[zilik]

At 800 hours TT (and over Cuba) the Denso alternator on my 6a failed. I bought the unit from Niagra 7 years ago and really thought it would last to TBO. I had the Denso rebuilt with all new internal parts while in Dothan Alabama on our way home from the Cayman Islands. The gentleman who did the work thought the brushes were bouncing at high speed. Could be.

Gary

 

[gmcjetpilot]

Niagara, reply, comment, questions?

At 800 hours TT (and over Cuba) the Denso alternator on my 6a failed. I bought the unit from Niagara 7 years ago and really thought it would last to TBO. I had the Denso rebuilt with all new internal parts while in Dothan Alabama on our way home from the Cayman Islands. The gentleman who did the work thought the brushes were bouncing at high speed. Could be.

Gary

I don't work for Niagara but have their alternator. Sorry you had a problem. What was the problem?

When you title said FAILURE, you got my attention, since I have two of them. After reading it sounds like you just wore your brushes down? and it just stopped making power while you where flying after 800TT of service. IS THAT CORRECT?


FIRST: These are the same brushes B&C uses and everyone for that matter. It sounds like they wore out after 800TT. That may not be uncommon for any alternator used at high RPMs, hot and with dirt.

Second: I ALSO assumed they should last close to TBO (2000 hours), but if you are spinning it at 9750 RPM in cruise, its possible you just plan wore them out. Bushes cost $1.50 and are easy to change (about 10 minutes).

May be this should be something you (and all of us ND folks) should change every 500 hundred hours or every 3 to 5 year? I got 1000 hours out of my ND Niagara alternator before selling the plane, at which time it was still going strong. My current project is not flying and have a similar alternator. I'll make note of this and add it to my airframe log book maintence schedule. Thanks for the info.


To be honest, the weak link of ALL ND alternators, including B&C, which is a ND based alternator, are the brushes. They just wear out. I called repair shops around the country and asked what was the number one thing that wears out or breaks on ND alternators, the brushes. I guess depending on RPM and environment they will wear at differnt rates. A brush change is easy and cheap anyway.

RPM:
The Niagara alternators come with a 2.5" pulley. If you have the Large Lycoming Flywheel pulley (9.75" verses 7.5" diameter), you have a ratio = 9.75/2.5 = 3.9. At engine RPM = 2,500 the alternator is at 9750 rpm.

I have the 7.5" dia flywheel so my ratio is 3 to 1, which puts me at 7,500 rpm at the alternator in cruise (2,500 rpm engine). So a ratio of RPMs means I might last 30% longer or 1040 hours, Yipeee. Wow 240 more hours. You could change the alternator pulley to a 2.8" one, but its easier to just replace the brushes every few years or 500 hours.

BRUSH JUMP, could be at 9,750 rpm? Again all ND alterantors are very similar including the $450 B&C alternator, which have the same brushes and brush holder (I think).

Call or write Niagara at: [email protected] or USA 800-565-4268. It is winter North of Toronto big time and I think the owner is in Florida, but checks in. You should let them know. They might like to know or have some info on how to get more brush life.


Let me know if I can help. I would be interested in knowing what the problem was in a little more detail if you please:

What was "rebuilt"? (what was done)
What is the part number on the alternator?
What was the indication or symptom that indicated the problem?
What did the Sweet Home Alabama alternator rebuild cost you ?
If the brushes where bad why did you "rebuild" it and not jsut replace the brushes?

Best Luck, George

 

[Highflight]

I thought I saw a reference somewhere that B&C disassembles the new alternators they get and balance them as part of making them suitable for AC use.

If true, you can't argue that a balanced rotor would run more smoothly and thus avoid "chatter" of the brushes at higher rpm's. That should also add more time to the life of the brushes as well.

http://www.bandcspecialty.com/QuickFacts_L-40.pdf

Maybe that's one of the things that make B&C's sell at a premium?

 

[rv6ejguy]

Having worked on ND alternators for nearly 25 years, brush wearout causes about 95% of ND "failures". GMC is right, change these every few years are you are very unlikely to have a problem and this is a 10 minute job on most models. On the auto conversions, we use a 4 inch pulley to slow the rotor speed way down as it is just a waste of bearing, brush and slip ring wear turning these too fast. The typical 70A model we spec puts out 20A at only 1000 rpm rotor speed and will jam out over 60A at only 3000 rpm.

Our studies with an infrared thermo gun indicate that the body and rectifier pack can get pretty warm without cooling air at high amperage rates. If you are using these hard, either have a fan setup or a blast tube aimed at it. 50 SCFM airflow through the body lowers temps up to 35C in some cases. Without it, we have seen temps up to 76C which can't be good for anything.

Brush jump is not an issue with these and even half length brushes as they typically turn over 20,000 rpm in auto use on some engines at redline and outputs scope just fine.

 

[gmcjetpilot]

That is some writing

I thought I saw a reference somewhere that B&C disassembles the new alternators they get and balance them as part of making them suitable for AC use.

If true, you can't argue that a balanced rotor would run more smoothly and thus avoid "chatter" of the brushes at higher rpm's. That should also add more time to the life of the brushes as well.

http://www.bandcspecialty.com/QuickFacts_L-40.pdf

Maybe that's one of the things that make B&C's sell at a premium?

First: they (B&C) says they "balance for good bearing and bracket life"?
(no mention of brushes)

Second: the rotor is spinning on sealed precision bearings and the brushes are mounted to the case. I don't think there is any eccentric stuff going on; no I am sure of it. Mechanically the shaft that the brushes ride on are not wobbling, balance or not. This is part of the basic design of the alternator on stock ND alternators. Extra balance can't hurt.

Third: The alternator is bolted to a Lycoming doing some wild vibrations, so this may be a bigger factor than anything?

Fourth: They talk about balance 5 times and precision or precise another 3 times in, their sales brochure. It claims that they balance to their "exacting precision tolerance", "computerised two-plane precision balancing.....requires a trained operator and represents additional overhead", "leads to better service life". I just have to say, how much better service life? Brushes wear, balance or not balanced. Is it another 100 hours of brush life.? Frankly their sales brochure is full of fluffy and sensational emotional Blah Blaaa that is not befitting a technical sales brochure. It is long on flowery words and short on fact. WITH THAT SAID, I think that they sell and support a nice product, but the balance thing is one step above the gold anodize job they do to the case in regards to VALUE added in my opinion.

Fifth: Their brochure says the "automotive internal regulator has no OV protection". It is just a faults hood.
http://www.transpo.de/Catalog/Images/IN252.jpg
http://www.transpo.de/catalog/spec_d/IN227.gif
(notice last item, item 11)

The auto industry has steadily increased the amount of electrical power their alternator's produce per pound. They are past 10 amps / pound! Back in the day it was like 2-3 amps / lb. One of the INOVATIONS, was better windings and high RPMS. The Generators of 60's would explode at the 9-10 thousand RPM's, that we turn our alterantors routinely. Do you think the manufactures have not already figured out how to balance an alternator and make them last? My last 3 stock ND alternators on my cars go about 180,000 to 1/4 million miles with no problem. No doubt B&C does a better job and it must help a little.

Also with a B&C the cost of 3 times regular stock ND alterantors, don't you thing it is cheaper to replace the brushes every 500 hours? I honestly don't think the B&C alterantors have significantly longer brush life, but I am ready to be dazzled and convinced that a B&C set up is worth almost ($800) $637 corrected. Who knows, I have two kidneys, may be I can sell one and buy a B&C.

Take Care George

 

[rv8ch]

Cuba

At 800 hours TT (and over Cuba) the Denso alternator on my 6a failed....

That's very interesting. What kind of hoops do you have to jump through to overfly Cuba? What's their ATC like? (sorry to hijack this thread)

 

[zilik]

When you title said FAILURE, you got my attention, since I have two of them. After reading it sounds like you just wore your brushes down? and it just stopped making power while you where flying after 800TT of service. IS THAT CORRECT?

The alternator would work fine at idle putting out 14+ volts (sorry no amp gauge). At 2400 RPM system voltage would drop. Cycling the alternator on/off only confermed it was not outputting anything. Playing with engine RPM I could sometimes get the alternator back online. While in the Caymans I pulled the cowl, checked all connections and crimps but could find nothing wrong.

Upon leaving Cross City FL. the alternator would no longer output any noticable voltage and since it was a long way to Denver we decieded to stop in Dothan Alabama to pick up a new (cheapo autostore rebuilt) alternator. There was no autoparts store that could cross refernce the number. I went to a alternator repair and he told me my particular alternator was installed on Kabota's and other such small tractors. We went to the kabota and Ford store and low and behold found a new one for 400+ bucks. I passed and went back to the alternator rebuilder. It bench check fine, but at low rpm. BTW, the alternator becomes almost to hot to touch when outputing full amperage at low RPM. I do not know what RPM but much slower than my lycoming spins it. Upon dissasembaly the brushes looked fine, but the contacts on the armature (?) did not look so good. I chose to have the complete guts replaced with new, leaving only the case and field windings original. So far after another 100 hours the rebuilt seems to be doing well.

RPM:
The Niagara alternators come with a 2.5" pulley. If you have the Large Lycoming Flywheel pulley (9.75" verses 7.5" diameter), you have a ratio = 9.75/2.5 = 3.9. At engine RPM = 2,500 the alternator is at 9750 rpm.

I have the 7.5" dia flywheel so my ratio is 3 to 1, which puts me at 7,500 rpm at the alternator in cruise (2,500 rpm engine). So a ratio of RPMs means I might last 30% longer or 1040 hours, Yipeee. Wow 240 more hours. You could change the alternator pulley to a 2.8" one, but its easier to just replace the brushes every few years or 500 hours.

I have the smaller lycoming flywheel pulley and standard 2.5" Denso pully.

What was "rebuilt"? (what was done)

See above text

What is the part number on the alternator?

It's on the plane and not handy so I don't know. It is a Niagra 40 amp unit.

What was the indication or symptom that indicated the problem?

See above text

What did the Sweet Home Alabama alternator rebuild cost you ?

Steep, as I recall, I could have bought a new Denso from Niagra for a little more.

If the brushes where bad why did you "rebuild" it and not jsut replace the brushes?

See above text

Gary

 

[gmcjetpilot]

Yes and Yes and Bummer

The alternator would work fine at idle putting out 14+ volts (sorry no amp gauge). At 2400 RPM system voltage would drop. Cycling the alternator on/off only confirmed it was not outputting anything. Playing with engine RPM I could sometimes get the alternator back online. While in the Caymans I pulled the cowl, checked all connections and crimps but could find nothing wrong.

If I may say so you did everything right and what else could you do, really.

Upon leaving Cross City FL. the alternator would no longer output any noticeable voltage and since it was a long way to Denver we decided to stop in Dothan Alabama to pick up a new (cheapo autostore rebuilt) alternator. There was no autoparts store that could cross reference the number. I went to a alternator repair and he told me my particular alternator was installed on Kabota's and other such small tractors. We went to the kabota and Ford store and low and behold found a new one for 400+ bucks. I passed and went back to the alternator rebuilder. It bench check fine, but at low rpm. BTW, the alternator becomes almost to hot to touch when outputing full amperage at low RPM. I do not know what RPM but much slower than my lycoming spins it. Upon dissasembaly the brushes looked fine, but the contacts on the armature (?) did not look so good. I chose to have the complete guts replaced with new, leaving only the case and field windings original. So far after another 100 hours the rebuilt seems to be doing well.

Well Bummer. It sounds again like you where in between a rock and Alabama (no offense, love Alabama). So you eye balled the slip rings and they where worn. Look I concur that you will not find the Niagara at an autostore. It comes off a Ishikawajima General engine (for tractors/folklifts). It is similar to Toyota folklift application and apparently a Kabota. It is an industrial application, so the car shop will not have it. BTW the alternator is available for about $140-$180 low retail/wholesale but they are a bit of a hunt. At $400 you where getting the gouged price. One time there was a sale and found a few for $100. I am sorry I did not by them when a had a chance.

I have the smaller lycoming flywheel pulley and standard 2.5" Denso pulley.

That should not be a problem, but than again it is going a whole bunch faster than ideal, but still we are talking about a few 100 hour difference, with a slower turning alternator. If you are interested in a larger pulley try these guys:
http://www.cantonracingproducts.com/alternators/alternators.html#alternator_pulleys
-OR-
http://www.powermastermotorsports.com/racing_accessories.html

It's on the plane and not handy so I don't know. It is a Niagara 40 amp unit.

I know what you have, it is the 100211-1680. 40 amp.

Steep, as I recall, I could have bought a new Denso from Niagara for a little more.

Truly a bummer, I hate that. Sometimes they charge an arm and a leg and don't do squat. The good news is it sounds like you got what you paid for, in that if they replaced all the parts you mentioned, it would cost close to the new. Since you saw the rotor slip ring/armature and it was bad than that explains the cost.

Did you get any of the old parts??? If you did and have the old parts and don't want them, I will take them and pay for shipping. I would like to send them off to a company to do some analysis. Did they replace the regulator? If they did, if it was the brushes and the slip rings why replace the regulator.

If I can think of or find out why this may have occurred, I'll get back to you, George