Yet Another Voltage Regulator Failure

[todehnal]

Thanks Jack, Wow! You get twice the current capabilities with the Hektic. Sounds great. I do have the blast tube installed, but my concern is more with the ambient temps, and like you, I'm not excited about the new location in the cabin. I was considering a small heat shield in front of the regulator. The blast tube should provide all of the airflow that we need, if we can just reduce the radiated heat from the engine, it might work better, even with the Hektic unit. Do you recall anyone trying the heat shield idea?

Tom

[Bill_H]

Today I did a test of airflow into the liquid coolant radiator duct at idle. I taped a wooden dowel well into the duct, well to the right of the oil cooler. I had ribbon streamers on the dowel. I started the engine, ran it at 2200 rpm, and the better half videoed the dowel. There is ALL KINDS of airflow into that duct at ground idle!

So I intend to proceed with my plan as shown in the picture below.
Issues:
Not real hot about the idea of having the VR in the cabin.
Think that a scoop as shown will provide SUBSTANTIALLY more VR cooling airflow at idle (and perhaps airborne) than the current blast tube source.
I want the location to not interfere with the operation of the Bender Baffle.
I intend to use the existing blast tube, not a larger one.
The connector for the blast tube will come off of the scoop at an aft angle, not at 90 degrees.
I think relocating the regulator itself into the duct at a point forward of the Bender Baffle will have some space (and maybe support rigidity) issues. I will recheck that when I take the cowl off; it is still a possibility.
I also intend to move the oil cooler forward by 1 inch based on the already-shown-here-on-the-forum mod for that.

I'll have pics after I make this mod in late April-early May (2015.)

I had also been wondering about the heat shield idea, I may add that as well. If it is too big though it could mess up airflow in that general area under the cowl. Basically I am thinking just a small vertical piece of aluminum just to block radiant heat from the exhaust.

Comments on the plan are welcome!

[f1rocket]

Originally Posted by todehnal

Do you recall anyone trying the heat shield idea?

Tom

Go to my pictures earlier in this thread. I have a three-sided heat shield around my garden tractor voltage regulator. So far, so good on mine. (about 20 hours)

[Hotscam]

Awaiting the Sikent Hektik which is on order I installed the third Ducati today which I always carry as spare since the first one let me down at a bad location for parts.

This time I enlarged the outer cooling ribs up about 2 inched fitted with heat conductive paste and keft the blow tube where it was.
Also fitted an aluminium heat shield between exhaust pipe 4 bend and the regulator about 4 inches high and 4 inches wide.
Fitted a few thermal indicators to detect any differences.

Will keep you informed of the results

[Bill_H]

Randy is referring to THIS post in a different thread.
http://www.vansairforce.com/communit...3&postcount=62

My thought about a heat shield is much more open that this box with 1/4 inch clearance on 3 sides. I am thinkng about just a piece of 4x4 inch aluminum "blocking the view of the exhaust pipe to the regulator" probably located at the foreward edge of the base the regulator sits on.

[aerofurb]

And the UK update....

Our VR started to fail so we replaced it a couple of months back (150 hours or so total time).

Interestingly we've been trying some mods that have been appearing here (we thought of them first, honest...!).

We also used a spare Dynon OAT probe as a poor man's fire warning system by mounting next to the GPS aerial under the top cowling. This we have now relocated to use as a VR area temp monitor.

Firstly we made a simple blast screen around the VR - blanks off one side and the front. The theory here is to stop hot air from the upper levels of the coolant rad from feeding straight onto the VR.



We had cut the original blast tube at an angle to try and catch a bit of breeze sometime back. It now sports a bit of extra tube slipped inside it to bring the blast tube further into the scoop and to align it into the airflow. Its held in place with a couple of tyraps that are themselves covered by the inlet SCAT ducting.





The cowl temp probe was relocated to above the VT but that was still not an accurate monitor so it now sits behind the blast screen.



We've only managed a couple of flights since the mod. Checking on Savvy Analysis it is interesting to see the VR area temp go up to the low 50 degC (120 degF +) pre flight (8 degC ambient (46 degF)) , then come down to high 30 degC (98 degF) in flight when the ambient had dropped to below 5 degC (41 degF). The temp then increase again on the taxy in post flight.

We have simple blanking plates over the coolant and oil cooler radiators.



This year, we further blanked off the blanks (!) by taping up some of the holes.



Thanks to thoughts raised here, I am now thinking of blanking off the top couple of rows of the coolant radiator blank to restrict the airflow exiting the coolant rad above the cabin heater pick up area - the area where it can reach the VR. After that, we'll go for the feed of the main radiator ducting.

I've changed VRs on Tecnams and personally (based on the huge amounts of information on the internet from all sorts of Rotax powered machines) I don't think the VR failure rate is an RV-12 biased problem.

Some excellent info on this thread - thanks to everyone for contributing.

[todehnal]

Originally Posted by f1rocket

Go to my pictures earlier in this thread. I have a three-sided heat shield around my garden tractor voltage regulator. So far, so good on mine. (about 20 hours)

Thanks Randy. I finally fond it. Great Job!!...........Tom

[f1rocket]

Thank you Bill for providing the right link to my previous post. Too many voltage regulator threads!

[Hotscam]

Originally Posted by Bill_H

Randy is referring to THIS post in a different thread.
http://www.vansairforce.com/communit...3&postcount=62

My thought about a heat shield is much more open that this box with 1/4 inch clearance on 3 sides. I am thinkng about just a piece of 4x4 inch aluminum "blocking the view of the exhaust pipe to the regulator" probably located at the foreward edge of the base the regulator sits on.

Just what I did two days ago, but also rivited additional aluminium larger ribs on the outer two of the ducati, but these stay below the heat shield.
Fitted thermo strips on various places to get some data.
Have not been flying yet since the weather is terrible (45 knot winds). Probably this weekend

[rgmwa]

.... (with apologies to Aerofurb, Bill and others for shamelessly stealing their ideas )

As my long awaited first flight is still delayed while CASA proceeds at glacial speed to implement a fairly straightforward legislation amendment that is affecting a number of Australian builders, I thought I might as well use the downtime to try to improve the VR cooling. Nothing new or radical here, except that I decided to have two blast tubes feeding the VR cap instead of just one. Easy to do, and seemed like a good idea. I glassed a 7/8" dia tube air scoop into the shroud inlet duct and another one into the top of the radiator duct, and connected both to the VR cap. The radiator inlet tube hangs down about 3" inside the duct. Also added a heat shield (the bottom is unpainted) with heat transfer paste under both the VR and the shield. The front of the shield is angled mainly for easier access to the AN4 bolt.

Shroud scoop:


Radiator duct scoop:


Heat shield:


Assembled:


Is it necessary and will it work? I don?t know, however our summer temperatures are often up around 40C (104F), so it's worth trying. If the regulator fails, then either the modifications didn?t help, or perhaps I just had a bad regulator, or both. If it doesn?t fail, then either the system works and/or maybe I have a good regulator.