You guys are making my head hurt again. :?
Paul is definitely not the only "bear" in these woods.
If I'm understanding things, we have several different ideas going on, for how to get true drive independence, all with some level of multiple gear stages for both the motor and the pedals, right? One solution that would help would be to have two standard freewheels with splines that can fit over a standard 9-speed Shimano cassette, which is why Luke and Miles were hacking away with safe-cracking tools, is that right? Assuming that task was solvable, I think that would open up lots of possibilities. If you put two freewheels on an SRAM Dual-Drive, for instance, which has a 3-speed internal hub, that would give the motor and the pedals three speeds, and you could optimize the ratios to the rear for the motor and the pedals independently. An offshoot of this would be to use a 3-sprocket front dérailleur which then gives the pedal drive 9 speeds.
Another related option, one that interests me quite a bit, is to put the dual splined freewheels on a standard 9-speed hub, without the internal gears. This could be used on a standard 21-speed or 27-speed setup with the triple front dérailleur. My 21-speed Townie is the candidate I'm thinking of, but this is also pretty much exactly what D needs, I think. This gives three speeds for the pedals, which is plenty for many applications, but only one for the motor. With delta-wye switching, however, you get two speeds with a ratio change of 1.73:1, which would be like going from a 100t sprocket down to a 58t sprocket. As one of the few here that have actually used both the 3210 and the 3220, I wholeheartedly believe that two speeds is more than enough for
any 3220-based setup, even on a 26" bike and unless you need a very wide performance range, I would also argue the same for the 3210.
Are there any other dual freewheel options other than fitting them to a splined Shimano cassette? Also, I looked at all three internal hub-types I have here, the SRF3, a 3-speed SRAM, a Nexus-3 and a Nexus-8, and I just don't see how you can have room for adding two standard freewheels, however they are attached, on a standard width dropout. Maybe instead of doing a 9-speed spline, you took a standard freewheel and made it slide onto the 3-splined hub, in place of the cog, that might leave enough room. If the first freewheel had say, half the threads left, you could then use a threaded pipe to screw on the 2nd freewheel. You'd also need a clever way to replace the circlip, which is used to hold on the cogs. Maybe this isn't needed, if there's no space left for the freewheels to go anywhere, side-to-side. One problem with this idea, though, is it would be hard to use an ENO for this first FW, because it has that "shoulder" on the end. Although the pedal-driven FW can be a standard model, you'd probably want to use the better quality ENO FW for the motor drive, and from a motor installation point-of-view, it simplifies things to have the motor drive inboard of the pedal chain.
I'm also not done looking at LH drive options, using the disk brake mount. Even the internal hubs are coming with these as options now, and this might be an easier nut to crack, for my delta-wye two-speed option. What is needed here is I think two adapters, one to "attach" the freewheel to the brake mount, and one that would mount a standard #219 Extron sprocket, which has a 4-12"/116mm bore, to the freewheel. Custom #219 sprockets could also be done,, which would eliminate the need for the 2d adapter, but those Extron composite sprockets look pretty nice.
Finally, there is still the option of putting the 3rd freewheel on the motor shaft, but you then would have the extra drag in pedal-only mode of the pedals still spinning the motor chain. Anyway you cut it, having all three freewheels in back, one for the wheel, one for the pedals and one for the motor, is still the most optimum solution.
-- Gary
