Whot's this and is it any good ?

[Gillstay]

I think this was intended to give a better change at the rear derailleur . Am I correct and did anyone ever try one out ? Thank you.

 

[fossyant]

Wot, got no piccys ?

 

[Gillstay]

damn it, just need to get the post up before the sarcastic remarks arrive.

 

[Gillstay]

Missed it.

 

[fossyant]

Never used one - handy if you've got a tight turn.

 

[Gunk]

I think it’s a shiftmate, allows you to mix Campagnolo and Shimano groupsets, I’ve used one, the cable wraps around the pulley altering the indexing

 

[Gillstay]

Aha. So such as Campagnolo changers and Shimano cogs ? There is more to it than meets the eye. I wondered why it was so well made.

 

[Gunk]

Aha. So such as Campagnolo changers and Shimano cogs ? There is more to it than meets the eye. I wondered why it was so well made.

exactly, I was using a Sora rear mech with a Campagnolo Chorus cassette. Worked a treat!

 

[simongt]

Looks similar to what I think was termed a 'travel agent' which was intended to take up slack if you had Vee brakes in conjunction with drop bars and associated brake levers.

 

[Fab Foodie]

I’ve got the same worktop….

 

[Gillstay]

exactly, I was using a Sora rear mech with a Campagnolo Chorus cassette. Worked a treat!

Well I cannot work out in my head why that would make it work, but glad to know what I can do with it.

 

[Gillstay]

I’ve got the same worktop….

Great, but is it in your shed full of bikes ?

 

[Fab Foodie]

Great, but is it in your shed full of bikes ?

No, my kitchen.
The bike shed has bespoke granite worktops….

 

[MichaelW2]

Well I cannot work out in my head why that would make it work, but glad to know what I can do with it.

It has two cable barrels of different diameter fixed together, both rotating in the housing. The input barrel connects to the cable shifter on the bars. Every click rotates the barrel x degrees in rotation.
The output barrel has a cable to the rear derailleur. For every click shift of x degrees, it converts into a length of cable pull appropriate to your mech/sprocket combo.

 

[andrew_s]

Before Travel Agents and Shiftmates, there were similar devices with a single pulley, which were intended to give easier gear changing by replacing the tight loop of cable outer by the rear mech with a relatively straight section, plus the pulley, and it looks like the OP's photo is one of these.
The name escapes me for the time being.
[edit: Avid Rollamajig]

They never really caught on, so either any improvement was minimal, or it was offset by problems caused by the pulley device.