The advantage of derailleur gears is that it is all about cable pull without any push. The rear changer spring tries to maintain the same tension whichever gear is selected. So anything which intervenes in the cable system is always under tension. This simplifies bellcrank design down to resisting only tension between the pivot and the the cable anchor points. Two radius arms, fixed together, but with different lengths matching the 1:1.38 ratio, will provide our increased cable pull per click. Indexing with the the Campag Ergo lever should be identical with an MTB shifter. As per the images in the next post. There should be no extra lever resistance when changing gear because the pull tension is so much lower on the rear changer. All thanks to the very long actuating lever.
Complex, but superbly styled to appeal to the [middle of the track] MTB'er without bottomless pockets. Other MTB changers can run up to nearly 4 times the price. This one still does 11 speeds but without some of the bling and weight saving measures of the top end stuff. The cable stop is at the top in the right foreground and the cable clamp below that in the image. It all looks very compact, when folded up like this, but can stretch to 11 speeds and a giant, 42 tooth largest sprocket. It even has a clutch to limit chain suck and floppiness over the rough stuff.
Just in case there is any doubt about the size of this thing I have arrowed the marking on the 36 tooth bottom gear. The largest sprocket measures 146.5 mm in diameter across the tooth tips. That's 5 3/4" in old money!
The cassette feels surprisingly light considering all the metal involved. It must be all that air filling in all those empty spaces. I presume this level of complexity is laser cut these days rather than CNC milled. Or even water cut?
The obverse shows the 11tooth sprocket tucked under the locking ring and held by a retaining clip all mounted on a dummy plastic free-hub for carriage and display. Sram really know how to make a cassette go faster with all those pretty perforations! You could clean the whole thing with a blast of soapy water. Or collect an even larger load of muck than a solid object! Still, it's a truly remarkable engineering design for what could otherwise be a very heavy and clunky object.
Now all I have to do is design and make a suitable bellcrank to carry out the 1:1.38 increase in cable pull using the simplest possible mechanical conversion.