By the way,
Tracy's ECU can
be powered through two different ways. The original intended way and a
sneak circuit way through the powering of the injectors. I found this
out when I wired a switch to the EC2 CPU power terminal. When I
turned off the switch the EC2 did not turn off because the injectors still had
voltage and there was a sneak circuit that kept the EC2 with DC power.
Tracy may
have eliminated that sneak circuit in later versions - but its there on
mine.
Yes; I had noted
that on mine as well – at least that the light would stay on if the injectors
were on. I don’t think I verified whether the engine would continue
running with the ECU off.
Al
----- Original Message -----
Sent:
Monday, May 02,
2005 2:28
PM
Subject:
[FlyRotary] fuses vs circuit breakers - or something
else
I
think the key point in this discussion is not so much fuses vs circuit
breakers; but that we follow the philosophy of not having single point
failures in the flight critical systems. The rotary engine has dual
plugs/rotor, most induction systems have two injectors/rotor;
Tracy’s ECU has dual
units built in (although unfortunately, common input power point); and most
of us are using dual fuel pumps. Separate and independent feeds to
each of these can eliminate single point failures.
The
choice of fuse or breaker is as much opinion as it is technical fact, and a
winning argument for either in our airplanes isn’t going to happen.
There are advantages and disadvantages to both.
I
have separate and independent power feeds to each set of coils, to each set
of injectors, to each pump, and to the ECU. I have a mix of breakers
and fuses. I happened to choose fuses (blade type) for the injectors, coils,
and pumps somewhat along the lines of Jim’s argument – I can protect those
wires with 15 amp fuses. The ECU has one circuit through a breaker,
and one fused. These circuits are as simple and direct as possible.
Battery - to fuse - to
disable switch – to component. No intermediate contactors or
connectors to fail. Of course I also have two
batteries.
Fuses, of course,
cost nothing, and can be changed out on a whim; so there is no reason for
them ever to be old and fatigued. CB’s are a thermal switch; a bit more
complex, expensive and generally difficult to change, so they are likely to
get old. That will be the only point I will make either
way.
You
choose; CB or fuse. I think that choice is less important than how you
design and execute your circuit.
FWIW,
Al
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Russell Duffy
Sent: Monday, May 02,
2005 8:21
AM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Re: finally changed to fuses vs circuit breakers
You've been working field service long enough to
know
that fuses go bad, too. They de-solder; they break due
to
vibration; the ends corrode and lose connectivity.
I've
seen this happen on cheesy fuse holders. I have never seen, or
heard of it happening on an automotive fuse. Now, don't start
telling me stories of some crappy old car that had rats in the fuse holder,
because that ain't comparable.
I have
items like fuel pumps separately fused, and to the wiring rating, so they
should never blow unless there's a good reason. Items like the EC-2
are directly tied to power, via two attachment points. This is
how Tracy recommends it,
because the controller will be it's own
fuse.
If I
had the panel space, and believed CB's offered any significant benefit, I
wouldn't care about the cost and weight.
Gotta
go pick up my new company van, and replace a switch in
Mobile.
Rusty
(discussion for entertainment only)