Tell us more!
How does it ride?
Is there any slop?
How does it compare to the Schlumpf in terms of shifting feel?
How much added weight?
Amazing work!
absolutely beautiful !
Wow! Great job on everything from the 3D model designing through to the machining and assembly. Please keep updating this thread with your progress.
Unbelievable dedication to the sport. Great job. I can’t wait for hear more.
What a beautiful project. You’ve done a lot of really careful work, there. The nice thing about the jackshaft design is that the cogs can be changed if you find that your initial choice of gear ratios is too aggressive. The adapter with the dropouts to hold the three-speed hub could use some radii on the top corners. You will be reaching back there to catch something during a UPD and it looks like it will want to bite your hand.
I think these geared unicycles get easier to ride with larger wheel diameters and especially with heavier wheels.
this is completely mind blowing, I love it !!!
Yes, great execution of this idea! Please give us a detailed review of riding this machine.
You’ve got a BUNCH of interested thread readers, with more to come, I’m sure.
How much does she weigh after all that?
This is a really cool project. I wonder if the brake mounts will be strong enough for the torque from the S3X. I guess you should know before long.
I had thought about using a through axle hub to do this as well. I think with a Nightrider frame, and a 29" wheel you may have enough space to put the jackshaft hub inside the frame. That would be pretty cool.
Post a vid Of it in action!
Brilliant!
Amazing build! Good on you. I can’t wait to see it in action!
Wowsers
Great engineering! cant wait to hear all the hoopla of the finish product.
Good job!
I was looking on a site where they were testing the SX3. In a not very well documented way, they listed the backlash at the hub to be 15 degrees. That’s really big. Are you going to measure the backlash on this set up? I always used the deflection at the pedal axle of a 6", or 150mm, crank. I have listed figures for various hubs that I built from 0.5mm to 1.2mm deflection at a radius of 6" and I think the Schlumpfs measure about the same. As I remember, Pete’s jackshaft builds were better than that. Maybe they seemed better than that because the high friction chain/cog connection damped it so much.
Beautiful work, Justin. If it comes out anything like the electric-assist uni you had at MUni Weekend last year, it’s going to be a winner. The gearing sounds kinda high, but as Harper pointed out, this system allows you to change your cogs at will. And if the end result is to marry that setup with an electric-assist system, the gearing may be just right. Also that will probably help with the momentum issues of the smaller wheel.
Videos please! 
Arg… Justin… so much suspense!
We all want to know how it went, if everything worked as planned, the shifting, the weight, the backlash…
You’re hard on us!
Oh wait… it hasn’t been filmed yet… need a hand filming?
You have my complete attention ! Great project,I hope that hub does what we all hope it will do.
john
Wow, what a great hack! I wish I had come up with somwthing like that.
Let us know how it rides. I wonder if it could be made a little narrower and upd friendlier. Also wondering how this could be attached to an Oregon frame, I think that might be a good idea.
That’s a nice bit of work for sure.
What if you used a wider Nimbus frame (Shadow/Oregon) which have more spacing and the V frame so that the shifting hub could be placed directly under the seat post and out of teh way; it’d also be easier to secure on four sides.
But watch out, you may ruffle some feather for encroaching on another shiftable hub 
From an entirely different review I read more about the backlash. The guy reporting was running a 50 chain ring and a 15 cog. He measured the backlash at the crank with a TDC indicator to be about 3 degrees. For a 150mm crank this translates to about 8mm of deflection for his gearing. With his 50/15 ratio, 10 degrees of angular backlash would be required at the hub to produce this. Your cog ratio is 33/24 so the 10 degrees will be reduced to about 7 degrees but that’s still 19mm of deflection at the pedal axle of a 150mm crank. That’s about 15-20 times the equivalent backlash of the internally geared hubs.
I will be very interested in any backlash information that you can report. Also, and more importantly, how you interpret the backlash when riding.
Can you take some video?
That’s really nice. I hope there isn’t too much slack in the drive - lots of cyclists say the Sturmey hubs (both the old ASC and S3X) ruin the “fixed” feel because of the amount of backlash. On the other hand, it may be possible to learn to ignore it.
(Just thinking quickly, so this may be rubbish, but…)
Wouldn’t it be possible to reduce the backlash at the pedals by using larger sprockets on the wheel hub and smaller ones on the gearbox so the overall gearing remains the same but the gearbox spins faster? Then a given amount of slop at the gearbox will result in less at the pedals won’t it…? Presumably it would make the drive slightly less efficient, but may be nicer to ride (assuming it’s too baggy now - perhaps it isn’t!)
Really nice to see somebody with the skill, equipment and enthusiasm to build something the rest of us have just been speculating about
Shame the nuvinci hub only drives one way - that would be the holy grail of gearing (although they’re pretty heavy aren’t they?)
Rob