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Yet Another Voltage Regulator Failure

That manometer pressure reading is not that simple. Take a one inch piece of the
existing blast tube and blow through it as hard as you can. Now do the same with a
2 foot piece. You won't detect a difference. R may equal Rho D V over mu and all that (I'm a M.E.)
but for the low flows we are talking about I do not think that the friction losses in the corrugated
tube are the governing factor.

Actually the pressure at the "start end" of the tube doesn't tell the whole tale. If delta-p
is the only thing driving air through the tube, then you need to look at the other end - the
ambient pressure at ground idle next to the exit point of the voltage regulator radiator fins.
That could be higher than might be thought because of the air blowing in from the prop through
the starboard inlet, as well as the air exiting the coolant radiator. That has the effect of pressurizing
The entire compartment.

I think the currently-as-designed tangential connection to the shroud is a much bigger
factor and (as you pointed out) the poor generation of airflow from the root of the prop
for a non-moving plane. Think of it - why would that air going into the shroud want to
make a right angle turn into the blast tube? Shoot, there could even be a vacuum effect there!

I was thinking about modifying the existing setup by sticking the blast tube INTO the
shroud rather than the current flush mount - either at an angle or with a 90 degree
turn so it is facing the prop. But that seemed a poorer idea than what I am showing.
If a goodly amount of air is blowing through the duct at ground idle- and I think it certainly is because
it is certainly blowing through considerable resistance of the oil cooler, then it would also
have "no choice" but to go through the scoop I show.

Thoughts?
 
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That manometer pressure reading is not that simple. Take a one inch piece of the
existing blast tube and blow through it as hard as you can. Now do the same with a
2 foot piece. You won't detect a difference. R may equal Rho D V over mu and all that (I'm a M.E.)
but for the low flows we are talking about I do not think that the friction losses in the corrugated
tube are the governing factor.

Actually the pressure at the "start end" of the tube doesn't tell the whole tale. If delta-p
is the only thing driving air through the tube, then you need to look at the other end - the
ambient pressure at ground idle next to the exit point of the voltage regulator radiator fins.
That could be higher than might be thought because of the air blowing in from the prop through
the starboard inlet, as well as the air exiting the coolant radiator. That has the effect of pressurizing
The entire compartment.

I think the currently-as-designed tangential connection to the shroud is a much bigger
factor and (as you pointed out) the poor generation of airflow from the root of the prop
for a non-moving plane. Think of it - why would that air going into the shroud want to
make a right angle turn into the blast tube? Shoot, there could even be a vacuum effect there!

I was thinking about modifying the existing setup by sticking the blast tube INTO the
shroud rather than the current flush mount - either at an angle or with a 90 degree
turn so it is facing the prop. But that seemed a poorer idea than what I am showing.
If a goodly amount of air is blowing through the duct at ground idle- and I think it certainly is because
it is certainly blowing through considerable resistance of the oil cooler, then it would also
have "no choice" but to go through the scoop I show.

Thoughts?

My home made manometer is not a very precise instrument but it will tell you if air is moving inside the tube. It's a start and its better than not knowing what's going on. Now is it enough to cool the fins? I have no idea it is why I dropped the idea of the blast tube and decided to immerse the VR into the air-stream flowing through the tunnel. I believe that VANs came to the same conclusion about the blast tube, unfortunately they did not pick the best location for the VR. :rolleyes:
 
Yes, I liked your relocation. It looks like there is enough room to do that ahead of the Bender Baffle. For really cold ambient temps when the baffle is closed, even if the air in the duct was relatively stagnant, it would be much colder than the inside-the-cabin mounting position and there will still be turbulent air there. So, another possibility... Still mulling it over!
 
Yes, I liked your relocation. It looks like there is enough room to do that ahead of the Bender Baffle. For really cold ambient temps when the baffle is closed, even if the air in the duct was relatively stagnant, it would be much colder than the inside-the-cabin mounting position and there will still be turbulent air there. So, another possibility... Still mulling it over!

I don't know much about the inner works of the Bender Baffle but I believe that if it was cut about 6" below the tunnel's top it would allow room for the regulator in the location I have selected. There is not a lot of places to put it without having to do some fiberglass work because the sandwich fastening requires a horizontal surface. As the top part of the radiator is not feeding the cockpit heater vent, note that the protruding regulator in not in the way of the air flow heating the cockpit. The impact of having a 6" shorter baffle on the effectiveness in coolant heating would have to be evaluated but hey, it's what experimental is about!
I am still mulling a more global baffle device that would serve both radiators as oil temperature is the main pita for me in cold winter days. Another good improvement VANs ought to think about for the RV-12.2... but this belongs to another thread.
 
I think - -

that in cold weather, my "Heater Damper Door" mod requires that the air duct flow needs to be reduced by 90% ( or more ) to get the CHT's up to over 200 which is what it takes to get serious warmth.

The oil therm is also required as far as I am concerned if in a colder climate. It reduces warm up a SERIOUS AMOUNT.
 
Don't you just love "EXPERIMENTAL"! I like the innovation, but I'm going to stick with the "bop 'til you drop" philosophy!😁
 
Just blew the third Ducati in 420 hours. 😡
Charge /discharge current started jumping + 3 to - 6 and voltage dropped to 11.9 Volts
The temperature strip i put on shows 85 deg C has been the max while the spec is supposed to be 90. Spaghettt regulator.
Will order a Silent Hektik.
 
Hi Hotscam,

Having a -4 to +8 amp movement is normal on many Dynon and Rotax installs because the Rotax is a noisy engine and Dynon isn't going to fix it. It is quite involved.
85c is still too hot. You need to find a new location. If a failure is temp caused it isn't the fault of the reg/rec. Move it either into the cockpit as Vans has described or just low inside the engine cowl where there is cooler air flows and it won't sit and bake after engine shut down. Where it is mounted stock up on the left side just behind the #4 exhaust isn't a good spot. My reg/rec never has seen over 140F. Most of the 50K Rotax engines don't have reg/rec problems. It seems the RV12 has far more reg/rec issues per capita than most. These types of failures are usually caused by incorrect location installations and or wiring issues and loads.

Just using a different reg/rec isn't the fix.
 
Just blew the third Ducati in 420 hours. 😡
Charge /discharge current started jumping + 3 to - 6 and voltage dropped to 11.9 Volts
The temperature strip i put on shows 85 deg C has been the max while the spec is supposed to be 90. Spaghettt regulator.
Will order a Silent Hektik.

Hey Jack, I see that you have dual SVs. Just curious. Is your regulator still in the original location? If so, that gives us a pretty good idea of the temps that the regulator sees in that location. Maybe moving it ain't an all bad idea.

Tom
 
Yes i have a dual dynon but power switch the fuelpump.
The pump is on at take off and landings at which time the second SV1000 is switched off. These consume about the same current.
Thus the total consumption is never higher than the standard.

The regulator is in the old location and I am not keen on a hot regulator above my knees inside the cabin.
The silent hektik has considerable lower losses and allows for double the current.
This will make a difference but I am aware the location is not the best.
On the other hand most Rotax installations have the ducati under the cowl without blow tube.
There is quite a history of failures and not just in RV12's.
This was the reason to to develop the Silent Hektic.
Will kerp you informed about the results
 
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
 
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!
Baffle2.JPG
 
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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
 
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.
 
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Thank you Bill for providing the right link to my previous post. Too many voltage regulator threads!
 
Randy is referring to THIS post in a different thread.
http://www.vansairforce.com/community/showpost.php?p=956223&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
 
And the Australian update

.... (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:
16420412213_9807a3e781_z_d.jpg


Radiator duct scoop:
16420411673_474344f932_z_d.jpg


Heat shield:
16420412173_6fe036e151_z_d.jpg


Assembled:
16420412243_fdc16c5dd1_z_d.jpg


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.
 
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No need to apologise - all's fair....! I'm sure we will have dual coolant pipes soon as well ;)

I modified our coolant radiator blank today (see pic above in post #66) so the only taping of the holes is now the top 4 rows.

This means the coolant rad is blanked off above the cabin heater ducting area - so no air blowing towards the VR.

VR area temp was about 20 degC less during the pre flight warm up and power checks (allowing for small OAT change).

This has dropped the air temp inside our 'extra' blast screen by around 13 degC in flight over what we had in the previous post with respect to OAT (ie for similar OAT).

I also experimented with IAS effect. It would appear that the VR area temp drops by around 1 degC per 10 kt increase in IAS. This was between 85-120 kt (4100-5000rpm) and the VR temp increased initially as the rpm was increased but dropped off quickly once the rpm had stabilised at the higher level and IAS.

Many thanks to Savvy Analysis for making all this info dissecting possible! :)
 
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