Brake light switch location

[STEVENM63]

Can someone tell me, or better yet, post a picture of where to mount a brake light switch? I am trying to put a race bike back on the street and it doesn't have a switch mounted. I assume that only the rear brake actuates the brake light and there is not a switch for the front brake, correct?

Steven

[JimF]

Yes. that is correct. There is no front brake switch. There should be a bracket on the frame, with a hole facing forward just behind the brake. The threaded top of the switch pokes through the hole and a large nut secures it.

The actuating rod of the switch has a hole in it, and there is a small hole in the back 'elbow' of the brake pedal.

A very loose and stretch spring secures in each hole so as to pull on the actuator early and then stretch quite a bit without adding excess pressure to the switch or resistance to the brake lever.

On the Mach 1 the bracket is up above the swing arm, presumably owning to the curved brake lever.

m1 brake switch.jpg

On the street frame it is below the swing arm.

other brake switch mount.jpg

Be aware too that just to add more confusion to the mix, the switches came in opposite flavors. One was normally closed and momentary open when the brake was depressed (NC MO) and the other switch was normally open and momentarily closed by the brake actuation. I think the NC switch was vor the battery bikes, and the NO was for the magneto bikes.

Jim

[Nick]

Late model Triumphs had a brake light switch integral with the front brake cable. You could simply cut up one of those cables to fit your Duc, plug in the two brake light wires and you're good to go. The cable could be modified for use with either the front or rear brake.

[DewCatTea-Bob]

Late model Triumphs had a brake light switch integral with the front brake cable. You could simply cut up one of those cables to fit your Duc, plug in the two brake light wires and you're good to go. The cable could be modified for use with either the front or rear brake.

____ OR, ya could rather make-use of just a single mercury-switch that's set-up to be activated by (any chosen amount of) deceleration.


Dukaddy-DUKEs,
DCT-Bob

[DewCatTea-Bob]

[quote= JimF ...
" the switches came in opposite flavors. One was normally closed and momentary open when the brake was depressed (NC MO) and the other switch was normally open and momentarily closed by the brake actuation. "

____ That's correct, as the battery-powered and the AC.powered electrical-systems required such differing brake-switches !
__ 'Normally-closed' or 'normally-open' refers to the steady-state that the switch is regularly kept-in when NOT activated,, so a switch's circuit is either normally-kept 'closed' (and current-passable, [thus = 'nC'] ), or, normally-kept 'open' (and not current-passable, [thus = 'nO'] ).



" I think the NC switch was vor the battery bikes, and the NO was for the magneto bikes. "

____ I know Jim actually knows-better than that, (he just got it mixed-up) ! ...
__ The AC.powered systems employ the normally-closed switch so that it normally short-circuits it's passed-current to ground (when the brake-light is to be kept off),
and the battery-powered systems employ the normally-open switch so that it normally does-not pass current (from the battery) to the brake-light, (to keep the light switched-off, [just-like most-all standard brake-switch circuits do] ).


Dukaddy-DUKEs,
-Bob

[Jordan]

Late model Triumphs had a brake light switch integral with the front brake cable. You could simply cut up one of those cables to fit your Duc, plug in the two brake light wires and you're good to go. The cable could be modified for use with either the front or rear brake.

The same British made Burgess switch was used on certain Ducatis. They work well enough until the rubber part inside it degrades - then you're up for a new cable.

[Jordan]

___ OR, ya could rather use just a single mercury-switch that's set-up to-be activated by (any amount of) deceleration.


Dukaddy-DUKEs,
-Bob

That's a neat idea Bob, but what happens when you go downhill?

[DewCatTea-Bob]

[quote= Jordan ...
" but what happens when you go downhill? "

____ That's a fairly good point Jordan...
As you must already realize, the grade of a hill will certainly indeed somewhat skew the sensitivity-setting of such a (disposition dependent) brake-switch,, but if it's not pre-set too near-to a horizontal angle that's overly sensitive, in the first place,, then even on downgrade-hills, the switch could still work & become* activated as expected, (* except on an extremely steep hill-grade, where ya would probably apt-to be already braking on anyhow).
__ Furthermore,, with regular std.mechanical-type brake-switch activation, the brake-light only gets activated just according-to some-odd limited set span-amount that the brake-lever itself (along-with the switch-linkage) gets displaced to (and-then, begins to rather-lightly engage the internal brake-mechanism and merely slightly-pressurize the brake-shoes against the drum), which then most-likely has the brake-light activated before any real* significant deceleration thereafter possibly becomes actually necessitated, thus quite-possibly falsely wasting the brake-light's actually-intended warning-effect.
Whereas with a (properly set) mercury-switch,, IT can only become activated just with ACTUAL deceleration, thus a non-false (* & non 'cry-wolf ') braking-warning !


Enlightening-Cheers,
DCT-Bob