
to operate it can be in need of cleaning. This usually requires disassembly
of the motor. No lubrication is normally used.

Don Young, USA
Thanks for all your input, yes Don it is a cetrifugal start motor, i'll take it apart and check the contacts. David
stereotype is offline Find More Posts by stereotype
Old Jul 28, 2007, 02:21 PM
eskimobob
Guest
n/a Posts
Re: Electric motor problem

I have this problem on two bits of kit I have just bought second
hand. I can clearly hear that the centrifugal switch does not always
'click' back in when the motor stops so I assume that some lubrication
is required. I'm planning on investigating further when I get some
enthusiasm...

Old Jul 28, 2007, 09:01 PM
Don Young
Guest
n/a Posts
Re: Electric motor problem


"eskimobob" <martinberriman@gmail.com> wrote in message
news:1185650472.389200.142730@b79g2000hse.googlegr oups.com...
>I have this problem on two bits of kit I have just bought second
> hand. I can clearly hear that the centrifugal switch does not always
> 'click' back in when the motor stops so I assume that some lubrication
> is required. I'm planning on investigating further when I get some
> enthusiasm...
>

I think cleaning is called for but I do not think that these mechanisms are
generally lubricated. It might be ok in an enclosed motor where the dirt is
kept out if no lubricant gets on the switch contacts.

Don Young, USA


Old Jul 29, 2007, 04:42 AM
Bob Minchin
Guest
n/a Posts
Re: Electric motor problem


"eskimobob" <martinberriman@gmail.com> wrote in message
news:1185650472.389200.142730@b79g2000hse.googlegr oups.com...
> I have this problem on two bits of kit I have just bought second
> hand. I can clearly hear that the centrifugal switch does not always
> 'click' back in when the motor stops so I assume that some lubrication
> is required. I'm planning on investigating further when I get some
> enthusiasm...
>


Lubrication is normally the enemy of these switches as it harbours dirt.
Complete cleanliness is normally the the best way IMHO

Bob


Old Aug 16, 2011, 12:19 PM
Emimec
Guest
n/a Posts
Electric motor problem

Firstly, lets establish that I am not an electrician..........

I have a pedestal drill, 3 phase, with a Memota (MEM) push button starter
(NVR). Motor is the common "Hoover" style 1/3 or 1/2 horse, cant remember
which.

The motor does not start on its own, you have to "spin" the chuck to get it
to go under its own steam (Electric). Also, the motor seems to lack any real
"guts", it will stop rotating fairly easily. The motor case seems to get
reasonably hot to the touch.

This drill is only used for countersinking 16mm dia full depth in a pre
drilled 10.5mm hole in mild steel. Its common to do a batch of 70+
countersinks in a session.

Would I be right in thinking 1 phase has gone down ?, if so, does it point
to the motor or the starter ? Is there a test I can make to eliminate one or
the other, or does my description of the problem already do this to the
experienced person ?

A volt meter shows all 3 phases coming in to the starter from the supply
source.

Help/advice most appreciated
Bob
Old Aug 16, 2011, 01:26 PM
Mark Rand
Guest
n/a Posts
Re: Electric motor problem

On Tue, 16 Aug 2011 18:19:37 +0100, "Emimec" <emimec.19@NOSPAMbtinternet.com>
wrote:


>
>Would I be right in thinking 1 phase has gone down ?, if so, does it point
>to the motor or the starter ? Is there a test I can make to eliminate one or
>the other, or does my description of the problem already do this to the
>experienced person ?
>
>A volt meter shows all 3 phases coming in to the starter from the supply
>source.
>
>Help/advice most appreciated
>Bob
>


Sounds like you've got an open circuit phase in the starter or motor.

In order or simplicity:-

Take the junction box cover off the motor and remove the wires coming from the
starter. Arrange them so they won't touch anything (insulting tape, bit of
wood, whatever...). Measure the voltage between said wires when starter is on.

That'll tell you if it's the starter or the motor. If the meter has got a
resistance range, measure the coil winding resistances. Measure between phase
and star point if visible. otherwise, measure phase to phase. Noticeable
differences between the three readings will indicate an open circuit.

Taking the non-drive end off the motor and looking at the windings will
indicate major magic smoke escape.


Regards
Mark Rand
RTFM
Old Aug 16, 2011, 02:32 PM
Emimec
Guest
n/a Posts
Re: Electric motor problem

"Mark Rand" <randm@internettie.co.uk> wrote in message
news:ancl475k5jpg9rpaviu5rf6m5ups8civp6@4ax.com...

> On Tue, 16 Aug 2011 18:19:37 +0100, "Emimec"
> <emimec.19@NOSPAMbtinternet.com>
> wrote:
>

>>
>>Would I be right in thinking 1 phase has gone down ?, if so, does it point
>>to the motor or the starter ? Is there a test I can make to eliminate one
>>or
>>the other, or does my description of the problem already do this to the
>>experienced person ?
>>
>>A volt meter shows all 3 phases coming in to the starter from the supply
>>source.
>>
>>Help/advice most appreciated
>>Bob
>>

>
> Sounds like you've got an open circuit phase in the starter or motor.
>
> In order or simplicity:-
>
> Take the junction box cover off the motor and remove the wires coming from
> the
> starter. Arrange them so they won't touch anything (insulting tape, bit of
> wood, whatever...). Measure the voltage between said wires when starter is
> on.
>
> That'll tell you if it's the starter or the motor. If the meter has got a
> resistance range, measure the coil winding resistances. Measure between
> phase
> and star point if visible. otherwise, measure phase to phase. Noticeable
> differences between the three readings will indicate an open circuit.
>
> Taking the non-drive end off the motor and looking at the windings will
> indicate major magic smoke escape.
>
>
> Regards
> Mark Rand
> RTFM


Many Thanks.
Will do this Saturday morning.
Bob
 


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