> Randall (our resident Electrical genius) - your thoughts?
IMO the whole lockout idea would not suit me at all. For one thing, I
generally start the engine first, with the handbrake still set, so that I
can use my right foot on the throttle (as needed to keep the engine running
for the first few revolutions) and still have the brakes set. Although you
can "heel and toe", it's a lot easier with the handbrake IMO. And on my TR3
(which doesn't have a front bumper at the moment), there is a very flimsy
edge of sheet metal that would contact the curb if I let the car roll
forward just a few inches while starting.
Having an override switch just moves the problem to a new level. If you use
a switch that will stay in the override position, then it's just as easy to
forget as the handbrake, which kind of defeats the purpose. If you use a
momentary switch, then it becomes really difficult to start the engine from
under the hood.
Besides, I really dislike cars that think they know what I want better than
I do. There are just too many times when I want to do something unusual,
and I don't want the car getting in my way. One of the attractions of the
TR3, to me, is that it will try to do whatever you ask it to do; no
backtalk, no question.
But if you really want to do this, my approach would be to use a relay, and
let the handbrake or override switch ground the coil (similar to the way the
OD lockout switches ground the OD relay coil). That way you don't have a
hot wire running down to the handbrake switch. Worst case, if the wire to
the handbrake switch shorts to ground, then the switch simply becomes
inoperative and the car is not disabled, set on fire, etc. And a latching
override switch could simply be in parallel with the handbrake switch.
I think to use a momentary override would require either a special relay or
a second standard relay. Might be a way to do it with a single standard
SPDT relay plus a resistor, but the resistor value would depend on the relay
characteristics.
-- Randall
triumphs@autox.team.net
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