Today's Message Index:
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1. 05:28 AM - Re: Re: Landing gear electric actuator circuit (Robert L. Nuckolls, III)
2. 09:03 AM - Re: Re: Landing gear electric actuator circuit (Robert L. Nuckolls, III)
3. 11:33 AM - Re: Landing gear electric actuator circuit (user9253)
4. 12:00 PM - Re: List subscription problems? (GTH)
5. 03:58 PM - Test (do not open [was Re: List subscription problems?] (GTH)
6. 07:15 PM - Re: Landing gear electric actuator circuit (jdubner)
7. 10:19 PM - Total Loss Electrical System (H. Ivan Haecker)
Message 1
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| Subject: | Re: Landing gear electric actuator circuit |
At 08:51 PM 3/10/2019, you wrote:
>I am the OP but have lost track of where we are with all the thread
>drift. However, for me it is important NOT have a short across
>the motor when de-energized.
Not sure there was 'drift' so much as
a cooperative sifting of options. I'm
assuming that operating this particular
system without dynamic braking has a
demonstrated track record of satisfactory
operation and service life? I.e. dynamic
braking was shown to be of no value in
meeting design goals?
>
>
>There are two reasons why: with a short there is some back EMF and
>it contributes to additional force required to mechanically drive
>the motor by a mechanical means. (There is a 5/16" hex drive that
>can be turned with a ratchet.) It changes it from just "very
>difficult" to "impossible", at least in my aircraft.
Yup, did an actuator controller a couple
years ago wherein dynamic braking was necessary
but needed to 'go away' for manual actuation
by hand-crank. That's a pretty easy thing to
do which I can illustrate if you're interested.
>And with a short across the motor I cannot connect a power source
>(through a switch) directly to the motor to lower the gear. And
>that is why I am not happy with the circuit in my original posting.
Electrical failures of a robust design in
this situation will be very rare. Your
system operates say 20 seconds per
flight cycle? 100 flights a year is 2000
seconds or just over 1/2 hour.
Actuation systems in aircraft a generally
qualified at full load and environmental
extremes for thousands of cycles. This
system in your aircraft won't even be
broken in by the time the aircraft is
scrapped.
You have a mechanical backup for the electrical
system so going the extra electrical backup
system seems more a lack of confidence
in the primary system configuration than
a real hedge against a gear-up landing.
>I've devised an H-bridge circuit with four SPST (or two DPST) relays
>that does not leave a short across the motor and does not require
>the switch to handle motor currents (which I've measured at 6 to
>over 10A (depending on load).
The greatest stress on controls in PM motor
systems isn't the maximum operating draw.
It's INRUSH current over the duration of
contact bounce during closure. While the
motor is spinning up, current through the
circuit may be 3-10 times the running
current. If a contact bounces 5-10 times,
then wear-and-tear on contacts is more
a function of inrush characteristics and
switch mechanics than anything to do with
flight cycles and running current.
>I hope to breadboard the H-bridge version sometime this week using
>four Omron G8V-1C17T-R-DC12 I have on hand. It's relatively small
>compared to the Bosch-style relay and has a resistor built in across
>the coil for arc-suppression.
Will be interested to see your next iteration . . .
in the mean time, I'll see if I can dig up
the notes on the selective dynamic braking
design.
Bob . . .
Message 2
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| Subject: | Re: Landing gear electric actuator circuit |
> Will be interested to see your next iteration . . .
> in the mean time, I'll see if I can dig up
> the notes on the selective dynamic braking
> design.
Found the files. Here's an AeroElectric
Connection drawing that adapts the idea
from that program to a page-per-system
file . . .
http://www.aeroelectric.com/PPS/Landing_Gear/Canard%20Pusher%20Gear.pdf
The dynamic braking path is asserted only
while the gear select switch is in a
gear-up or gear-down position. When operating
the gear, the pilot would not release the
switch until the expected limit light
illuminates. During the reaction time from first
light to pilot release of the switch, the
gear system would be brought to a rapid
halt through the selective dynamic braking
relay.
Once the pilot is satisfied with gear
position, the switch is released which
also drops the dynamic braking relay.
Hence, during power failure or failure of
electrical controls, there will be no
impediment to using a manual, hand-crank
feature to lower the gear.
Bob . . .
Message 3
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| Subject: | Re: Landing gear electric actuator circuit |
Would this circuit work? The intent is to slow the motor quickly until the
induced voltage drops below zener voltage. The motor would then coast until
stopped. It should be easy to turn the motor slowly by hand. A resistor could
be connected in parallel with the two zener diodes.
I do not know if it will work, just asking.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=488012#488012
Attachments:
http://forums.matronics.com//files/nose_gear_joe_8_137.jpg
Message 4
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| Subject: | Re: List subscription problems? |
/Le 26/02/2019 21:09, Robert L. Nuckolls, III a crit:
/
> /
> List being 'dropped' for reasons unknown.
> / /
> ....
> / /
> Has anyone else experienced this difficulty? /
Been dropped on march 5th.
It seems my messages are getting through, though.
Contacted Matt 24h ago, awaiting news.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 5
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| Subject: | Re: List subscription problems?] |
/Le 26/02/2019 21:09, Robert L. Nuckolls, III a crit:
/
> /
> In each case, the victim was able to renew
> their membership through the /subscribe page
> on matronics.com
> / /
> Has anyone else experienced this difficulty?
> /
Hello all,
This is a test message.
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 6
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| Subject: | Re: Landing gear electric actuator circuit |
nuckolls.bob(at)aeroelect wrote:
> At 08:51 PM 3/10/2019, you wrote:
>
> > drift. However, for me it is important NOT have a short across
> > the motor when de-energized.
>
> Not sure there was 'drift' so much as a cooperative sifting of options.
You're very charitable, Bob -- I'm totally adrift. There are three separate postings
with suggestions ranging from quite useful to eliminating the retractable
gear so we'll have to agree to disagree on this.
I'll try to streamline this by listing my constraints and criteria.
1. A mechanical backup would be preferable but is not feasible on this particular
Long-EZ. This is because the mechanical drive would need to be located on
the center of the instrument panel where the EFIS goes and it would be exceedingly
difficult to activate.
2. For backup gear lowering only (not raising) I've decided to connect a power
source through a backup gear down switch directly to the motor. No relays, no
limit switches, different wires and connections. Same motor, same or different
power source (T.B.D. but wired to the battery bus). The motor probably won't
fail in my lifetime but the relays, microswitches, and wiring are a different
situation.
3. I don't need or want back EMF helping to hold the gear up or down. I know
this because I can bounce up and down on the landing gear and it won't budge with
or without a short across the motor. But I absolutely, positively must have
no short across the motor to implement #2 above.
--
Joe
--------
RV-8A
Independence, OR
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=488019#488019
Message 7
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| Subject: | Total Loss Electrical System |
I am currently converting an aircraft that has no electrical system
whatsoever to a toal loss system (no alternator) with a battery that is
used for starting only..My question is as follows: For starting only, do I
just need a starter contactor wired directly to the battery with a fat wire
and a fused small wire for its coil connected to a momentary contact switch
on the panel? Is there any need for a master contactor? And if I later
decide to add a couple of small current drawing devices such as a hand-held
gps and an intercom, can they also be directly connected to the battery
with small fused wires? It seems that I would still want to avoid running a
master contactor due to its current draw. Thanks for any advice.
Ivan Haecker
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