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Yet Another Voltage Regulator Failure

DHeal

DHeal

Well Known Member
Well, I finally joined the club. :( At 133 hours HOBBS (one year since initial flight), I went out to fly today and my alternator/generator is no longer charging (battery voltage falling through 12.3 v with -7 amps at 5,300 rpm).

Yesterday's flight was normal (13.9 volts and 1 amp as usual) and today - suddenly nothing. I haven't done any trouble-shooting yet. FYI, my RV-12 has had the cooling shroud/tube since new and I usually run everything (lights, strobes, AP, ADSB, etc.) all the time. The regulator is mounted in the engine compartment per the original plans. No weird odors or anything unusual - just no apparent charging.

And here I thought that this issue was only affecting others. HA!!

ps - Can someone point me to the email that explains how I can electrically test my voltage regulator? Thanks!
 
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It would be interesting to see what procedures are being used while on the ground at idle. Using all lights, accessories plugged in to the 12v adapter, powered headsets etc... Wonder if the heat issue is more pronounced on the ground under heavy electrical load and low RPM. longer waits for oil temp in the colder weather. Just some thinking.
 
Can someone point me to the email that explains how I can electrically test my voltage regulator? Thanks!
Click to expand...
Test the Rotax Regulator
Read Mike Miller's post (6).
If you have some way to connect a voltmeter to the regulator while you sit safely inside of the cockpit, here are some more tests to do while the engine is running:
Measure the AC voltage between the two yellow wires coming from the dynamo. It will vary with RPM. Any AC voltage means the dynamo is working.
Measure the voltage between the regulator case (not aircraft ground) and terminal "C". It should equal battery voltage. If not, there is a wiring problem.
Measure voltage between the regulator case (not aircraft ground) and terminal "B" or "R". It should be greater than 13.5 volts at 3000 engine RPM.
 
Maybe someone can clear up a question I have. Since the ROTAX generator has a permanent magnet field rotor it would seem the generator either puts out less than load at low RPM or higher than load at high RPM as opposed to a regulated field that matches output to load. Our regulators as I understand it dissipate the extra output at high RPM as heat. If that understanding is correct then doesn't a high load result in less heating of the regulator?
 
DHeal said:
Well, I finally joined the club. :( At 133 hours HOBBS (one year since initial flight), I went out to fly today and my alternator/generator is no longer charging (battery voltage falling through 12.3 v with -7 amps at 5,300 rpm).


And here I thought that this issue was only affecting others. HA!!
Thanks!
Click to expand...

David, welcome to the club! I suspect you may have the same vintage regulator as mine (1202 marked on the top of the housing means 2012 year of fabrication) which just failed. It turned out that a kind member of this group managed to repair it. It had 3 cold solders (I had found one by visual inspection and repaired it without success, he found 2 more and completed the repair successfully). If you are curious to learn more, it would be interesting to find out if you have the same defects. We have not been able to determine if these defects are due to a manufacturing quality issue or the result of overheating+vibrations in the RV-12 environment. The good thing is that if you have the same defects, it is possible to repair them and you will get a spare regulator. I am currently working on relocating my new regulator inside the cooling tunnel while keeping my spare regulator at the initial location on the firewall. In case of failure I will be able to reconnect the regulator cable to the spare unit, avoiding to be stuck in a remote airport waiting for a delivery from Lockwood.
 
Guys, there are two very good existing threads on this topic. See THIS ONE page 8 for actual measurements by Jean-Pierre that seem to indicate that the VR gets no cooling air flow through the current blast tube at idle rpms, because of its current source location on the inlet to the cylinder shroud.
http://www.vansairforce.com/community/showthread.php?t=122197
If so, the metal cap on the VR is actually making the situation worse on the ground.

It could well be that, instead, attaching a small scoop on the inside of the duct going to the coolant radiator, then attaching the blast tube to that, (with a disconnect for lower cowl removal) might be a better solution than relocating the VR inside the cabin. Even sticking the existing blast tube through that duct, pointing it forward, and securing it with a cable tie or clamp might work without fabricating a little scoop (again with disconnect).

Soapbox: It's really better for all of us if we add to existing on-topic threads rather than start new ones and then start rehashing the same questions. The "NEW POSTS" link always brings up threads with added posts. A new, different thread every time someone has a failed VR (for example) is not a good idea! Sorry, pet peeve.
 
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Bill_H said:
Soapbox: It's really better for all of us if we add to existing on-topic threads rather than start new ones and then start rehashing the same questions. The "NEW POSTS" link always brings up threads with added posts. A new, different thread every time someone has a failed VR (for example) is not a good idea! Sorry, pet peeve.
Click to expand...

Bill, may be but as long as you are doing a fine job providing the links to relevant threads, we are covered :D (I was thinking of you when writing my initial response and saw it coming :eek:)
 
Maybe someone can clear up a question I have. Since the ROTAX generator has a permanent magnet field rotor it would seem the generator either puts out less than load at low RPM or higher than load at high RPM as opposed to a regulated field that matches output to load. Our regulators as I understand it dissipate the extra output at high RPM as heat. If that understanding is correct then doesn't a high load result in less heating of the regulator?
Click to expand...
This is how I understand it. There are at least 3 ways to regulate the rectified voltage.
1. A transistor in series with the load drops the voltage. As the load increases, so does the current and heat in the transistor.
2. A transistor in parallel (shunt) with the load shorts out the generator and drops the voltage. As the load increases, current through the transistor decreases and so does the heat in the transistor.
3. SCRs in series with the load turn on during only part of the generator AC cycle to control the voltage output. Since a SCR is either on or off, and not partly on like a transistor, the SCR does not get as hot. As the load increases, the SCR is turned on for a longer part of the AC cycle and thus gets hotter (but not as hot as a series transistor would).
The Rotax Ducati Rectifier/Regulator uses SCRs (as do most modern permanent magnet dynamo regulators). Thus a greater load results in higher temperatures.
For more information, read Bob Nuckolls' post message #6.
 
Bill_H said:
If so, the metal cap on the VR is actually making the situation worse on the ground.
Click to expand...

Not sure how the shroud makes it worse. There is enough space around the VR that the VR would benefit from whatever the ambient temperature in the compartment is. What the shroud does do is protect the VR from receiving a direct blast of heated air from the radiator AND any radiated heat waves from the hot exhaust or other transmitters.

In any event, I'll find out eventually if it works or not.
 
Great thread and informative posts!! The Link that Joe Gores posted about the test procedure (post 4) is super!! The picture, with that big 22,000 uF capacitor mounted next to the regulator, does give me pause. There is no way that big capacitor can be incorporated into that little box that Van provides. Smoothing out voltage spikes would seem to be important. Are we sure that we don't need one of these in our installation??? Just looking for something that will make life a little easier for that regulator.

Tom
 
todehnal said:
Great thread and informative posts!! The Link that Joe Gores posted about the test procedure (post 4) is super!! The picture, with that big 22,000 uF capacitor mounted next to the regulator, does give me pause. There is no way that big capacitor can be incorporated into that little box that Van provides. Smoothing out voltage spikes would seem to be important. Are we sure that we don't need one of these in our installation??? Just looking for something that will make life a little easier for that regulator.

Tom
Click to expand...

There is a 22000 uf cap incorporated into the AV-50001 switch module.
It is a lower voltage rating (high voltage is not needed) so it's physical size is smaller.... similar to a "D" sized flashlight battery.
 
Rotax has made several changes to the Ducati Voltage Rectifier Regulator over the years. There are at least three versions, all with unique part numbers. The two most recent versions are found in the RV-12, and both have had unacceptable failure rates. The two versions have different failure modes. It?s important to separate the two when looking for a solution, as a fix for one version may have no effect on the other. Rotax P.N. 365-347 ( Ducati P.N. 343620) this was manufactured until 2009, and was replaced by Rotax P.N. 365-349 (Ducati P.N. 362001.) Based on the timing of the redesign, it may have been component obsolescence, not reliability issues, that drove the change.

First we will look at P.N. 343620, we reference the Ducati P.N. because this number is stamped in the top of the regulator, also found here is it?s four digit date code. This version is similar to older versions in its choice of power component packages. The Regulator?s power output circuit utilizes a full wave bridge with SCRs in half the bridge that act as a switch to turn the bridge on and off. The positive half of the bridge uses two power diodes in a leadless package called a ?button case,? the cathode side of the button is soldered directly to a copper plate and a lead soldered is to the other side of each diode. The plate is electrically insulated from the regulator case with a thermally conductive silicone pad. The assembly is held to the case with one insulated screw. The negative half of the bridge consists of two power SCRs. The anode tab of the SCRs TO-220 package is screwed (grounded) to the case, with thermal joint compound applied. Leads from the diode plate assembly, the SCRs and the ground connection are soldered to the bottom of a control PCB mounted in the case. The case is filled with a thermal potting compound. Its hardness is 85 Shore A. The common failure point with this version is the separation of a diode from the copper plate. The diode assy. generates about 30W of heat, at full output. Increased thermal resistence from both the silicone insulator and poor plate fit, may not permit enough heat transfer to the case at peak power output. Each SCR can generate almost 25W of heat, no failures of the SCRs or SCR leads were observed.

The current production regulator is P.N. 362001. This version incorporates several changes including modifications to the cutoff voltage circuit on the control PCB and the replacement of the obsolete ?button case diode assembly? with a leaded, bridge rectifier package. There are no changes to the regulator housing from older versions. The bridge rectifier package screws to the case using the same screw hole from the old ?button diode assembly? plate. The bridge rectifier package is installed with thermal joint compound under it. The Regulator uses the positive half of the bridge rectifier package in its power output bridge, and the negative half of this package is used to supply a negative voltage reference to the control PCB. The negative half of the power output bridge uses the same power SCRs as the previous version regulators. Again the SCR leads, bridge rectifier leads and ground lead solder to the bottom of control PCB in the regulator housing. The case is filled a new gel type thermal potting compound. Its hardness is 60 Shore A. The common failure point in this version is SCR lead separation at the PCB or lead shearing at the SCR body. Some fretting was also observed at the bridge rectifier solder connections on the PCB. The SCR design and mounting have not changed from the previous version, so the cause of the failures may be related to the new gel type potting compound. The change to a bridge rectifier package, with its improved heat sinking, seems to resolve the diode to plate failure issues associated with the earlier version regulator.

link to Rotax P.N. 365-347 / Ducati P.N. 343620 internal schematic and assembly (3-page PDF file)
https://drive.google.com/file/d/0ByPxADyU-DwPdTQ3NWp5LW9iOHc/view?usp=sharing

Link to Rotax P.N. 365-347 / Ducati P.N. 343620 failure results
https://drive.google.com/file/d/0ByPxADyU-DwPZGM4c1dYRlc0MTg/view?usp=sharing

link to Rotax P.N. 365-349 / Ducati P.N. 362001 internal schematic and assembly (4-page PDF file)
https://drive.google.com/file/d/0ByPxADyU-DwPWTBBcGlUeENTcHc/view?usp=sharing

link to Rotax P.N. 365-349 / Ducati P.N. 362001 failure result photos
https://drive.google.com/file/d/0ByPxADyU-DwPYm1rYUVsbUJyQ3M/view?usp=sharing

--------------------------------
12/2016 update

Below are links to 3D models of the regulator assembly, these files are only viewable in Solidworks. Members of EAA can download a free copy of the student edition of Solidworks as one of there EAA member benefits. Go to the EAA website for more info.

Solidworks 3D model of Rotax Regulator 965-349
https://drive.google.com/file/d/0ByPxADyU-DwPQmlIYndpWEh1MkU/view?usp=sharing

Solidworks 3D model of Rotax Regulator 965-347
https://drive.google.com/file/d/0ByPxADyU-DwPNEhOd2gwZFR6U3M/view?usp=sharing

Mike Miller
 
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Thanks Scott, and Mike. Your posts of facts, and detail on RV-12 systems, such as this, somewhat troublesome voltage regulator, are greatly appreciated.

Tom
 
jnmeade said:
Here is a discussion of similar problems and one solution on CT Flier. Credibility is always an issue, but I've found chanick to be logical and consistent.
http://ctflier.com/index.php?/topic...er-longish-and-techie/?hl= voltage regulator
Click to expand...

Kurt (Chanick?) and Mike Miller are real professionals and most of us, experimenters are not, at least in the field of power electronics. Although I don't understand completely the details of their analysis, their experimental work gives the feeling that following their advice puts us on solid ground. Notice that both, while recognizing the weakness of the Ducati regulator do not advocate jumping off the wagon. This confirms that Rotax and Ducati people are not the dummies one would think they are in front of this avalanche of Regulator/Rectifier failures. I like Kurt's last words: "For once, I agree with Rotax's choice". As for Mike Miller, his actions speak for him: he repairs the failed units and keeps them on his RV-12!
As far as I am concerned, I will stick with the Rotax/Ducati regulator and will focus on providing it a better cooling while avoiding overloading as much as possible. More on this later.
 
Ditto

I just had the same happen as in the initial thread yesterday. 196 hours, discharge -4 amps, voltage dropping as I flew. Alarm everytime I keyed the mike.
Just order a rectifier from cps..They gave me a p/n 965-349 (same for Lookwood), this is not the same number as is mentioned in this thread.
Can someone explain?

Gary
120117
 
KRAUSEGB said:
I just had the same happen as in the initial thread yesterday. 196 hours, discharge -4 amps, voltage dropping as I flew. Alarm everytime I keyed the mike.
Just order a rectifier from cps..They gave me a p/n 965-349 (same for Lookwood), this is not the same number as is mentioned in this thread.
Can someone explain?

Gary
120117
Click to expand...

You have got the right part. The 965-347 mentioned in Mike's post are older regulators manufactured around 2008, as he indicated Ducati made changes when going to the 965-349 which is the current version.
 
Mike Miller - my VR was just starting to show symptoms of failure when I replaced it. (Not "kicking in" until over 3500 rpm had initially been achieved.) If I sent it to you, could you fix it so I would have a better spare? "No advertising" here but I would, say include a bottle of sweet and spicy (not dill) homemade "Pilot Pickles!" Or maybe a jar of Bill's Mad Scientist Atomic BBQ sauce...
 
Bill_H said:
Mike Miller - my VR was just starting to show symptoms of failure when I replaced it. (Not "kicking in" until over 3500 rpm had initially been achieved.) If I sent it to you, could you fix it so I would have a better spare? "No advertising" here but I would, say include a bottle of sweet and spicy (not dill) homemade "Pilot Pickles!" Or maybe a jar of Bill's Mad Scientist Atomic BBQ sauce...
Click to expand...

Bill, I don't know that Mike wants to get into this business, I recommend you contact him by PM. I suspect that you will find the same defects as in mine: failed SCR solders as shown on the pictures of his post. You can remove the filling in the back of the case, it is rubbery and although a bit tedious you can tear it apart with pliers after cutting it all around the case. Once done check first the SCR solders, although they might look good, if you can see the leads of the SCR, try to pull them with your nail. Easy to redo the solders.
 
WingedFrog said:
Bill, I don't know that Mike wants to get into this business, I recommend you contact him by PM. I suspect that you will find the same defects as in mine: failed SCR solders as shown on the pictures of his post. You can remove the filling in the back of the case, it is rubbery and although a bit tedious you can tear it apart with pliers after cutting it all around the case. Once done check first the SCR solders, although they might look good, if you can see the leads of the SCR, try to pull them with your nail. Easy to redo the solders.
Click to expand...

So after you dig out the filler, and re-solder the necessary connections, what do you do about refilling that empty cavity??

Tom
 
todehnal said:
So after you dig out the filler, and re-solder the necessary connections, what do you do about refilling that empty cavity??

Tom
Click to expand...

After discussing the issue with Mike who repacked his own repaired unit, I decided to do nothing. Three reasons, first because the adequate fillers are sold in large quantities, they are expensive; second although the filling material is somewhat heat conductive, most of the heat is created on the other side of the PC board and it is clear that the filler is not intended at transferring the heat to the surface against which the Regulator is secured ; third as it will be my back-up unit, I will just make sure that it is sealed to prevent dust and humidity to come in. Once re-installed in the current location (the active unit will by then be in the cooling tunnel) I will seal it with high temp RTV. Once my active regulator has been relocated and tested I will run for a few hours on the stand-by to check that it can play its back-up function satisfactorily.
 
Follow-up report: I installed my replacement Ducati VR under the panel shelf per Van's suggested location (see John Peck's excellent earlier posts and pictures re: "Relocate"). There was no way I could (or would desire to) run the thick, shielded alt/gen power cable through the existing throttle/choke/heater cable firewall penetration hole - there was no room for it, rubbing/wear looked like a potential issue, and the hole was already well-sealed with firewall sealant.

I used a Uni-Bit to drill a new 0.75" hole through the firewall just under the existing throttle/choke/heater cable firewall penetration hole. Installed a grommet with a 0.50" center hole and rerouted the power cable through that directly to the relocated VR. The other two wires can be rerouted from inside the avionics compartment down through an existing wiring hole to the VR. The existing wires are all sufficiently long to reach the relocated VR. I then sealed the new grommet area with firewall sealant.

Test flight yielded 13.9 volts / 1 amp at 5,250 rpm with everything working (all lights, SV avionics, AP, ADSB, etc.) which is what I expected to see per my past operating experience. :) I was surprised to note how hot the VR gets - you cannot hold your hand on it for more than 5-10 seconds. :eek: You northern folks will appreciate this new passenger knee-cap heater this winter.

My new operating procedure is to delay turning on electrical accessories until just before departure to hopefully reduce the load / heat within the VR (particularly during idle operations) - not sure if that helps, but maybe? Here's hoping my newly-relocated VR is happy for many hours to come.

-- David

ps - I now carry a spare VR - just in case. ;)
 
Mission accomplished!

I completed today the relocation of my Ducatti Voltage regulator into the radiators cooling tunnel. I tested the result in a 1/2 hour flight with no indication that anything was different than before the relocation regarding amperage displayed by Skyview.
As I am not able to insert pictures on this site, I gave a detailed description of the steps I used in my builder blog here:
http://vieilleburette.blogspot.com/2015/03/ducatti-voltage-regulator-relocation.html
Sorry for the inconvenience!
 
WingedFrog said:
I completed today the relocation of my Ducatti Voltage regulator into the radiators cooling tunnel. I tested the result in a 1/2 hour flight with no indication that anything was different than before the relocation regarding amperage displayed by Skyview.
As I am not able to insert pictures on this site, I gave a detailed description of the steps I used in my builder blog here:
http://vieilleburette.blogspot.com/2015/03/ducatti-voltage-regulator-relocation.html
Sorry for the inconvenience!
Click to expand...

Link is not working!:(
 
Right - none of the pictures show. Unlike other pics on your site that are hosted at blogspot, all of these seem to link to a Google email account. Please fix - want to see these pics!
 
Bill_H said:
Right - none of the pictures show. Unlike other pics on your site that are hosted at blogspot, all of these seem to link to a Google email account. Please fix - want to see these pics!
Click to expand...

Try the link in my signature at the bottom of this post, it should work.
 
Good Job Jean-Pierre!
100_3788s.jpg

Pictures can not be directly posted on VansAirforce. Instead, a url is posted of the picture that is located on some other website.
 
Bravo!!!

Bravo !!! Jean-Pierre ? in theory, I do like your solution for not installing the voltage regulator inside the cockpit. The thought of placing a high current device prone to failures with a good probability of creating smoke inside the cockpit when it does fail does not sit very well with me.

That said, I applaud your creativity and on the surface love your idea of moving the regulator to an area where there is bountiful airflow moving across it. My concern is with thermal mass ? in that having the regulator bolted to a metal firewall (especially when using some thermal paste) will aid in drawing a considerable amount of heat away from the regulator. I feel the fins on the regulator are anemic at best for the amount of heat it generates. The fiberglass, which the regulator is mounted onto, will not aid much in drawing heat away from the regulator. This could possibly be a big factor when on the ground during very hot days after a flight.

For me the big question is will improved airflow alone across the regulator be enough to cool it on the ground during hot days? ? I suspect it will because, in theory, the regulator should be much cooler upon landing because of the massive amount of air flowing past it prior to landing.

Since you have two regulators now, it would be an interesting experiment to mount temperature test strips on both regulators and during a hot day fly on one regulator with maximum current load, land and do some ground operations. Then move the wiring connector over to the backup regulator on the firewall and repeat the test.

Great thinking outside the box and moving the regulator inside the box!
 
Very nice!
I like the extender cable idea. In my case I want to move the OEM regulator. But I also want to install the Bender Baffle and that particular location is right in the way. I need to get under the hood and examine some alternatives. Also thinking about not moving the regulator but adding a scoop inside the plenum (upstream of the Bender Baffle) as the source of the existing blast tube.
 
I left my voltage regulator in the original location but attached the blast tube to the radiator duct. The fitting is made from scrap aluminum tube. Slits were cut in the end of the tube to make the splayed legs. Originally I used a rubber "O" ring instead of the safety wire, but the "O" ring broke. The safety wire is not easy to work with without pliers.
IMG_1308a.JPG


IMG_1314a.JPG
 
Thanks guys for your comments which contribute to the experimental spirit of this forum. Lots of food for thought, here are my own views about some comments:

- About the heat transfer from the contact of the regulator housing with the firewall, if you look at the housing, the eyelets through which it is bolted are protruding which means only the eyelets contact the firewall, not the sides and certainly not the potting mixture as you have noticed it is concave and in recess from the base. While this compound is heat conducting as noted by Mike Miller, its temperature at the surface is not as high as that of the fins and I suspect that the slight space created by the protrusion of the eyelets allows enough air to circulate to provide some cooling. Furthermore, some folks on this forum mentioned that their firewall can get very hot too, particularly in the area close to the regulator because of the radiation created by the nearby exhaust pipe.

- Conflict with the Bender Baffle: I know, I intend to provoke John into a duel to solve the issue :D

- Blast tube off the cooling duct: It was my initial thought but after measuring the dynamic pressure inside the cooling duct at idle RPM, I did not find the pressure of 5mm of water was sufficient to guarantee enough cooling during ground operation.

Getting serious about the baffle, my preference would be to have such a baffle at the air inlet so that both oil and water radiators get the restricted cooling. I hope some crafty guys will come with something like a diaphragm camera. I don't know a lot about John's baffle but I am pretty sure it is possible to have both "Bender Baffle" and "Bernoux Back-up" coexist peacefully as the footprint of the regulator is not that big.
 
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Joe, what did you do inside the radiator duct? Did you let the tube stick out a bit and cut it off in a 45 degree angle to direct air into the tube? Or did you just rely on the pressure inside the duct to allow some air to escape into the blast tube?
I have received my Silent-Hektik regulator/rectifier from Germany and plan on installing it over the weekend while also changing the air pickup to the radiator duct. Interesting about the Silent-Hektik is that the base of the case is flat, milled aluminum. That will allow to use thermal paste to conduct some of the heat to the mounting surface and away from the regulator. Very solid construction all around. I'll post pictures in my blog when I'm done.
 
Did you let the tube stick out a bit and cut it off in a 45 degree angle to direct air into the tube?
Click to expand...
No, the tube does not protrude into the air duct. The diameter of the hole drilled into the air duct is the same as the inside diameter of the tube. So it relies on pressure differential for air flow. I made that modification 2 years ago. The regulator has not failed . . . yet.
I thought of another way to hold the black blast tube inside of the aluminum fitting. Strike the outside of the aluminum with a punch to make dimples protrude on the inside. When inserting the blast tube, it will have to be forced past the dimples. Thus no tools or fasteners will be needed to insert or remove the blast tube.
 
I've left my regulator on the firewall and don't plan to move it under the panel at this stage. In all this discussion about the best way to get air to the regulator, what happens when it does get there? The shroud is a pretty tight fit and even the corners are sealed, so where does the incoming air go? I'm sure Vans thought this through when they designed it so there must be a reason for the tight seal, but I'm wondering if the shroud shouldn't have some exit holes or preferably an outlet duct to allow the incoming air to flow over the fins and escape?
 
Thanks Joe. I was relying on memory (always risky at this age), so I'll have a closer look when I get back to the hangar. Who knows, there may still be room for improvement.
 
No, not at all. I just completed a 12 hour cross country and it's working flawlessly. I like the higher amperage rating, metal bottom, and general robustness of the German model.
 
Here is the report of my Silent-Hektik installation.

All went well and it works great. Charges at 2+ Amps after startup at 1900RPM with all electrics working (landing light off).

IMAG0294.jpg


IMAG0295.jpg
 
Bender Baffle AND New Blast Tube Scoop

Here is the modification I am thinking of doing. I want to have both the Bender Baffle and to
relocate my existing blast tube to be sourced from the duct. I intend to incorporate a scoop
as shown and not increase the diameter of the blast tube.

I intend to try to get some idea of airflow in the duct on the ground at idle. It makes sense that
it would be much more than through the cowl holes behind the root of the prop blade. I am
going to tape a wooden dowel vertically in the center of the duct, just to the right of the
fishmouth opening. I will have yarn tufts on it. Then with engine idling, have a helper
(carefully - zoomed) take video of what the tufts are doing. If there is a decent amount of
flow, it would seem that this arrangement would provide a lot more ground airflow to the
regulator than that tangential opening on the side of the cylinder shroud.

Comments on the plan are welcome!
Baffle2.JPG
 
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NACA scoop?

I am with you Bill on a possible scoop design. As I have watched things come around and discussions about getting air to the VR for cooling I envisioned a small NACA scoop taking air from the current cooling tunnel or another location on the cowl. Even the cylinder cooling shroud location with a different way to accept the air coming in might do better than the current tube through a hole. However, my tube in the shroud is cut at an angle so it forms a type of scoop, but it could be much better. And I really don't know the air flow to the VR currently, but I don't think it's any better than the other.

I am encouraged with the other VRs used and some of the cooling techniques being tried. I am not interested in putting the VR inside the cockpit. A local friend who has a Kitfox and has flown behind the 912 for many years has his VR inside, and over the years has gone through 5 of the things. He said this most recent one has lasted the longest so he's hopeful design changes within Ducati have improved. He too is looking into the German one mentioned in this thread.

I will keep watching and reviewing results. Thanks all!!
 
Bill and Torsten, I would recommend that you measure the dynamic pressure you get in your blast tube at idle RPMs. The tool needed is easy to fabricate: a pressure gauge made of 1/4" plastic tube filled with water and shaped as a U. You just need to make a slit in your blast tube to slide your fabricated pitot (just the extension of the pressure gauge tube attached to a thick wire and shaped as a L) in it. Once done you can easily patch the tube. The type of the original tube in addition to being too narrow was also not good for a laminar flow with its kind of corrugated surface. This was not a problem in flight when there is plenty of RAM air but it was during ground operations which is why it is important to find out what kind of airflow you get at idle RPMs.
 
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