BRAKE LIGHT SWITCH

My scooter never had a stop light switch fitted as I guess this was fitted to the later models in response to legislation.  I had a look through various web sites and Blogs in the hope of finding how best to fit a switch.  The best I found was at billy192.blogspot. There is a picture of the switch mounted to the frame.  I particularly like the switch that was shown as it had a metal body. 

 I looked everywhere (if you Google "motorbike brake switch" using images you pretty soon get fed up with the options available) and couldn't find a suitable one with a metal case.  In the end I had to settle for a switch with a plastic body but with two lock nuts so that I could adjust the position of the switch in its mounting.

The switch can be bought for under a fiver and comes complete with the coupling spring 







Having found a switch the next problem was how to mount it.  Billy192 had gone for a bracket secured to the center tube using a couple of pipe clips.  I fancied a different approach.  I even considered welding a bracket to the frame but discounted this on the grounds it would be permanently altering the frame.  

 I decided that I could design a bracket that would only need a single hole to be drilled in the existing rear brake cable bracket.  This proved much more difficult than I had anticipated.  Having no right angle drill (something for next Christmas) I couldn't get a conventional drill into position.  In the end I managed to use a chuck and turn it by hand.  Starting with a 2.0mm drill I progressively opened the hole to the 5.0mm I finally needed.  It's a very slow process!

Trying to visualise a bracket can be difficult.  I have found in the past that the process can be speeded up by using paper or card.  This allows me to change things quickly before I attempt using metal.

In this case I used a scrap piece of paper and cut and folded it until I was confident that it would work.  It showed me where the critical dimensions were and allowed me to think how I was going to make it.

 This is my final bracket.  Its a bit different from the paper version but then that is the point of the paper prototype.  It allows you to see where things need adjustment.

The 5.0mm hole allows the the bracket to be "pulled" into the bracket on the frame.  The top flange prevents the bracket from twisting.  It is difficult to obtain a tight fit with two bends especially since the top bend is not parallel to the bottom bend.  To overcome this I made the bracket in two parts and welded them together.  In this way I could I could adjust the fit before welding.






The next task was to find a way of connecting the switch to the foot brake.  My switch required a pulling action for the contacts to be made.  There are no obvious attachment points and I didn't want to modify the actual pedal lever itself.  (I guess I could have found a different switch which would have been operated by the pedal lever pressing against it.  The switch would then have had to be mounted in front of the lever in a more exposed position.)
The actual movement of the brake cable is about 3.0mm.

My solution was to modify the inboard of the two cable clamping plates.  Welding a strip of steel to the clamp plate provided a point to attach the brake switch plunger.

This how the components are configured

The final installation

Using a buzzer across the switch leads I adjusted the two securing nuts until the switch made contact after approximately 1.0mm of cable movement.  Once the switch contacts have made further travel of the cable is taken up by the spring section. 






In Conclusion?  I think it will work as a stop light switch.  It's reasonably protected by the brake lever assembly both mechanically and environmentally.  How could I have improved the design?  Looking at "billy192's" configuration he has mounted his switch above the brake cable bracket so that it is less vulnerable.  I think this is a better position but at the time I did not fit the legshield to check clearance, perhaps I should.