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  #81  
Old 10-29-2019, 08:26 PM
WingsOnWheels WingsOnWheels is offline
 
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I have a crowbar OV module on my internally regulated auto alternator as well. The alternator B lead is connected to the buss via an 80amp contactor. The contactor coil is powered from the main buss using what would normally be the field breaker. The crow bar connects the breaker to ground. If a OV occurs, the crowbar trips the breaker and disconnects the alternator from the buss. The current flyback would likely kill the internal regulator, but it must have had a fault anyway to cause the OV.
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  #82  
Old 11-02-2019, 08:02 PM
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gmcjetpilot gmcjetpilot is offline
 
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Quote:
Originally Posted by dave4754 View Post
A friend here had a surge go through his Cessna Skymaster and $40K later he restored the panel to service. One needs good protection.Dave
Scary. $40K. Nice panel. What did he blow? I ask because most modern avionics runs on 10 to 30 volts and they have their own OV protection. Old school avionics were virtually unprotected... power went right in the board where the semiconductor had low voltage ratings (capacitors, transistors, diodes, IC's). Avionics have improved from the "classic" stuff.

Quote:
Originally Posted by WingsOnWheels View Post
I have a crowbar OV module on my internally regulated auto alternator as well. The alternator B lead is connected to the buss via an 80amp contactor. The contactor coil is powered from the main buss using what would normally be the field breaker. The crow bar connects the breaker to ground. If a OV occurs, the crowbar trips the breaker and disconnects the alternator from the buss. The current flyback would likely kill the internal regulator, but it must have had a fault anyway to cause the OV.
That's how I did it, but my Alternator is only 40 amps and run a 50 Amp CB. The max draw of the plane night is no more than 25-30 amps (LED's are amazing). With that said I have a OV relay on the Aux bus as well to isolate the electronic ignition and run from Aux battery only.
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Last edited by gmcjetpilot : 11-02-2019 at 08:07 PM.
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  #83  
Old 11-02-2019, 09:52 PM
gasman gasman is offline
 
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Quote:
Originally Posted by Paul 5r4 View Post
From the information I have, primarily the alternator spec sheet I ran the numbers regarding alternator pulley size & rpm and alternator amp outputs at each. These numbers are based on my 55 Amp alt.

1. With engine RPM at 800 and a 2.75 inch alternator pulley, the alternator revolutions are about 2837. The alternator is putting out close to 40 A.

2. With engine RPM at 2400 and a 2.75 inch alternator pulley, the alternator revolutions are about 8507. The alternator is putting out 55 A.

3. With engine RPMs at 800 and a 4 inch alternator pulley, the alternator revolutions would be 1950. The alternator would be putting out about 31 A.

4. With engine RPM at 2400 and a 4 inch alternator pulley, the alternator revolutions would be 6685. The alternator would be putting out 55 A.

Sooo, if one goes to a 4" alt pulley, at close to idle power/landing phase of flight, the alternator outputs would be in my case about half. Like I've mentioned, I'm VFR only so not an issue for me. If you are IFR coming in through the clouds and have low engine/alt rpms on final approach make sure your full current demands can be met with the larger alt pulley. Yesterday when I taxied out after replacing the alternator, (old one was 60 amps), at idle power I turned everything switch in the cockpit on to see if it could handle it which it did. I know a couple years ago it would not have because I had high current draw lights. Now I'm nothing but LED's and they take almost nothing!

EDITED: I am a numbers kind of guy and can't help thinking of weird stuff sometimes. It makes perfect sense that the life of an alternator with a 2.75 pulley would be shorter. The "extra" rpms in a one hour flight are something like 109320! And for one hundred hours of flight time the extra alternator rpm are in the neighborhood of 10,932,000!!!
I figured the alternator I just removed having lived a 475 hour life turned about 237,000,000 RPM's over its life. I know useless information but interesting.
Best understood as revolutions over it's life.
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  #84  
Old 11-16-2019, 08:30 AM
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gmcjetpilot gmcjetpilot is offline
 
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Quote:
Originally Posted by gasman View Post
Best understood as revolutions over it's life.
Good point, but these auto alternators are able to run up to 9000 rpm all day, but logic would say it will live longer at 6000 RPM. With that said how many ND or ND clone alternators die because of bearing failure? On the pro side, higher RPM makes more power and more cooling air.

If you use a small diameter Lyc ring gear pulley, there are different diameters, and a large 4" alternator pulley, at lower engine RPM's (approach) your alternator will have below rated output. Is that a big deal? Not really if your alternator is making enough power even below full rated output.

With all the state of art avionics and LED lights most RV's have lower electrical system demand than in the past. However I don't underestimate builders to load the plane with electric heated seats or other high draw items.
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Last edited by gmcjetpilot : 11-16-2019 at 08:33 AM.
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  #85  
Old 11-16-2019, 08:41 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by gmcjetpilot View Post
Good point, but these auto alternators are able to run up to 9000 rpm all day, but logic would say it will live longer at 6000 RPM. With that said how many ND or ND clone alternators die because of bearing failure? On the pro side, higher RPM makes more power and more cooling air.

If you use a small diameter Lyc ring gear pulley, there are different diameters, and a large 4" alternator pulley, at lower engine RPM's (approach) your alternator will have below rated output. Is that a big deal? Not really if your alternator is making enough power even below full rated output.
Apparently quite a number of clone alternators do suffer premature bearing failure as a result of installing **** bearings during manufacture or rebuild.

From looking at test charts, your average ND alternator will produce about half its rated amperage at around 2000 rotor rpm. If we assume 1300 rpm on final and even a 2 to 1 pulley ratio, that means your 60 amp model can still jam out over 30 amps which is probably fine for most applications.
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  #86  
Old 11-16-2019, 09:12 AM
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Quote:
Originally Posted by rv6ejguy View Post
Apparently quite a number of clone alternators do suffer premature bearing failure as a result of installing **** bearings during manufacture or rebuild.

From looking at test charts, your average ND alternator will produce about half its rated amperage at around 2000 rotor rpm. If we assume 1300 rpm on final and even a 2 to 1 pulley ratio, that means your 60 amp model can still jam out over 30 amps which is probably fine for most applications.
Not all clones are the same. I found the ones from Taiwan were better than ones for China, but that was 10 years ago.

If you can get a new ND that is best, but most of the genuine Japan made small ND's for cars are no longer in ND production. However I got a new 40 amp ND made in Japan, for a kabota tractor. It was old new stock and got it cheap. Even at 20 amps it makes enough for my needs except right after start when battery draws higher charge amps for a few seconds. So I delay turning on all the bells, whistles and lights a few seconds right after start, until the battery charge settles down.

I have a small Lyc ring gear puller now, so my alternator RPM's are lower at engine idle. However I need to upgrade to a cool SDS billet ring gear pulley to fit dual SDS EI hall effect sensors.
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  #87  
Old 11-16-2019, 09:35 AM
BillL BillL is online now
 
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Default PP 60A Bearings - FYI

I have been gathering a lot of information on the PP bearings, and bearings in general for alternators. The brand of the PP bearings is NTN, but made in a TPI plant in Taiwan. TPI makes branded bearings for you if you want a Smith bearing. The plant uses Japanese bearing steels, and has a good range of greases. I believe this is one.

Speeds: NTN literature has a nomograph for bearing grease life, the limiting factor for us. Even operating at 2700 Engine/9600 alt RPM, the bearing life at rated load is in excess of 15,000 hrs. Don't worry about the speed.

The bearing loads for the PP are quite low relative to the rating.
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  #88  
Old 11-16-2019, 09:37 AM
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gmcjetpilot gmcjetpilot is offline
 
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Quote:
Originally Posted by rocketbob View Post
Here's a better device for handling OV events.
http://www.periheliondesign.com/lovm.htm
Quote:
Look at the schematics George.
I see, should have been clear. So he has two schematics.

The first is put his OV switch on the ON/OFF lead to the IR alternator. It may work fine, but don't like it. I have seen people do this, and when they "tested it", bad things happened, the least of which is they fried the internal VR that was OK before the test. Or when they turned the alternator OFF nothing happened. However others swear by the ON/OFF IGN lead working like a charm to turn the alternator OFF and ON while under load. It is not what that lead was made for however. It is to reduce parasitic drain when ignition is off and alternator is stopped. When you turn on the IGN (car) the alternator is not turning. In an emergency OV condition it may work. I just don't trust it.

The second idea is a mighty contactor (relay). I thought of that. My criticism is minor. First is weight, and second 2 amps to hold it closed (although you could use a latching contactor). If you "test it" and kill the B-lead the alternator will not love it. Will it damage it? Don't know, may be, may be not. The solution is DON'T TEST IT. It is also a single point failure, but I suppose you could reset it (if you did not kill the alternator). But if you have an OV why would you want to reset it. It will work, but the CON for me is the weight and continuous draw of the contractor. Not bad just overkill may be. I like perihelion designs and gadgets, definitely cool good ideas.

The other way is put a B-lead circuit breaker in the panel with an OV crow bar. If you get OV, the CB will trip. Forget the crow bar and pull it manually. This does not jive with the tend to go with fuses remotely mounted. The CB is re-settable, but why would you want to at that point. This is similar to the perihelion relay minus the weight and current drain. All these ideas are brute force. Is OV really that bad? How many cars have OV? How many cert airplanes with old power systems (mostly from automotive industry) have had OV (some did and argue more than modern IR alternators). OV matters more with electrically dependent ignitions we have today, but you can isolate the EI. However on the other hand as mentioned before, most glass cockpits have filtered power supplies that run on 10 to 30 volts.
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Last edited by gmcjetpilot : 11-16-2019 at 09:52 AM.
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  #89  
Old 11-16-2019, 09:56 AM
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Toobuilder Toobuilder is offline
 
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Concerning bearing life, I know of some situations where an OH unit was procured from the local auto parts emporium and opened up. The inner seal on the front bearing was missing, exposing the guts to the dust and grit. Coincidence?
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  #90  
Old 11-16-2019, 10:41 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by BillL View Post
I have been gathering a lot of information on the PP bearings, and bearings in general for alternators. The brand of the PP bearings is NTN, but made in a TPI plant in Taiwan. TPI makes branded bearings for you if you want a Smith bearing. The plant uses Japanese bearing steels, and has a good range of greases. I believe this is one.

Speeds: NTN literature has a nomograph for bearing grease life, the limiting factor for us. Even operating at 2700 Engine/9600 alt RPM, the bearing life at rated load is in excess of 15,000 hrs. Don't worry about the speed.

The bearing loads for the PP are quite low relative to the rating.
Good to know. Is the the case on current build alternators? Can you trace how far back this is the case? We have seen several reports here where bearings were on their way out in less than 100 hours. Would be nice to know where those ones were made.

For genuine Denso, you can go here and type in your zip to find a dealer close to you: http://densoautoparts.com/where-to-buy.aspx#
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 436.1 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm



Last edited by rv6ejguy : 11-16-2019 at 10:48 AM.
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