Today's Message Index:
----------------------
1. 04:20 AM - Re: Electrical question (Wayne R. Couture)
2. 07:04 AM - Re: Electrical question (Elsa & Henry)
3. 07:05 AM - New RV Wanabee (michael michael)
4. 08:49 AM - Re: Electrical question (kempthornes)
5. 09:34 PM - OSH parking (Wheeler North)
6. 10:14 PM - Vans Amp Gauge (Wheeler North)
7. 10:19 PM - Re: Electrical question (Meketa)
8. 11:22 PM - Re: Movie ()
Message 1
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| Subject: | Re: Electrical question |
--> RV-List message posted by: "Wayne R. Couture" <commando@cox-internet.com>
Doug,
Use a Double Pole, Single Throw (DPST) switch and power each light from
one side of the switch!
Wayne
----- Original Message -----
From: "Doug Weiler" <dougweil@pressenter.com>
Subject: RV-List: Electrical question
> --> RV-List message posted by: "Doug Weiler" <dougweil@pressenter.com>
>
> Fellow Listers:
>
> Here's a question for the electrical experts out there...
>
> My newly flown RV-4 has two wing-tip landing lights. These are the
> Duckworth lights and I have 100W bulbs in them. By my calculations these
> two lamps draw about 14 amps total (they are wired thru one switch and a
20
> amp fuse.) Today I had the switch fail. It got hot and started putting
out
> very bad fumes and the terminal connections even melted (the fuse did not
> blow). Anyway I bought all my switches from American Champion (they are
> installed in their Citabrias). I specified that this particular landing
> light switch should be rated for 20 amps. But it failed after 20 hours on
> the airplane. But when I removed the damaged switch, I see that there are
> no specs on it at all.
>
> The other switches I have installed are different and have specs engraved
on
> the side. Here's what it reads:
>
> 10A 250V AC
> 15A 125V AC
> 3/4 HP 250V AC
> 1/2 HP 125V AC
> 4.2 AL 125V AC
>
> It is a Cutler Hammer switch but I cannot find any model number on it.
>
>
> So my question is: Do you think this switch would handle a 14 amp load of
> my landing lights?
>
>
> Doug Weiler
> N22DW RV-4 (26 hours)
>
>
Message 2
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| Subject: | Re: Electrical question |
--> RV-List message posted by: "Elsa & Henry" <elsa-henry@darlor-watch.com>
Doug,
It's the in-rush current to a cold filament that kills switch contacts! If
you have a good ohm-meter, it would be interesting to measure the resistance
of your lights circuit (un-powered, of course). You will be surprised at
what you get!----For instance, the standard 120 volt 100watt household lamp
has a cold resistance of around 10 ohms, which equates to an instant
in-rush current of 12 amps as compared to the nominal (hot filament) current
of 0.83 amps. That's why these bulbs usually fail the instant of switch-on.
Also AC rated switches are not applicable to DC because the arc caused by
switch-on in-rush is not longer than half a cycle of the AC frequency (8.3
mS for 60HZ). Therefore their contacts do not have to be as robust as
DC rated switches Whereas switching DC can cause a an arc of duration
depending mostly on the circuit resistance, speed of contact make/break and
the inductance of the circuit.
The late Bill Benedict, ex GM of Van's wrote a very good article on the
subject of AC vs DC switches in the RVator a few years ago
Cheers!! --Henry Hore
Message 3
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--> RV-List message posted by: "michael michael" <top_gun_toronto@hotmail.com>
Well. I`m hooked.
I`m in love with RVs. I`m new to this scene & i`m starting from nothing
tools wise.
I`m intrested in talking to anyone who wants to sell. Kindly treated tools,
Unfininshed kits. Videos. Help guides & anything else you think a newbee
needs.
I`m in Canada. Here we new to have a pre-cover inspection. So any kits that
have already been Reveted closed. (Wing or tail feathers) won`t be good for
me.
I`m also willing to pick up cash in hand, if your close to the border. I
live near Niagra Falls. I`m willing to drive 6-7 hrs to pick up
Any advise about where to go to find second hand stuff would be great.
I`ve realy enjoyed reading the postings on here. I`m a little lost now but
I`m sure as i start to build the kit I`ll be reading everything on here
daily.
I`m going to Airadventure. Do kitbuilders bring second hand stuff to swap
there?. Are there guys there selling tools? & help videos? Its my first time
there, not sure what to expect.
Thanks
Michael In Canada.
Message 4
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| Subject: | Re: Electrical question |
--> RV-List message posted by: kempthornes <kempthornes@earthlink.net>
#139 Oct 97 "Robert L. Nuckolls, III" "A Switch is a Switch or is it?"
Check out this very relevant email from good old Electric Bob (in the
archive) It is a pretty complete guide to switch selection, ratings etc.
K. H. (Hal) Kempthorne
RV6-a N7HK flying!
PRB (El Paso de Robles, CA)
Message 5
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--> RV-List message posted by: Wheeler North <wnorth@sdccd.cc.ca.us>
ahh Gert,
you guys got it easy up there at North Point, you want to hear whining try
taking a C-195 all the way down to Fon du lac past row 165. One can actually
hear the whine over the sound of the round engine. The further south you go
the louder it gets. ;{)
Seriously folks, I only had two pilots who truly tried to kill my orange
vest last year, with me in it; and neither of them had signs, nor did they
know squat about hand signals. Take the time to throw your AIM in the
cockpit and study those again before you get to Ripon.
Gert, if you run out of room, we love homebuilts down in VAP or VAC.
Also, guys keep your eyes open for yahoos, some greats from last year, 230
pounder sitting on the leading edge bottom wing of a stearman in the rain,
enjoying a smoke, a 180 pounder standing halfway out the wing of a navion so
he could get the whole cockpit in his view finder (that one left dents),
dozens of juvenile darters trying to beat a path in front of the prop, and
lots of clandistine smokers. Keep your nostrils open and if you smell one,
ask them nicely to put it out, and then smack 'em if they give you a dirty
look.
Oh, and there was one little rodent whose parents thought it perfectly
acceptable to let him chase Shawn Tucker down the taxiway. Just so everyone
knows, the EAA gets a major distance wavier for the airshow demonstrations.
Without it there would be no aircraft or people parking east of the n/s road
between the road and the west taxiway for 18/36. This wavier depends soley
upon EAA's ability to keep every non orange vested body part west of the
showline perimeter during the entire time the NOTAM is in effect. This
includes toes, fingers, chairs, umbrellas etc. Enjoy the show and don't get
too upset if I step on your overhanging toes, or if your unattended
chair/cooler/kid gets deported.
One final note, when you are departing you also need an orange vest to get
you out regardless of how close you are to a taxiway. We are doing our best
but sometimes there are many more departers then there are vests,
particularly if the WX looks like pending funcky. In any case don't fire up
without an orange vest close by.
See ya all out there on the flight line, I'll be voluteering at Arlington as
well, so I may see some of you sooner than later.
W
do not archive
Message 6
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--> RV-List message posted by: Wheeler North <wnorth@sdccd.cc.ca.us>
Guys,
I'm getting a little fed up with Van's amp gauge, and in particular with
their lack of response to the fact that it is a bad design.
I haven't talked to them about it in a while, but I will share with you the
saga so far.
1. It has never read correctly in that when I turn things on it doesn't seem
to change much (when reading alternator load) unless its a major user like a
light going on.
2. It goes massively haywire when the either radio is in xmit, and I have
met dozens of folks with this problem.
3. It is the only Amp gauge I have ever seen that needs a postive and
negative source along with the shunt lines. Consequently when the master is
activated it then provides a path for current to bypass the instrument
circuit breaker when wired as per Vans schematic. If the amp gauge power
source is disconnected Item 2 stops happening to the other Vans gauges which
go wacky with xmit.
4. I was doing some work troubleshooting a serial data problem this week so
I had my Fluke 99 DSO out there and decided to get a hard measure of the
alternator load with various devices turned on. It turns out that this amp
gauge is misreading by 14 amps, ie it reads zero until there is 14 amps
going through the shunt. (my charging system is set up so I can switch the
gauge between reading battery charge, or alternator load)
Now you might think "well you must have a bad gauge" Well, I have two of
these brand new bad gauges, as well as two of the shunts, and no combination
of them makes this system read correctly. I even took them completely out of
the aircraft and hooked them up to my recently calibrated power supply and
found that the shunt V drop was normal, but the gauge would not read until
the current got fairly high (My little pwr supply does not put out 14 Amps).
Now, how do I feel about this. Well, I attempted to solve this several years
ago with Vans and they were very resistant to the idea of there being a
problem. If it were happening in certified aircraft they would have had an
AD slapped upside their putzy gauge in seconds as this design is potentially
very dangerous.
So those of you who are considering this line of gauges, be forewarned,
there are still some bugs in this design, and I'm not the only one who has
had these problems. I strongly recoommend if you are using this gauge, get a
valid means to assess actual current flow through the shunt. In this
installation I could have a 13 amp discharge and the unit would say all is
well.
I guess I should try talking with Tom G about it again and see if they would
ever be willing to look into the problems this design is having.
Any thoughts folks???
I like the gauge face, maybe I can swap it into a real amp gauge and just be
done with it. ;{)
W
Message 7
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| Subject: | Re: Electrical question |
--> RV-List message posted by: "Meketa" <acgm@gvtc.com>
Doug
Like Wayne stated the easiest solution would be to use a
SPDT switch to split the circuit, running half the total
current to each switch contact. I would recommend a
high quality switch such as a sealed Microswitch, Eaton, or
Honeywell.
Cutler-Hammer is made by Eaton, what was the type and which
terminal connectors did the failure switch have? Was the switch
contact the failure point? I had a Carling brand switch (supplied by Bob
Knuckolls) short to the case. The obvious cause was the staked rivit
holding the terminal blade was loose which heated the blade and switch,
distorted the moving contact holder which touched the case which is
grounded. This was on a strobe circuit which is always left in the on
position and has fairly low current draw. The wire terminals and switch
contacts were still in good condition.
Be sure and use high quality terminals and good crimping
technique. This is where many problems start. Blade/push-on
/Fast-On terminals are bad about getting loose and causing
high resistance if quality terminals are not used. The quality
ones are not as readily available as ring terminals, do not
compromise. For higher amperage draw and safety items I
prefer screw terminals.
Others have suggested using relays. Unless a mini-type small
amperage switch is used, a shorter run of the thicker gauge
wire is desired due to positioning of the circuit devices or some
other specific need, a relay is no better than a good quality switch.
In fact it just gives more to go wrong. The switch contacts on
a 30 amp Bosch fog lamp relay are no larger (likely smaller)
than the high quality switch. Relays do have their place, unless
there is a good reason not here.
Another topic has been how to convert AC rated switches to
a DC rating. A high quality switches 115 volt amperage rating
is comparable to the amperage rating in 14 volt DC. Bob
Knuckles has an article on his web site giving some information
on this subject. If this was not the case landing light and
pitot heat switch failures would be an everyday occurrence.
To sum it up. Use high quality switches, wire, connectors, etc.;
properly design and install all circuits using good crimping and
installation techniques and there is little chance of problems.
George Meketa
RV8, N444TX, 338.3 hours
> Fellow Listers:
>
> Here's a question for the electrical experts out there...
>
> My newly flown RV-4 has two wing-tip landing lights. These are the
> Duckworth lights and I have 100W bulbs in them. By my calculations these
> two lamps draw about 14 amps total (they are wired thru one switch and a
20
> amp fuse.) Today I had the switch fail. It got hot and started putting
out
> very bad fumes and the terminal connections even melted (the fuse did not
> blow). Anyway I bought all my switches from American Champion (they are
> installed in their Citabrias). I specified that this particular landing
> light switch should be rated for 20 amps. But it failed after 20 hours on
> the airplane. But when I removed the damaged switch, I see that there are
> no specs on it at all.
>
> The other switches I have installed are different and have specs engraved
on
> the side. Here's what it reads:
>
> 10A 250V AC
> 15A 125V AC
> 3/4 HP 250V AC
> 1/2 HP 125V AC
> 4.2 AL 125V AC
>
> It is a Cutler Hammer switch but I cannot find any model number on it.
>
>
> So my question is: Do you think this switch would handle a 14 amp load of
> my landing lights?
>
>
> Doug Weiler
> N22DW RV-4 (26 hours)
Message 8
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--> RV-List message posted by: <mphill@gcctv.com>
Please see the attached zip file for details.
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