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  #21  
Old 04-30-2018, 09:40 AM
OkieDave OkieDave is offline
 
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Default

Nice setup. I'm glad it's working out well.

I previously had a Socata TB-9 Tampico that had a similar--though much less elaborate--SCAT-tube-fed shroud around the alternator, and it'd burn one out about every 300 hours. Not well-implemented--but, again, it wasn't nearly so elaborate. Yours appears to be fully enclosed to positively put the cooling air where it needs to be, then extract it effectively. I like it!
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  #22  
Old 05-01-2018, 04:30 AM
molson309 molson309 is offline
 
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Quote:
Originally Posted by Hartstoc View Post
...snip ...

The most important point in my post is that when you demand a given load from an alternator spinning at a lower RPM, much more heat is generated in the rectifier section than would be for the same alternator were it belt-driven.

...snip..
- OH
Other than from less cooling air from the built in fan, why would the rectifier section run any hotter at lower RPM?
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Last edited by molson309 : 05-01-2018 at 04:30 AM. Reason: added "from"
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  #23  
Old 05-01-2018, 10:04 AM
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chuckwn chuckwn is offline
 
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Default Alternator

Does the alternator work at idle RPM?

If you have a long ground taxi time before takeoff, will the battery be depleted and all radios go dark?
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  #24  
Old 05-02-2018, 05:41 AM
vic syracuse vic syracuse is offline
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Default Some testing I've done...

I have tested the B&C 40 amp vaccum pad alternator on my RV-10 this way to see if it would handle a realistic failure of the main alternator:

Assuming a belt breakage in flight on the main alternator, I turned off the main alternator 20 minutes from landing and turned on the standby. (yes, you can wire the regulators such that the backup alternator will come on automatically, but I have a field switch for each of them). I then landed and taxied in for fuel. After that, I restarted the engine and took off only using the backup alternator. The battery appeared to be back up to a full charge in about 20 minutes of flight. This was with the Earthx 1200 battery.

I haven't added any cooling shrouds, and I have tested this multiple times. So far, I am pretty comfortable that it will work if/when needed, and I could come home on the standby, without having to pull the prop to change a belt out in the field.

I do change the prop belt every 500 hours.

I used to have the SD-8 as a backup, but as everyone knows, it was just barely adequate and one had to carefully manage electrical loads after a primary alternator failure. Not so anymore with the 40 amp backup. It caries a full-up flight load of avionics, lights, and pitot heat.

Just my experience.

Vic
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  #25  
Old 05-18-2018, 05:32 PM
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Hartstoc Hartstoc is offline
 
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Quote:
Originally Posted by chuckwn View Post
Does the alternator work at idle RPM?

If you have a long ground taxi time before takeoff, will the battery be depleted and all radios go dark?
Sorry for the delayed response- I was pleasantly surprised that amps went positive and the low voltage indicator off at around 1,000 RPM, so once you are taxiing or in the runup area no problem.

Since starting this thread, I have completely removed the belt driven alternator and cut the pulley off of my flywheel- now installing dual lightspeed ignition and the mini-sensors, magnet ring, and all adjustment svrews are FULLY accessible with the top cowl removed. Also installing Hartzell composite CS prop, will report back on all soon.
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  #26  
Old 05-18-2018, 05:47 PM
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Hartstoc Hartstoc is offline
 
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Default Another delayed reply:

Quote:
Originally Posted by molson309 View Post
Other than from less cooling air from the built in fan, why would the rectifier section run any hotter at lower RPM?
A partially depleted battery “demands” a certain load at any given voltage . The regulator is “demanding” that the alternator maintain a certain voltage. The alternator tries really hard to satisfy these demands, but at low rpm it just cannot. Attempt to satisfy these demands at low rpms results in the generation of a lot of heat in the rectifier section, because the total work required is divided between fewer cycles. At high RPM the alternator has no problem satisfying this load demand, and the work required is divided over many more cycles. It is a little bit like an engine being “lugged” under a great load at low RPM. Things heat up quickly.

Generally speaking, the spline drive alternator turning at 1.3 x engine RPM is requiring the same total work from each revolution as the belt driven version gets to spread over 3 or 4 revolutions, so heat becomes a more critical issue. I’m very confident that my installation addresses this issue adequately, and there is no longer a pulley on MY flywheel!- Otis
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RV-7A (bought)
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  #27  
Old 05-18-2018, 06:02 PM
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Hartstoc Hartstoc is offline
 
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Default

Quote:
Originally Posted by vic syracuse View Post
I have tested the B&C 40 amp vaccum pad alternator on my RV-10 this way to see if it would handle a realistic failure of the main alternator:

Assuming a belt breakage in flight on the main alternator, I turned off the main alternator 20 minutes from landing and turned on the standby. (yes, you can wire the regulators such that the backup alternator will come on automatically, but I have a field switch for each of them). I then landed and taxied in for fuel. After that, I restarted the engine and took off only using the backup alternator. The battery appeared to be back up to a full charge in about 20 minutes of flight. This was with the Earthx 1200 battery.

I haven't added any cooling shrouds, and I have tested this multiple times. So far, I am pretty comfortable that it will work if/when needed, and I could come home on the standby, without having to pull the prop to change a belt out in the field.

I do change the prop belt every 500 hours.

I used to have the SD-8 as a backup, but as everyone knows, it was just barely adequate and one had to carefully manage electrical loads after a primary alternator failure. Not so anymore with the 40 amp backup. It caries a full-up flight load of avionics, lights, and pitot heat.

Just my experience.

Vic
Vic- Yes, I’d feel comfortable with your setup as a backup(though I think the actual max output of that unit on the spline drive is well below 30Amps). My goal was a bit different- to delete the belt driven alternator compleletly, so I needed the comfort of a broader margin, especially since my bird will soon be “electron dependent”. The BC462, capable of an honest 40+ amps true output on the spline drive, my nominal 23Amp max continuous operating load, and the positive cooling I’ve provided, all coupled with B&C’s legendary reliability, together provide me with that margin of comfort.- Otis
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-2018 VAF donation!!-
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  #28  
Old 05-19-2018, 06:24 AM
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Bob Martin Bob Martin is offline
 
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Default Great

Otis,
Great write up and photos....
Nice craftsmanship as well.
Well thought out and follow thru.
This is what experimental is all about.
Thinking this might make a good article in Kitplanes....
Thanks for sharing.
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  #29  
Old 05-19-2018, 09:20 PM
BlndRvtr BlndRvtr is offline
 
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Otis, what engine is this alternator mounted on? I am also considering going all electric and using a B&C spline drive alternator on my IO-360-B1E.
Concerned about overcrowding with mags and spin on oil filter.

George
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  #30  
Old 05-20-2018, 08:42 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by Hartstoc View Post
Attempt to satisfy these demands at low rpms results in the generation of a lot of heat in the rectifier section, because the total work required is divided between fewer cycles.
Can you offer a reference to support the claim? It's a curiosity question. I suspect the answer require math, and the difference is tiny.

Moving to the practical, everything I find says rectifier power loss (heating) = forward voltage drop x current. Overall, total loss from all factors rises with RPM. Most of those losses also take the form of heat.

Good paper on alternator efficiency here; see pages 16 through 28:

http://www.delcoremy.com/documents/h...ite-paper.aspx

Take particular note of Fig 28.

The Bosch Automotive Handbook also offers guidance.



B&C's datasheet puts 14V output for the 462-H at 41.3 amps at 2450 engine RPM, so 15-25A is not pushing it hard. Did Nathan recommend the cooling shroud? No mention of it in the B&C literature.

The shroud appears to be a personal preference, not a requirement to make the installation a success.
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