Today's Message Index:
----------------------
1. 06:59 AM - Re: Re: Mag timing HS6A is the book wrong? (Roger Kemp)
2. 10:51 AM - Magneto failure CD-5 (glipaz)
Message 1
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| Subject: | Re: Mag timing HS6A is the book wrong? |
Ah, mental masturbation...the book has always worked for me but I'm getting old
and senile.
Doc
Sent from my iPad
> On Jul 4, 2017, at 4:48 AM, JL2A <info@flyingwarbirds.com.au> wrote:
>
>
> I think my esteemed colleague woodja has come up with the answer:
>
>
>>
>> advance on magneto is calculated as the angle the advance moves on the device
itself ,
>>
>> nothing to do with piston , prop or anything ...thus ,
>>
>> I read the magneto is geared at 1.125 internally. This from Tech specs ...
>>
>>
>> So 27 degrees of magneto advance only equals 27/1.125 , or 24 degrees of piston
advance .
>>
>> 24 degrees from 31 +|-1 degree (from tech specs ..)
>>
>> is the TDC degrees piston firing point ,
>>
>> equals 7.0 degrees of piston advance required ,
>>
>> which , multiplied by .787 equals
>>
>>
>>
>>
>> 5.5 degrees of prop advance.
>>
>> Remarkably close to the table ...
>>
>>
>> ie exact.
>>
>>
>> ..And +/-1 degree of piston is , funnily , +-.7 degree of prop , coincidentally
the limit variation...
>
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=470679#470679
>
>
>
>
>
>
>
>
>
Message 2
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| Subject: | Magneto failure CD-5 |
Conundrum:
At runup, Mag 2 failed (engine turned off). Engine ran smoothly on Mag 1. Returned
to chocks and opened Mag 2 to discover a broken points spring. Obvious
hard break. Replaced points and opened Mag 1 to inspect. Discovered that
the rotor on Mag 1 was completely loose (all three bolts were loose). Tightened
rotor on Mag 1, closed both mags and fired it up. Started easily. Mag
2 now worked fine but now Mag 1 failed. What?!
Thought it might be a switch problem. Tested Mag switch to make sure it was not
a wiring short to ground and it checked ok. Back to the Mag.
Inspected rotor and cap. Ok. Checked points. Open fine. Replaced cigarette.
Still wouldn't fire. Replaced coil. Still wouldn't fire. Finally replaced
Mag. Motor fired and tested fine on both mags. Runup Mag check normal.
Note: we turned the bad Mag 1 by hand and could not get a spark out of the cigarette
and the Mag turned fairly freely, without the normal flopping that the magnets
provide.
The mystery is this: assuming Mag 1 was fine and Mag 2 had a hard break prior
to shutdown (prior Mag checks on Mag 1 were fine) how did it fail after tightening
down the rotor? Why is it now producing no spark and seems to have lost
its magnetism? Prior to this both Mags worked fine on previous runups and flights.
Gil Lipaz
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470795#470795
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