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tonyrenshaw268(at)gmail.c
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 Posted: Thu Jun 17, 2010 8:36 pm Post subject: Relay to act as kill switch |
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Gidday,
I am electron averse. They take on personalities whenever I interact, and most often I think they are female. Suffice to say, they do what they want to, and change their minds! So, I'd like to kill them off from my aft mounted battery. I am planning a kill switch in the passenger headrest area, but was wondering running a single Rotax alternator if anyone has advice on whether I could run a "relay" that would isolate the large battery voltage with a small charge via a panel mounted switch? Rather than a big kill switch like the great one Bob Borger is using from Flaming River
http://www.flamingriver.com/index.cfm/page/ptype=product/product_id=64/category_id=133/home_id=231/mode=prod/prd64.htm
is there another way of achieving this same goal? I suppose in the case of a crash it would mean that you would have voltage still coming forward of the relay to the switch, on the panel, but it would be small and could be choked to be of low amperage? couldn't it? That way a short would kill a fuse and not create a large spark as a source of ignition. Would it be possible then to wire the relay such that when it was isolated, it would also turn off the power forward of it to operate the relay too, so that there would be "NO" power coming forward? I suppose then the switch would become useless at turning power back on, so maybe a relay could be used in another way?
Is there any point in being able to isolate....kill off alternator voltage ?? I'm not sure if the Rotax alternator has an inbuilt function or whether its voltage must be monitored by such a device if included, prior to the battery. Is this the right idea for setting up the alternator circuit?
Reg
Tony Renshaw
P.S. I apologise if this is covered in the manual, however I am away from the book for a few days with work, and am crunching away these ideas remotely.
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grahamsingleton(at)btinte
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| Posted: Thu Jun 17, 2010 11:38 pm Post subject: Relay to act as kill switch |
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Tony
you must have a large capacitor across the battery to prevent the alternator going over voltage
Graham
From: Tony Renshaw <tonyrenshaw268(at)gmail.com>
To: europa-list(at)matronics.com
Sent: Friday, 18 June, 2010 5:30:49
Subject: Relay to act as kill switch
--> Europa-List message posted by: Tony Renshaw <tonyrenshaw268(at)gmail.com (tonyrenshaw268(at)gmail.com)>
Gidday,
I am electron averse. They take on personalities whenever I interact, and most often I think they are female. Suffice to say, they do what they want to, and change their minds! So, I'd like to kill them off from my aft mounted battery. I am planning a kill switch in the passenger headrest area, but was wondering running a single Rotax alternator if anyone has advice on whether I could run a "relay" that would isolate the large battery voltage with a small charge via a panel mounted switch? Rather than a big kill switch like the great one Bob Borger is using from Flaming River
http://www.flamingriver.com/index.cfm/page/ptype=product/product_id=64/category_id=133/home_id=231/mode=prod/prd64.htm
is there another way of achieving this same goal? I suppose in the case of a crash it would mean that you would have voltage still coming forward of the relay to the switch, on the panel, but it would be small and could be choked to be of low amperage? couldn't it? That way a short would kill a fuse and not create a large spark as a source of ignition. Would it be possible then to wire the relay such that when it was isolated, it would also turn off the power forward of it to operate the relay too, so that there would be "NO" power coming forward? I suppose then the switch would become useless at turning power back on, so maybe a relay could be used in another way?
Is there any point in being able to isolate....kill off alternator voltage ?? I'm not sure if the Rotax alternator has an inbuilt function or whether its voltage must be monitored by such a device if included, prior to the battery. Is this the right idea for setting up the alternator circuit?
Reg
Tony Renshaw
P.S. I apologise if this is covered in the manual, however I am away from the book for a few days with work, and am crunching away these ist" target="_blank">http://www.matronics.com/Navigator?Europa-List
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gregoryf.flyboy(at)comcas
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| Posted: Fri Jun 18, 2010 2:44 am Post subject: Relay to act as kill switch |
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Hi Tony,
Because of the high currents needed from the rear battery, one could
substitute the relay with a solenoid of high amperage. Since it might be
hard to find a non-expensive relay to do the same.
If the solenoid needs a small amount of power on the coil to keep it on,
then when you flip the switch, there would be no power from the battery,
going forward, and no small amount of power from the panel to the solenoid
(and no female-minded electrons running around  ).
I am not positive they exist, but you might be able to find a solenoid that
will stay either on or off after the original signal to turn if off/on is
taken away. I know there are small relays like this, there are probably
solenoids this way too. If that is the case, then you could actuate the
solenoid and take the original power away, when turning it off...or on. In
the event of a crash, (unlike the previous solenoid, which is spring driven
in one direction) the force could slide the internal bar in this 'noid' to
the on position, so be careful to have the 'off' position on the side that
it would slide to, if a crash happened.
There is another option. Many/most? Fuel injected cars have a cut-off switch
in the event of an impact. This is so, because the high pressure pumps would
supply a lot of fuel to a fire, after the fuel lines were severed, which is
almost guaranteed to happen in a high impact crash and metal fuel lines.
This switch could be used to turn off pretty much whatever you like, and it
would happen right at the moment of impact. I am not sure of their current
rating right now, but they are pretty high, possibly even being capable of
cutting power off to the entire vehicle. Might be worth looking into, since
it kind of matches the application. They have a reset button on them, in
the event that you want to turn them back on, and would be very cheap at a
second-hand automotive recyclers (U-Pull-it, and such).
As far as killing off alternator power, are you talking about in the event
of a crash? If so, it would happen automatically if the engine were off, and
not turning. Since we are all skilled pilots ), one might be able to
assume that the engine was off, if we are going down. There are ways to
short out the windings from the alternator, to keep the current looping from
the output of the alternator, back into itself, which keep the voltage way
down (along with a chance for a spark), but I am not sure if the
complication is necessary or needed. Besides, it adds one more thing that
can fail, and in the bad way of cutting off the alternator.
Hit me with questions if you like, otherwise...I hope this helps a bit.
Greg Fuchs A050
--> <tonyrenshaw268(at)gmail.com>
Gidday,
I am electron averse. They take on personalities whenever I interact, and
most often I think they are female. Suffice to say, they do what they want
to, and change their minds! So, I'd like to kill them off from my aft
mounted battery. I am planning a kill switch in the passenger headrest area,
but was wondering running a single Rotax alternator if anyone has advice on
whether I could run a "relay" that would isolate the large battery voltage
with a small charge via a panel mounted switch? Rather than a big kill
switch like the great one Bob Borger is using from Flaming River
http://www.flamingriver.com/index.cfm/page/ptype=product/product_id=64/categ
ory_id=133/home_id=231/mode=prod/prd64.htm
is there another way of achieving this same goal? I suppose in the case of a
crash it would mean that you would have voltage still coming forward of the
relay to the switch, on the panel, but it would be small and could be choked
to be of low amperage? couldn't it? That way a short would kill a fuse and
not create a large spark as a source of ignition. Would it be possible then
to wire the relay such that when it was isolated, it would also turn off the
power forward of it to operate the relay too, so that there would be "NO"
power coming forward? I suppose then the switch would become useless at
turning power back on, so maybe a relay could be used in another way?
Is there any point in being able to isolate....kill off alternator voltage
?? I'm not sure if the Rotax alternator has an inbuilt function or whether
its voltage must be monitored by such a device if included, prior to the
battery. Is this the right idea for setting up the alternator circuit?
Reg
Tony Renshaw
P.S. I apologise if this is covered in the manual, however I am away from
the book for a few days with work, and am crunching away these ideas
remotely.
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frans(at)privatepilots.nl
Guest
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| Posted: Fri Jun 18, 2010 4:03 am Post subject: Relay to act as kill switch |
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On 06/18/2010 06:30 AM, Tony Renshaw wrote:
| Quote: | So, I'd like to
kill them off from my aft mounted battery. I am planning a kill
switch in the passenger headrest area, but was wondering running a
single Rotax alternator if anyone has advice on whether I could run a
"relay" that would isolate the large battery voltage with a small
charge via a panel mounted switch?
|
What you could do:
Mount a (car-style) relay (soleonid) of 40 Amps switching capacity next
to the battery. This connects the system bus with the battery. This
relay is activated by applying 12 Volts on its coil. The 12 Volt for
this is taken separately via a small fuse (about 1 amp), fed to the
switch on the instrument panel, and then to the coil. The switch is then
used to power up/down the ship. This fuse should be mounted as closely
as possible to the battery.
This is a pretty normal way to control the system bus. So far so good.
Now you add a separate KILL switch. This switch simply shorts the 12
Volt running to the power switch to ground. Throw this switch, and the 1
Amp fuse blows.
After this has happened:
1) The power to the coil of the relay is gone. Thus the relay drops off
and cuts the power to the ship.
2) The power to the power switch, which runs via the separate fuse, is
gone too, as the fuse has melted. There is no wire left carrying any
voltage anymore in the ship.
3) There is no way to power the ship up again. Power is permanently
gone... until you replace the fuse.
Needless to say that this KILL switch needs to be of a very good
quality, and guarded by a mechanical latch. As with all protections, you
introduce a small quantity of failure points as well. If the fuse
inadvertently blows (they sometimes do), power to the ship is gone. If
the KILL switch fails in the ON position, or is inadvertently switched
ON, power is irreversibly gone too.
Also, for this system to make sense, you should have no permanently
powered items in your ship (like the manual recommends for the stall
warner and vertical trim).
Another thing you could do is to obtain an old fashioned ELT. They are
scrap now 121.5 is no longer monitored by satellites. It should be
possible to get them on eBay for scrap value. Go for the switch inside
that activates by any (de)acceleration over 6G's, and use that one to
blow your fuse automatically. Again, of course you introduce another
failure point.
Personally, I didn't go all this far. What I did is to feed the system
bus via a car-style relay of 40 Amps mounted next to the read mounted
battery. The relay is permanently connected to the +12Volt, as is its
coil. The other end of the coil is connected via the system switch to
ground.
So, if the aircraft is powered down, the only voltage carrying wire is
the wire to the switch... but it is connected to the 12 Volts with the
coil of the relay in series with it. So, if this wire is shorted to
ground, the only thing that will happen is that it activates the relay
(which then powers up the ship). This is the worst that can happen.
Reasons that I didn't go any further are:
If you want to be sure that all spark-potential power is gone, you
shouldn't bring laptops, mobile phones, camera's etc. with you. The
modern lithium-ion batteries pretty much explode when they are shorted,
which is likely to happen if they receive a dent or are ruptured,
punctured or whatever during a crash.
Even without power to the ship, it is likely that crashing will
generated some sparks by its own, due to friction of metal parts. With
the fuel tank behind your back, with its connections just 1 cm above the
airplane bottom, it is unfortunate that a fire is very likely in a
serious crash.
I have been considering to make a fuel dump. A large valve to allow the
fuel to escape while still being airborne. Without fuel, sparks are not
dangerous anymore. Of course this makes only sense if you know the crash
is going to happen (just like with the kill-switch) and you have the
ship under control enough to make a controlled crash landing. Kill
switches or fuel dumps are worthless of course if you are going to dive
above Vne into the ground anyway.
I didn't implement a fuel dump, as this would introduce a potential
hazardous failure point in the fuel system. Imagine the fuel dump to
activate inadvertently...
What you should do in my opinion in case of a Rotax 914, is to have a
one way valve in the fuel return line. If the engine breaks off the
airplane, the tank can not syphon itself empty via the broken fuel
return line. And of course, if you have to make a crash landing, but are
able to delay the event, such as in case you left your gear behind on
the runway, or your rudder cable broke, or your elevator is stuck at the
140 knots position, or whatever... you'd better fly your tank almost
empty before attempting to land.
So, in case of an anticipated crash landing, I will just close the fuel
valve, throw the master switches, and go for the best. If the crash is
severe enough that it ruptures the fuel tank, changes are that it wasn't
a survivable crash anyway.
Frans
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frans(at)privatepilots.nl
Guest
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| Posted: Fri Jun 18, 2010 5:56 am Post subject: Relay to act as kill switch |
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On 06/18/2010 06:30 AM, Tony Renshaw wrote:
| Quote: | is there another way of achieving this same goal? I suppose in the case of a crash it would mean that you would have voltage still coming forward
|
Thinking about it, and your electron aversion...
Why not connect the battery via two plugs that can be pulled apart.
Make a hatch below the battery, closed with a safety pin, connected to a
rope leading into the cockpit. No fancy electrons needed.
In an emergency, on final for your crash landing, pull the rope. The
weight of the battery will for sure pull the plugs apart on its way out.
Bye bye battery.
Advantages:
1) No fuses, no switches, no wires, no relays, no mess. No female
electrons to bug you during final on your crash landing. Just a rope and
pin. People have relied on these for ages for various of purposes. Every
mechanic understands how it works.
2) There is nothing to spark left, no relays that can switch on again
due to the forces acting upon them, no battery that might get punctured
by your elevator mass balance arm and emit a shower of sparks as a
result, your knee can't bump into the master switch and power up the
ship again during the most critical stage of the crash, everything with
sparking ability is just simply dumped overboard.
3) The aft-mounted battery won't bump into your head, it is already
gone. One thing less to worry about.
4) The reduce in weight might well be an advantage in getting the
aircraft to a stop. The lighter the aircraft is, the less mass you have
to decellerate.
Just keep it simple.
Of course you have to attach a red "for emergency use only" label to the
rope and brief your passengers not to pull on it while asking "what is
this for" when your are circling his home vilage. If you want to be
fancy you cat attach a small parachute to the battery. This has the
additional advantage that you can test the system overhead your airfield
and it won't cost you a new battery.
Frans
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gregoryf.flyboy(at)comcas
Guest
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| Posted: Fri Jun 18, 2010 10:45 am Post subject: Relay to act as kill switch |
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Just keep it simple.
Of course you have to attach a red "for emergency use only" label to the
rope and brief your passengers not to pull on it while asking "what is this
for" when your are circling his home vilage. If you want to be fancy you cat
attach a small parachute to the battery. This has the additional advantage
that you can test the system overhead your airfield and it won't cost you a
new battery.
Frans
_______________________________________
In keeping it simple, it is getting complex....and jovial. Maybe it's the
fatigue of late night, and the mood is right.
I am feeling somewhat fatigued myself, so to contribute to the comedy, here
is my addition.
Explosions can put out fires. Why not attatch a small thermonuclear device
in the back, with a rope connected to the trigger. Then when things go bad,
the explosion 'fixes' everything...and no chance of pain. Also, this way,
there is nothing left to fall out of the sky, but little pieces of glass and
..ok one heavy engine, but that is all. Too jovial you say? All right,
maybe I am a little too fatigued, and maybe a little light-headed
too.........time to sleep and all will be better. Tomorrow will be back to
business on the list
Greg
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gregoryf.flyboy(at)comcas
Guest
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| Posted: Fri Jun 18, 2010 11:55 am Post subject: Relay to act as kill switch |
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Hmmmm......this message took 4.5 hours to appear on the server, after it was
sent. That is by far the longest I have ever seen. The previous message,
sent just before it, only took a few minutes. I wonder why that is?(Thinking
aloud)
Do not archive
--
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frans(at)privatepilots.nl
Guest
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| Posted: Fri Jun 18, 2010 11:55 am Post subject: Relay to act as kill switch |
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On 06/18/2010 04:27 PM, Greg Fuchs wrote:
| Quote: | Explosions can put out fires.
|
That's right. And you can also use it to blow a hole in the fuel tank,
if you need to empty it in a hurry.
The Saturnus V rocket was already equipped with explosives, to separate
the stages, to separate the service module from the command module, to
release itself from the launch pad, and... to rip open the fuel tanks in
case of an airborn abort.
So, we should learn from that. If it is good enough for a Saturn V, it
ought to be good enough for an Europa. I like the idea of ripping the
fuel tank on final, and getting all gas out before "touching" the
landing spot. "ATC, we have a problem..."
Just make sure the switch is sufficiently latched against inadvertent use.
Frans
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gregoryf.flyboy(at)comcas
Guest
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| Posted: Fri Jun 18, 2010 2:25 pm Post subject: Relay to act as kill switch |
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| Quote: | Just make sure the switch is sufficiently latched against inadvertent use.
For God sakes, yes!!
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| Quote: | So, we should learn from that. If it is good enough for a Saturn V, it
ought to be good enough for an Europa. I like the idea >of ripping the fuel
|
tank on final, and getting all gas out before "touching" the landing spot.
"ATC, we have a problem..."
I think I just left matronics and turned on comedy central.
You could be a stand-up comic too, along with all your other skills
Maybe with a little more work, and a rocket, we could get our little Europas
to fly us to the moon. I think that would make a great doth spot. Anyone
want to go first?
--
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