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Alternators

JDA_BTR

Well Known Member
Researching alternators. Interested in having an emergency backup bus with backup battery, and an additional backup alternator on the engine. Already reviewed the Nuckolls drawings.

The firewall forward kit comes with the 60A plane power alternator. Easy enough. But.... all the rest after that is ours to figure out. So....

Which B&C alternator is a direct bolt-on replacement to the Plane Power one?
If I tell Vans to remove the PP alternator from the firewall-fwd kit what else do I tell them to remove? What else to get from B&C instead?
Which style of alternator mounting does the IO-390 have (boss or case-bolt-on)?
Which B&C vacuum pad alternator is best for a backup? (with SB1B controller)
Will a vacuum pad alternator interfere with anything else under cowl?

Where do most people mount the SB1B controller, or the regulator for the primary alternator for that matter?

My goal is to have an IFR platform that is flyable with an alternator failure, or battery failure for a considerable time.
 
I've done something similar to what you're contemplating. This is my second build and I have followed Nuckols both times. I used Z-14 as a guide for this plane.

I kept the standard PP alternator from Van's. It's belt driven up front and is internally regulated (which is fine since it has the ability to have the field circuit disconnected from the cockpit).

I added a second alternator from B and C along with the regulator. The alternator is mounted on the vacuum pad in the rear above the right mag. I got the BC410-H 20-40 amp which clears the oil filter and also does not interfere with anything on the firewall in Van's RV-14 plans. I expect to get a nominal 30 amps at typical cruise RPM.

I used the LR3C-14 controller instead of the the standby version. If I'm going to have a second bus it might as well be active. Almost all of the Garmin instruments have a second power lead with a built in diode so that they can be connected to two isolated busses without back feeding. I use some bridge rectifiers to get dual power feeds to the 625 the com and the AP servo's. The AP servo's get a dedicated switch to kill power to them if need be.

Here are the bridge rectifiers on way overly massive heat sinks. They could probably just be mounted to the aluminum subpanel directly, but I got these for about a buck a piece at a surplus store and they look very old school.

picture-58


If you build it with two alternators and two batteries you should look at his Z-14 drawing. This allows both busses to be operating full time and can be cross fed if need be.

I mounted the regulator on the cabin side of the firewall just behind the rudder pedals and low enough to get at from underneath the panel.

The second alternator will have enough power to run everything including pitot heat. Since I have pitot heat only for inadvertent flight into icing, the emergency already exists if I need it and I should be looking to get out of it immediately.

This is the fuse panel I built.

picture-46.jpg


Note the two ATC mountable resettable circuit breakers for the alternator field circuits. Here is the back.

picture-66.jpg


Here is the location of new FF equipment required for my installation. Note, these contactors are for bus cross feed and external power. The wiring is just temporary here.

picture-7



I built a battery box under the passenger seat with a local contactor.
 
Plane power

Doing a complete Garmin panel upgrade on a friends RV7a. He bought it a couple of years ago. Has B and C alternator Along with the LC3 regulator. Probably some sort of aero electric designed electrical system. It is a well built airplane but he has been plagued with electrical problems for the 2 years he has owned it. Guess what, we're ripping out the old wiring and starting over with a Plane Power alt and a simple single buss system. Something a reasonably mechanically inclined person can understand and fly confidently at NIGHT.

G3X with back up battery.

Again, my 2 cents!
 
Power Deuce Schottky Advanced E-Bus Diode

If you want a more efficient, at 14 volts, diode set, the schottky will save space and make much less heat at a lower forward voltage drop.
 
Doing a complete Garmin panel upgrade on a friends RV7a. He bought it a couple of years ago. Has B and C alternator Along with the LC3 regulator. Probably some sort of aero electric designed electrical system. It is a well built airplane but he has been plagued with electrical problems for the 2 years he has owned it. Guess what, we're ripping out the old wiring and starting over with a Plane Power alt and a simple single buss system. Something a reasonably mechanically inclined person can understand and fly confidently at NIGHT.

G3X with back up battery.

Again, my 2 cents!

Hmmm. If he, like many of us, had been plagued by, for instance, a strong tendency to roll left, would you replace the airplane with a Cessna, as your go-to fix? I mean, what you would have started with is "probably some Van's design", so.....

Charlie
;-)
 
mismatch

This is the fuse panel I built.

picture-46.jpg


Note the two ATC mountable resettable circuit breakers for the alternator field circuits. Here is the back.

picture-66.jpg
Bob, looks good. Do you have more info on those circuit breakers? They look like they fit in a standard fuse location. BTW, I'm sure you know, but some of the fuses don't match the labeling next to them. :)
 
Yes, those fuses were staged for the photo. I didn't have all the sizes I needed so I just tossed some in.

They are a Cooper Bussman product and they are designed to fit in an ATC fuse slot.

Here are links to the data sheets for two different types I found.

http://www.cooperindustries.com/content/dam/public/bussmann/Transportation/Resources/catalog_pages/BUS_Tns_227_ATC_CB.pdf
http://www.cooperindustries.com/content/dam/public/bussmann/Transportation/Resources/catalog_pages/circuit-protection/bus-cbt-ds-series-22x-circuit-breakers.pdf
 
If you want a more efficient, at 14 volts, diode set, the schottky will save space and make much less heat at a lower forward voltage drop.

Yep, but the parts were all in my spare parts bin. No ordering, no shipping, no waiting.

They do take up way too much space, but for my purposes, the heat and voltage drop is not worth sweating over, and I like em.
 
Has B and C alternator Along with the LC3 regulator. Probably some sort of aero electric designed electrical system. It is a well built airplane but he has been plagued with electrical problems for the 2 years he has owned it.

Not sure that I would rate either the Plane Power or B and C alternators as one being better than the other. My experience with both has been positive.

As far as a well built plane goes - I've met, and in your line of work I bet you have too, many top notch plane builders who couldn't wire a light bulb - and they are usually happy to tell you so!

Sounds to me like all the blame really lies with the original builder rather than Aeroelectric or B and C. It seems he may have crafted an overly complicated electrical system in a manor beyond his skill set.

A G3X and a backup battery work fine when installed and used properly, just like a more robust system. Trade offs.
 
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Starter Contacter orientation

I just attended the SportAir class on electrical systems and the instructor advised against orienting the starter motor contactor vertically (as shown in picture below). The g-forces of aerobatics can cause the contactor to close thus engaging the starter uncommanded. He advised to mount it 90 degrees to vertical. How are others mounting their starter contactors?
picture-7
 
The g-forces of aerobatics can cause the contactor to close thus engaging the starter uncommanded. He advised to mount it 90 degrees to vertical. How are others mounting their starter contactors?

First, neither of those are starter contactors. They are both continuous duty contactors, in this case, for ground power and bus cross feed. They are not part of the kit and Van's has no responsibility for them.

Second, for what it's worth, the starter contactor supplied by Van's in the firewall forward kit mounts at about a 45? angle.

I have no knowledge about the efficacy of the SportAir workshop remark.
 
I also took the sport air workshop with Smash and found it curious that the -14 has its start/master solenoids mounted at the 45 deg. I might have to call Vans to ask their thoughts on the subject.
 

I don't agree with Bob's analysis since it is clear that he doesn't know which way the plunger of the contactor is moving relative to the vertical axis of an airplane if the brackets are mounted flush to a firewall ( In this configuration, the plunger could never be aligned with the longitudinal axis).
He also mentions looking at hundreds of T.C. aircraft...... I wonder how many of them were approved to purposely be experiencing 6+ g's during flight on a regular basis.

The contactors are mounted at 45* on the RV-14 because it is convenient for structural reasons and that then largely takes care of any possible issue as a result of pos. or neg G's.

BTW, there is nothing wrong with mounting the start contactor with the plunger vertical as long as you know which way the plunger moves, you mount it so it can only be influenced by neg. G's, and then you avoid high neg G's (likely 99.9% of all RV owners do).
 
Easy to prove or disprove. Weigh the plunger. Measure the force required to overcome spring force to close the contacts, if oriented that way. Compare.

If oriented the other way, measure the force required to open the contacts against force applied by the coil while it's active. Compare.

While I don't know this with certainty, I suspect that Bob's done that.

Charlie
 
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