Today I helped a friend convert a Landrider autoshifting bike over to manual shift, as the person it's for doesn't like the autoshifting; it causes problems with pedalling for them.
So they didn't want the autoshifting derailer/etc, and I now have it. It is based on a simple old Falcon derailer just like bikes I have from the 70s, but with a custom-made back end that has a pulley-driven shaft with a split flyweight on it. Pulley on the wheel behind the cassette drives it.
"rear" view, showing the wheel pulley, belt, and the shaft pulley circled in red.
Bottom-rear view showing the flywheel held open in a fully-shifted state, with the pivoting seesaw lever that does the shifting circled in green, and that drive pulley in red.
A shot from underneath showing where they once designed in a manual shifter override but didn't bore the holes or thread them. Maybe those only exist in earlier models.
It would not actually work as a pull-cable anyway; it'd have to be a pushrod to work. This shifter moves backwards from the way all others I've ever had do. It starts on the lowest gear, and tension on it from the flyweights/lever pulls it to the highest.
This is the separate plastic pulley that seats between the cassette and the spokes/hub.
The other side, you can see the notches/etc for the spoke heads to fit. Luke, this is what I need to get into CAD file for those adapters.
Anybody got a 3D scanner? I'd love to have this thing in aluminum, as a solid disc to use for all sorts of adapters!
A better angle; had to increase brightness/contrast to see the indentations for the spoke heads.
So the idea is that once CB2 is running, I'm going to stick this in place of the regular rear derailer. Theoretically, assuming the motor power doesn't destroy it
it should shift gears automatically to keep more optimal gearing. I'll have to come up with a manual pushrod shifter for it too, in case something happens to the belt or autoshift part of the mechanism.
Since it'll be on a 24" wheel instead of a 26", I may have to play around with the 2 screws that appear to adjust the balance of the seesaw pivot. If they do what I think they do, I might get enough adjustment range to alter the rate at which gears shift vs wheel speed.
When my friend and I went to a bike shop for some parts he wanted for the Landrider/etc., we ended up at the same shop I'd bought that box of assorted parts at the swap meet of, back a couple months or more. I'd also at the same day bought a used Shimano Biopace 28/38/48 crankset that I installed to great success and comfort on DGAmII, and figured I'd probably never see another one just waiting for me on the shelf like that.
I even said as much to him as I was digging thru the used parts shelf, and guess what?
Right there, another one, in even better condition!
Like the other, it has both cranks, the ovoid chainrings, and a BB cup set, bearings, and crankshaft and bolts.
So now I have one for CB2 as well--I had figured I'd have to pull the one off DGA once I got CB2 working again--now I don't have to. Of course, with this on CB2, I have to add a tensioner for the chain, since it will not be the same all the time as it would with round chainrings.
I'll tell ya, though, if you've got bad knees, these things definitely make a difference in when the forces on them happen during cranking harder, and that makes a world of difference to the level of pain when real effort is required for any reason, like startups.
It appears to help most on the largest chainring, so despite common sense, I typically leave the front on the largest and shift down to largest in back to get lower gears, only downshifting in front when I know I can't do it with the big ring, which fortunatley is not very often here in Phoenix.