Today's Message Index:
----------------------
1. 08:10 AM - CONTACT EXTRACTOR (racerjerry)
2. 12:43 PM - Re: Contactors (Peter Pengilly)
3. 02:08 PM - Re: Contactors (Sacha)
4. 11:28 PM - Re: Contactors (Etienne Phillips)
Message 1
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Subject: | CONTACT EXTRACTOR |
Can someone give me the (working tip end) dimensions of the Bendix/King contact
extraction tool p/n 047-05099-001 that is used to remove contacts p/n 030-01107-00xx
as used on KT 76 and KX 155. Please no guesses I need a caliper on
this one. I will be working under extremely difficult conditions.
Apparently, this tool is also known as Molex p/n HT-1884
Thank you for your help.
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=411998#411998
Message 2
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Sacha,
Apologies, I'm not very familiar with Rotax components. It would be good
to know how much current a Rotax starter pulls - I guess it is likely
that as the engine is only 1200cc the draw would rather less than a
starter for a 5/6 litre Lyc. I believe a Lyc starter pulls between 200
to 500A depending on starter type and compression ratio. If a Rotax
pulls substantially less the potential for the starter contactor to weld
itself shut would be lower (probably not a linear relationship), and so
the risk of a problem that much lower. You may decide you can tolerate
the risk without additional mitigations.
Peter
On 02/11/2013 21:10, Sacha wrote:
>
>
>>> If a modern starter with a piggy-back solenoid is fitted,
>>> to avoid the master relay handling the starting current, the jumper that
>>> normally energises the solenoid can be brought into a cockpit switch to
>>> disable the starter if the the starter contactor does weld on. A small
>>> additional parts count, but the switch never does any switching except in
>>> emergency.
>> You're speaking about the solenoid on the starter motor? I don't recall
>> seeing any external jumper there (the engine is a Rotax 912). I'll have a
>> check next time I'm down at the hangar.
> I couldn't find anything there unfortunately. The starter motor just has one
terminal for the fat positive wire.
>
>
Message 3
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Thanks Peter
Actually I realized today that I can easily use the semi-useless alternator off
warning light that I fitted on my panel as a "starter on warning light" with
minimal rewiring. Since 99.9% of the time I'm going to be on the ground while
starting my engine, I think I can live with the fact of not being able to disable
the starter motor if the contactor gets stuck somehow since I can just shut
down the engine.
Out of interest I will try to measure how many amps are drawn by the starter next
time I'm down at the hangar. Though I suspect this would vary somewhat depending
on temperature.
I've almost finished the CAD drawings of my electrical system so I'll be submitting
them to the list for review and criticism soon.
Sacha
On Nov 3, 2013, at 21:42, Peter Pengilly <peter@sportingaero.com> wrote:
> Apologies, I'm not very familiar with Rotax components. It would be good to know
how much current a Rotax starter pulls - I guess it is likely that as the
engine is only 1200cc the draw would rather less than a starter for a 5/6 litre
Lyc. I believe a Lyc starter pulls between 200 to 500A depending on starter
type and compression ratio. If a Rotax pulls substantially less the potential
for the starter contactor to weld itself shut would be lower (probably not a linear
relationship), and so the risk of a problem that much lower. You may decide
you can tolerate the risk without additional mitigations.
Message 4
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Hi Sacha
Being able to pull the mixture control whilst on the ground will stop the
engine from producing power, but if the start motor is still energised due
to the failed contactor, won't it keep cranking until you pull a terminal
off the battery? I'm not that familiar with the starters used in aviation
(I hand-swing my engine), so am unsure if they have a disengage mechanism
like they do on cars.
Thanks
Etienne
On 4 November 2013 00:07, Sacha <uuccio@gmail.com> wrote:
>
> Thanks Peter
> Actually I realized today that I can easily use the semi-useless
> alternator off warning light that I fitted on my panel as a "starter on
> warning light" with minimal rewiring. Since 99.9% of the time I'm going to
> be on the ground while starting my engine, I think I can live with the
> fact of not being able to disable the starter motor if the contactor gets
> stuck somehow since I can just shut down the engine.
> Out of interest I will try to measure how many amps are drawn by the
> starter next time I'm down at the hangar. Though I suspect this would vary
> somewhat depending on temperature.
> I've almost finished the CAD drawings of my electrical system so I'll be
> submitting them to the list for review and criticism soon.
> Sacha
>
> On Nov 3, 2013, at 21:42, Peter Pengilly <peter@sportingaero.com> wrote:
>
> > Apologies, I'm not very familiar with Rotax components. It would be good
> to know how much current a Rotax starter pulls - I guess it is likely that
> as the engine is only 1200cc the draw would rather less than a starter for
> a 5/6 litre Lyc. I believe a Lyc starter pulls between 200 to 500A
> depending on starter type and compression ratio. If a Rotax pulls
> substantially less the potential for the starter contactor to weld itself
> shut would be lower (probably not a linear relationship), and so the risk
> of a problem that much lower. You may decide you can tolerate the risk
> without additional mitigations.
>
>
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