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)