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Old 2016-07-21, 01:31 PM   #16
MartinC
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Waaoow Justin please make it work for U18! I'm not sure I want to use this before my races, but I DO want to try at least to start with it This is just impressive how fast you physically build this project after, I think, a long and intensive phase of design-thinking. It's like you pre-thought of everything, and so everything becomes feasible and almost simple when you build it. That really gives a feeling of magic!
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Old 2016-07-22, 08:40 PM   #17
Justin LE
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Originally Posted by MartinC View Post
This is just impressive how fast you physically build this project after, I think, a long and intensive phase of design-thinking. It's like you pre-thought of everything, and so everything becomes feasible and almost simple when you build it.
Ha ha Martin, yes you would know all too well! This is pretty much a spot on summary, it's been a design that's had 3-4 years of incubating in the back of my mind, so the less than 2 weeks it's taken to build it isn't telling the full story.

And speaking of story's I got it in a state I could ride it my 13km commute home on wednesday night to check that all systems were a go:
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The mechanics all worked great, and the amount of backlash on the cranks from the gears is so small to be imperceptible. There was one issue that I hadn't anticipated though. There was enough eccentricity in the gear drive that the strain gauge for sensing torque also had an offset signal that would undulate just from the position of the crank rotation, to the tune of a +- 10 Nm error even without any actual torque being present.

So as a result I had to dampen/average the torque signal in software so that there wouldn't be pulses in the motor power at each wheel revolution, and that meant that the torque control was a bit laggy. But when I turned off the automatic torque assistance while riding, then it was really clear how much easier it was to ride with the torque control versus without, even with the delayed response.

It then got a bit more of a workout last night at the Vanuni hockey meetup. Tynan had it down within short order
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and other fellow Ben who had never ridden a schlumpf before got the hang of it after 5 minutes or so.

However, after this workout I could hear a regular "tick tick tick" sound coming from inside the hub indicating something mechanical rubbing. So everything came apart to see what's up and it turns out that two of the press fit planet carrier pins were starting to work their way out of the plate, and the fronts of the pins were rubbing and wearing against the the motor stator support.
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We're trying in a mad rush to remachine a new planet carrier out of steel instead of aluminum, and then I'll be able to spot weld the backs of the pins in place so that they'll be locked in position for good. A steel carrier will give me (and Harper too I imagine ;-) ) a lot more confidence in mechanical drive holding up to the rigors of field testing for 2 weeks at Unicon.

While I've got it all apart, I'm also taking the opportunity to redo the strain gauges so that I have two pairs on opposite legs of the sun carrier, and the hope being that running two sets instead of just the one pair I used previously will help to average out offset variation in the torque signal.

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I know that the best ride experience will be had if the pedal torque is immediately and accurately amplified by the motor, that would be the ticket to having a geared 29er feel as easy to mount and ride as an ungeared 20 or 24"

-Justin

Last edited by Justin LE; 2016-07-22 at 08:42 PM.
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Old 2016-07-22, 10:09 PM   #18
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... Man that's a sexy frame. Reminds me of a black sheep fork.
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Old 2016-07-23, 10:50 AM   #19
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Impressive! Crazy! Scary (40kph)!

Really great work!
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Old 2016-07-23, 12:00 PM   #20
Justin LE
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... Man that's a sexy frame. Reminds me of a black sheep fork.
Yeah it was actually the dry run prototype that was kicking around from the project with the Nuvinci unicycle, where I needed the shape done this way for stiffness along the chainline to the jackshaft which was located behind the seat tube:
http://www.unicyclist.com/forums/showthread.php?t=92919


Without linking the pair of curved tubes together though it has quite a lot of flex in it, so it's not an ideal design as built but I like the curves and elegance and it seemed a fitting frame choice to use with this build.
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Old 2016-07-23, 12:19 PM   #21
Justin LE
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Impressive! Crazy! Scary (40kph)!
Really great work!
Thanks. I didn't hit 40 kph yet, just 30kph, we'll need shorter cranks than the 150's which are currently on there to do 40+, and probably a braver rider than myself!

Anyways, we got the new steel planet carrier all machined up:
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And now the backs of the pins are welded in place, so no more concern about the planet carrier being a weak link in the mechanical system.
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Since reassembling it with these fixes it rides amazing. The new strain gauge system holds the zero torque point much better so I've been able to dial up the responsiveness, and the mechanically things feel tighter.

There have also been a few rounds of firmware enhancements. I've now got it so that you have an up-down push button for the setting the bias torque of the motor in Nm, and a potentiometer knob for adjusting the gain amplification of your pedal effort.

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Riding along, I would first dial the gain up to a value that makes it much easier to balance the unicycle but doesn't overshoot on each down stroke of the cranks. Then whenever there was an up hill ahead I would hit the "up" button a few times to give the desired level of hill climbing torque, and similarly on the downhills I'd hit the "down" button until the braking force was just right.

It works freaken amazing. Now we've got to pack it all up for travel to Spain and realllly look forwards to letting the wider community test this out and see what it's good for.

Hope to see many of you at Unicon in just a few days.

Last edited by Justin LE; 2016-07-23 at 12:20 PM.
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Old 2016-07-23, 01:08 PM   #22
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You repair parts and make modifications faster than most people can post on the forum. I was just going to suggest that you peen the pins into the aluminum plate and you've already machined a steel one and spot welded them. You rock, Justin.
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Old 2016-07-23, 02:02 PM   #23
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That's amazing.
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Old 2016-07-23, 05:12 PM   #24
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Nice! Hope to catch a glimpse of it at Unicon.

Will it travel with you as checked luggage? If so, I hope there are no problems with security.
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Old 2016-07-30, 04:47 PM   #25
Justin LE
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Nice! Hope to catch a glimpse of it at Unicon.

Will it travel with you as checked luggage? If so, I hope there are no problems with security.
Well, it turns out that I did have problems with my flight to Unicon but not related to the unicycle, rather my passport went missing at the worst possible time! So had to get a rush/replacement on that and had an extra couple days in Vancouver to do some more upgrades before the event.

Rather than have the batteries hanging from a bag in the handlebar, I welded up an extra set of tubes to the frame so that they could be properly supported behind the unicycle. This also linked the two frame tubes together which increased the overall frame stiffness a good amount.
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I found a perfect sized seat bag from a bike shop to fit in this area which can hold up to 4 of the small 100Wh packs, and the result is pretty clean.
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It also gave us some time to make a little film showing the unicycle in action
https://www.youtube.com/watch?v=-C1n6XAypag

So far it's generated a lot of interest at Unicon but nobody has broken 40kph yet, I'm still working to convince the skilled riders to put some more faith in my engineering here
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Old 2016-07-30, 05:55 PM   #26
Juni
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I wish I could be there to have a try... It really is a masterpiece *drool*
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Old 2016-07-30, 06:33 PM   #27
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Uh-MAZING! That's pure genius!
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Old 2016-08-02, 09:26 PM   #28
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Some fantastic engineering there. Impressive work!

I wonder if you can answer a question for me? I have been thinking about how unicycle hubs are constructed, specifically, how the axle is connected to the flanged hub part? I am currently building a little Arduino based CNC machine with the first goal of machining some bearing parts so that I can construct my own frame. Beyond that, I would like to look at making my own hubs. Any thoughts? Thanks for any information
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Old 2016-08-06, 12:16 AM   #29
Justin LE
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Some fantastic engineering there. Impressive work!
Thanks.

Quote:
I wonder if you can answer a question for me? I have been thinking about how unicycle hubs are constructed, specifically, how the axle is connected to the flanged hub part?
On the all-steel nimbus hubs like this they are welded on, and you need to be a bit careful about that detail when machining them down. Not only is there a risk of removing too much of the weld bead, but the material properties are different on the welded area and sometimes that results in damage to the cutting bit.

Other hubs are made with interference press-fit parts, and aluminum hubs (like mad4one) would typically be machined either from solid bar stock or from a forging.

Quote:
I am currently building a little Arduino based CNC machine with the first goal of machining some bearing parts so that I can construct my own frame. Beyond that, I would like to look at making my own hubs. Any thoughts?
Machining the hub and hub flanges is the easy bit, but the spindle with the ISIS splined taper would be a real challenge. I've never bothered to attempt this and have always hacked up old spindles (either from bicycle BB's or from other uni hubs) or doing these custom unicycle hub projects.

A square taper spindle seems easier to machine than ISIS, but would have to be a strong metal like steel or titanium.
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Old 2016-08-06, 01:07 AM   #30
Justin LE
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I wish I could be there to have a try... It really is a masterpiece *drool*
Well sorry that you didn't get a chance this time around, but if you are in the US I'll have it (or a future model) at the 2017 NAUCC event in Seattle next summer. The good news is that lots and lots of people at Unicon did get to give it a go and the feedback was super useful and for the most part positive. For anyone who had significant Schlumpf experience it was no problem to hop on and ride, but there were even a few people who had never ridden a geared hub before and managed after just a minute or two to be pretty comfortable on the machine.

Here we were at the city where the downhill competitions were held. The guy coming off the unicycle Christoph has also built his own internal geared hub with the ring and sun gears reversed so that it has like a 2.5:1 ratio, which unfortunately I didn't get a chance to see but he'll be racing with it in the marathon ride tomorrow.
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Katja from Germany had visited our Vanuni club in Vancouver several years ago and really schooled us in hockey, and it was nice to see her again.
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I was also really in Roger's opinion on this project, especially as he's known for spinning fast with short cranks on big wheels. He found the automatic assist a bit weird and preferred having the pedal torque multiplier turned way down and using the up/down button for steady power assist. While for most people, the torque multiplier from the motor is what is needed to make it rideable.
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And Finally, Anne-Sophie has grown quite skeptical of testing any my unicycle creations since getting injured on my earlier prototypes some 5 years ago. But after sooo many people at unicon were giving the thumbs up on this one she at last gave it a go and cracked a smile too:
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