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Fergus Kyle
Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada
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 Posted: Sat Jul 19, 2008 5:22 am Post subject: Ignition cables |
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Bob N:
I have a Rotax 914, which among other things reveals a pair of
ignition wires terminated in female bullet connectors. I have read
discussions regarding Radio Magnetic Interference and must route these to
switches such that I can disconnect them at the firewall for instrument
panel removal and engine removal both.
In view of the engine bullet connections, I opted to relay the wires
in RG400, using BNC connectors at both sides of the firewall - two double
female BNC bulkhead, on 1/32" stainless steel mini-panel through the
firewall. The choice then became which BNC males would I use for the f/w
contacts. I opted for male BNC crimp connectors - for ease of installation
on RG400 and easy disconnect either side. Using solder models seemed a
painful exercise in view of the fidgety steps required, (ham radio
experience here). The cabin side will continue in RG400 to Ignition switches
on the instrument panel.
The Europa instrument panel is minimal and proper distance 'twixt
ignition wires and others dictated a thorough braid grounding, at the bullet
end to the engine casting and (following manufacturer's instructions) at the
earthing end of the ignition switches to achieve proper shorting for safety.
All connectors will be buttressed by heatshrink for security and to
forestall unprogrammed shorts or broken wires - both of which are safety
considerations.
Never having had connection problems with BNCs over 30 years, I
thought I had chosen well, but I'm a flyer not a builder so beg confirmation
that my thinking is correct.
Should I box in the switches electrically to continue shielding all
the way to the finger point, or is the interference minimal at that point in
your estimation? I hesitate to add another last minute mod to the many
already waiting to spring..........
Your sage guidance ( and perhaps of others) greatly appreciated -
when you have time...
Cheers, Ferg
Europa A064
Wiring wiring wiring
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nuckolls.bob(at)cox.net
Guest
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| Posted: Sun Jul 20, 2008 9:43 am Post subject: Ignition cables |
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At 09:19 AM 7/19/2008 -0400, you wrote:
| Quote: |
Bob N:
I have a Rotax 914, which among other things reveals a pair of
ignition wires terminated in female bullet connectors. I have read
discussions regarding Radio Magnetic Interference and must route these to
switches such that I can disconnect them at the firewall for instrument
panel removal and engine removal both.
In view of the engine bullet connections, I opted to relay the wires
in RG400, using BNC connectors at both sides of the firewall - two double
female BNC bulkhead, on 1/32" stainless steel mini-panel through the
firewall. The choice then became which BNC males would I use for the f/w
contacts. I opted for male BNC crimp connectors - for ease of installation
on RG400 and easy disconnect either side. Using solder models seemed a
painful exercise in view of the fidgety steps required, (ham radio
experience here). The cabin side will continue in RG400 to Ignition switches
on the instrument panel.
The Europa instrument panel is minimal and proper distance 'twixt
ignition wires and others dictated a thorough braid grounding, at the bullet
end to the engine casting and (following manufacturer's instructions) at the
earthing end of the ignition switches to achieve proper shorting for safety.
All connectors will be buttressed by heatshrink for security and to
forestall unprogrammed shorts or broken wires - both of which are safety
considerations.
Never having had connection problems with BNCs over 30 years, I
thought I had chosen well, but I'm a flyer not a builder so beg confirmation
that my thinking is correct.
Should I box in the switches electrically to continue shielding all
the way to the finger point, or is the interference minimal at that point in
your estimation? I hesitate to add another last minute mod to the many
already waiting to spring..........
Your sage guidance ( and perhaps of others) greatly appreciated -
when you have time...
|
I think you've made this much too complicated my friend. The 914's
ignition wiring is no more "ugly" with respect to noise and
installation imperatives than our beloved mags . . . and probably
even less so.
The "bullet" connectors are more problematic than the kind
of wire you use. These are large area, low pressure connections
not unlike our glass-cartridge fuse holders of yesteryear.
Knife splices under heat-shrink are much more aircraft-friendly.
You could run an ordinary twisted pair of 20AWG wires to the
switches on the panel but at most, ordinary shielded wire treated
at the ends with techniques described in
http://aeroelectric.com/articles/shldwire/shldwire.html
would be entirely sufficient to your task. You could put
rings or fast-ons on one end for the switch and knife-
splices on the other end to connect to the engine.
I'd save that RG400 for those magical radio signals
that truly benefit from the capabilities of high quality
coaxial cable.
Bob . . .
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Fergus Kyle
Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada
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| Posted: Sun Jul 20, 2008 7:01 pm Post subject: ignition cables |
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Bob N,
As usual you have been right on the money in my instance.
First of all, confronted with the bullet connections (hardly metric,
for a 914) I presumed that it must be something much more complex and thus
my first query.
Secondly, I employ a Dynon engine display unit with its multitude of
small wires bunched almost exactly where the Mag switch lines were to enter
the instrument panel. I imagined the worst.
Third, it appears the switches will have to site almost up against
my other weakness, a 10inch screen run by a MiniMac for GPS, APRS,
navigation etc.
All of this left me with the fear that even the slightest ignition
RMI would affect the second two, and determined to run it with the securest
coax cover I know - the RG400. To realise that your solution, the looping of
the centre coax wire out of its shield and termination (a task I have
performed perhaps hundreds of time in HF gear) is enough - convinces me I'm
in the wrong hobby.......
Nevertheless, having today produced a stainless steep panel for twin
feed-through BNC females at the firewall and a alu box which houses the back
of the two switches, I am committed to completing the fiasco and will
probably have the cleanest ignition result in four counties.....
Ah well - a purified soul leads to a good night's sleep.
Again many thanks for your help and advice.
Ferg
PS - and because I was trying to use a 2-blade coax stripper, I couldn't
fathom the dimensions.
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nuckolls.bob(at)cox.net
Guest
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| Posted: Mon Jul 21, 2008 6:08 am Post subject: ignition cables |
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At 10:57 PM 7/20/2008 -0400, you wrote:
| Quote: |
Bob N,
As usual you have been right on the money in my instance.
First of all, confronted with the bullet connections (hardly metric,
for a 914) I presumed that it must be something much more complex and thus
my first query.
|
<snip>
| Quote: | All of this left me with the fear that even the slightest ignition
RMI would affect the second two, and determined to run it with the securest
coax cover I know - the RG400. To realise that your solution, the looping of
the centre coax wire out of its shield and termination (a task I have
performed perhaps hundreds of time in HF gear) is enough - convinces me I'm
in the wrong hobby.......
|
Naw . . . there are many recipes for success in every venue
and not every chef gets there by the same roads. The nice
thing about these activities is the daily opportunity to
go to bed tonight knowing something new that we did not wake
up with this morning.
| Quote: | Nevertheless, having today produced a stainless steep panel for twin
feed-through BNC females at the firewall and a alu box which houses the back
of the two switches, I am committed to completing the fiasco and will
probably have the cleanest ignition result in four counties.....
|
Very good my friend. What you've proposed will certainly
function as needed.
| Quote: | Ah well - a purified soul leads to a good night's sleep.
Again many thanks for your help and advice.
Ferg
PS - and because I was trying to use a 2-blade coax stripper, I couldn't
fathom the dimensions.
|
Hmmm . . . do I recall having shipped some strippers
up to you guys in Toronto . . . or was that somebody
else? I think that was right after I did the seminar.
Were those 2-blade strippers?
Bob . . .
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