DanH

DanH

Legacy Member
Mentor
Has anyone seen this before? Plane Power alternator....works fine but the cooling shroud appears to have vibrated to death.

I'll check the ring gear sheave for out-of-round. Beyond that thought I am at this moment clueless.

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Wow, not sure what I'm looking at. Can you outline where the chunk is missing? The shroud looks stout enough where it would be tough to get into resonance.
 
Mounting

Dan,
Check your alternator mounts. Make sure they are secure. I would suggest you attempt to stiffen the mounting of your alternator. The PP unit is based on the "small" ND [30 to 60 amp] alternator. The pivot point on these units only extends a bit more than 50% of the alternator's depth. The large ND units extend 100% of their depth. In automotive use, the slotted adjustment bracket is always triangulated [3 mounting points, including the alternator]. Vans bracket does not give you the same stiff mount that the original automotive applications do.
Charlie
PS The pivot mount on the small ND units only attaches to the forward section of the alternator housing. The larger ND units [60 to 95 amps] have the pivot mount cast into both the forward and rear ward sections of the case.
 
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Yes ...

Yes,

I have seen this on MY Plane Power (well almost). I caught it before it broke off and safety wired it. Those shrouds seem to be made of VERY thin metal and with a little shaking, it cracks.

I had planned to call Plane Power about it but since you have one that has BROKEN OFF, I think you have a better "case" to find out what is happening.

If you get an answer, please post.

Thanks,
 
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AlexPeterson said:
Wow, not sure what I'm looking at. Can you outline where the chunk is missing? The shroud looks stout enough where it would be tough to get into resonance.
Click to expand...

Yeah, that surprises me too. As Mr. Clark says, the shroud material is quite thin, but shape and three mount points make resonance seem like a remote possibility. However, clearly it does resonate.

First point of failure was probably in the corner behind the B terminal, next to the case. The crack would proceed up the bend between the B and the plug, after which the rest would be short work.

A dot of silicone between the rectifier base and the shroud would kill the vibes.

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This was hung on PP-supplied bolt-on mounts. The bracket and tension arm are both in good shape.

James, did yours break near the B post?
 
Will check ...

I noticed a crack in mine so I safety wired it to keep it from coming off.

Next time I have cowl off, I will make a note of where the cracking started and report back.

James
 
I previously said three mount points should discourage resonant vibration, but that's wrong. In the picture below you can see how the regulator side (on the right) lacks a mount screw or other support and is thus free to vibrate. The original failure was probably where marked, at a small-radius formed bend near the base of the B-terminal (some material is missing in this photo; I've drawn it in for illustration). The rest follows quickly.

Material appears to be 0.030" 1100 aluminum.

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Just got off the phone with a nice lady at Plane Power. When I mentioned a broken shroud, she immediately asked "Aluminum or steel?", and then volunteered to send a new steel shroud at no charge. Good service.

Current production alternators get steel shrouds. If you have an aluminum shroud inspect it carefully at the next opportunity.
 
RV8R999 said:
Dan, is your eng/prop dynamically balanced? Didn't you have an exhaust crack too?
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Dynamic balance wasn't done until about 20 hrs ago, as it was never a shaker. When we did balance the initial numbers were in fact small. The internals were balanced to within a gnats arse at BPE.

Did have a crack in the 4-into-one collector, and it's now running with a slight mod suggested by the vendor.
 
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RV8R999 said:
Dan, is your eng/prop dynamically balanced? Didn't you have an exhaust crack too?
Click to expand...

It may well be that Dan's Plane Power alternator itself is not balanced. B&C alternators are individually balanced and I've never heard of this type of failure on a B&C.
 
Maybe

Just a dab of strategically placed silicone would stop this type of vibration.

bird
 
We had the same problem with ours several times. They replaced it for free every time but the alternator itself would break also. We are close enough to the factory that we could take it there and wait for it. But the frustration of failure and them always saying it was caused by the plane made us switch to a B&C. We had the engine balance checked and it is pretty close to perfect but they would not belive us. The straw that broke was when they said no more warranty. Have had no problems with the B&C but have not flown it much cause of other problems.
 
Before my -6 became a project again, I had a bit over 1000 hours on a Nippondenso forklift alternator and never had a moment of trouble with it.

Come to think of it, I've never heard of ANY failures with said alternator as I have a number of friends flying with one or very similar variations of ND alternators.

Just curious if anyone else has had problems with stock automotive alternators. Not counting the alternators Van's use to sell...those were junk.
 
Well, a shroud arrived today.

The "new" shroud is aluminum, just like the broken one. There was a note in the box from Jan, the office manager at Plane Power, stating she was mistaken about the shrouds being steel on current production alternators. I find that odd given her first question Monday on the phone was "Aluminum or steel?". And this one has been previously installed on an alternator.

To prevent another failure I'll take two steps. First, a couple well placed dabs of silicone sealant should damp the vibrating cover. Second, the edge of the cover needs to be deburred just like any other airplane part. The old cover appears to have cracked exactly where I find a nice notch on the new one. It should have a label saying "Break Here" ;)

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NP alt

Just curious if anyone else has had problems with stock automotive alternators. Not counting the alternators Van's use to sell...those were junk.
Click to expand...

Bob,
Mine didn't make twenty hours and packed it in. On went the B&C and
fine ever since.
 
DanH said:
Charlie, got a source?
Click to expand...

I'd look at the local "Pick A Part" type junkyard or a local automotive electrical rebuilder as the most likely sources. Are you friendly with any of your local auto parts stores? If so, they could probably rob one off of a core trade-in for you. I'll check tomorrow regarding an exact model, but I'd say a 2000 or up Honda Civic alternator would probably work.
Charlie
PS I'll check with my local parts vendor after the holiday
 
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