[alcladrv]

My Van's 60 amp alternator has just bitten the dust after 182 hours. It's been installed in an RV-7A with ECI O-360 and a fixed pitch prop. The -7A with this engine/prop combo is known to be a bit tail heavy, especially after being painted, which mine is not at this point.

I know extra weight reduces performance, but those planes with the extra weight of a constant speed prop balance out a little better.

So, in my case, it seems like installing a heavier alternator, hopefully more durable than the Nippon Denso 60 amp rebuilds, would help alleviate 2 problems, more durable alternator (perhaps higher capacity than 60 amp) and more weight about as far forward as you can get.

Has anybody considered this train of thought and tried it out? Comments? Opinions?

Thanks for your help,

Mike

 

[Mel]

The biggest problem with heavier alternators is that they are usually larger. The RV cowling is pretty tight in the alternator area.

 

[gmcjetpilot]

A couple of ideas

Here is a good article by a RV builder who converted a 90 amp unit. He calls it a 60 amp continuous. Most alternators are only good for full rating (like 60 amps) for short periods. You should keep load below 70%.

http://www.miramarcollege.net/programs/avim/faculty/north/alternator/index.htm

If you have a 60 amp alternator consider 40 amps as your max with the engine RPM up. At idle the max may only be 20-30 amps depending on pulley sizes. A bigger alternator can fit, its been done like the larger unit above, but they weigh a LOT more.



Another idea is get a Plane power unit. They have a fan corrected for proper CCW rotation, better bushes and an extra OV protection module. They also offer larger alternator capacities.

You could also fix the one you have. What died? The bushes, Rectifier, voltage regulator? It may just need a replacement part. The ND's are modular in that components bolt in easily. If its the stator or rotor you may just want to trash it, however those are also can be field replaced.


Last Van sold some bad alternators in my opinion. Some alternators go 800, 1000 or 2000 hours, some like yours only 150-350 hours (or less). That is unacceptable. OEM nippon densos on cars go 100's and 100's of thousands of miles. Rebuilds and clones much less. So in part it is the nature of the beast. You can't get new ND's in the model we have so rebuilds and aftermarket clones is all we have. There are good ones but there are lots of sub standard aftermarket parts as well.

You have the option of getting a replacement at your local auto emporium, with a life time warranty! Get the replacement and make the installation better. You may have better luck with the replacement unit.

Remember on a car the alternator is high and up front where it gets air and is away from exhaust. Also the vibes are probably less. In the lower front of a RV cowl, there is not a lot of air and its next to the exhaust. Consider an air blast tube on the voltage regulator and a heat shield on the #1 pipe. The radiant heat will cook the back of the alternator. heat = death / cool = life.

 

[alcladrv]

Thanks for your responses.

I checked out the article you linked to. It was interesting reading, but in the last paragraph came a bit of a punchline. I don't know how the ND compares to the Prestolite discussed in the article, but, after modifying the Toyota alternator, he said it came in 1 pound less weight than the Prestolite.

He also said the Toyota fit right in on the "wide deck" Lycoming. I'm not knowledgeable enough to know how a "wide deck" Lycoming compares to my ECI O-360.

I had some time yesterday, so I took the old Van's 60 amp unit to the local independent auto electric shop that some local car repair shops use. He checked it out using an oscilloscope and found bad diodes. I got a little education on his rebuilding philosophy. He reuses the original bakelite brush holders, because the chinese and mexican units use plastic holders which can deform. Only one of my brushes was making contact, the other wouldn't springback into place. The regulator was suspect as well.

Turns out that he had a rebuilt one on the shelf with a cast rear bracket instead of the stamped one on mine. My stamped bracket had broken on one of the lugs, similar to a picture I saw elsewhere on this site. He said that would constitute core damage. He said the rear bracket is a "floater" and probably snapped because it was tightened up before the front bracket. He said to make sure that the front bracket is tightened-up first.

On his Fluke voltmeter, my unit's voltage had varied from 14.5 to 15.3. The rebuilt unit was rock steady at 14.4. I gave him $102 and my core, and left to install the rebuild on the plane.

It fit without difficulty. I made sure to tighten the front bracket first and anchored the blast tube in place. While running the engine afterwards, I observed the voltage on my Grand Rapids EIS to be pretty steady at 14.6. Is that .2 volts instrumentation variance fairly normal?

I'll change my startup procedures to turn the alternator on with the battery and hopefully get better life out of this one.

Thanks for you help,

Mike

 

[gmcjetpilot]

Yea it weighs more

Thanks for your responses.

I checked out the article you linked to. It was interesting reading, but in the last paragraph came a bit of a punchline. I don't know how the ND compares to the Prestolite discussed in the article, but, after modifying the Toyota alternator, he said it came in 1 pound less weight than the Prestolite.
Mike

Oh its heavy. The super small ND (using memory now so warning) at 40-45 amps or the small frame NDs are about 5-6 lbs. The Med frame 55 amp units are about 6-7 lbs. The the bigger 60 amp units are about +8.5 lbs. The bigger 80 amp unit like the one in the article is about 11 - 11.9 lbs. Light for certified airplane stuff. I had generators on my old piper twin. They where like anchors.

So yea, you are going to add at least 3 or 4 lbs. That is alternator weight by the way, no brackets.

In exchange, if you put a 80/90 amp unit on, you have an alternator with a much larger stator and rotor. It runs much cooler, has bigger rotor shaft, bearings, slip ring and higher rated diodes. In other words it is working at a LOW percentage of its max rating. You asked. It should last longer and be more reliable. However 4 lbs is a lot of weight, but could be worth it if you want more reliability and also capacity.

Take Vans 60 amp unit, which is really a 55 amp by ND, not 60 amps. The ND rating is at a fixed lower RPM like 5,000 rpm I recall. Cars have to make juice at idle and low RPM, right, not just at highway speed. If you take 70% of 55 amp you get about 38 amps. If you are drawing more than that continuously, the common wisdom from the grey hair experts is don't, get a bigger alternator. That is it, about 65-70% of rating max continuous. With cars now a days its not uncommon to see +90 to even 130 amp alternators. Unfortuantely they are too big for our use.

Normally I say 60 amps is plenty. However add fancy electronics, heated pitot, high powered exterior lights you can get to 40 amps and beyond easy. 40 amps on a 55 amp (60 amp vans unit) is going to cook it. Unless you have extra cooling you will cook it sooner than later.

My worst case for my RV, a deluxe VFR x-country, semi-glass day night, is about 30-32 amps at night. Add heated pitot and some extra goodies I can see where you can get well over the recommended 38 amp max continuous.

You have to put the weight in to put the electrical crud in. Its a vicious cycle, more stuff adds weight and than you need a bigger alternator.

Again Plane power has a 70 amp unit that will bolt in and the alternator is about 9-3/4 lbs.