Handlebar mounted Schlumpf gear change system

Rob Higgins, from Birmingham UK, designed a bar mounted Schlumpf gear change system on his KH36. I never met him, he sadly died in 2019. I bought his uni online from friends who were managing his estate - I was quite new to unicycling at the time and neither they nor I realised what a unique unicycle it was. Sadly the system was worn and no longer robust, and I have since dismantled it, but I wanted to share the design with the unicycling community so people can appreciate Rob’s work and also maybe be inspired to try something similar. Sadly I didn’t take any decent photos, but I’ve included a few that I have.

Rob’s system came in two parts:

  • A plate that ran down the face of each crank (probably inspired by the Schlumpf EZ-Shift levers - eg as seen here), looped around the pedal spindle and one end and screwed into the gear change button near the other end, before bending around the base of the crank and extending towards the wheel.

  • Two ‘black boxes’, one at the base of each fork, connected to two handlebar-mounted brake levers. Squeezing a brake lever would cause a small wedge to protrude from the corresponding black box, so that as the rear of the crank passed that point (when the pedal was at its lowest point), the crank plate would be pushed outwards, thus pulling the gear-change button outwards and changing gear.

The main innovation over the Schlumpf EZ-Shift levers (which extend the button press area to cover the whole crank face) was to bolt the crank plates to the buttons so that they could be pulled outwards as well as pushed inwards. Squeezing a gear-change brake lever indirectly caused this to happen.

Cranks and Push/Pull Plates
These are steel, attaching at one end around the pedal spindle, and at the other end screwed into the gear change button using a new bolt of the same width and thread as the grub screw previously used in the button, which it replaced. I expect the length of the bolt had to be altered to ensure it both secured the plate to the button, and went the exact distance in to secure the button on the shifting rod.

At the axle end the plate protrudes beyond the crank end and bends 90 degrees around the (flattened) crank base. See photos.

The Black Box and gear shift levers
The ‘black boxes’ were mirror images of each other, operated by cables from the handlebars. They were hand crafted with metal shaped as required, and were very well greased! The cable was held in place in a slot and relied on the strength of the crimping of the cable end to keep them attached - I guess Rob knew to squeeze only very gently, but I didn’t… When the cable is pulled, a wedge swivels out beneath the box and this hits the crank plate end as it passes, pulling out the button and changing gear.

The bar end had a central brake lever and a smaller gear-change lever on each side.

Diagram of working principle
Hopefully this gives an idea of how it works - not the most technical of drawings!

Thoughts about generalising the idea
Rob had an older KH36 frame with Magura rim brakes and used 150mm Nimbus Venture cranks. As such he wasn’t dealing with curved crank arms or an external disk brake. The cranks were modified – they were flattened off at the base so that the L shaped extension of the crank plates hugged closer to the crank, and they had cut-outs on the frame side to stop them fouling the frame-mounted ‘black box’. The two gear shift brake levers were attached to a ShadowHandle frame with adapters (cut off MTB bar end extensions I suspect).

It might be possible to use just one side of the system for a uni with an external disk brake. The button on that side could be pushed in by pushing the crank plate with heal or side of foot, then pull out again with the use of the bar mounted brake lever.

Inexpert video
I have some video I took of lockdown me trying to explain the system - but I managed to break it whilst doing so! Also another video when I dismantled it. Not sure if they would be of interest, but if you’re on Facebook then you can see them here (photos and comments - with my video of the system working buried in the comments) and here (the dismantled system).


This is such a great write up of what was clearly an innovative way to get the hub to shift via cable actuators.

I love how someone has gone to such lengths to extend what the schlumpf hub does / is. Perhaps that’s why I liked the hubs, geared unicycling so much.

It’s like the cutting edge of an already edgy / quirky sport, or discipline within a niche sport.


[As for those Facebook videos - I think you might find the forum accepts direct video uploads now so those without FB can view directly here.

I could be wrong… ]


Well, yes, but no. The current video file size limit is 4MB, so you can only upload small/short video clips :film_strip: but @holyroller’s videos are 13MB and 40MB.


That’s quite ingenius to do the following:
a.) Creating a “lever” that rides with the cranks.
b.) Using a bicycle cable and grip to make something protrudes and “trip” the rotating lever.
c.) The lever then activates the hub clutch by “pulling” it out, instead of pushing in.

As a mech engr, I can appreciate this mechanical linkage system.
However, you know what I was thinking for this application?
I would simply just consider a solenoid with a small lithium battery and bluetooth activation from my cellphone.


Or better still, built into the hub without the need for hacking the buttons. As in, bring unicycle geared hubs into this decade like the bicycle ones are.


The issue with a battery powered shifting mechanism is where you put it. It needs to have quite a bit of power in order to shift a Schlumpf, but equally be very thin in order to not collide with your shoe.

Bicycle hub gears with electronics shifters typically have the shifting mechanism outside the hub gear, and physically they’re still quite large.

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This is a 2 speed bike hub with internal wireless shifting. This one is not unicycle suitable, and maybe the forces on unicycle hubs mean to the shifter needs to be bigger than this one, I would have no idea. Just saying the tech does appear to be out there.

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If you look at that one, you’ll see there’s a “smart Thru Axle” which has at least the battery and wireless receiver housed at the end of it.

I’m not entirely sure how the shifting occurs, but the package isn’t all internal.

I think for us, Q-Axle would be the best bet, as you get a lot more space inside the axle to fit in batteries and tech. I’m sure you could fit a linear actuator, battery, and wireless receiver in there.


Some ten years ago, someone else created a vastly different system to shift from the handlebars. I seem to remember it was Justin from Canada (the same guy who designed ant built an electrical assisted unicycle - a real unicycle, not an automatic balancing electric monowheel). I thought I had pictures as he brought it to Unicon but I can’t seem to find them. I still vaguely remember how it worked.

He showed his system to Florian Schlumpf who was duly impressed, and intended to take it into production. But Kris Holm vetoed it: too complicated and too many potential warranty and liability issues.

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I remember this one. It was more complicated and prone to failure than the one presented here.
edit: Here it is: Seeking geared unicycle prototype demonstrater/collaborator for startup company. - #82 by bouin-bouin

Good to see a bit more detail of that system - I’ve only seen a single photo of it before. The frame side lever on the fork looks more robust than Rob’s little black boxes. Maybe someone could combine the two ideas.
Neither system solves the problem of shifting only occurring at on point in the crank’s rotation, which could be a long way to travel on a g36 in high. Would be great to get a system that did a more instant shift

Well, I can get a couple of seconds to fit here of the (greasy!) insides of the fork mounted black box in action

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This is how it worked:

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Do you (or does anyone) remember when this was shown at Unicon? With a date, I might be able to find back my pictures of it.

The date on the photo I posted is Feb 2018.

bouin-bouin posted the photos in February 2017 and said, that it was at Brixen Unicon which was 2012.

Thanks, now I found back my own pictures taken in 2012. I think they are clearer than the one posted above, but they lack the explanatory text. I don’t think I ever posted them.