modding thumbies for more gears?

[catf]

that question about the 8th index position reminded me of an idea i had a while back. this is the part of the shifter that makes it 8 speed

i think in theory you could custom machine a replacemant part indexed for 9 or 10 speed. pull ratio and distance is the same, just need more pits closer together. problem is it would be complex to make cos it needs to interface with the shifter body, so getting something prototyped from a cad design was never gonna me worth the cost or effort. but im thinking these days it might be possible to do it on a 3d printer, so it would be loads cheaper.

i guess first question is has anyone done it already? and if not is that cos nobody else would be interested? i mean if ppl want thumbies that bad you can use tt road ones. ive got some. so its kind of limited appeal, only for ppl who want retro shifers with modern drivetrains. i really like m732. something about them is special for me, probably how old i was when they were made, but these days i only ride single speed

would there be much demand if i got round to doing this project? or more likely, if someone else feels inspired, id be interested in chipping in.

 

[foz]

I've thought about doing this but don't have enough time for the projects I've already started, let alone new ones :facepalm:

cable pull is near enough the same for 7 (2.9mm) and 8 speed (2.8mm) which is why the 7 speed thumbies work well enough with 8 speeds, 9 speed pulls a little less cable (2.5mm) but 10 speed MTB pulls 3.4mm so you probably couldn't get that to work (it would need a larger diameter barrel for the cable to pull round, like the microshift thumbies have) You might be able to make something for 10 speed road compatibility (2.3mm per gear)

 

[Thias]

9speed would fit, I think. As a 9speed cassette fits onto a 7speed freewheel, the distance between the lowest and the highest gear (=cable pull) should be nearly the same. You would have to "fit" 9 holes into the same segment of the circle.
10speed is different.

The problem will be the material itself. That original "donut" is hardened steel. (That stuff is VERY hard. I tried to repair one by drilling the holes deeper. No way drilling it!) And still its the first part that wears out in a thumbie. A 3D-printed plastic or sinter metal part wouldn't last a month.

 

[hamster]

I wonder if the bits from inside a 9 speed bar end shifter are interchangeable..?

 

[gil_m]

Re:

...just run them on friction mode

I run 9/10/11 speed set ups on 4 bikes, all running a 10sp chain and 9sp mech

There are that many cogs in the same space these days you just nudge the shifter and jump/drop 3 gears, you soon get used to how much to "nudge" the shifter to fine tune the index and if your currently riding SS anything will be a bonus

You kind of understand the need for indexing when running 7 gears but once you up the number of gears friction mode works so well

 

[catf]

well wasnt too bothered about the durability tbh, its such a gimmiky thing to do anyway, but they can 3d print all sorts of materials these days. not hardened steel though theres a guy 3d prints titanium lugsets for bonding to carbon tubes. very cool.

didnt know the cable pulls were different though. truth be told ive never run over 8speed anyway, just assumed 10 would be the same cos the axle width stayed at 135mm while the chain got thinner.

cheers for the info. retrobike never fails to make me feel like a know-nothing idiot

 

[rogerzilla]

Re:

If you don't want original looks, you can buy them new for any number of speeds. Ok, they're bar-end shifters on a different mount, but they work the same. Try SJSC.

 

[xerxes]

Re:

Sturmey Archer make thumb shifters for a range of speeds: https://www.ebay.co.uk/sch/i.html?_from ... cat=177824

 

[rogerzilla]

Re:

Never seen those before! Might change my Kilauea to 9 speed - it's a new Deore hub and 9/10 speed 105 road mech so would just need shifter and cassette.

 

[hamster]

The Sturmey ones are essentially bar-end shifters on an adaptor like Paul Components Thumbies. A secondhand set of bar-end shifters and these might be cheaper:
https://www.sjscycles.co.uk/gear-spares ... ars-black/