fietsbob

Try it, then report back what you learned. once you are finished.

Rick@OCRR

I voted for "Cool Idea . . . " since I just (three weeks ago) installed SRAM E-Tap on my spare carbon framed bike and while it was rather pricey, it works so perfectly that I really like it, even given the change in shifting protocol.


I have ridden a friend's Di2 equipped bike and that works very well too (but there are still those wires to deal with). So, if (big IF) you could have a home-installable electronic shifting system for about $200 that would be excellent (either with or without wires).


Have to admit though, I don't really think the OP's goal is achievable. Hope I'm wrong!


Rick / OCRR

Retro Grouch 

"Meh" does not accurately reflect how strongly I feel about this idea. "NO, NO, NO, NOT EVER!" would be more like it. If that makes me a luddite, I'm good with that.

Doug5150

I think that electronic shifting could be very nice, but I don't think it's worth bothering with using regular deraillers on.
A lot of the problems with conventional bikes has to do with the external gears and deraillers.
It's coming to the time to get rid of them. Except on UCI bikes, of course....

Rollfast

I gave up on geared bikes by my 20s and have been a cruiser rider since. I thought the 'Autobike' was just an improvement on when my derailleur was falling apart and shifting itself.


I love the bikes and that's why I leave them to people with money and repair skills for them.


I could break cables without trying as well so coaster brakes were for me. So I marvel at your bikes and soldier on with mine

Leebo

Meh. One more thing to break or freeze in the cold. Improvement how?

IrishBrewer

To make this practical, you would probably have to remove the springs on the derailleur so the servos can be reasonably small and don't continuously have to hold tension (a huge drain on batteries). Also, you would want some sort of mechanical lock on the derailleur position, again so it can locked into gear between shifts without consuming batery power.

I've never used Shimano's Di2 but I've heard the battery life is extensive (good for 500+ miles) with a modestly sized battery. So, they've made it very efficient to minimize the chance that you'll be in limp mode because your shift battery ran out.

Doug5150

I don't know anything about Di2 but this is part of the reason that I said that using conventional derailleurs is a bad idea. It would be better off in the end to just build your own derailleurs that wouldn't use a return spring at all.

The only reason you need a particular derailleur nowadays, is because it is made to work with some particular mechanical shift indexing system, that is built to work with some arrangement of chainrings and a rear cluster with a set number of cogs. With a totally-digital system, there would not be any mechanical indexing--you would have to program that in yourself, and then the "index" would just be a series of settings in the computer's memory. So it could be made to work with any different arrangement of chainrings and rear cogs you wanted, perfectly.
,,,,,,
For this reason alone I doubt normal drive train companies would ever do this, as they'd sell a lot less different sets of parts.

If the gear selector was digital, you could have it do a few neat things:
...you could have it access ALL the gears in ascending/descending order, and you could tell it to skip gears that are duplicates or that cross-chain badly. There would just be a [shift up] button and a [shift down] button and the computer would know what combination to use for the next-higher and next-lower gear in the programmed setup, even if it involved switching both the rear and front derailleurs.

...if you had a pedal-sensor, you could make the electronic shifter NOT shift when you are putting pressure on the pedals. It could automatically shift in-between pedal strokes, every time. A lot less crunching that way...

...if you had a bike-speed sensor, you could program the shifter to ignore shift-button presses below a certain (riding) speed, so you'd never accidentally shift it while standing still and have the gear-crunching issue when trying to get started.

...also if there was a speed-sensor, you could set the shifter to work differently at different speeds--such as, at moderate speeds it could "over-shift" a bit more, and then back down to the target chainring or cog (just like what you do manually with friction gears) so you'd get faster shifts that way.

An Arduino Pro Mini only costs $1.50 for Chinese clones, and measures about 5/8" x 7/8".
I dislike using RC servos however.
Stepper motors are more precise (they don't accumulate positional errors), they are built more robust and they don't require a constant signal just to hold a stationary position.
If I was doing this, I would start out trying to use a nema-8 motor, and if that's too weak and slow then try using a nema-11.

IrishBrewer

Indexing is almost always part of the shifter, not the derailleur.

Doug5150

Yea but different shifters and different derailleurs aren't mixable due to the leverage differences in different derailleurs.

Also in the last few years I noticed a problem that other people said a lot of front derailleurs now have: they don't have very much total adjustment range in them at all... The 2-piece cranks use the spacers to adjust the chainring position, but the older 3-piece setups (square taper) don't have that ability.

wphamilton

These are some good ideas and wouldn't be that hard to implement, adding some sensors of course. The advantage to his using an Arduino board is you can easily add inputs and controllers to it, and program it with a more or less standard language. The tricky part IMO is engineering the mounting of the linear actuator and at the correct angle. And buying the right ones with the right specs - doing that kind of research, and testing, is where OP could put a kit together that would really be worthwhile. Casual hobbyists like me could take it from there.

Benjamino

Guys, it's not about if it makes it better or not, it's about bragging to your nerdy friends (not meant as a pejorative remark). On my touring bike or road bike, no effing way. On my converted ebike which has a battery on it already which doesn't rely on accurate shifting or, um, a traditional drive train to move, oh duck yes.

Let's get real, a lot of engineering goes into making something like this work the way it should with a high degree of reliability. For 'performance' I'll leave the hard work to Shimano. Otherwise, it would just be a fun problem to try and solve.

Kimmo

No, no, no. The whole idea is for it to be compatible with any derailers. The return springs on the derailers can simply be countered on the other end of the cable, like many shifters do. Except that to do it accurately enough to minimise the net tension on the actuator, the spring would have to be non-linear, like so:



Obviously stepper motors would be the go, but that's for a bespoke actuator. In the meantime, RC servos will cut it on the prototype.

wphamilton

I was hoping for a linear actuator with a direct mounted jockey wheel, to get rid of the rear derailleur and cable.

XShifter

Well, that is exactly where I started. A big clunky box with arduino. The remote was a garage door opener with my own PCB installed. Not very marketable.

This was not nearly as easy as it seemed. Normal servos absolutely will not do the job. I needed to design a servo to accomplish this specific task. It had to be tough, precise and watererproof. The XShifter is the result of all this work.

I know I've gotten a few sales from the members of this forum. I really appreciate the support. This is really a revolutionary idea that the OP proposed. It is the most flexible and scaleable solution available. We've only scratched the surface of where it's going.

AnkleWork

Sort of like redesigning a hydraulic press to drive a few nails.
Next up: rounder wheels.

fietsbob

Neither is it a Place where electro-mechanical, post grad engineers hang out, they're busy in the Robotics Labs ..

try Cal Tech and MIT..