Why do some of the RV-12 VRs die young?

[Mich48041]

The Ducati mounting holes for 1/4" bolts are about 3 5/8" apart center to center.

[jweir43]

Thanks, Mike. For whatever reason those google docs gave me a "file not found" error. I'll see if my Chrome browser will bring them up.

As I understand it, this little sucker takes in an AC wave and outputs a nominal 12 volts at 20 amps or so. Did I get that right?

Now, where in the aircraft do those 20 amps get used? And is there any regulation at all on the incoming AC, or is it just a linear function of engine speed. Any idea what the minimum/maximum frequency of the AC is?

That'll get me started to think.

Jim

[DaleB]

Originally Posted by jweir43

Thanks, Mike. For whatever reason those google docs gave me a "file not found" error. I'll see if my Chrome browser will bring them up.

As I understand it, this little sucker takes in an AC wave and outputs a nominal 12 volts at 20 amps or so. Did I get that right?

Now, where in the aircraft do those 20 amps get used? And is there any regulation at all on the incoming AC, or is it just a linear function of engine speed. Any idea what the minimum/maximum frequency of the AC is?

That'll get me started to think.

Jim

Can't answer the frequency question, and I don't know the voltage but have read that it's 15 - 20 VAC at idle and 30 - 40 at cruise RPM. I don't know how accurate that is, but the frequency will certainly depend on engine RPM.

Power is used for the fuel pump, EFIS, COM radio, transponder, intercom, autopilot, Garmin 496 in older airplanes, strobe/nav/landing lights in some. EFIS setups can be single or dual Dynon D180, single or dual G3X Tough, single or dual Dynon Skyview, Skyview Touch or HDX. COM radios are SL40 or GTR 200. Oh, there's also a 12V power outlet. I may have missed one or two minor items.

[deene]

Hi Jim, welcome aboard.

Some additional Rotax regulator/rectifier info:

Normal regulator/rectifier performance:
Output voltage range: 13.9-14.5 VDC
Max current: 22 A (other sources show 18-20A)
Max temperature: 80 deg C (176 deg F)

Here is a link to a nice test program document on the Rotax electrical system by a competent EE:

http://www.scflier.com/index.php?/to...trical-system/

[Mich48041]

The 22,000 microfarad capacitor does not do a very good job of stabilizing the voltage. Last year, I conducted an experiment by disconnecting the battery while the engine was running. The voltage fluctuated between 13.25 and 14.7

[pilotyoung]

In the last three weeks I have had two very experienced Rotax mechanics tell me the problem with the Ducati is that the RV-12 does not have a dedicated ground wire. Those mechanics told me when the Ducati is used in other small aircraft, where they run a dedicated ground wire, the problems don't exist. It relies on getting ground through the chassis. When my Ducati failed, I replaced it with a John Deere from Amazon and I installed a dedicated ground wire to the case. It worked fine for about 40 hours and I just replaced it with the Silent Hektik. The John Deere didn't fail. I just decided I wanted overvoltage protection and the Silent Hektik incorporates this feature. Also, the Silent Hektik has a terminal for a dedicated ground. I just installed the Silent Hektik today while I am doing the annual condition inspection. I should be finished by Wednesday and will see how it works. It does have a terminal for an alarm light and I hooked it up to my Dynon Skview HDX. My installation copies another gentlemen from Vans Airforce and I am taking cooling air for the blast tube from the fiberglass duck on the pilotside that supplies air to the radiator. I think it is a neat installation and should work well. I also put a thermo strip on the Voltage Regulator so I can determine the temperatures it is exposed to. Lastly, I must confess none of these ides are original with me. I got them all off of Vans Airforce and I think you creative people for posting your ideas.

[Phantom30]

Originally Posted by Mich48041

The 22,000 microfarad capacitor does not do a very good job of stabilizing the voltage. Last year, I conducted an experiment by disconnecting the battery while the engine was running. The voltage fluctuated between 13.25 and 14.7

Joe....I am a novice when it comes to electronics. When my VR took a dump, I switched to the SH VR (and after reading an German artical; added a 32,000 microfarad capacitor..which they recommended).

Everything has been rock solid since then....the bloody capacitor is ?big?.. Your thoughts?

[rvbuilder2002]

Originally Posted by Phantom30

Joe....I am a novice when it comes to electronics. When my VR took a dump, I switched to the SH VR (and after reading an German artical; added a 32,000 microfarad capacitor..which they recommended).

Everything has been rock solid since then....the bloody capacitor is ?big?.. Your thoughts?

I'm not Joe, but I can tell you that when Van's began working with S H for an installation on the RV-12 their engineers said the existing 22000 mf cap was fine.

[h&jeuropa]

Mike Miller put together a nice replacement for the Ducatti. Here is the thread
http://www.vansairforce.com/communit...or#post1296750

Post 45 has the details. I have constructed mine and installed it, but until the weather clears I won't have a chance to test it in flight. The cost was about $75.

Jim Butcher

[Mich48041]

I have not observed any benefit to adding a large capacitor to the output of an alternator.
The ability of 22,000 mfd capacitors to store and release electrons is very
small compared to the output of an alternator. A battery does a much better job.
_ A good experiment would be to disconnect that big 32,000 microfarad
capacitor to see if it makes any noticeable difference.