Shimano ‘twist grip control’

[twojs.bike]

I was given a few boxes of old bike parts. (Mostly junk)

Anyone know what this shifter is for? It has two cables. Labeled Shimano Twist Grip Control.

 

[rickpaulos]

The early Positron derailleurs used a pull-pull cable & shifter. The rear derailleur did not have a return spring so the shifter had 1 long cable that made the round trip. Pulled the der out, pulled the der in. They didn't work. It used full length cable housing which adds a lot of friction. The more common stem shifter had a set screw in the lever to afix the cable to the lever. That screw would dig in to the braided cable and not hold it in place. Shifting was very loose and sloppy and would quickly not be able to reach low or high gear.

The Positron II series used a solid wire that could push and pull. Also in a full length cable housing but it wasn't a wound housing as it needed to resist stretching and compression when shifting. The precursor to modern index cable housing with it's linear wires embedded in the plastic.

More history on the Positrons here:
https://www.disraeligears.co.uk/site/shimano_positron_dg100_1st_style_derailleur.html

 

[twojs.bike]

Interesting and thank you!

I have a handful of positron derailleurs. All the single piano wire version.

Maybe I should list all of them for sale. Probably not very many people (if any) that actually want this type of stuff. The history is kind of interesting.

 

[GeePig]

You just need to find that one person with a broken gear selection handle, who is trying the restore their bike.

If only I were that person!