More airflow to the RV-12 Voltage Regulator - Proven!

[Bill_H]

Well, Vans clearly believes the problem to be temperature related, else why change the plans to relocate the VR to the inside of the cabin? I presume that belief is backed by evidence?

I had to replace my VR at ~120 hours. (Lots of other threads on that.) So I wanted to increase cooling without relocating it to the interior. This was a different approach than some others that have been posted. There's no question that there is more flow with the scoop - just point it at your own face!

Tony, I question that 45 minute rise to full temp as being applicable. That was on a lab bench, with fins uncovered - not next to an exhaust pipe and covered with a metal cap with just a whisper of air through it.

[Phantom30]

Originally Posted by rvbuilder2002

Well, just one persons opinion.... We never run out of those here do we...
(please keep in mind I wrote possibility. I am not saying you are wrong. I am simply saying that I don't think your test has unequivocally proven anything..... just my opinion)

The best way to verify would be using a true manometer with one port connected to the air supply hose and the other adjacent to where the regulator is mounted.
If there is a pressure differential between the two points then that will translate into a flow from the lower pressure to the higher pressure.
The higher the differential, the higher the flow.

You could "borrow" a digital manometer from your local "heating & airconditioning company and run test in actual ground and flight conditions I.e. Cowling closed. Test results would be interesting..

[rgmwa]

Bill, I'm not quite sure how you took my comment, but it was intended to be tongue in cheek. I've done something similar to you, so I'm pleased to see that the scoop works as you thought it would. Time will tell if it works for the VR. I hope it does.

[Bill_H]

It is a bit more complicated than measuring a "static pressure differential" at the start of the blast tube and at the exit of the cooling fins on the VR. (See Bernoulli...) What you are really wanting to measure is the FLOW or VELOCITY of air in the blast tube itself. A small inline rotameter or something like that would be better for exact readings.

[Dave12]

Originally Posted by Boyd Birchler

I had a similar problem on my wife's Rans S7. The Duccatti regulator/rectifier fried at about 370 hours. I replaced it with a John Deer "clone" regulator rectifier PN AM101406 that I bought on Ebay for $60 bucks.

I made a "crude" cooling tube ( made out of a piece of 3/4" hot water rated PVC pipe and formed the curves with a heat gun) which I stuck out through the right front nostril/air cooling intake and routed to blast air over the rectifier/regulator.

I do not know if it is the cooling air or the regulator I used but it is working perfectly 700 plus hours later.

The John Deer clone is 1/3rd the cost, can be purchased locally if your in a jamb while away from home. In our case it seems to be more stable on the voltage gauge.

Please check your PM's.

[WingedFrog]

Originally Posted by MMiller

I examined six failed regulators, four were from various RV-12's. None of the RV-12 failures indicate ambient overheating was the cause of the failure. Three failures were the new version regulator, Ducati # 362001. All three indicate vibration was the cause of the failure.
.....
In all six regulators, there were no failed electrical components, only failed connections. With that said, this regulator can generate a lot of heat at full output, so cooling is a good thing. Van?s likely moved the regulator into the cabin to comply with Rotax temperature requirements for the regulator.

Mike Miller

I love the "E" in Experimental! The mandatory "Experimental" marking in our RV-12s should be taken as a badge of honor!
Great job Bill for one more alternative in our collective effort to "save the regulator".
I believe that Mike zeroed in on the fundamental issue with objective observation after a remarkable investigation. As a result I decided to go a slightly different way, discussed in a previous post:
http://vieilleburette.blogspot.com/2...elocation.html
As it is not clear that any solution is superior so far but as it is also clear that the voltage regulator is poorly cooled at the initial Firewall location, my solution documented above aims at minimizing the burden of replacing the VR in case of failure during a long trip away from my home field. In my case, if the VR fails, the only tool I need to continue my trip is a Phillips screwdriver (to open the upper cowl). Of course, this assumes that you have a backup VR on board which is part of my solution. This extra cost is small compared to getting stuck somewhere waiting for a replacement.

[Bill_H]

Jean-Pierre - I would have done your exact mod except that I also wanted the Bender Baffle and there didn't seem to be room. I made that decision before I removed the cowl and made a bunch of measurements and actually found out the size and rotation of the baffle. I now think that your mod would fit forward of the baffle. But I wanted to test my scoop mod anyway!

My old regulator had just "started" to exhibit the impending fail behavior (not kicking in until the first time ~3500 was reached). So I carry it as a backup. I did open it up and looked at the CB and did not see such clear indications of a bad connection.

With the VR located forward of the baffle, and the baffle closed, there would still be a lot of VERY cold air in the duct surrounding the regulator (you don't close the baffle unless ambient is very cold!)

If I get a failure with the scoop I will move to your mod (revised). The fiberglass duct top is not very thick forward of the baffle, so I would also reinforce it with some layers around the square hole.

Your mod is also better because post-shutdown the regulator is not exposed to the hot under-the-cowl temps, with its tight cap installed.

[WingedFrog]

Bill, regarding the failed connections, they are sometimes difficult to find. I found a bad one but there were 2 more that were less visible that Mike found. I think he is right about the vibrations being the cause but I believe that the high temperatures are an aggravating factor. At some point the contact becomes intermittent before failing completely. Your regulator had not failed completely therefore it is not surprising that the failed solders are not visible. In any case I would not trust it as a back-up. Check the documentation provided by Mike in his previous posts, you should be able to locate the critical solders which correspond to the SCR leads. I would just redo these solders and check the VR again.
My point was not to claim my cooling solution is better than any other proposed including yours. I believe that with the improvements in cooling these regulators will be good for a few hundred hours. My point is whether your VR fails at 100 hours or 400, when you get there it would be nice not to end up stuck somewhere.

[Hotscam]

After blowing the third VR in about 500 hours I think I found a solution that works and is simple.
Ducati claims the max temperature is 195 F
I attached temperature measuring strips to every VR I installed and found they all indicate 180 as the max, so it blows earlier than specified but there may also be hot spots.

On the last one I riveted two additional heatsink plates on both sides combined with the blast cap rivets. Just aluminium scrap as long as the VR and 3 inch wide.
Also fitted a large aluminium screening plate about 8 inches wide and 4 inches high between the VR and close exhaust pipe, using the VR mounting bolts and some conductive paste.
After about 50 hours the temperature is max 160 F which looks like a much better margin to the 195.
Keep my fingers crossed but bought a Silent Hektik for just in case

[Handclutch]

I like the idea of the shield. A lot of heat must radiate off the exhaust, probably even more so after shut down when airflow ceases. Has anybody tried wrapping that bend with exhaust header tape as a means of insulation? I've never had any experience with it and am aware of conflicting views about whether it damages pipes, although main issue seems to be moisture retention with pipes exposed to rain (motor bikes).

Jack Moore