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Alternator failure

 
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grant.corriveau(at)TELUS.
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PostPosted: Tue Jun 10, 2008 9:36 pm    Post subject: Alternator failure Reply with quote

During the pre-taxi checklist this evening I thought my alternator
output was a little low. I usually see 13 volts and I was only
seeing about 12.5v. I switched the alternator off then on to be
sure it was actually putting out, which it was. So I pressed on for
a lovely evening putter around the area.

After about 20 minutes I glanced over and saw the volts were down to
11 at zero amps, so I landed. It was nice to know I had two fresh
batteries available (one only a month old) -- converted auto engines
without magnetos introduce new failure modes that had to be
incorporated into the electrical system design.

Anyway, my next task is to find an appropriate replacement alternator
- hopefully a lighter one. This one has 60 amps output, but do I need
that much? I'd prefer to save a few pounds if possible.

Suggestions?

Grant
GHTF
601hds/CAM100


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grant.corriveau(at)TELUS.
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PostPosted: Wed Jun 11, 2008 9:48 pm    Post subject: Alternator failure Reply with quote

Well what do you know! It just goes to prove once again that we
shouldn't waste time "fixing" problems before they're properly
diagnosed and understood. Today I popped the top cowl, ready to
remove the alternator - thinking "wouldn't it be nice if it was only
a broken wire..." Only to discover that it was a broken wire!

The main output terminal eyelet was broken. I'm pretty sure this
happened when my friendly mechanic found my main terminal nut was not
completely tight and he tourqued it up for me. But at the same time
I think he bent the terminal eye back against the alternator to lie
flat (I always in stall wires with a small offset bent into the
terminal to keep the wire away from anything that could cause
chaffing). This double bending on a large terminal must have started
a crack which finally broke through completely.

My repair is now a simple re-fit of the alternator feed wire or just
the one terminal. Sweet. Not often problems pan out this way.

While I was at it I determined that my alternator drive pulley is on
the engine crankshaft end. The alternator has an equally-sized
pulley so engine rpm is basically alternator rpm, which is excellent
for my system. So my alternator research was not wasted. Now I know.

Thanks for all the helpful ideas listers,

Grant
GHTF 601HDS/CAM100


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amyvega2005(at)earthlink.
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PostPosted: Thu Jun 12, 2008 1:55 am    Post subject: Alternator failure Reply with quote

WHoa dude ! sounds like you have power to run a 747!. You probably only need 20 amps. UNless you run at night alot, thern 25 amps.
any thoughtss?

JUan

--


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moorecomp



Joined: 14 Aug 2006
Posts: 32

PostPosted: Thu Jun 12, 2008 6:35 am    Post subject: Re: Alternator failure Reply with quote

"grant.corriveau(at)TELUS."]During the pre-taxi checklist this evening I thought my alternator
output was a little low. I usually see 13 volts and I was only
seeing about 12.5v. I switched the alternator off then on to be
sure it was actually putting out, which it was. So I pressed on for
a lovely evening putter around the area.

After about 20 minutes I glanced over and saw the volts were down to
11 at zero amps, so I landed. It was nice to know I had two fresh
batteries available (one only a month old) -- converted auto engines
without magnetos introduce new failure modes that had to be
incorporated into the electrical system design.

Anyway, my next task is to find an appropriate replacement alternator
- hopefully a lighter one. This one has 60 amps output, but do I need
that much? I'd prefer to save a few pounds if possible.

Suggestions?

Grant
GHTF
601hds/CAM100"

I don't know if it will fit on the CAM100 or not, but checkout what Mark Langford has on his sight for his Corvair.

http://home.hiwaay.net/~langford/corvair/dynamo.html

Best regards,

Craig Moore A&P
Mancelona, MI


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jetboy



Joined: 22 Jul 2006
Posts: 233

PostPosted: Thu Jun 12, 2008 2:21 pm    Post subject: Re: Alternator failure Reply with quote

A word of caution using the dynamo circuit in the corvair article.

It is not good practice to allow a situation (for any type of alternator regulator) where the voltage sense wire(yellow) and the regulator output wire(red) are able to not be connected with each other whilst the alternator may be in operation. By wiring the sense wire after the master switch and the output wire to the battery you have a situation where there is low voltage at the sense connection so the regulator turns full on putting 40 volts to the battery. In some cases there is no output when the sense wire is off depending on the particular regulator design.

The Kubota lawn tractors have a similar dynamo system reportedly less expensive than the JD., this is what is used for Jabiru engines. This regulator is series switching type so does charge in short pulses whereas the larger 3 phase field regulated types do have a smoother more constant output. The Denso one pictured in the Corvair article should be ideal for the CAM100, or even one of each type for security of supply because the dynamo type are usually not up to much more than 15 amps - The B+C one I recall is 8 amps possibly because it uses a linear regulator - smooth output but they get hotter.

Ralph


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