"A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away"

 

(Antoine de Saint-Exupery) 

Di

28

Aug

2012

Hidden throttle

Hidden throttle systems for 1 inch handle bars are available at nearly every Harley Davidson custom parts provider. The thing gets complicated if the handlebar has a diameter of 22mm. Also in the case of the ExesoR Cafe Racer project a standard clip on handle bar is applied, of course with a diameter of 22mm. The solution was found after many hours of research in the “World Wide Web”. By coincident a NSU Motorcycle spare part page was found. In the 1950´s some models use a throttle which was moving linear in the handle bar. The whole mechanism was ordered immediately with the hope for getting it applied on the standard clip on. The technique was simple but several changes on the right clip on were necessary. The big issue was to widen the last 20mm of the clip on pipe from a diameter of 16mm to 18mm. This venture was more complicated than supposed because of the welded on pipe clamp it was no more possible to fix the clip on in a turning machine. Also fixing it tight enough on the milling machine for processing with a 18mm milling cutter was not possible because is unpropitious shape. The problem was solved by widen the hole by using an 18mm drill. Once this was done, the pipe had to be processed on the milling machine. A 10mm wide slot had to be milled in the pipe for the slider. A first function test was positive. The displacement of the throttle cable from closed throttle to open throttle is about 45mm. This should be enough to actuate the Keihin carburetors. Next step will be to fit the miniature stainless steel START push button in the clip on pipe.

10mm milling cutter
10mm milling cutter
hidden throttle assembly with slider
hidden throttle assembly with slider

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