Meet the All-Roadster. Or, at least, the bare bones of it. And ignore the wheels. They are there to hold the beast up for the pics, but won’t be any use once it is built because the bike will use disc brakes and those wheels don’t have disc-compatible hubs.
So, what’s it all about? ‘All-Roadster’ is my little joke; the frame and fork are close in concept and execution to the existing Roberts Roughstuff model but with one small refinement: the frame will accept either derailleur gears or hub gearing.
Which hubs? Not a SRAM T3 or Sturmey S3X, both being too narrow across the locknuts. The standard 135mm mtb measurement instead suits such beauties as the Rohloff Speedhub, Shimano Alfine and SRAM i-Motion 9. The two latter are, of course, much less expensive than the fabled Rohloff, and will be put to the test on this very machine although that’s not to say a Rohloff won’t be pressed into service at some point.
Why the ability to take either hub or derailleur gears? The 135mm OLD common to both as detailed above makes such versatility easy to achieve, with but one problem to overcome assuming the use of disc brakes. These must be centred on the wheel spindle, meaning that if they are attached as usual to the stays and fork, chain tension cannot be adjusted by moving the wheel back and forth.
Instead, the plan is to use a tensioner, which will be OK because unlike a fixed wheel transmission, there is no pull on the underside of the chain. There are two outer cable stops on the underside of the chainstay, one to work with a rear derailleur and one further forward to accommodate a hub gear shift cable.
Componentry will include road lever-compatible disc brake calipers and a double chainset even with the geared hub since the tensioner will be able to take up slack. Various shifting mechanism for the hubs will see operation. The frame will take a wide selection of tyres and the whole thing should be capable of going anywhere accessible to a fully-rigid mtb while offering many of the advantages of a road riding position.
Watch this space….
