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Thanks re: brake light switch ideas

To: british-cars@autox.team.net, fordnatics@freud.arc.nasa.gov
Subject: Thanks re: brake light switch ideas
From: Roland Dudley <cobra@cdc.hp.com>
Date: Thu, 12 May 1994 13:58:03 -0700
Thanks to everyone who responded to my brake light switch query.  I got
a variety of suggestions and most of them would probably work in one form
or another, though some would require modifications I'd prefer not to make.
My preferencd is a completely reversible arrangement that doesn't
require drilling lots of holes or otherwise modifying exiting hardware.  I
might have to be a little flexible on this, but I don't want to do
anything drastic.  A couple of years ago I did drill and tap a drain
hole in the bottom of the pedal box after cleaning out 30 years
accumulation of crud.  An extra small hole or two might be acceptable.

I think the suggestion with the most potential for my particular
arrangement came form Tim Mullen.  In his words:


     I don't remember which car it was on (I think it was the Lotus),
     but I have seen switches that the brake petal _pulls_ instead of
     _pushes_.  A spring connects the petal to a hole in the switch
     plunger.  The switch is adjusted to let the spring be slightly
     slack, and the when the petal moves, the spring pulls the switch
     plunger and activates the lights.  More petal movement just
     stretches the spring.  A system like this might allow a simple
     setup...

I might even be able to connect such a switch to the hole used to attach
the pedal return spring.  As to the electrical connection, I would
probably run a couple of wires to the existing switch and either attach
directly to the connector terminals in parallel or just disconnect the
old switch all together.  Figuring out some up-stream parallel
connection probably isn't worth the effort since it would require a lot
of ohm-ing out; plus I would probably have to cut into existing wiring.

Judging from some of the responses my earlier description of the snake's
layout wasn't too clear so I've included an ASCII representation below
to clarify things for the curious.  It's not exact but gives the general 
idea.

                         ^
                         |     
                    Brake Pedal                       |
                       |  |                           |<-fire wall
                       |  |   __sheet metal cover     |         
_floor_line_...........|..|../..................._____|
            |          |  |         plunger rod | 
    steel   |  pedal-->|  |     _      |      +-|----
    pedal   |  arm     |  |    | |     v      | |
    box---->|          |  |    |o============== | Rear master cylinder
            |          |  |    | |            | |
            |          | _|____|_|<-balance   +-|-----
            (_OOOOOOOO_)(o______o)  bar         |
            |   ^      |  |    | |            +-|-----
            |retrun    |  |    | |            | |
            |spring    |  |    |o============== | Front master cylinder
            |         /    \   |_|     ^      | |
            | bottom-->(  )         plunger   +-|----
            | pivot   \____/         rod        |
            | (3/4" tube thru box)              |
            |___________________________________|

The clutch pedal is also in the box and pivots on the same 3/4" tube.

Roland


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