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kenryan
Joined: 20 Oct 2009
Posts: 429
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 Posted: Mon Jul 04, 2016 7:55 am Post subject: Z-13/8 Questions |
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Thanks Giles. Does that mean that you would run both pumps from the same battery bus, or just the main pump? I thought about putting them both on the battery bus but that would violate the clearly stated requirement that "...the fuel pumps are connected on two completely independent power supplies." On airplane that you are familiar with that have both generator and alternator, do they both feed the same battery? Rotax in British Columbia steered me away from trying to combine the outputs, even though that is what is shown on the installation manual drawing.
The way I have things drawn now I have the main pump wired to the integrated generator (as shown in the 914 installation manual) but I have the auxiliary pump wired to a battery bus. The auxiliary pump should run continuously as long as the external alternator is working. If both alternator and generator were to quit, then it would be battery only on the auxiliary pump.
My current drawing is different from the Rotax 914 installation manual in that I don't have the integrated generator connected to the main bus (except through a momentary contact switch for exciting it into action). So the only thing the generator and regulator are doing is powering that one pump. I also plan on mounting the regulator on the cabin side of the firewall, where it is cooler. I am thinking that given the low load and cooler environment, the regulator might be more reliable.
All comments are appreciated. My starting/charging/fuel pump wiring is still all on paper only at this point, so I can still make changes.
Ken
On Mon, Jul 4, 2016 at 4:55 AM, GTH <gilles.thesee(at)free.fr (gilles.thesee(at)free.fr)> wrote:
| Quote: | Le 03/07/2016 à 21:30, Ken Ryan a écrit :
| Quote: | Thanks Gilles. As I tend to be biased towards the manufacturer when it comes to guidance, I am referring heavily to the Rotax 914 installation instructions. Can you tell me specifically which areas that you feel are suspect? If you could do that it would help me to evaluate their "suggestions" against my installation.
|
Hi Ken and all,
It took me some time to download and peruse the latest 914 Installation Manual (February 2015).
Concerning the ignition switches, it seems there has been no changes since the 1996 version that was current when we wired our project. The manual just mentions
"Type : two separate, suitable on-off switches" (page 114 newer edition)
The Rotax 914 relies on two electrical pumps to keep running.
Rotax suggests to feed the main pump from the voltage rectifier/regulator, and the aux pump from the main bus.
If the regulator fails - not a rare occurence - you are left with only the aux pump and the battery to stay aloft.
I feel a critical pump should run direct from a battery bus.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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stephencliverichards(at)g
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| Posted: Mon Jul 04, 2016 8:31 am Post subject: Z-13/8 Questions |
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I understood Rotax recommended separate switches so you could turn the engine on the starter with ignition off to check oil pressure after a oil change. We have fitted a keyed ignition switch as we were given one and a start pushbutton, Not ready to run engine yet.
Clive
From: GTH (gilles.thesee(at)free.fr)
Sent: 03/07/2016 20:25
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Re: Re: Z-13/8 Questions
Le 03/07/2016 à 17:17, Ken Ryan a écrit :
| Quote: |
With the Rotax the rotary keyed ignition switch is not allowed. Independent toggles for the ignitions are clearly specified.
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Hi Ken and all,
Didn't know about that.
Maybe it concerns the latest engines. Or maybe it is in the new installation documents, but as Rotax didn't change the engines already flying, I would not lose sleep on the keyswitch vs separate switches problem.
Hundreds of airplanes have been flying for years with a standard ignition keyswitch for their Rotax without the slightest issue.
I'd even state that the Rotax circuit wiring suggestions are to be taken with a grain of salt, especially concerning the 914.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Mon Jul 04, 2016 9:41 am Post subject: Z-13/8 Questions |
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Thanks for that info Stephen. Makes sense to me.
On Mon, Jul 4, 2016 at 8:30 AM, Stephen Richards <stephencliverichards(at)gmail.com (stephencliverichards(at)gmail.com)> wrote:
| Quote: | I understood Rotax recommended separate switches so you could turn the engine on the starter with ignition off to check oil pressure after a oil change. We have fitted a keyed ignition switch as we were given one and a start pushbutton, Not ready to run engine yet.
Clive
From: GTH (gilles.thesee(at)free.fr)
Sent: 03/07/2016 20:25
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Re: Re: Z-13/8 Questions
Le 03/07/2016 à 17:17, Ken Ryan a écrit :
| Quote: |
With the Rotax the rotary keyed ignition switch is not allowed. Independent toggles for the ignitions are clearly specified.
|
Hi Ken and all,
Didn't know about that.
Maybe it concerns the latest engines. Or maybe it is in the new installation documents, but as Rotax didn't change the engines already flying, I would not lose sleep on the keyswitch vs separate switches problem.
Hundreds of airplanes have been flying for years with a standard ignition keyswitch for their Rotax without the slightest issue.
I'd even state that the Rotax circuit wiring suggestions are to be taken with a grain of salt, especially concerning the 914.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jul 04, 2016 1:13 pm Post subject: Z-13/8 Questions |
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At 07:55 AM 7/4/2016, you wrote:
| Quote: | Le 03/07/2016 21:30, Ken Ryan a écrit :
| Quote: | | Thanks Gilles. As I tend to be biased towards the manufacturer when it comes to guidance, I am referring heavily to the Rotax 914 installation instructions. Can you tell me specifically which areas that you feel are suspect? If you could do that it would help me to evaluate their "suggestions" against my installation. |
Hi Ken and all,
It took me some time to download and peruse the latest 914 Installation Manual (February 2015).
Concerning the ignition switches, it seems there has been no changes since the 1996 version that was current when we wired our project. The manual just mentions
"Type : two separate, suitable on-off switches" (page 114 newer edition)
The Rotax 914 relies on two electrical pumps to keep running.
Rotax suggests to feed the main pump from the voltage rectifier/regulator, and the aux pump from the main bus.
If the regulator fails - not a rare occurence - you are left with only the aux pump and the battery to stay aloft.
I feel a critical pump should run direct from a battery bus. |
How is one 'critical' and the other not?
The magic in having two pumps and separate
power sources is that the likelihood of
dual failures in any given tank of fuel
is vanishingly small. If the engine runs
per published performance specs on either
pump, then there are no 'critical' pumps,
just one pump backing up another pump.
How would you ever get down to one, battery
operated pump? Wasn't his airplane going to
get an external alternator in addition to
the stock, 912/914 PM alternator-rectifier/regulator?
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Mon Jul 04, 2016 1:16 pm Post subject: Z-13/8 Questions |
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| Quote: |
If the regulator fails - not a rare occurence |
The failure driver for the Rotax/Ducatti R/R
has root cause in thermal considerations . . .
where the ship attempts to use full rated output
from the power source.
What kind of fuel pump are we talking about?
How much current does it draw? Certainly nothing
approaching the 18A capability of the power
source.
It seems that the rather strange recommendation
for dedicating the stock Alternator-R/R to simple
powering of the fuel pump is a hedge . . . with
loads limited to a fraction of the system's
advertised output capabilities, the regulator
should last a very long time.
Bob . . .
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Mon Jul 04, 2016 1:41 pm Post subject: Z-13/8 Questions |
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Thanks for those comments Bob. Your reasoning makes sense to me.
Sent from my Android. Sorry Steve. On Jul 4, 2016 1:23 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: | Quote: | | Quote: |
If the regulator fails - not a rare occurence |
The failure driver for the Rotax/Ducatti R/R
has root cause in thermal considerations . . .
where the ship attempts to use full rated output
from the power source.
What kind of fuel pump are we talking about?
How much current does it draw? Certainly nothing
approaching the 18A capability of the power
source.
It seems that the rather strange recommendation
for dedicating the stock Alternator-R/R to simple
powering of the fuel pump is a hedge . . . with
loads limited to a fraction of the system's
advertised output capabilities, the regulator
should last a very long time.
Bob . . .
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gilles.thesee(at)free.fr
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| Posted: Mon Jul 04, 2016 2:23 pm Post subject: Z-13/8 Questions |
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Le 04/07/2016 à 17:52, Ken Ryan a écrit :
| Quote: | Thanks Giles. Does that mean that you would run both pumps from the same battery bus, or just the main pump? I thought about putting them both on the battery bus but that would violate the clearly stated requirement that "...the fuel pumps are connected on two completely independent power supplies."
|
On our airplane the main pump runs from the main battery bus any time the ignition switch is on.
The aux pump runs from a dedicated aux battery fed through a battery management module.
| Quote: | On airplane that you are familiar with that have both generator and alternator, do they both feed the same battery?
|
I'm aware of only one other Rotax aircraft with two alternators, but I don't know how they wired their machine.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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gilles.thesee(at)free.fr
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| Posted: Mon Jul 04, 2016 2:29 pm Post subject: Z-13/8 Questions |
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Le 04/07/2016 à 18:30, Stephen Richards a écrit :
| Quote: | I understood Rotax recommended separate switches so you could turn the engine on the starter with ignition off to check oil pressure after a oil change. We have fitted a keyed ignition switch as we were given one and a start pushbutton, Not ready to run engine yet.
|
I'll bet the two separate ignition switches are for the magneto checks before each flight.
Rotax doesn't give recommadations for the starter switch, which may or may not be combined with an ignition keyswitch.
It's up to the homebuilder.
There are different ways of priming the oil circuit, but no problem for oil pressure if you perform the oil changes as recommended. Unless you drain the oil lines, but then the procedure is in in the maintenance manual, separate starter switch or not.
--
A+
Gilles
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gilles.thesee(at)free.fr
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| Posted: Mon Jul 04, 2016 2:44 pm Post subject: Z-13/8 Questions |
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Le 04/07/2016 23:10, Robert L. Nuckolls, III a crit:
| Quote: |
If the engine runs
per published performance specs on either
pump, then there are no 'critical' pumps,
just one pump backing up another pump.
|
Hi Bob,
Of course.
I'd say that for us the "critical" one is the pump that we think should run anytime the ignition is on.
And the backup the one that is pilot operated.
I saw so many voltage regulator failures around that I would not like to depend on the regulator to keep the engine running
| Quote: |
How would you ever get down to one, battery
operated pump? Wasn't his airplane going to
get an external alternator in addition to
the stock, 912/914 PM alternator-rectifier/regulator?
|
The point was "why do you say some of Rotax suggestions are to be taken with a grain of salt ?", not any suggestion as to how Ken should or shouldn't wire his airplane.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Mon Jul 04, 2016 5:57 pm Post subject: Z-13/8 Questions |
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Gilles, I hear you loud and clear on depending on the regulator to keep the engine running. At this point, I am considering that to the the weakest point in my proposed design. But, I am not convinced that there is a significant probability of regulator failure, given that my plan is to run only the pump (approx 5 amps) off the generator. That would mean that the regulator is only being stressed to less than 1/3 capacity. Also, given that I plan to install the regulator on the cabin side of the firewall, that would further mitigate heat issues. Like Bob, I'm thinking this should significantly lower the probability of regulator failure.
My question for you, and for the group, is this: what is the normal (if there is a normal) mode of failure for these regulators? Do they just suddenly stop working, or is there typically some warning of failure?
As always, thanks. It's amazing how many things there are to consider.
Ken
On Mon, Jul 4, 2016 at 2:41 PM, GTH <gilles.thesee(at)free.fr (gilles.thesee(at)free.fr)> wrote:
| Quote: | Le 04/07/2016 à 23:10, Robert L. Nuckolls, III a écrit :
| Quote: |
If the engine runs
per published performance specs on either
pump, then there are no 'critical' pumps,
just one pump backing up another pump.
|
Hi Bob,
Of course.
I'd say that for us the "critical" one is the pump that we think should run anytime the ignition is on.
And the backup the one that is pilot operated.
I saw so many voltage regulator failures around that I would not like to depend on the regulator to keep the engine running
| Quote: |
How would you ever get down to one, battery
operated pump? Wasn't his airplane going to
get an external alternator in addition to
the stock, 912/914 PM alternator-rectifier/regulator?
|
The point was "why do you say some of Rotax suggestions are to be taken with a grain of salt ?", not any suggestion as to how Ken should or shouldn't wire his airplane.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
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user9253
Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan
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| Posted: Tue Jul 05, 2016 3:37 am Post subject: Re: Z-13/8 Questions |
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Mike Miller has done autopsies on several failed Ducati regulators and he attributes the failures to poor manufacturing and vibration, not from heat. Some RV-12 owners have reported a gradual failure where they get low voltage alarms at RPMs where they used to have normal voltage. Each regulator could fail differently.
Some builders are reluctant to mount the regulator inside of the passenger compartment because they do not want to breath smoke if the regulator does fail in that location.
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Joe Gores |
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gilles.thesee(at)free.fr
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| Posted: Tue Jul 05, 2016 4:26 am Post subject: Z-13/8 Questions |
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Le 05/07/2016 13:37, user9253 a crit:
| Quote: | | Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com> (fransew(at)gmail.com)
Mike Miller has done autopsies on several failed Ducati regulators and he attributes the failures to poor manufacturing and vibration, not from heat. Some RV-12 owners have reported a gradual failure where they get low voltage alarms at RPMs where they used to have normal voltage. Each regulator could fail differently.
Some builders are reluctant to mount the regulator inside of the passenger compartment because they do not want to breath smoke if the regulator does fail in that location.
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Hi all,
In the past years we performed some study of the Rotax alternator and regulator.
My buddy Jerome Delamarre studied the functionning of the switching regulator, and conducted some thermal analysis of the unit. It seems there is definitely a thermal issue with the regulator.
I published some data here
http://contrails.free.fr/elec_ducati_en.php
The rest of the study will be published some day in an indefinite future 
Re the smoke, the components are potted inside a metal case, and the failed regulators I saw showed no external trace of failure. So the possibility of smoke seems to be remote.
For instance, about 500 Dyn'Aero MCRs have the regulator inside the cabin, and although the cases of regulator failures are not infrequent, I never heard of a smoking unit.
What *can* be happen though, is a capacitor bursting, very disturbing for the crew they told me.
Bottom line, after some thorough analysis of the Ducati regulator and a Schicke, we elected to install a Schicke GR4. Worked flawlessly since the beginning.
FWIW
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Tue Jul 05, 2016 7:07 am Post subject: Z-13/8 Questions |
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Thanks Joe, all good points.
On Tue, Jul 5, 2016 at 3:37 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
Mike Miller has done autopsies on several failed Ducati regulators and he attributes the failures to poor manufacturing and vibration, not from heat. Some RV-12 owners have reported a gradual failure where they get low voltage alarms at RPMs where they used to have normal voltage. Each regulator could fail differently.
Some builders are reluctant to mount the regulator inside of the passenger compartment because they do not want to breath smoke if the regulator does fail in that location.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=457742#457742
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Tue Jul 05, 2016 7:25 am Post subject: Z-13/8 Questions |
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Thanks for the input. Reading the information you linked to, it looks like your conclusion was that if the regulator is making full power (240 watts) then in order for the operating temperature to remain safe, the ambient temperature must be no greater than MINUS 59 C (-74F). Meanwhile, Rotax says that ambient temperature must not exceed PLUS 90 C (+194F). That's quite a discrepancy, -74F vs +194F. Please, tell me I have mis-interpreted your paper.
On Tue, Jul 5, 2016 at 4:24 AM, GTH <gilles.thesee(at)free.fr (gilles.thesee(at)free.fr)> wrote:
| Quote: | Le 05/07/2016 à 13:37, user9253 a écrit :
| Quote: | | Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com> (fransew(at)gmail.com)
Mike Miller has done autopsies on several failed Ducati regulators and he attributes the failures to poor manufacturing and vibration, not from heat. Some RV-12 owners have reported a gradual failure where they get low voltage alarms at RPMs where they used to have normal voltage. Each regulator could fail differently.
Some builders are reluctant to mount the regulator inside of the passenger compartment because they do not want to breath smoke if the regulator does fail in that location.
|
|
Hi all,
In the past years we performed some study of the Rotax alternator and regulator.
My buddy Jerome Delamarre studied the functionning of the switching regulator, and conducted some thermal analysis of the unit. It seems there is definitely a thermal issue with the regulator.
I published some data here
http://contrails.free.fr/elec_ducati_en.php
The rest of the study will be published some day in an indefinite future
Re the smoke, the components are potted inside a metal case, and the failed regulators I saw showed no external trace of failure. So the possibility of smoke seems to be remote.
For instance, about 500 Dyn'Aero MCRs have the regulator inside the cabin, and although the cases of regulator failures are not infrequent, I never heard of a smoking unit.
What *can* be happen though, is a capacitor bursting, very disturbing for the crew they told me.
Bottom line, after some thorough analysis of the Ducati regulator and a Schicke, we elected to install a Schicke GR4. Worked flawlessly since the beginning.
FWIW
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
|
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user9253
Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan
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| Posted: Tue Jul 05, 2016 7:39 am Post subject: Re: Z-13/8 Questions |
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The ambient temperature can be greater if the air is moving.
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Joe Gores |
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Tue Jul 05, 2016 8:20 am Post subject: Z-13/8 Questions |
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So I guess if it's in the high pressure area of the engine compartment, it should be good in flight, but maybe not so much during taxi and cool down? Maybe a timer like this:
https://www.youtube.com/watch?v=CJG2f2ZjPxQ&t=0s
could be connected to a computer fan such that the fan always runs when the master switch is on, and continues to run for a period of time (10 minutes?) after the master switch is turned off. Alternatively, it could be set to come on only after the master switch is turned off.
The regulator on a UL engine that I installed on a Zenith had two features for dissipating heat: 1) it was mounted to aluminum engine shrouding using a heat conducting gel to facilitate heat transfer from the regulator body to the aluminum engine shroud and 2) it was blasted by cooling air through a dedicated 1 inch scat hose.
On Tue, Jul 5, 2016 at 7:39 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
The ambient temperature can be greater if the air is moving.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=457750#457750
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jul 05, 2016 9:05 am Post subject: Z-13/8 Questions |
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At 06:37 AM 7/5/2016, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
Mike Miller has done autopsies on several failed Ducati regulators and he attributes the failures to poor manufacturing and vibration, |
vibration in a potted assembly?
Has he published a teardown report?
| Quote: | | Some RV-12 owners have reported a gradual failure where they get low voltage alarms at RPMs where they used to have normal voltage. Each regulator could fail differently. |
Color me skeptical . . . these regulators have
been in production for decades. There must have
been thousands sold. Over that period of time
and numbers of examples, I find it curious that
a constellation of failure modes would emerge.
At the debut of the 912/914 series engines on
this side of the pond . . . a SINGLE phase
PM dynamo in the 18-20A class was really pushing
the state of the art. The control devices
capable of handling that much current would
normally have been mounted directly to metallic
heatsinks with fins.
To my knowledge, production examples still
expect the potting compound to bring BTUs to
the outside world. Why Rotax continues to
sell/recommend this device is curious considering
the fact that there are much more robust/modern
devices available.
The OBAM aviation community has been slicing/dicing
this sad piece of technology for too long. It
has been thermally challenged since day-one.
I cannot argue against 'constellations' of
other failure modes . . . but debating a broader
spectrum of issues seems a waste of $time$.
It's like worrying about whether or not the
a/c and stereo are working in a car with
3 flat tires.
| Quote: | Some builders are reluctant to mount the regulator inside of the
passenger compartment because they do not want to breath smoke
if the regulator does fail in that location. |
Has one EVER 'smoked'? Has a 'smoked' R/R
every been preserved for examination? Our ranks are
rife with anecdotal information on a product
with a very long service history . . . and
and continues to be offered by a company with
a lot of 'skin in the game'. Why jepoardize
consumer relations on a product costing
$thousands$ by sticking with a demonstrably
marginal accessory that probably costs them
less than $50?
I've observed some pretty strange marketing
decisions by big-name manufacturers.
To be sure, there are really powerful cultural
forces in company behaviors. I could tell you
some interesting stories about the intractability
of several supposed European 'project partners.'
So just maybe, the Rotax decision to stay with
Ducatti has nothing to do with science and
economics.
[img]cid:.0[/img]
My advice to Rotax customers. Pitch the Ducatti
R/R right out of the box . . . or put it up on
eBay. There's a bunch of ultralights flying the
912 that can probably make good use of an R/R that
should probably be rated at 10A.
The Silent-Hektick electronics cavity volume
is a fraction of that in the Ducatti. Square-
inches of fin area for heat dissipation is much
greater. Further, the thing is RATED at 47A . . .
so de-rating to run it on an 18A Rotax dynamo
seems a rational decision that goes toward
longevity and serviceability.
There are probably other devices out there
with equal or better performance than the Ducatti.
There will come a time when incandescent landing
lights will be a thing of the past along with carburetors,
VOR receivers and E6B computers. It's time for the
Ducatti R/R to be retired as the best Rotax could
offer at introduction . . . but long since
surpassed by better ideas.
Bob . . .
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gilles.thesee(at)free.fr
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| Posted: Tue Jul 05, 2016 9:32 am Post subject: Z-13/8 Questions |
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Le 05/07/2016 à 17:23, Ken Ryan a écrit :
| Quote: | Thanks for the input. Reading the information you linked to, it looks like your conclusion was that if the regulator is making full power (240 watts) then in order for the operating temperature to remain safe, the ambient temperature must be no greater than MINUS 59 C (-74F). Meanwhile, Rotax says that ambient temperature must not exceed PLUS 90 C (+194F). That's quite a discrepancy, -74F vs +194F. Please, tell me I have mis-interpreted your paper.
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Hi Ken,
You correctly read the info on my webpage.
We got the regulator thermal characteristics actually measured in a lab.
Concerning what Rotax says, well unless they publish their own results, I'd stick with the grain of salt
Especially when you consider the failures around as soon as people draw much current from their alternator & regulator.
Besides they are not wrong : temperatures no greater than 90 C doesn't mean that 70 or 80 C are safe...
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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gilles.thesee(at)free.fr
Guest
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| Posted: Tue Jul 05, 2016 9:49 am Post subject: Z-13/8 Questions |
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Le 05/07/2016 à 18:18, Ken Ryan a écrit :
| Quote: |
two features for dissipating heat: 1) it was mounted to aluminum engine shrouding using a heat conducting gel to facilitate heat transfer from the regulator body to the aluminum engine shroud and 2) it was blasted by cooling air through a dedicated 1 inch scat hose.
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Add to that a safe and cool place with no exhaust, turbo, engine block radiating or convecting heat at the regulator (i.e. not in the engine comparment , and everything will be well.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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user9253
Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan
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| Posted: Tue Jul 05, 2016 10:04 am Post subject: Re: Z-13/8 Questions |
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I am not taking sides here, just reporting Mike Miller's postings. Joe G.
| Quote: | My motivation for the analyses was based on the abysmal failure rate, with no good data available on a cause. I can’t make any broad claims as to the cause of the failures, only claims based on a sample of one unit. I think the electrical design is fine, simple and safe for the use in a VFR aircraft, I’m not so sure about the mechanical design/assembly. I first thought the failures were based on the stress of thermal cycles. After the analysis I think it’s simply vibration. I base this on the review of the fretted solder joints you can see in the pictures. The main failure on mine (and I’m guessing yours too) is a broken lead on the SCR (the SCR is the “power switch” that controls the regulator output.) The likely cause of the failure is the movement between SCR’s bolted to the case (required as a heat sink) and “floating PCB in the epoxy jel. Your post questioned the SCR installation with the bent over leads to attach to the PCB. This is not uncommon, for a component requiring a heat sink. I would be confident your regulator is fixed by re-soldering the SCR leads. I would touch up all three pins, on both SCR‘s, also inspect all the other solder connections for fretting. I don’t think you need to remove the PCB from the case, unless an SCR lead is broken at the component (like mine was.) I use several epoxy potting compounds here at work, so for me repotting was a non issue. I did use a harder epoxy to reduce the gel effect. I suggest you not remove the board from the case, and after you are finished, cover the bottom with high temp RTV. There are no heat issues on the bottom of the regulator. All you want to do is seal it up, Just my opinion.
Oh, the reason you found two layers of epoxy, its part of the manufacturing process. The regulator is filled with epoxy, placed in a vacuum chamber to remove the air bubbles, after curing it’s “topped’ off again.
I asked LEAF about the two failed regulators I returned under warrantee. They said they just trash them, Rotax doesn’t want them back. They also told me, Rotax will not give me anymore credits for failed regulators, because the problem is the aircraft/aircraft design, not the regulator. I sent Vans a feedback form for the failures, not to blame Vans for the problem, I just thought they would have more pull with Rotax to get it fixed. With that said, I think Rotax knows there is a problem, I say this based on the cost of the regulator. $160.00 may be a lot of money, but it’s cheap as Rotax prices go. I’m guessing Ducati sells it for about $50 to Rotax, but it goes through Kodiak, in the Bahamas, then a distributor (LEAF/Lockwood,) each tacking on freight and markup, before we see it. " |
See http://www.vansairforce.com/community/showpost.php?p=1092091&postcount=23 for pictures
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