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  1. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    Given that the CSK series are already bearing supported, you could probably drop the additional support bearing and just run a CSK40 as-is, no?
  2. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    The crank axle's steel. Of course. I R An Idjit. Nah, I was suggesting that a stress riser failure mode of a shrink fit on a presumed aluminium axle certainly wasn't a good choice compared to a potential failure mode of "chewed up keyway buggers up pedalling". Hence the suggestion of a...
  3. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    OK. I'd probably have solved the problem differently, the slightest play in the keyway and it *will* get all chewed up by the key, especially if the carrier, like the nub of remaining crankset, is aluminium. My gut feel would be to lathe the whole of the spider off, then shrink fit or loctite...
  4. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    Please, don't consider my previous comment in any way a criticism. As you say, only time will tell, and if you've managed 1100km so far on it, it's doing pretty well. I'm interested in your construction, by the way. My understanding is that you have the crankset with a 35mm OD carrier mounted...
  5. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    That's top bananas, that is. Very, very, nice work. I assume in this picture, the milled cutout is for the key? If so, I think that's the bit I'd be worried about breaking.
  6. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    Yeah, a direct mount approach would be great. But it's not going to happen, at least not for an off the shelf solution, there's too many competing, incompatible "standards" out there. Take a look at this, bearing in mind that's just a compatibility matrix for the major cranksets and bottom...
  7. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    This veers wildly offtopic, and I'll shut up after this but... Yes, there have been major improvements in bike technology over the years. But there's been a lot of change for the sake of change. There's only so many ways you can innovate around a bike, after all. Here's some inspired by your...
  8. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    Back to the original question, it's gonna be relatively hard to do, and it's liable to pull your right hand crank well outboard. Option 1 would be to make up a new spindle (or modify the existing spindle) that mounts just the spider, and run a separate shaft down the inside for the cranks...
  9. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    The bicycle industry is extremely good at producing solutions to non existent problems, especially when it means you have to pay extra for the privilege. Put it this way. Selling a bottom bracket to an OEM (at OEM prices) that will in 99% of cases last the lifetime of the bike is less...
  10. simon.s

    Freewheeling Design for the Shimano Hollowtec II Crankset

    Stiffer, yes. Stronger, arguably, they're certainly harder to bend. See "stiffer". They have a much shorter life, even with only a human pushing on them. Bearings go out fast, you're lucky to get 2K km with only human input, I'd expect a lot less with motor drive as well. People pan square...
  11. simon.s

    DIY vivax style.

    Cutting into the downtube and then welding it back up would be doable, but leaves you with a totally inaccessible / unserviceable motor. Leaving it open is going to result in a bent bike (not to mention obviating one of the advantages of shoving it all in the frame in the first place...
  12. simon.s

    DIY vivax style.

    I think if you're looking to put 200W or more into the crank through a or several bearings, things might get sticky. Torque = 9.5488 * kW * rpm, so if we assume 100W and peak power at 30-60rpm, we need to handle about 60N.m, that's in spec (although towards the upper end) for (for example) an...
  13. simon.s

    DIY vivax style.

    Firstly, you're mixing efficiency and friction. Yes, high-ratio bevel drives, especially if they aren't hypoid, are low efficiency. But I'm not talking high ratio for the bevel drive, 3:1, maybe 4:1 max - at that point they are 90-95% efficient, friction shouldn't be an issue - we're turning...
  14. simon.s

    DIY vivax style.

    Of course I'm reinventing the wheel. In this case, an enormously expensive wheel. Sure, I could buy a bottom bracket kit, hang a load of batteries off the frame and end up with something ugly and heavy that rides right now (well, as soon as the post gets it to me, but hey). What I'm aiming...
  15. simon.s

    DIY vivax style.

    You might have to wait a while, this is liable to be a "slow burn". For mounting, I'm thinking a steel or aluminium (probably alu for heat dissipation) sleeve for the motor and gearbox, machined to an OD a couple of 100ths of a mm or so less than the seat tube ID, drill out the water bottle...
  16. simon.s

    DIY vivax style.

    Ah, yeah, hadn't thought about noise. There's 3 components to the noise produced : 1 - motor noise. I suspect this is the most important. This can be attenuated by using quieter motors (duh), slower running motors (by undervolting a larger motor, for example) and by using an FOC driver...
  17. simon.s

    DIY vivax style.

    So, been reading here on and off for - well - ages now, and whilst there's a metric shedload of really really good information, there doesn't seem to be much interest in DIYing along the vivax line. I'm guessing that's down to the low power side of things and complexity of the drive system...
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