Rectifier regulator location help

[Hotscam]

We had two failing regulators in 300 hours.
Both just quit during cruise flight and not in extreme ambient temperatures or high engine loads.
The effect was the current reading going from -13 to + 1 Amp and back all the time in a period of a few seconds.
On the last one I installed a number of thermo strips and found the all time max (over more than one year) has been 82 degrees C. This is with all options installed and active.

The official spec says max 90 degrees C but more sensible is not to exceed 80 which it did more or less.

I made a full test setup with a car battery ; large AC transformer 22volts @30 Amps max to sumulate the real thing.
I used a car headligth as a load at the battery.

What I find on both broken regulators is that when activated the charge current is about 1 Amp and stable with no battery load. When I load the battery with the lamp the regulator charges about 13 Amps which is correct. When I remove the load the charge current starts hunting between 0 and a few amps which dies not stop until I disconnect the source power (transformer)

Installed the third one now and improved the airflow into the blow tube.
I don't like the idea of the regulator inside and await the results of others who did this.
A better regulator such as the John Deere seems like a good alternative. Anybody using it for some time now? It is easier to get and cheaper.

[cactusman]

This article is interesting - the failure rate is pretty consistent across the industry of airplanes using the 912, so much so it seems prudent to have an extra regulator in your airplane away repair kit.

http://contrails.free.fr/elec_ducati_en.php

[rgmwa]

Originally Posted by Hotscam

Installed the third one now and improved the airflow into the blow tube.

How did you improve the airflow?

[RFSchaller]

John,

You're reading my mind. I bought a John Deere regulator as a spare and will make up an install plan with standby harness --- just in case. I also have a spare fuel pump. If this keeps up I'll have to enlarge my hangar!😜

Merry Christmas!

Rich

[WingedFrog]

Originally Posted by cactuspilot

This article is interesting - the failure rate is pretty consistent across the industry of airplanes using the 912, so much so it seems prudent to have an extra regulator in your airplane away repair kit.

http://contrails.free.fr/elec_ducati_en.php

Thanks John, very enlightening indeed. Of course this is research dating back to 2003, 10 years ago. The Rotax/Ducati regulator may have evolved since then but as what we see now is still an excessive failure rate it may not have. In this context, I feel even more that the relocation of the RV-12 regulator may prove futile in the long run. Only time will tell but for those who don't want to wait, the John Deere regulator may be a good option (and one that our fellows S-SLA owners don't have).

[tomkk]

Originally Posted by WingedFrog

Thanks John, very enlightening indeed. Of course this is research dating back to 2003, 10 years ago. The Rotax/Ducati regulator may have evolved since then but as what we see now is still an excessive failure rate it may not have. In this context, I feel even more that the relocation of the RV-12 regulator may prove futile in the long run. Only time will tell but for those who don't want to wait, the John Deere regulator may be a good option (and one that our fellows S-SLA owners don't have).

Which John Deere regulator? p/n AM101406?

[Dave12]

Originally Posted by rgmwa

How did you improve the airflow?

One easy thing you can do is to pull a little of the slack (if you have it) of the conduit and turn the end of it 90 degrees inside the air horn. Turn it into the airflow from the scat hose. Drill 2 tiny holes in the air horn and use a tie wrap to hold it in place. Make sure not to bend the conduit so sharply that it crimps.

[rgmwa]

Originally Posted by Dave12

One easy thing you can do is to pull a little of the slack (if you have it) of the conduit and turn the end of it 90 degrees inside the air horn. Turn it into the airflow from the scat hose. Drill 2 tiny holes in the air horn and use a tie wrap to hold it in place. Make sure not to bend the conduit so sharply that it crimps.

Presumably the whole duct is pressurised in flight by ram air, so the orientation of the end of the conduit shouldn't make much difference to the amount of air flowing to the regulator. On the other hand, if there was some kind of secondary venturi effect generated at the right-angle junction of the small conduit with the much larger main duct, that might inhibit the flow of air into the conduit, so your idea may be worth trying. Can't see that it would do any harm anyway. As Groucho Marx said (more or less), "It's only a theory. If you don't like it, I've got plenty more".

[WingedFrog]

Originally Posted by Dave12

One easy thing you can do is to pull a little of the slack (if you have it) of the conduit and turn the end of it 90 degrees inside the air horn. Turn it into the airflow from the scat hose. Drill 2 tiny holes in the air horn and use a tie wrap to hold it in place. Make sure not to bend the conduit so sharply that it crimps.

This way of scooping the air from the conduit would likely improve the air flow to the regulator. I am concerned that you would intercept a significant part of the air cooling the cylinder fins. My preferred solution is to do the same thing after relocating the blast tube pick-up to the larger cooling conduit going to the coolant radiator. From the air stream I receive through the heater vent, there seems to be plenty of air flow available there. This would require minor surgery on the fiberglass conduit and also an easy way to disconnect the tube when removing the lower cowl. I think it is the best option at this point to keep cooling the regulator with forced air as the research studies listed earlier have recommended.

[rgmwa]

Originally Posted by WingedFrog

This way of scooping the air from the conduit would likely improve the air flow to the regulator. I am concerned that you would intercept a significant part of the air cooling the cylinder fins. My preferred solution is to do the same thing after relocating the blast tube pick-up to the larger cooling conduit going to the coolant radiator. From the air stream I receive through the heater vent, there seems to be plenty of air flow available there. This would require minor surgery on the fiberglass conduit and also an easy way to disconnect the tube when removing the lower cowl. I think it is the best option at this point to keep cooling the regulator with forced air as the research studies listed earlier have recommended.

I wondered about that option too. However the air in the duct flows past the oil cooler and runs up against the coolant radiator, so I imagine that the air in at least parts of the duct could get quite warm, which is not what you want for air going to the regulator. At least the air coming from the engine shroud inlet should be cool. Perhaps the best option would be to graft a fibreglass stub onto the side of the shroud inlet at an angle that would direct air smoothly into the conduit. Shouldn't be too difficult.