Zero/Ben!
Very useful information for anyone considering a conversion; thanks for passing it along.
May I share some of my observations and concerns?
Co-Motion Cycles is located here in Eugene, OR, and I was impressed on a recent visit with how their belt-drive version of the Rohloff really requires "systems-engineering" to work successfully -- at a level beyond what is required for a happy and wholesome Rohloff experience. Speaking for myself, I don't think the incremental convenience it offers is worth the extra cost and effort or disadvantages for me. Others may well differ, depending on their priorities and use.
A retrofit
can be done -- I have seen one example firsthand*, and it appeared to work flawlessly -- but much depends on the frame used, the effective "gearing" (ratios) chosen, and the skill and engineering expertise of the person doing the modification. Once done, the original frame is nowhere near "original" anymore, and right in a place crucial to its long-term strength and reliability. That would be a prime deterrent for me in going to belt drive, but there's more, as detailed by Andy Blance in his soliloquy published in the brochures. For one thing, it gets one further from standardized parts (even for a Rohloff, which is non-standard compared to the majority of derailleur options), and it makes it more difficult to adjust gearing as you wish (a big stopper for me).
[*split chainstay using a zig-zag cut in a solid insert secured by
two 5mm bolts, a custom job. The close tolerances required the seatstay halves be levered apart to pass the belt, and this is where the crimped belt mentioned below met its fate; it really required two persons' hands to do properly. A second, better method I have seen from afar is employed by Dutch maker Avaghon and uses double, overlapped Rohloff OEM sliding dropouts, one welded to the seatstay, the other to the chainstay. The same 6mm bolts that hold the sliding dropout in place also secure the two stays at the drops. A brilliantly simple and secure approach from the looks of it, but requires the sliding dropouts rather than an eccentric].
I do worry about what might happen if even a small twig flipped into the belt-drive. This recently happened to me on a remote logging road with my chain-driven Rohloff Nomad. A pencil-sized twig was flipped up by the front wheel and landed squarely on the lower chain run and was sucked back to the cog-chain intersection. The twig was nipped cleanly in two with no damage, but I kept thinking how this might have cost me a derailleur hanger on one of my other bikes. I'm not so sure a belt would survive such an event unscathed. A rock or a jamming wad of mud might do the same. The belt is effectively rigid at maximum tension, so if something has to give, I think you'd see it in stress on the belt fibers or on the cog-drive "bumps".
Still the concept and technology of belt-drives continue to fascinate me, so I keep current on developments. Thinking aloud, the listed advantages of belts over chains are:
1) Quiet to silent running.
2) No messy oil to foul trousers or legs.
3) No maintenance during its service life.
Well, if I can fit a Chainglider over my Rohloff-equipped Nomad's chain, I'll have matched most of these advantages. A well-lubed chain in a Chainglider is supposed to be quiet, my trousers and legs will be shielded from messy oil stains, and maintenance intervals will be
extended but not eliminated. This last is a shortcoming compared to belts, but in exchange, I pick up another advantage: No ingestion of sticks and such as I detailed above ('cos the chain will be fully shielded). Also, I can use standard replaceable and repairable drive components -- chainring, chain, and (proprietary but long-lived) cog/sprocket. A carried spare cog doesn't cost much in weight or bulk and won't be necessary for a very long time (especially if it can be reversed for added service).
Though I take a cut-down toothbrush and ex-mascara brush with me on-tour and floss the chain prior to re-oiling it (and have been known to stop at automobile repair shops and borrow use of their solvent tanks and compressed air), it now strikes me as better to extend the interval between cleanings by keeping the chain cleaner in the first place. I realize a Chainglider might not meet my needs where talc-fine playa finds its way into every nook and cranny, but if it helps on my rides here in the generally cool-and-damp Willamette Valley of home, that will be fine. If I wish, I can always revert to an exposed chain and bash/trouser guard for my desert runs.
I think the reply you received from Shand is a good one, spot-on for all the things that need addressing to have a happier belt-drive experience. You did us all a real service in passing it along so better, more fully-informed decisions can be made. I think Shand did a terrific job answering your questions, and I can only add that with regard to alignment, it remains critical for belt drives; they just do not tolerate the same minor levels of misalignment chains can without resulting in excess wear or outright breakage. Things have to be spot-on for belts, and that includes installation. I saw one break prematurely after it had been twisted to fit through a tight, angled opening in a seatstay. Yes, it was the mechanic's error, but the effect on lifespan was startling. You also asked...
I have also read that because belt systems have to be tensioned with a high force (10 Newtons was quoted) that it causes wear on the bearings etc.
Like you, I have not *seen* the effects of such wear, but they can be interpolated from the test data comparing chain- to belt-drive friction levels over at Friction Facts, as detailed here:
http://www.thorncycles.co.uk/forums/index.php?topic=2433.msg30187#msg30187 Their downloadable report is free after registration.
I love hearing about belt-drives and new approaches, but for now, I'll stay with chains as they're proven for me in my experience for my sort of use. I'm open-minded and a bit cautious all at once. That said, I think belts might prove most viable for use on recreational and commuting bikes rather than for expedition/world touring that included a lot of off-roading.
Please keep us in the loop if/as you pursue this. I'd love to hear how it all goes and what you learn along the way. Thanks for sharing what you have so far!
All the best,
Dan. (...who is not currently in need of a good, stiff belt, but wants to avoid a stiff chain)
