M20E Lower Cowl Removal / Generator Swap?

[Oliver]

Our M20E's generator has died. It's definitely not the regulator. 

Our local mechanic told me on the phone that I should check the brushes and also, if they are OK, to go ahead and remove the generator. He would then finish the job next week. Since he doesn't have much Mooney experience, I am not too comfortable about this. I looked at it today: Checking the brushes, as well as removing the generator both seem to be a major PITA.

I am therefore wondering if I shouldn't rather just drop it off at the Mooney service center (also very time consuming). 

In order to get access to the brushes or to remove the generator, it appears necessary to remove the center section of the lower cowling, with the cowl flap, the ram air, the oil cooler and the landing light in it. It also appears to be attached with quite a number of screws as wall as a brace on either side.

Our plane has an only 3 year old paint job and I am concerned that either I or our mechanic would scratch it up, when removing or reinstalling this section of the cowling.

Advice / suggestions are appreciated... 

Oliver

[carusoam]

 A whole decision tree...

1) alternators are mostly better than generators.

2) rebuilding a generator can be done at a local shop (sort of). It's probably an AC/Delco from 1965.

3) completely rebuilt ones are available from aircraft spruce.

4) if you have a Zeftronics voltage controller that less than 10 years old, that a good sign.  (Check your logs)

5) Getting a lightweight alternator with a new Zeftronics controller is like going to M20C heaven.

6) Getting a rebuilt generator to go with a relatively new Zeftronics controller was my idea of M20C heaven.

7) The coolest thing about a generator....

- it can bring a completely dead battery back to life.  (Once dead, batteries don't really come back to full life.)

- it can generate electricity without a 12V signal.  Alternators can't do this.

- starting an engine with a completely dead battery can be pretty hazardous. Nobody tries to hand prop engines that are 180hp or more, any more.  They used to, with crummy / painful results.

8) brushes are available from the same AC/Delco shop.

9) by the time you get access to the brushes, you realize how worn the surface is that the brushes run on.  Hinting at the generator OH again.

10) Once you get the generator out you realize, putting a locally OH'd one in, doesn't really make sense.  You only want to do this job once.

11) while you are in there check the hose that blows on the generator it should be connected on both ends.

12) It is a job for one person, by the time you have been through all these steps, you get so good at it, you are the expert.

13) changing out the belt requires pulling the prop.  That is a certain expertise that I will never gain.

14) the lowest cost solution is probably ordering an OH'd generator from aircraft Spruce and working with your mechanic to pull the first one, and install the new one.

15) make sure you aren't holding on to an old sticks and stones and springsoriginal type voltage controller.  They are old wreckage waiting to happen.  Have you seen any melted solder spinning from the generator?

 

How does this sound?

I used to have an M20C, this is only PP ideas, not a mechanic...

 

Best regards,

-a-

[Oliver]

@carusoam: Thank you for your response. I already went through this decision making process and consciously decided to stick with the generator in combination with a Zeftronics regulator.

[carusoam]

See my additional updates in the first response.

The Zeftronics controller also has a few LED outputs that would be helpful to have mounted on the instrument panel.

Best regards,

-a-

[Oliver]

Thanks again.

The Zeftronics controller is almost new. Besides of a number of other tests, the generator's field coil showed a resistance of over 400 Ohm - about 50 times too high!
Just replacing the entire thing sounds like a good idea.

Do you have any suggestions of what the best approach is to remove the lower cowl center section?

[RLCarter]

My E had a generator and mechanical regulator, I was going to replace the mechanical controller with the new solid state type but after finding the generator was toast I elected to go with an alternator conversion ( found one on sale for the same money ). The conversion does require more work, but it isn't that bad. Lower cowl isn't all that hard to remove, I did mine by my self would have been easier with two people.

[carusoam]

It's been several years, and my memory isn't that strong from a aging too rapidly...

the oil lines were left attached.  Everything was pretty tight in there.  An induction tube may have come out as well...

I probably had a few words added to my colorful language at the same time.  It is really helpful to have a mechanic you can work with on this...  Being outside in September isn't going to be very helpful either.  I did mine in an August when I really needed the plane to be flying.  That's what makes it so memorable!

While in ther check on the felt insulation between the generator and the cowl. It may be original.

Best regards,

-a-

 

[Oliver]

We have a hangar + a heater. 

I think I'll look at it again tomorrow and have another chat with our local mechanic. I want to make a decision whether to do it locally or to bring it to the Mooney center before Monday.

[carusoam]

It's a local mechanic friendly type of job.  But some people like the MSC level of attention for the extra level of get it rightednesss!

You have one generator and one battery, do you fly IFR in IMC with it?

More things to run up the decision tree,

-a-

[N201MKTurbo]

It has been awhile, but I think this is the process. 

Remove the four bolts holding the oil cooler in place. Remove he clamps holding the oil cooler hoses to the heat shield. Unhook the ram air cable and unbolt one side of the ram air boot. Remove the wires from the landing light. Undo the four screws holding the lower frame to the airframe. Undo the cowl flap linkages. Undo the support rods at the firewall.

You are done, nothing to it!

[Oliver]

Yes, IFR in IMC.

This is actually one of the reasons why I decided to stick with the generator + a modern regulator: I'd rather have an electrical system which is still operational with a dead battery than one which charges the battery at (slightly) lower rpm, but in which a dead battery takes everything with it.

[Oliver]

Just now, N201MKTurbo said:

It has been awhile, but I think this is the process. 

Remove the four bolts holding the oil cooler in place. Remove he clamps holding the oil cooler hoses to the heat shield. Unhook the ram air cable and unbolt one side of the ram air boot. Remove the wires from the landing light. Undo the four screws holding the lower frame to the airframe. Undo the cowl flap linkages. Undo the support rods at the firewall.

You are done, nothing to it!

Thank you. I'll look at it again tomorrow.

[N201MKTurbo]

If you tie the oil cooler to the #2 exhaust pipe with some lock wire and fish the hoses out from under the heat shield, you can remove the cowl by your self.

[jamesm]

It has been my experience  with the  zeftroinc generator controller and  delco remy generator that resistance have to match to what zeftroncs calls out. I had purchased an overhauled generator  and  it would not work the zeftronics  generator controller.  Lucky I hadn't sent my original generator back. so I sent back the overhauled generator.  When I had a generator installed. I would  have to on occasion flash the  field  of the generator. I would usually pull the generator take to  an auto  wrecking yard to put the generator   on their tester  to ensure that their was output  from the generator after that it work like a champ.  If you do decided to pull the generator to have work done on it,  just remember It spins opposite from car and the direction does matter.  I had gotten pretty good pulling the  lower cowl and generator but you right not it is not a fun job.

Hope this  helps,

James '67C

Edited September 11, 2016 by jamesm

[DXB]

1 hour ago, Oliver said:

Yes, IFR in IMC.

This is actually one of the reasons why I decided to stick with the generator + a modern regulator: I'd rather have an electrical system which is still operational with a dead battery than one which charges the battery at (slightly) lower rpm, but in which a dead battery takes everything with it.

I did not know this about my alternator. My subsequent reading tells me the statement is accurate, and I understand my alt field switch a lot better now.  These "unknown unknowns" in aviation, as Donald Rumsfeld would call them, scare me.

But what are the chances that a battery is strong enough to start the plane and then becomes too weak to power the alternator on the same flight? 

[kortopates]

1 hour ago, DXB said:

I did not know this about my alternator. My subsequent reading tells me the statement is accurate, and I understand my alt field switch a lot better now.  These "unknown unknowns" in aviation, as Donald Rumsfeld would call them, scare me.

But what are the chances that a battery is strong enough to start the plane and then becomes too weak to power the alternator on the same flight? 

Not unusual at all. You are describing a weak battery and it will be obvious by the high amperage charging load after startup. Get to know what this is normally with a good battery and don't rush to take off when you see this. if the load doesn't come down right away you are much better off shutting down and putting a charger on it. Plus you're alternator/generator will last much longer.  

Its also a huge false of sense of security flying your bird with a dead battery because you think you can get away with it with because the generator will still work. Of course the plane is still un-airworthy with a battery with less than at least 80% of its rated capacity since it will do you little good if you loose your generator or alternator.  

[Guest]

I have removed the generator without removing the lower cowl on my E model, I did have to remove the cylinder #1 exhaust pipe though.  

Clarence

[Yetti]

I think the generator is longer than the alternator..  I had to remove the Alternator to replace the starter.  It was done by loosening the front bolts of the lower cowl and letting it rest against the Prop.  With some towels on the prop to keep from scratching it.   It's a tight fit for yetti paws, but workable.   Had to reach across the other side of the engine to get the cotter pins into the bolts.  Flashlights help, being able to visualize position of bolts and holes and a feel for lining things up so the cotter pins go in goes a long way to not throwing tools across the hanger.   I also have some foceps that I use alot do pins and safety wire.

[Oliver]

8 hours ago, DXB said:

I did not know this about my alternator. My subsequent reading tells me the statement is accurate, and I understand my alt field switch a lot better now.  These "unknown unknowns" in aviation, as Donald Rumsfeld would call them, scare me.

But what are the chances that a battery is strong enough to start the plane and then becomes too weak to power the alternator on the same flight? 

Firstly, let me clarify, that I am not really concerned about the sudden death of the battery as this is pretty unlikely to happen. As it is however also not unheard of, it is certainly something to take into consideration, particularly before spending all the $$$ on a conversion. If the battery is only old and tired, the remaining capacity will still be sufficient to also keep an alternator running, one wold therefore be OK in either case.

In case of an sudden internal failure of the battery, things might however look different. If an electrode or the internal connection to the terminal breaks, either due to corrosion or mechanical stress (vibration, ham fisted mechanic over tightened the cable connection), the battery would go offline immediately. A generator would in this case keep the electrical system up. With an alternator, the entire cockpit would go dark, without any warning.

Another possibility would be a short inside the battery. In this case, the electrical system would go down, no matter whether a generator or an alternator is installed. Leaving the legalities aside, with a generator powered system it would be possible to disconnect the battery, jump start the plane from a car (we have a 12V system), and to fly home or at least to the next shop, with a functioning electrical system.

With an alternator, the battery would have to be replaced on site, no matter how inconvenient this might be.

A brief article, discussing batteries and what kills them: https://www.batterystuff.com/kb/articles/battery-articles/secret-workings-of-a-lead-acid-battery.html

Generators also produce a cleaner electrical output, as they directly generate DC, whereas alternators generate AC, which then has to be rectified.

Again, I am absolutely not opposing alternators. Weighing the costs, pros and cons, I however just did not feel that a conversion is worth it and that we are better off with a generator + a modern regulator. YMMV of course...

Edited September 11, 2016 by Oliver

[jamesm]

Don't forget to add corrosion,  aging wiring and terminal connections  as possibility of failures, especially in the field  circuit of generator/alternator you won't get output from your changing device.  So if you  have the original  60's early 70's  vintage wiring and  terminal connectors or a loose ground on the master switch  could ruin your day.  I  agree with you on the noise output of the alternator  it  is really really  dirty from a signal prospective. However  another a plus for the alternator is it is not pushing  50 amp through it's brushes  and  more chance of  arc flashing on the armature like on the generator. The alternator is about 10th of the current being passed  through it's slip rings  on the alternator  so no heavy coil wire on the armature like on a generator.   Also making alternator  about 9 lbs lighter you can get higher current output from the approved  alternator choice.

Honestly,  I  have not had to  pull my alternator  for failure reasons  since  I replaced the  generator in 2007 about 240 Hrs on it trouble free hours.

 

Just a thought,

James  '67C

[geoffb]

It's probably just brushes. I ran my brushes to failure. Univair has them, dirt cheap, something like $7.00 for the pair. Pulling cowling is a PIA, especially the first time you do it with the screws holding the intake boot to the ram air door being the worst part, followed by the adel clamp holding the ram air cable housing. Brush replacement is stupid simple once you have the generator in your hands. Inspect the commutator for wear and threading, make sure your mica is still undercut and check the bearings still good.

Or if you don't want to mess with it, or want someone to take a look, it's a standard 50A delco out of millions of old GM cars, lots of tractors, etc. Any auto electric shop can take a look.

[orionflt]

oliver,

I have the generator from my C that I removed for a alt conversion. the generator worked when removed, but I would still check the brushes if you are interested in it let me know.

Brian

[Oliver]

I managed to remove the lower cowling, as well as the generator. As stated by geoff, removing the ram air related components was the hardest part and pretty frustrating.

Anyways, it turned out that the brushes were worn, one of them to failure. The generator looked generally good, bearings ran smooth, since removing it is such a major pain, I however decided to still have it overhauled. I should have it back by tomorrow.

It turned out the the rubber duct between the throttle body and the cowling also has some holes in it, I therefore ordered a new one from Southwest Texas Aviation. Superfriendly lady, excellent service but $294, incl. 3-day shipping! Yikes! 

Thanks again for your help!

Edited September 16, 2016 by Oliver

[carusoam]

Going the OH route should refresh the surfaces that the brushes run over, and makes sure the soldered parts are still connected properly.  A little over voltage melts the solder joints...

The rubber connection has been out of production in the past.  Nice to know you were able to get a good one.

Flying is more comfortable with systems that work like they are supposed to...  

Best regards,

-a-

[geoffb]

$294 is a whole lot less than I paid for my last flex duct.  I think it was more like $400 from LASAR.  That's the biggest POS part in the entire plane.  Glad you got it out OK, you should get many, many hours out of it now.