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More Tri-Pacer Generator Info

 
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jnmeade



Joined: 27 Sep 2012
Posts: 12

PostPosted: Sat Dec 21, 2019 4:59 am    Post subject: More Tri-Pacer Generator Info Reply with quote

The generator is an Aerotechlou rebuilt and installed in 2014. It is
almost certainly a Delco Remy 35 amp and I'm assuming it is a type "A"
circuit as described in their literature. We're trying to run down the
paperwork. There is a vision port which can be viewed and from that the
brushes look well seated and the commutator is clean and serviceable. The
VR is a Zentronic G1350 which looks to be of modern design (no mechanical
points). Troubleshooting on the Aerotechlou site says remove the field
wire and jumper the field terminal to aircraft ground. Remove the
armature wire and measure the voltage to ground with a DC voltmeter and
the engine running. The voltage should follow engine RPM.

I'm going to do this by taking the wires off of the voltage regulator,
which is on the firewall, instead of the governor. The governor is
virtually inaccessible. To get at it one must pull the prop and the front
cowl. Not inclined to do that until it's the only choice. I understand
this does not isolate the wires, but if the wires are the problem the prop
and cowl have to come off anyway or get someone with smaller fingers.


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nuckolls.bob(at)aeroelect
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PostPosted: Sat Dec 21, 2019 9:20 am    Post subject: More Tri-Pacer Generator Info Reply with quote

At 06:56 AM 12/21/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "James Meade" <jnmeade(at)southslope.net>

The generator is an Aerotechlou rebuilt and installed in 2014. It is
almost certainly a Delco Remy 35 amp and I'm assuming it is a type "A"
circuit as described in their literature. We're trying to run down the
paperwork. There is a vision port which can be viewed and from that the
brushes look well seated and the commutator is clean and serviceable. The
VR is a Zentronic G1350 which looks to be of modern design (no mechanical
points).

EXCELLENT! An updated system . . . nice that your
vintage bird can stay as close to original as
possible/practical.

Quote:
Troubleshooting on the Aerotechlou site says remove the field
wire and jumper the field terminal to aircraft ground. Remove the
armature wire and measure the voltage to ground with a DC voltmeter and
the engine running. The voltage should follow engine RPM.

An excellent data point . . . but this only says
the brushes are 'mostly' in good contact. Since
system charging currents flow in the brushes,
a voltmeter falls way short of duplicating
a 'proof load'. When you do this test, add
at least one, if not 2, 55 Watt head lamps to
the load. Adding this load makes flaky brushes
more likely to demonstrate their problems.

And this test isn't a sure bet . . . you've described
situations where the system DID produce adequate power
for significant periods of time . . .


Quote:
I'm going to do this by taking the wires off of the voltage regulator,
which is on the firewall, instead of the governor. The governor is
virtually inaccessible.

Good idea.

Quote:
To get at it one must pull the prop and the front
cowl. Not inclined to do that until it's the only choice. I understand
this does not isolate the wires, but if the wires are the problem the prop
and cowl have to come off anyway or get someone with smaller fingers.



Sounds like your on a promising track to discovering
root cause. Run the traps on the manufacturer's
recommended troubleshooting procedures. If no
joy, get back here and we can offer further advise
on how to track down the problem.

Do you put a lot of hours on this a/c? That generator, under
moderate loads should have a brush life on the order
of 200-300 hours . . . maybe better. But your inspection
window should confirm/deny brush wear as the problem.

The symptoms you describe DO suggest that it's
a brush problem. If the VR is solid state, then
probability of failure is low . . . probability
of intermittent failure lower still . . . but
not zero in any case.

Keep us appraised of your progress . . . we don't
often get to witness the detective work on
vintage problems!


Bob . . .


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jnmeade



Joined: 27 Sep 2012
Posts: 12

PostPosted: Sun Dec 29, 2019 8:10 pm    Post subject: Re: More Tri-Pacer Generator Info Reply with quote

The problem is a 25A circuit breaker that seems to have become intermittent. I say that based on it having "reset" itself at least once.
Removed field wire and jumpered it to ground. Removed armature wire and put a DC voltmeter in series with it to ground. At idle the voltage was about 6 VDC. At 1500 RPM the voltage was 28VDC. This seems to prove the generator is producing current. All electronics were off and we only ran this test for a couple of seconds.
Reinstalled the voltage regulator and observed that the green VR light was off at low RPM and the GO red light was on because generator voltage was below battery voltage. Advancing RPM the green VR goes on and the red GO light goes off. Seems like the VR is OK.
Why does ammeter show discharge when charging system tests good?
Started fiddling with generator circuit breaker (probably original in 1955 airplane) and found it would engage and the ammeter showed an appropriate charge and response to RPM and load changes.
For now, I'll treat it as a transient and watch it, but if it recurs the circuit breaker will need to be changed out.
Thanks for the tips and encouragement.


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skywagon185(at)gmail.com
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PostPosted: Sun Dec 29, 2019 9:32 pm    Post subject: More Tri-Pacer Generator Info Reply with quote

I have seen CB's, especially old ones, do some strange behavior; like stuck open after reset, permanently stuck closed.
You maybe on to the problem about needing to change out the CB....

On Sun, Dec 29, 2019 at 8:16 PM jnmeade <jnmeade(at)southslope.net (jnmeade(at)southslope.net)> wrote:

Quote:
--> AeroElectric-List message posted by: "jnmeade" <jnmeade(at)southslope.net (jnmeade(at)southslope.net)>

The problem is a 25A circuit breaker that seems to have  become intermittent.  I say that based on it having "reset" itself at least once.
Removed field wire and jumpered it to ground.  Removed armature wire and put a DC voltmeter in series with it to ground.  At idle the voltage was about 6 VDC.  At 1500 RPM the voltage was 28VDC.  This seems to prove the generator is producing current.  All electronics were off and we only ran this test for a couple of seconds.
Reinstalled the voltage regulator and observed that the green VR light was off at low RPM and the GO red light was on because generator voltage was below battery voltage.  Advancing RPM the green VR goes on and the red GO light goes off.  Seems like the VR is OK.
Why does ammeter show discharge when charging system tests good?
Started fiddling with generator circuit breaker (probably original in 1955 airplane) and found it would engage and the ammeter showed an appropriate charge and response to RPM and load changes.
For now, I'll treat it as a transient and watch it, but if it recurs the circuit breaker will need to be changed out.
Thanks for the tips and encouragement.




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