Yet Another Voltage Regulator Failure

[Bill_H]

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?

[WingedFrog]

Originally Posted by Bill_H

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.

[Bill_H]

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!

[WingedFrog]

Originally Posted by Bill_H

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.

[JBPILOT]

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.

[RFSchaller]

Don't you just love "EXPERIMENTAL"! I like the innovation, but I'm going to stick with the "bop 'til you drop" philosophy!😁

[Hotscam]

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.

[Loki]

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.

[todehnal]

Originally Posted by Hotscam

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

[Hotscam]

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