Converting from generator to alternator

[mooniac15u]

I had the PlanePower conversion installed on my 1963 M20D a little over a year ago when the generator died.  Best money I have ever spent on my plane.  I can now run all my radios and all my lights while taxiing at big airports.

 

Jeff

[carusoam]

Is your D still on it's original legs? Or are they folding now?

Welcome aboard,

-a-

[mooniac15u]

My D was converted to retractable gear way back in the 60's.  I'm only aware of a couple left with fixed gear.

 

I actually recently had an issue with that retractable gear and ended up having to do a belly landing.  I suppose I would have been better off with the fixed gear.

[jetdriven]

My D was converted to retractable gear way back in the 60's.  I'm only aware of a couple left with fixed gear.

 

I actually recently had an issue with that retractable gear and ended up having to do a belly landing.  I suppose I would have been better off with the fixed gear.

All the fuel saved by the owners since the 1960s would not only pay for the cost of the gear up, but the entire cost of the airplane a couple times over.

[carusoam]

It was "upgraded" to electric operation?

-a-

[mooniac15u]

It was "upgraded" to electric operation?

-a-

No, it's manual (J-Bar).  That would be quite the conversion though; all the way from fixed gear to electric.  I wonder if anyone has done that with a D.

 

In my case a retraction tube broke and the right main gear wouldn't extend.

[carusoam]

That doesn't happen very often...

-a-

[captainglen]

There are pros and cons to both courses of action. Alternators are lighter but reducing weight so far forward shifts the CG aft. Alternators are more reliable but produce more electrical noise that sometimes require expensive filters. Generators produce lower voltage at lower RPM while alternators put out well at idle RPM. Generator brushes wear out fairly quick making alternators far more reliable. Although alternators can put out far more current your existing aircraft wiring will only support 50 amps so the breaker will still have to be a 50 amp breaker but older Mooney's are not known for having high electrical demand. The simple to install  kit from Aircraft Spruce lists as follows:

SAL12-70

SAL12-70 HARTZELL GENERATOR CONVERSION KIT

07-01301

$779.00

[chrixxer]

After tripping the generator breaker in flight, and with some planned avionics upgrades that might tax the old tech (and with relatively long waits for IFR release fairly common, due to the proximity of LAX)... thinking an alternator conversion may make sense (along with the Concorde battery).

How involved is it to install 70A-capable wiring and breaker? (1966 E, original windshield.)

Edited May 25, 2017 by chrixxer

[MB65E]

Should not be too expensive to install the alternator kit from Planepower. 

New front baffling rework

mounting the alternator

propeller removal and install

new belt

wiring

mounting the VR

Other airframe wiring and CBs, lights, shunts and etc.

A good shop should be able to do it in a day or two. 10-15hrs???

Great support from plane power.

Awesome upgrade!

-Matt

[steingar]

On 3/7/2013 at 5:03 PM, rockydoc said:

What is the procedure for converting my 1965 M20C from a generator to an alternator.

I must have taken my stupid pill.  I thought the procedure was to give the aircraft to the mechanic along with a big check...

[1964-M20E]

9 hours ago, chrixxer said:

After tripping the generator breaker in flight, and with some planned avionics upgrades that might tax the old tech (and with relatively long waits for IFR release fairly common, due to the proximity of LAX)... thinking an alternator conversion may make sense (along with the Concorde battery).

How involved is it to install 70A-capable wiring and breaker? (1966 E, original windshield.)

I'm not sure what you are planning but when I had my E I upgraded to the 70A plane power and left the original 50A alternator breaker.  I had late 80s early 90s vintage avionics and it worked fine never had any problems.

 

Newer avionics generally draw less current then their predecessors.

 

 

[MyNameIsNobody]

Meanwhile my generator with updated controller just keeps quietly soldiering on without any issue whatsoever...

[Gary0747]

Go Zeftronics and LED lighting check the generator brushes occasionally and you will likely never have a problem.   Paul Lowen several years ago when asked this question about alternator conversion  said "stick with the generator it is more reliable."

[MBDiagMan]

On March 7, 2013 at 4:15 PM, carusoam said:

Consider getting a modern voltage controller for the generator. Low cost, big improvement. Identical foot print.

 

Rebuilt generators are available from aircraft Spruce. Easy to install, check with your A&P for details.

 

The biggest problem of the old technology was the mechanical controller.

 

Modern controllers fix that and provide benefits such as LED information about system status. Search this site for Zeftronics controllers.

 

Alternators do provide a wider voltage vs rpm output. So if you have to ground idle for extended periods of time, the alternator may be better.

 

Best regards,

 

-a-

All true, but the biggest fundamental weakness of a generator versus an alternator is that all the current passes through the brushes in a generator.  Only the excitation current passes through the brushes in an alternator.  This makes the alternator much more reliable and long lived as well as charging well at idle speed which a generator is virtually incapable of.

[MBDiagMan]

On August 21, 2013 at 7:45 AM, mooniac15u said:

My D was converted to retractable gear way back in the 60's.  I'm only aware of a couple left with fixed gear.

 

I actually recently had an issue with that retractable gear and ended up having to do a belly landing.  I suppose I would have been better off with the fixed gear.

Well at least for that particular landing you would have been better off.

[MBDiagMan]

On May 25, 2017 at 4:33 AM, chrixxer said:

After tripping the generator breaker in flight, and with some planned avionics upgrades that might tax the old tech (and with relatively long waits for IFR release fairly common, due to the proximity of LAX)... thinking an alternator conversion may make sense (along with the Concorde battery).

How involved is it to install 70A-capable wiring and breaker? (1966 E, original windshield.)

The alternator me has been thoroughly discussed and described.  70 Amp service is a different kettle of fish however.  I fully expect that it would require some of your wiring to be replaced with heavier wire.

[carusoam]

MBD,

My alternator doesn't have enough output at taxi speeds to keep the warning light out...

My generator was still running strong after 40 years...

The system failure was its sticks and stones and springs VR...

The brushes were really long, incredibly inexpensive and easy to change out...

Trading in the generator was an easy low cost exchange at AS.

the one skill the generator had that the alternator doesn't... it can generate power when the battery is flat.  You are really having a bad day when this becomes valuable...  and taking on some physical risks becomes better than your personal safety.

drive belts for both have improved incredibly over the years.

 

you can't go wrong with either system...  Zeftronics and Concorde will improve either one! 

Best regards,

-a-

 

 

[RLCarter]

The weak link in a generator system is the controller (voltage regulator). My E had a generator at purchase, plan was new brushes and an electronic controller. The generator had a bad bearing that spun in the case making it cheaper to convert to an alternator than repair what was there. Chief Aircraft had a sale which was 50 bucks cheaper than anyone else. Front baffleing has to be modified, but I had already planed to rework it anyway. I opted to leave it at 50amps and haven't had an issue, by the way as circuit breakers age the get weaker and start tripping below their rating

[cctsurf]

If you're willing to stay with a generator, they are for sale on the used market for essentially dirt.  An excellent CB solution.  Because of the (IMHO) far better design of an alternator, I would not be willing...

A generator essentially produces whatever voltage the rpm of the engine makes it produce.  That voltage must then be limited (converting the excess voltage and therefore power as current flows -- overvoltage x amps = power dissipated in the regulator -- to heat) to not overvolt the equipment in the airplane.  Because we can control the output voltage of an alternator by controlling the voltage applied to the field, it can run much more efficiently, supply full voltage at much lower RPMs, and not produce too much voltage every time we fly our airplanes.

Thus, I'm not willing to CB myself out of an alternator.

[Gary0747]

Do generators have the need for crowbars and other gadgets to prevent the over voltage that an unregulated alternator can produce that can fry radios?  Or is a generator max voltage when connected to a battery significantly less at the rpms we spin them that overvoltage runaways are much less of a hazard?  It appears to me that I have read about many more alternator problems on this and other blogs than generator problems. Especially if you ignore the failures of the old Delco mechanical regulators which no one should still be using.   But my observations are likely anecdotal since there may be far fewer generators out there than alternators. 

[cctsurf]

1 hour ago, Gary0747 said:

But my observations are likely anecdotal since there may be far fewer generators out there than alternators. 

"Aye, there's the rub."  Most people in the 1960's and 1970's realized that the alternator was so much better than a generator that cars and airplanes were often converted just because of their advantages.  Most people won't do a $200-300 conversion to a modern regulator for their generator instead of going all the way to the alternator for a few hundred dollars more (yes it's twice, but in consideration of amu's it is small), therefore the number of generators still out there on planes is quite small.  As I mentioned, there are numerous generators sitting around in hangars because they are heavy and undesirable.  Go to the Fly Market at Oshkosh and you will see numerous generators for a few dollars a piece.

On a generator, the rpm at which it produces the nominal voltage is chosen as a compromise.  We want it to charge at a fairly low rpm, however, anything above that is going to produce an overvoltage that needs to be dissipated.  Thus if we are charging at ~1200 rpm, above that we are always producing an overvoltage...  Probably close to 24v at 2400 rpm.  A modern regulator will dissipate that, but if I consider a 5-volt overvolt at the regulator, it has to dissipate ~250 watts at 50 amps.  12 volts at 20 amps (more normal on our planes) is 240 watts, if we jump to 50 amps at 12 volts, we're running 600 watts of heat out that regulator.  Modern designs include better safety measures than the old ones did, which should be helpful in preventing overvoltages to the avionics, but I don't trust it.

The world of overvoltage protection comes mostly from the generator era... as I said, a generator is almost always running above the nominal voltage.  A decent alternator regulator includes all of these things.  However, they are much more rare in the alternator world.  Usually when an alternator fails have a blown diode or bad brushes.  Sadly, whoever wants to produce a regulator for planes must get it past the FAA before making it available to us as plane owners, which means that we are using regulators that are built to the minimum specification (just a regulator) rather than containing all of the modern amenities available in a automobile voltage regulator.

[Shep.G]

Just resurrecting this for a moment here.

Consensus still a "go" for this conversion? Got a '64 C I'm about to do a major avionics upgrade to, she's still on the old generator.

Price on this conversion is now up to $1800 via spruce

I'll already be in the vicinity wiring up EIS components.

Received warnings about cracking the case?

Edited April 29 by Shep.G

[Andy95W]

Personally, I’d keep your generator and put on a modern voltage regulator, if it doesn’t have one already.

If you really want an alternator, I’d go with a used Interav unit.  eBay or junk yards like Wentworth usually have them.  Get the alternator overhauled and use a brand new PlanePower voltage regulator.  You’ll be very happy.  @Alan Fox may have one as well.

[bcg]

Just resurrecting this for a moment here.
Consensus still a "go" for this conversion? Got a '64 C I'm about to do a major avionics upgrade to, she's still on the old generator.

Price on this conversion is now up to $1800 via spruce
I'll already be in the vicinity wiring up EIS components.
Received warnings about cracking the case?

I put one in my C last year when my generator went out. I did the work, it took me about 40 hours. I like having the generator though, it's nice to have 14.1V at idle when I'm holding for a release.

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