On 3 Dec 2012, at 20:33, Frans Veldman wrote:
> The official Rotax electrical installation diagram assumes that you
> don't have a ground connection at the switch end of your setup.
> Make sure you meet that assumption, or very unpleasant things can
> happen. This means that you have to double check that no ground wire,
> metal bracket, or whatever is attached to the ignition switch in any way.
Frans - thanks for your reply.
I don't want to keep flogging a dead horse as I think I have a satisfactory
answer
to my original question.
But it seems the diagram I attached to my earlier posting did not make it to the
list (for some unknown reason I didn't get an echo of the message myself so
can't be sure), and it clearly showed earth connexions to the 2 wire screens and
the 2 switch cases as well as to the 2 normally-open poles of the A & B
switches.
So, I have some difficulty understanding why you say that Rotax assumes
no earth at the switch end of the "p-leads".
The basic electrical circuit diagram in chapter 25 of the Europa builder manual,
although slightly different in detail from the one in the Rotax manual, also
calls for the screens on the magneto wires to be earthed at both ends.
In Bob Nuckolls' widely-respected AeroElectric Connexion, his wiring diagrams
show
the leads to the mags shielded and grounded at the switch end.
> If I would ever get corrosion on my battery or alternator ground
> connection, I would prefer a failure of my electrical system but with
> the engine still running, than the ignition screen taking over the
> ground connection for a short while before melting everything together,
> and giving me an electrical failure PLUS an engine stoppage.
I understand your concern - IF the normal earth should fail. I plan to use a B&C
common earth system which has on each side of the firewall a forest of male
blade connectors soldered to a brass plate. A brass bolt about 8mm diameter
passes
through the firewall to connect the 2 plates, and provide an anchorage for
a ring termination on a 10AWG wire from the battery. I consider the physical
integrity of that arrangement, and my planned maintenance schedule for it, good
enough not to cause me any sleepless nights.
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
| <rowlandcarson@gmail.com> http://www.rowlandcarson.org.uk
| Skype, Twitter: rowland_carson Facebook: Rowland Carson
| pictures: http://picasaweb.google.com/rowlandcarson
|