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1. 07:32 AM - Re: Rotax 912 UL alternator drop-out (Richard Girard)
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| Subject: | Re: Rotax 912 UL alternator drop-out |
John, My source on the teflon wire was personal experience and the
Aeroelectric connection. Based on Bob's recommendation I took a piece of
teflon insulated wire and cinched it down just as I would PVC insulated
wire. I did nothing to aggravate the installation, just let it set for a
couple of months. At the end of that time the wire was no longer snug
against the tubing and when the nylon tie was removed there was measureable
decrease in insulation diameter.
Rick
On Fri, Aug 9, 2013 at 8:04 PM, John Cox <rv10pro@gmail.com> wrote:
> Richard, I enjoyed reading your above post but I would also love to hear a
> reference to support your position on plastic zip ties and waxed cord. I
> am an EAA Tech Advisor and A/P with I/A for a major airline along with
> being ROTAX trained. Those products are used throughout the aircraft I
> service. I make my livelihood dealing as an Avionics Tech chasing Chafes,
> Shorts, Opens and errant electrons. I am always open for refreshing
> ideals. Flush cut wire cutters, wire spoons, a strong light source might
> also be on your hit list. What do you recommend?
>
> I do support the position that zip ties should not be used on engine
> mounts but that subject digresses from Tefzel Mil-Spec wire and your
> presentation that zip ties and cordage should not be used. We use black
> coated cordage aft of the firewall and white coated cordage within the
> higher heat regimes of forward of the firewall. Chafing, routing and
> security of wires is an important build skill.
>
> I look forward to the reference that drove your conclusion.
>
> John Cox
>
>
> On Fri, Aug 9, 2013 at 2:08 PM, Richard Girard <aslsa.rng@gmail.com>wrote:
>
>> Barry, Teflon may be a wonder product and a by product of the Manhattan
>> Program to develop the "Bomb", but it will not carry electricity. I have a
>> block in the shop that I tested with a VOM. It had infinite resistance and
>> a power supply connected across it showed zero voltage coming through the
>> block.
>> Perhaps you were referring to the insulation used on COPPER wire? If that
>> is the case WIRE size is WIRE size and the ability of the WIRE to allow
>> electrons to do what they do, flow, cloud, or kill Schroedinger's cat, does
>> not depend one whit on the insulation on the WIRE. The gage of WIRE is what
>> determines its ability to handle amperage. Too much amperage passed though
>> a too small wire makes what is known as a fusible link, perhaps not by
>> design or intent, but certainly in practice. The insulation may make it
>> possible to carry slightly more amperage without the INSULATION melting and
>> the INSULATION type may allow for great weight savings, say Tefzel vs. PVC
>> but again it's the COPPER WIRE that does the job and there are hundreds of
>> thousands of aircraft and millions of automobiles that have rubber
>> encapsulated cotton braid, PVC, Tefzel and other insulations that are
>> flying and rolling in perfect safety. The important thing is to use the
>> correct gage of WIRE for the circuit capacity and craft it to eliminate
>> places that might cause the insulation to be penetrated and short the wire
>> to ground.
>> Last, Teflon wire insulation has a problem and that is that it is soft.
>> Things like nylon ties or even waxed cotton wire lacing will cause it to
>> extrude out from under the tie and create a short. For that reason alone I
>> would not recommend its use in an aircraft.
>>
>> Rick Girard
>> do not archive
>>
>>
>> On Fri, Aug 9, 2013 at 7:32 AM, FLYaDIVE <flyadive@gmail.com> wrote:
>>
>>> Hi Paul:
>>>
>>> Sounds like you have a gorgeous plane.
>>> For a standard and 99.976% of the different types of batteries to charge
>>> you MUST keep the charge voltage between 13.8 to 14.2 VDC. Over 14.2 you
>>> start to overheat the battery. Under 13.8 the voltage is not there to
>>> remove the oxides for the battery plates.
>>> One thing you mentioned perked my ears up - Dual axis autopilot... Now,
>>> that is probably the highest single current draw in your plane. Were you
>>> in A/P? Did you hit and air bumps? When an A/P has to recover from an air
>>> pump the instantaneous current draw goes up sharply. The power is or
>>> should be drawn from the battery followed by the replenishment by the
>>> charging system. Now, from my reading Rotax has the worst charging system
>>> next to Banlon sock rubbing on a wool carpet. But, I would check things
>>> such as you mentioned - COOLING - It may be easier to install a small air
>>> scoop with a hose or fans (caution- fans have their own current draw) to
>>> blow air directly onto the ACU. This is done in quite a few planes where
>>> forced air is blown directly onto the radio stack. The other thing I would
>>> check is wire gauge size. First off it should be 'Teflon' wire and it is
>>> always better to go UP in size. IF the alternator output is rated at 18
>>> Amps the wire size should be no smaller than a 10 AWG and I would use 8
>>> AWG. This is one case where bigger is better. And weight for such a short
>>> run is not an issue. That takes care of the charging requirements. You
>>> will have to address the wire sizes for the other electronic equipment.
>>> Keep in mind Teflon wires allow you to use smaller gauge sizes. But,
>>> HEAT, forces you to use larger gauge sizes.
>>> From my Rotax readings - I would say Rotax is not supplying the
>>> advertized 18 Amps and it is not in a smooth DC waveform output.
>>> Power Reduction Sequence:
>>> Least needed First -
>>> Cell Phone ;-)
>>> iPad ;-)
>>> LIGHTS
>>> A/P
>>> Second Comm Radio
>>> Second Nav/GPS
>>>
>>> The only reasion I mention this is because an IPad under charge would be
>>> only about 1 Amp for a dead battery. A cell phone under charge - 0.1 Amp
>>> (100 mA). The other items sure can have high draw.
>>>
>>> Another thought - How warm/hot is the firewall? IF the firewall is
>>> warm/hot or if there is dead air under the dash, you may benefit by placing
>>> the ACU on stanchions or placing it on a heat sink. A TRICK that I did on
>>> my plane: I covered the glareshield with black speaker carpet. This
>>> created a heat shield for radio stack by creating a low heat
>>> transfer barrier, aluminum and thin leatherette passes the sun's rays/heat
>>> very easily. It also added some class to the plane.
>>>
>>> Good luck,
>>>
>>> *Barry*
>>> On Fri, Aug 9, 2013 at 12:42 AM, Paul Kuntz <paul.r.kuntz@gmail.com>wrote:
>>>
>>>> I have a homebuilt Pipistrel Sinus with a Rotax 912 UL that I flew to
>>>> Oshkosh and back last week. The panel has a dual Dynon Skyview display with
>>>> two-axis autopilot, plus radio and transponder. The total electrical load
>>>> with everything running is 7 to 8 amps. Occasionally it can go to 10 amps
>>>> if I'm charging cell phone and iPad en route. I'm pretty confident that I
>>>> have the electrical system wired so that the ammeter is measuring the total
>>>> electrical load.
>>>>
>>>> The alternator dropped out once on the outbound trip, but came back
>>>> after removing the iPad charging load. The symptom was a voltage drop from
>>>> 13.8 volts to 12.5 volts. On preflight the voltage may read that high for
>>>> a minute or so on a freshly-charged battery, but it quickly drops to 12.2
>>>> or 12.1 volts. In flight, the voltage would drop to 12.5 volts and stay
>>>> there for several minutes. I would think that if the alternator had
>>>> failed, I'd see the voltage drop to the same 12.1 volts that I see on
>>>> preflight, and keep dropping slowly. I can't see why it would drop to 12.5
>>>> volts and stay there, unless the voltage regulator is failing in a way that
>>>> I'm not familiar with.
>>>>
>>>> The alternator dropped out (same symptoms) a few times on the trip
>>>> back, but by reducing the load to 3 amps (one Skyview display, radio and
>>>> transponder), it stayed on line except for awhile when it seemed that the
>>>> mid-day sun shining on the dashboard was adding extra heat behind the
>>>> panel. That time we brought it back by directing cool air from a fresh air
>>>> vent forward toward the spot where the voltage regulator is mounted inside
>>>> the cabin on the back side of the firewall.
>>>>
>>>> So the problem seems to be heat-related. Does this make sense? The
>>>> Rotax alternator is supposed to be rated for 18 amps, and able to handle a
>>>> steady load of 14 amps easily. Does the Ducati regulator have a thermal
>>>> self-protect cutout? Do I perhaps have a regulator that is ready to fail
>>>> completely, or should I just put an avionics cooling fan behind the panel
>>>> to get the air moving?Any other ideas?
>>>>
>>>> Regards,
>>>> Paul Kuntz
>>>>
>>>> *
>>>>
>>>> ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
>>>> tp://forums.matronics.com
>>>> _blank">http://www.matronics.com/contribution
>>>> *
>>>>
>>>>
>>> *
>>>
>>> ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
>>> tp://forums.matronics.com
>>> _blank">http://www.matronics.com/contribution
>>> *
>>>
>>>
>>
>>
>> --
>> Zulu Delta
>> Mk IIIC
>> Thanks, Homer GBYM
>>
>> It isn't necessary to have relatives in Kansas City in order to be
>> unhappy.
>> - Groucho Marx
>>
>> *
>>
>> ist" target="_blank">http://www.matronics.com/Navigator?RotaxEngines-List
>> tp://forums.matronics.com
>> _blank">http://www.matronics.com/contribution
>> *
>>
>>
> *
>
> *
>
>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
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