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stephencliverichards(at)g
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 Posted: Sun Jun 19, 2016 9:29 am Post subject: Problem with starting |
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This still suggests to me that a intermittent ground is shorting out the armature or field is shorting out .
Clive
From: Alec Myers (alec(at)alecmyers.com)
Sent: 19/06/2016 14:51
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Re: Problem with starting
The strangest symptom is that twice the motor has cut out (and the bus voltage was pulled down) mid-crank while the prop was already turning at a good starting speed. I think that suggests it's not a bad spot on the commutator, for example.
I can rule out mechanical seizure at the crank because when the motor cut, the prop immediately bounced back off a compression stroke, and (I think) I can rule out a starter jam because the engine has started and run since.
I thought I was onto something with a possible fracture in the field winding but that won't explain things if the motor isn't shunt wound.
On Jun 19, 2016, at 09:29, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
I'm still not convinced you have a motor problem. The chattering relay points more to circuit / system and low voltage issues.
neal |
Except that a contactor powered from the same
battery that is being pulled down by what amounts
to continuous stall current may well drop-out
during closures only to re-close when the contacts
break and stall-current goes away.
12v battery contactors drop at about 2v . . . and
are not likely to be candidates for 'buzzing' but
it's not impossible. A easy experiment would call
for powering the starter contactor from a separate
source . . . like another battery. It may well
stop chattering. But the energies being circulated
will be profound.
I'm puzzled by the intermittent nature of the
symptom. This implies a root cause that
is transient or loose to rattle around. Having
the starter motor come to rest on a bad pass
in the armature windings could account for such
behavior.
It would sure be illuminating to put a data acquisition
system on it to capture all the voltages/currents
during the event.
Bob . . .
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bob.verwey(at)gmail.com
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| Posted: Sun Jun 19, 2016 11:55 pm Post subject: Problem with starting |
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I had the same problem recently....the thrust washer on the starter was worn and this caused the end of the commutator to short out intermittently.
Very frustrating as the starter bench tested fine...
On 19 June 2016 at 19:28, Stephen Richards <stephencliverichards(at)gmail.com (stephencliverichards(at)gmail.com)> wrote:
| Quote: | This still suggests to me that a intermittent ground is shorting out the armature or field is shorting out .
Clive
From: Alec Myers (alec(at)alecmyers.com)
Sent: 19/06/2016 14:51
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Re: Problem with starting
The strangest symptom is that twice the motor has cut out (and the bus voltage was pulled down) mid-crank while the prop was already turning at a good starting speed. I think that suggests it's not a bad spot on the commutator, for example.
I can rule out mechanical seizure at the crank because when the motor cut, the prop immediately bounced back off a compression stroke, and (I think) I can rule out a starter jam because the engine has started and run since.
I thought I was onto something with a possible fracture in the field winding but that won't explain things if the motor isn't shunt wound.
On Jun 19, 2016, at 09:29, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
I'm still not convinced you have a motor problem. The chattering relay points more to circuit / system and low voltage issues.
neal |
Except that a contactor powered from the same
battery that is being pulled down by what amounts
to continuous stall current may well drop-out
during closures only to re-close when the contacts
break and stall-current goes away.
12v battery contactors drop at about 2v . . . and
are not likely to be candidates for 'buzzing' but
it's not impossible. A easy experiment would call
for powering the starter contactor from a separate
source . . . like another battery. It may well
stop chattering. But the energies being circulated
will be profound.
I'm puzzled by the intermittent nature of the
symptom. This implies a root cause that
is transient or loose to rattle around. Having
the starter motor come to rest on a bad pass
in the armature windings could account for such
behavior.
It would sure be illuminating to put a data acquisition
system on it to capture all the voltages/currents
during the event.
Bob . . .
|
--
Best...Bob Verwey
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alec(at)alecmyers.com
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| Posted: Mon Jun 20, 2016 4:49 pm Post subject: Problem with starting |
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Progress.... I now have the motor on the test bench displaying its sometimes-run sometimes-short-circuit behaviour. And I have video of both.
Given that I just had it overhauled, new brushes etc., I think I am going to cut my losses and get a replacement motor - same model, from Hartzel.
On Jun 19, 2016, at 13:28, Stephen Richards <stephencliverichards(at)gmail.com (stephencliverichards(at)gmail.com)> wrote:
This still suggests to me that a intermittent ground is shorting out the armature or field is shorting out .
Clive
From: Alec Myers (alec(at)alecmyers.com)
Sent: 19/06/2016 14:51
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Re: Problem with starting
The strangest symptom is that twice the motor has cut out (and the bus voltage was pulled down) mid-crank while the prop was already turning at a good starting speed. I think that suggests it's not a bad spot on the commutator, for example.
I can rule out mechanical seizure at the crank because when the motor cut, the prop immediately bounced back off a compression stroke, and (I think) I can rule out a starter jam because the engine has started and run since.
I thought I was onto something with a possible fracture in the field winding but that won't explain things if the motor isn't shunt wound.
On Jun 19, 2016, at 09:29, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: |
I'm still not convinced you have a motor problem. The chattering relay points more to circuit / system and low voltage issues.
neal |
Except that a contactor powered from the same
battery that is being pulled down by what amounts
to continuous stall current may well drop-out
during closures only to re-close when the contacts
break and stall-current goes away.
12v battery contactors drop at about 2v . . . and
are not likely to be candidates for 'buzzing' but
it's not impossible. A easy experiment would call
for powering the starter contactor from a separate
source . . . like another battery. It may well
stop chattering. But the energies being circulated
will be profound.
I'm puzzled by the intermittent nature of the
symptom. This implies a root cause that
is transient or loose to rattle around. Having
the starter motor come to rest on a bad pass
in the armature windings could account for such
behavior.
It would sure be illuminating to put a data acquisition
system on it to capture all the voltages/currents
during the event.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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