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Alternator w/ tach drive??

CoreyB

I'm New Here
As luck would have it my alternator failed 500nm from home! I guess it’s karma. I bought a velocity as a 4 seat addition to my RV4. Original builder equipped the plane with an automotive alternator with an external regulator. I also discovered that my tachometer is electrically driven by an “AC” output on the alternator itself. As I understand, it’s a lug that connects directly to the stator to prove AC electrical impulses to tachometer.

Does anyone know of a compact alternator that has an AC or Stator lug??? At this point I don’t care if it’s externally or internally regulated. Internally regulated is ideal but at this point I’m desperate! Thank you!!

Pics show the destroyed cooling fan installed then removed.
 

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Have you tried taking it to a specialty shop the rebuilds industrial alternators? Maybe they would know of an easy replacement.
Interesting tach output, never heard of that before, also must be an interesting tach that can convert the crank vs alt pulley ratios.
 
The tach is indeed interesting. The tach gauge is an old VDO gauge which I seem to remember being common on older experimentals. My intent is to change everything over to a B&C setup but am just trying to get the plane home first.
 
Using a stator A/C output as a tacho signal is common on heavy vehicles, but not so much on cars these days. VDO tachometers are generally adjustable, so you can trim the tacho to read correctly to compensate for different pulley ratios (using a hand held tacho to read true crankshaft RPM).

Long story short - Some older car alternators may already have an external connection for a stator winding for tacho connection, but most modern automotive alternators won't. The good news is, most alternators can be modified to add this connection, and then just re-trim the tacho if required.
 
From my recollection, the small case ND alternators with the three prong connection have a Stator output. These are typically for 80's vintage engines.

Larry
 
Thank you gentlemen. I’ve found an alternator from a 1973 Ford Mustang that’s similar. The case is still a bit large but hopefully I can make it work.
 
From my recollection, the small case ND alternators with the three prong connection have a Stator output. These are typically for 80's vintage engines.

Larry

No, the S terminal is 'sense', as in run a wire to near the battery to sense the actual charging voltage the battery sees. The regulator then increases voltage to counteract the voltage drop in the B+ wiring from the alternator.

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No, the S terminal is 'sense', as in run a wire to near the battery to sense the actual charging voltage the battery sees. The regulator then increases voltage to counteract the voltage drop in the B+ wiring from the alternator.

I should have been more clear. I was referring to the externally regulated ND's. They have a Stator terminal, as most externally regulators had an S terminal.

Larry
 
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