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Cooling the alternator?

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Pilottonny

Well Known Member
I have read some previous threads about this isssue but I can not decide!

Shall I install a cooling tube on the baffles towards the back of the alternator, to cool it and spray it with water when flying in the rain, or shall I not cool it an thus keep it dry, but hotter? I am a bit confused! The manufacturer recomends to cool it, he does not mention anything about spraying water allover the electronics though.

In my car the alternator is not cooled and it has been running for over 3.000 hrs., without any problem. And I abuse it a lot: run with the lights on day and night, run the Airco summer and winter, use the heated seats, rear window heater, mirror heaters, etc. in the winter on short trips, etc.

Those that have installed a cooling tube: any problems in the rain?
Thiose that have gone without cooling: any heat assosiated problems?

BTW, I am installing the 60 Amp. Plane Power Alternator from Vans.

Thanks in advance for your replies.

Regards, Tonny.
 
Tonny,

I didn't install a blast tube during my original build, on the basic premise that my previous certified airplanes didn't have any*, and I didn't want to waste any pressure on the top side of the baffles. Wen I replaced the alternator several hundred hours later due to a wandering Voltage Regulator, I decided that my cooling to the cylinders was great, and wasting a little pressure wouldn't be a problem. I used a 3/4" corrugated line, mounted so it directed it's full flow on the VR on the back of the alternator. Does it help? I can't really tell you because the sample size is so small, but I have gotten three times the alternator life so far. I fly in rain - no issues. the VR is completely "potted" - there are no electronics exposed to the elements. Car alternators get wet when you drive through significant puddles - they don't seem to mind. I think the cooling air to the VR can't hurt, and maybe helps.

(On the other hand, I have never put in Magneto cooling tubes, as the Mag case is so big and bulky, blowing a little cool air on the outside doesn't seem to me like it would cool the working parts at all.)

Paul

* I decided later that this experience really isn't applicable, since the certified alternators had external regulators, and were physically larger - more thermal mass.
 
IIRC the red Van's demo/trainer used to eat alternators like candy, because of all the time it spent in slow flight for training.

I put temperature monitoring stickers on my alternator and was surprised at the very high temps I recorded. I now have a blast tube, directed at the diodes. I have flown in rain without any apparent issues.

FWIW I have those little stickers all over my firewall forward, and it is surprising how hot some things will get. On my airplane the right side of the accessory case got very hot until I moved some blast tubes around.
 
Collecting and assessing anecdotal experiences of other builders (who in this case may or may not be using the same alternator) is fine....for what it is.

When in doubt, I believe it is probably best to simply follow the manufacturer's advice. This one is easy. Plane Power Ltd's written instructions clearly state: "Supply ram air to the rear of the alternator by use of 1" scat tube or other suitable ducting."

That is what they say, that is what I did.
 
I'm with Rick. I was researching and debating this same topic until I read the note on the Plane Power drawing. It didn't take long (except for having to order the flange). I'd suggest following whatever your alternator supplier specs.
 
flyeyes said:
...FWIW I have those little stickers all over my firewall forward, and it is surprising how hot some things will get. On my airplane the right side of the accessory case got very hot until I moved some blast tubes around.
Click to expand...
I didn't know any better and put the blast tube on the front of my Van's alternator.



245 hours and no problems, even the few times I flew in the rain.

As for the temp's under the cowling, the E/P-mags have an internal temperature sensor and with the testing we have been doing for the Electronic Ignition Controller we are developing, we have found the temperature spikes don't happen in flight. They happen after you shut down on a hot ramp.

Other than opening your oil filler door and letting the heat out, I'm not sure there is much you can do.
 
I just replaced my Van's 60 amp alternator after about 200 tach hours with a Plane Power. The alternator shop that fixed the Van's one (I now have a backup) said the rectifier was "shorted". I take that to mean one or more of the diodes had failed. Did the lack of a blast tube cause the failure? I don't know. I installed a blast tube for the Plane Power because I don't know, and perhaps more importantly, because the instructions say to do so and not doing so might void any warranty protection. FWIW, I decided that 3/4" corrugated tube was "suitable ducting" in lieu of 1" scat.
 
Rain...?

Yesterday I flew through a moderate rainshower for the very first time with my -7
Then I'd to divert to a nearby field to let the shower pass before I could proceed further along my X-country route.

The diversion landing, the start up 2 hrs later, runup and takeoff was normal.

Then, after about 5 mins of flight, I got a "low voltage" warning and saw that the amps where -3 and the volt was 13,9 and dropping.
The amps stayed at -3 and the volt dropped to 12,7 during the next 2-3 minutes.

I tried to recycle the alt switch, no result.

Then I saw that suddenly the volt came up to 14,1 and the amps showed + 5.
The indications stayed like this for a few seconds, then dropped back again.

This cycle repeated itself 3-4 times, then the amps stayed on the + side and the volt stayed at 14,4 for the last of the 45 minute flight.

To me, it looks like the Plane Power alterator malfunctioned due to the rain and gradually dried up after takeoff and then came back to normal ops.

I've the black Vans tube installed as a blast tube getting air from the front of the right cylinder and going the the aft part of the alternator per plans.

I'ev not pulled the cowl yet and checked my wiring, so that'll be the next step.

Have any of you had a similar experience after flying through rain?
I'm thinking I better move the inlet of the blast tube to aft and above the right aft cylinder. Anyone done this? And what's the result? Poor alternator cooling maybe?
 
The refurbished car ones sold by Van's run backwards?

I was told that as installed the refurbished car alternators originally supplied by Van's before the recent change to Plane Power ones ran in reverse. No problem for generating alternating current but the cooling fan didn't work well in reverse so you needed to supply direct cooling air to the rectifier box to stop if burning out in short order. Not sure how apocryphal that story is. If Plane Power say to do it with their's it might well be :) But in general it's always worth following the instructions on the back of the can - what ever the product.
Jim Sharkey
 
ao.frog said:
Yesterday I flew through a moderate rainshower for the very first time with my -7
Then I'd to divert to a nearby field to let the shower pass before I could proceed further along my X-country route.

The diversion landing, the start up 2 hrs later, runup and takeoff was normal.

Then, after about 5 mins of flight, I got a "low voltage" warning and saw that the amps where -3 and the volt was 13,9 and dropping.
The amps stayed at -3 and the volt dropped to 12,7 during the next 2-3 minutes.

I tried to recycle the alt switch, no result.

Then I saw that suddenly the volt came up to 14,1 and the amps showed + 5.
The indications stayed like this for a few seconds, then dropped back again.

This cycle repeated itself 3-4 times, then the amps stayed on the + side and the volt stayed at 14,4 for the last of the 45 minute flight.

To me, it looks like the Plane Power alterator malfunctioned due to the rain and gradually dried up after takeoff and then came back to normal ops.

I've the black Vans tube installed as a blast tube getting air from the front of the right cylinder and going the the aft part of the alternator per plans.

I'ev not pulled the cowl yet and checked my wiring, so that'll be the next step.

Have any of you had a similar experience after flying through rain?
I'm thinking I better move the inlet of the blast tube to aft and above the right aft cylinder. Anyone done this? And what's the result? Poor alternator cooling maybe?
Click to expand...

I'm wondering if your alternator belt started slipping. Have you checked the tension?
 
jsharkey said:
I was told that as installed the refurbished car alternators originally supplied by Van's before the recent change to Plane Power ones ran in reverse. No problem for generating alternating current but the cooling fan didn't work well in reverse so you needed to supply direct cooling air to the rectifier box to stop if burning out in short order. Not sure how apocryphal that story is. If Plane Power say to do it with their's it might well be :) But in general it's always worth following the instructions on the back of the can - what ever the product.
Jim Sharkey
Click to expand...

The old 35a alternators Vans sold didn't come with fans. The rebuilt unit I got from Advance Auto (Duralast 14184) still has the fan but it runs backward. I figured air being moved in some direction was better than no air moving at all.

I have a ram tube aimed at the back of the alternator.
 
Sam Buchanan said:
The old 35a alternators Vans sold didn't come with fans. The rebuilt unit I got from Advance Auto (Duralast 14184) still has the fan but it runs backward. I figured air being moved in some direction was better than no air moving at all.

I have a ram tube aimed at the back of the alternator.
Click to expand...


Same here.

I believe that the sheet metal fan "sucks" through the alternator regardless of direction of rotation but that it works way better turning in the right direction - something to do with the side and angle that the tabs are bent to form the crude centrifugal passages that get the air moving radially and spun out away from the fan. Its like a very basic centrifugal compressor disk.
Jim
 
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yep...

Alternator belt tension: Good point! Thanks! I'll check when I pull the cowl.

I checked tension during the annual in June and it was fine but you never know....

I adjusted tension during the 50 hrs inspection in January and that was the first time the belt needed adjustment since installation.
 
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