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Right, I've had a bit more of a look it this and the more I look at it, the more I like the idea of having the transfer belt on the right side inboard of the main drive rings. Good weight savings according to Paketa as you're eliminating one spider-mount arm.
This is what Paketa have to say on the subject:
Custom Yoke to mount timing belt on drive side
The CAD-designed, CNC’ed chain stay yoke is a Paketa exclusive. Who else but the company that's been working with magnesium exclusively for ten years could engineer this subtle work of art? Paketa introduced the worlds first - and still the only - magnesium tandem in 2005, and brings more experience in magnesium bicycle construction than anyone on the planet. The yoke design allows the transfer sprocket to fit in as close as possible to the center line of the frame, yet still provides enough clearance for up to a 28 mm tire—enough for even Clydesdale-class tandem teams to enjoy the benefits of a light weight Paketa tandem.So I guess you would need a special chain stay yoke to acheive this?
Also, can someone explain what they're doing with the main crank set to be able to get the gates drive inboard of the small chainring? Some sort of fancy adapter?
From these pictures, I see di2 with Sram. I'm not familiar with Sram so assume that it works ok? So you'd just need two standard cranksets?
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So I guess you would need a special chain stay yoke to acheive this?
You somehow need to find a lot of space between the rear tyre and stoker's right pedal. Straight-through drive is a good idea for the sake of both the frame and the rear BB spindle and bearings, but something has to give. I managed to squeeze a 10-speed sync chain past a fat track final drive chain on mine with some 2mm thick chainring spacers. Some touring tandems use cranks with much wider Q-factor allowing a straight through drive with the timing rings outside the final drive rings. Paketa have given themselves a tough job trying to squeeze a wide belt and two final drive rings inside a conventional road crank Q-factor, which is why they have had to resort to their special yoke.
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dunno if it's any help but I was looking at a circecycles that's in for a service in my friends shop, it has both cranksets on the same side using a triple chainset. The granny ring takes the timing chain and the other two rings set up as a double.
gbj_tester
mustard
Definitely worth looking at the Things' blog: http://blog.tandemthings.com/
They used their Tandem for RAAM, which has some big long descents on it (especially in Colorado) and they've done a whole bunch of other rides with big descents.
They've got a Paketa tandem (magnesium) with Di2 plus some other fancy bits (such as an adapted drivetrain so that the timing chain is on the same side of the drive chain, so there's less power put through the frame laterally and so less frame flex).
Don't even want to think about the cost though.