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Main Alt and Spline Alt Alternative?

BMC_Dave

Well Known Member
After realizing I didn't need to spend exorbitant sums of money on an "aircraft" alternator, I'm wondering if there are any spline alternatives? I think the spline might just be aircraft specific so I'm probably SOL, thought I'd ask though.

Here's what I'm eyeing for my main: https://www.oreillyauto.com/detail/...ernator-remanufactured/r110911a/4602545?pos=2, though I'll have to do some surgery to switch to external regulation.

Backup will be on the accessory pad and will probably cost me $$$.

I will be buying the premium external primary and standby regulators, while I could roll my own for the effort those seem like a good value.
 
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There are automotive options that are 50 amps, CC rotation and externally regulated. I forget the lester number, but have posted it in the past.

Is was going to try machining a spline adapter, but it seemed like a lot of work and ultimately skipped the second alternator.

Larry
 
Rotation direction doesn't matter with virtually all current alternators; the internal fan will still cool it and the electrons don't care.

Many of the alternators for newer vehicles are set up for external regulation (the car's CPU handles that, along with door locks and toilet flushes).

Having said that, the external reg mod is typically fairly easy if you're handy with a soldering iron, but be aware that if it ain't broke...it might be after modding.

Having said *that*, I'm not enough of a machinist to do the spline drive adaptation. If you look at a spline drive alt, the entire front of the case is replaced with a casting that includes the bearing assy & nose to bolt on the engine. Perhaps one could make a pulley adapter for the spline drive, then use a belt to drive an unmodified alt (meaning you could get full output instead of compromised output), but failure after either attempt could put metal in the engine. (Ask Continental owners about gear drive starters.)

For me, doing rolling my own spline alt would be like floating sheet rock or installing blown-in insulation. :)

Charlie
 
Yeah that's what I figured, thanks for the confirmation. The pulley conversion sounds like an interesting project when I have more time.

If anyone has a P/N for a 60A+ auto alternator that's externally regulated I'd appreciate the advice.
 
So I cam across a matronics post that suggests modifying an IR ND alternator makes it incompatible with the B&C LR3 regulator, positive switching vs. ground switching. Is this the case?

http://www.matronics.com/forums/viewtopic.php?p=44331&sid=ce7f819de21fd1eafef16d81dfb9931e

As much as I'd like to have a drop in replacement I can easily source I'm leaning toward modifying an ND since that's what the "aircraft" alts are and they seem to have better reliability.
 
So I cam across a matronics post that suggests modifying an IR ND alternator makes it incompatible with the B&C LR3 regulator, positive switching vs. ground switching. Is this the case?

http://www.matronics.com/forums/viewtopic.php?p=44331&sid=ce7f819de21fd1eafef16d81dfb9931e

As much as I'd like to have a drop in replacement I can easily source I'm leaning toward modifying an ND since that's what the "aircraft" alts are and they seem to have better reliability.

Externally regulated alternators are pretty standard; they all use the same field polarity scheme (can't remember if it's neg or pos, but think it is POS). Internally regulated alternators are not standard (irrelevant to a stanadard installation, but relevant to a conversion process to externally regulated). The US manufacturers use one polarity and the Asian's use the other. However, when you do your surgery to make it external, you can make it whatever polarity you want it to be. However, the process is different for each polarity type and you'll need some guidance to properly wire it. The internal VR modules do not have polarity markings, so you have to figure it out by understanding the polarity of the other components it is wired to.

Do you really need 60 amps? Buying an OTS 50 amp externally regulated unit offers not only ease of installation, it allows you to easily swap the ALT away from home if it fails. They are $40 and available at any autozone.

Larry
 
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Larry makes good points, but since you seem to have my aversion to needlessly expensive stuff, there are alternatives.

If I were bound to the vac pad for the 2nd alt, I'd consider using B&C hardware justified by the 'floating sheet rock' metaphor. For the primary, I've used internally regulated versions for a couple of decades. The only real downside is lack of positive control. You can achieve that with one high current relay and an overvoltage protection module. Nuckolls used to detail that technique in 'the book', but pilots were 'testing' the function in flight with the alternator loaded down, and early IR alternator regulators would die when the load was 'dumped'. The solution for that is the He Haw principle: If it hurts when you do that, DON'T DO THAT. You can find the circuit for IR alternator OV protection by looking at the drawings that show the permanent magnet alternators. The 'B lead' from the PM alt's regulator feeds through a relay, and the OV module trips the circuit breaker that supplies coil voltage. So with the complication of one relay, you get $600 functionality for $60.

Charlie
 
Great info on alternator regulation, thanks Larry. My only aversion to going cheap externally regulated is that ND alts seem to have a good reliability history. I found this one: https://www.oreillyauto.com/detail/...ernator-remanufactured/r111273a/4602876?pos=0 which is a Hitachi rebuild, 60A externally regulated. If I were to be less conservative on my cruise loads I could just make 50A work if the alt you're referencing is a better quality.

Charlie: By saying "early IR" do you mean it's not as much an issue anymore? I would want a way to periodically test the function of the secondary alt without hurting the primary. After much research it sounds like the main failure of alternators is the internal regulator, hence my wanting to get away from it.
 
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If weight (or space) is a big concern, I'd weigh that alt you just linked. Hard to tell by just looking at the pic, but it appears to be a rather old model & could be 2-5 lbs heavier and a bigger frame than some of the more recent alts. Also, the external fan can bite you (or at least your cowl) if space is tight. Ask me how I know. :)

When I said 'earlier' it did imply that newer offerings were more robust when it comes to load dump. And most probably are; there are numerous engineering documents describing new regulators that are specifically designed for load dump immunity. Problem is, most of us homebuilders don't have access to the detailed mfgr specs that would tell us about a particular alternator. That goes triple for something that's rebuilt or overhauled; we can't know what the rebuilder stuck in the back.

The trick for avoiding load dump is to not do it with the alternator heavily loaded. Not hard, if you wait a few minutes after startup to test, to let the battery recover, and keep the high current stuff off while you test. Another (but more convoluted) trick is to have a way of monitoring both without turning one on/off, but that would require some fat Schottky diodes in the B lead paths, with voltage monitoring ahead of the diodes.

Charlie
 
Good points Charlie. Been looking for examples like you said, I think this is similar to what you suggested: https://www.bandc.aero/pdfs/505-500_rev_j.pdf

Minus the capacitor. I imagine I'd need a larger capacity relay, 60A for a 60A alt maybe, if they make those. Maybe a schematic of this with a IR alt is somewhere out there?
 
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Email me at [email protected] & I'll send you the old AEC pdf showing the circuit, and the parts list/schematic pdf for the OV module.

Troll ebay & Amazon for 12V automotive relays (the cube shaped ones that are everywhere in modern cars) You can get them up to around 100 amps. Be aware that the larger ones use bigger Faston terminals than the 'standard' 1/4". Or you can just use a regular master solenoid, but it'll be a lot heavier & consume more holding current.
 
Great info on alternator regulation, thanks Larry. My only aversion to going cheap externally regulated is that ND alts seem to have a good reliability history. I found this one: https://www.oreillyauto.com/detail/...ernator-remanufactured/r111273a/4602876?pos=0 which is a Hitachi rebuild, 60A externally regulated. If I were to be less conservative on my cruise loads I could just make 50A work if the alt you're referencing is a better quality.

Charlie: By saying "early IR" do you mean it's not as much an issue anymore? I would want a way to periodically test the function of the secondary alt without hurting the primary. After much research it sounds like the main failure of alternators is the internal regulator, hence my wanting to get away from it.

The alternator I used (from an 80's Honda spec) is an ND, so good quality. The "cheap part" comes from the rebuild. However, most rebuilds on externally regulated alternators only include a shaft polish, bearings and brushes; So not a big impact by going cheap. I think they just toss em if the stator or armature has problmes. Mine has worked faithfully for 600 hours. The big issue with "cheap" is the internal VR's, which are the most common cause of alternator failures, excluding the plane power which has many other flaws.
 
The alternator I used (from an 80's Honda spec) is an ND, so good quality. The "cheap part" comes from the rebuild. However, most rebuilds on externally regulated alternators only include a shaft polish, bearings and brushes; So not a big impact by going cheap. I think they just toss em if the stator or armature has problmes. Mine has worked faithfully for 600 hours. The big issue with "cheap" is the internal VR's, which are the most common cause of alternator failures, excluding the plane power which has many other flaws.

Might you have a part number or link, the Lester was made by Remy and didn?t look like a ND.
 
Might you have a part number or link, the Lester was made by Remy and didn’t look like a ND.

I used the Lester# 14158. The lester number is a 5 digit number used by the aftermarket for identifying alternator configurations; It does not denote an alt manufactured by Lester. The 14158 is an old style ND alternator, producing 50 amps and externally regulated. In my research, I could not find anything with greater output that fit in that early generation ND case size. You went up in physical size with more capacity. I am sure modern alternators produce more power in a smaller case, but I didn't realize there was a trend back to ER and assumed they were all IR and didn't want to modify.

I prefer using an alternator with the proper fan orientation, as it does make a diffeerence with external fans. Charlie may be right about internal fans, but with the externals it makes a difference. How much I don't know.

Larry
 
Ah, thanks Larry.

So I found this: http://www.aeroelectric.com/articles/Alternators/One-Wire_Alternator_Conversion.pdf

And that seems really easy, if I understand correctly. The only part that isn't clear is the re-wiring of the regulator. From looking at alternator schematics it really seems we're just tying one brush to the case+ground and the other brush to the field terminal right? The author says this works fine with a regular VR166 regulator. I can't determine if this method results in a positive or negative field polarity, but if I can get by with just a VR166 I'd be happy.
 
Ah, thanks Larry.

So I found this: http://www.aeroelectric.com/articles/Alternators/One-Wire_Alternator_Conversion.pdf

And that seems really easy, if I understand correctly. The only part that isn't clear is the re-wiring of the regulator. From looking at alternator schematics it really seems we're just tying one brush to the case+ground and the other brush to the field terminal right? The author says this works fine with a regular VR166 regulator. I can't determine if this method results in a positive or negative field polarity, but if I can get by with just a VR166 I'd be happy.

You need to know which brush is negative and which is positive. As I mentioned, some alternator's internal regulators feed POS and others feed NEG. You need to either know which style is used or be able to tell from looking at the alternator layout. You CANNOT assume that the feed from the VR to the brush is one or the other, as they are not standard.

If I remember correctly, if one brush is tied to the frame, you can assume the VR is feeding positive. However, if the VR feeds NEG, it becomes very difficult to determine polarity without knowing the pinouts of the VR, unless you find one brush tied to the B lead. If memory serves correctly, the ND's use a NEG VR feed.

You can probably assume all ND's are the same and therefore follow someone's instructions for that type of alternator, but not instructions for a different manufacturers alternator, unless you confirm it uses the same VR polarity scheme.


Larry
 
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Right on. I went ahead and picked up a ND IR alt and have started on the external regulator mod per the instructions. Going this route it looks like I can get down to a single B&C spline alt and 2 OV modules. Heck of a lot better than spending $2.5k+ on a whole package :D
 
Well that worked out well :D Tested the alternator with a jump starter, figured it was designed to be loaded and recharged, and a drill. Super sophisticated setup as you can clearly see. VR166 voltage regulator from O'Reilly's. I could feel the alternator kick on when it got up to speed, but my drill could just barely get there. I did end up re-soldering the bypass contacts for a better connection.

I am curious though, testing the alternator diodes I get 0.477V drop. Can anyone confirm this is good for alternator diodes? I can't find any information on what the ideal value should be.

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Depends on the array design & where you're measuring. It's not just one diode. If it's a new alternator, it's very unlikely you have a problem.

https://www.google.com/search?q=alternator+diode+array+diagram&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjO4u3j8fXfAhVO11kKHbaLDEsQ_AUIDigB&biw=1680&bih=946

Charlie

Oh yeah I don't think there's an issue. I was directly measuring each diode and they were all the same. I was just wondering what the normal value should be, a cursory Google couldn't even identify the type of diodes used.
 
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