Electric Assist Unicycle Build

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justin_le   10 MW

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Electric Assist Unicycle Build

Post by justin_le » May 21 2010 4:42pm

Hey Guys, not too much time to write much now, but here is a photo collection for one of the projects I finished and have with me in SF for the Maker Faire this weekend, which might be of interest to some on this forum. The goal was an electric ASSIST unicycle made from a direct drive hub motor. A unicycle that you can ride normally, but with the advantage of power going on the uphills and regen on the downhills to save your knees in both cases.

The implementation should be pretty self explanatory from the CAD section view:
U Uni Hub CAD Section.gif
Solidworks Model of unicycle hub assembly
U Uni Hub CAD Section.gif (51.97 KiB) Viewed 1980 times
Last edited by justin_le on Jul 19 2016 3:35am, edited 2 times in total.
Reason: Typo in title - fixed corrupt image
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Unicycle Side Plates

Post by justin_le » May 21 2010 4:48pm

Side covers started off as 9" x 9" by 1/2" thick aluminum plates from Metal Supermarkets, and are mounted to the rotary table for machining:
UA Aluminum Plates.jpg
Starts with raw metal stock and a rotatory table.
UA Aluminum Plates.jpg (61.27 KiB) Viewed 10411 times
Bulk of metal removed with a large diameter hogging bit:
UB Hogging Out.jpg
UB Hogging Out.jpg (70.14 KiB) Viewed 10411 times
And press fit cavity for ball bearing too:
UC Ball Bearing.jpg
Cavity for 20mm x 32mm thin section ball bearing
UC Ball Bearing.jpg (52.85 KiB) Viewed 10411 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Side Plate Finishing

Post by justin_le » May 21 2010 4:52pm

Inside corner of side plate rounded with a ball nose end mill:
UD Rounding Inside.jpg
UD Rounding Inside.jpg (53.05 KiB) Viewed 10502 times
All the spoke holes and mounting holes are drilled out on the spoke flange, which is part of the side cover plate rather than part of the rotor.
UE Spoke Holes.jpg
Center drilling 18 spoke holes + 9 mounting holes
UE Spoke Holes.jpg (46.21 KiB) Viewed 10502 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Unicycle Side Plate, outside

Post by justin_le » May 21 2010 5:03pm

After this, the inside surface of the side cover has been finished, so it gets taken off the table, flipped over, and put back on for machining the outside surface.
UF One Side of Plate Machined.jpg
Aluminum Plate after all inside machining complete
UF One Side of Plate Machined.jpg (49.59 KiB) Viewed 10410 times
UG Second Side Starting.jpg
Start of milling the outside surface
UG Second Side Starting.jpg (57.86 KiB) Viewed 10501 times
The flange is milled down 2.5mm thick, exposing all the spoke holes, and the rest of the cover is faced off just for aesthetics.
UH Surface Facing.jpg
UH Surface Facing.jpg (41.74 KiB) Viewed 10410 times
Outside is finished with a 3/8" corner radius bit for a nice rounded edge:
UI Outside Fillet.jpg
Outside Corner Radius
UI Outside Fillet.jpg (43.78 KiB) Viewed 10410 times
And finally, the side completed plate is parted off with a small 3/16" end mill:
UJ Parting Cover.jpg
Separating finished side cover from the raw stock
UJ Parting Cover.jpg (63.96 KiB) Viewed 10410 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Re: Electric Assist Uniycle Build

Post by justin_le » May 21 2010 5:08pm

The spindle for the cranks started off as an off the shelf cotterless unicycle hub from UDC:
UK UDC Hub.jpg
UK UDC Hub.jpg (37.9 KiB) Viewed 10408 times
One of the flanges was machined right off, but the other flange left in place as a means for coupling the pedal cranks to the motor casing via the right side cover.
UL Uni Spindle Machining.jpg
UL Uni Spindle Machining.jpg (55.85 KiB) Viewed 10499 times
The spindle diameter in the middle just happened to be exactly 20mm already, which was the size of ball bearing that I had going over it.
UM Spindle Complete.jpg
UM Spindle Complete.jpg (63.62 KiB) Viewed 10499 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Left Side Cover

Post by justin_le » May 21 2010 5:11pm

A second side plate was machined just like the first, only this one was made to fit a much larger 45mm ID thin section ball bearing to go over the aluminum stator support:
Attachments
UN Large ball bearing cover.jpg
Left side side cover, houses 45mm ID thin section ball bearing
UN Large ball bearing cover.jpg (50.88 KiB) Viewed 10408 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Unicycle Stator

Post by justin_le » May 21 2010 5:19pm

The stator was taken from a Nine Continent hub motor that was having hall issues. My plans had the stator bored out to a 46mm hole. However, you can see that if this is done, it would completely eliminate the welding on the center tube that holds the two stamped steel plates together. In order to keep things structurally sound, I first cut some small steel tubes and welded them to three of the "speed holes" that are punched out of the support plates in order to hold the halves together after the center was cut out:
UO Stator Rings.jpg
NC Stator with holes punched into plates and rings to fill them
UO Stator Rings.jpg (64.76 KiB) Viewed 10406 times
UP Tig Welding.jpg
TIG welding the rings in place
UP Tig Welding.jpg (79.29 KiB) Viewed 10497 times
Then the original axle hole was drilled:
UQ Stator Boring.jpg
Large diameter drill bits to remove original NC axle tube
UQ Stator Boring.jpg (47.1 KiB) Viewed 10406 times
And then bored open to exactly 46mm:
UR Stator ID.jpg
UR Stator ID.jpg (67.18 KiB) Viewed 10406 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Re: Electric Assist Uniycle Build

Post by justin_le » May 21 2010 5:28pm

The next step was the aluminum stator support, which plays the important roll of preventing the stator from rotating by being affixed to the unicycle frame, and of holding the stator centered in the hub even with the spindle on which it rests can rotate.

Starts off with 3" diameter 6061 aluminum from a scrap yard:
US 3 inch Aluminum Stock.jpg
Raw round stock chucked in the lathe
US 3 inch Aluminum Stock.jpg (63.01 KiB) Viewed 10403 times
A fair bit of machining to get her down to size:
UT Turning Al Down.jpg
Lots and lots of metal to remove
UT Turning Al Down.jpg (49.6 KiB) Viewed 10494 times
Close to the final shape:
UU Close to Parting Al.jpg
Various surfaces for ball bearing support, frame bearing clamp, etc.
UU Close to Parting Al.jpg (53.84 KiB) Viewed 10403 times
And the completed unit after parting off. The 6 holes are to bolt to the actual Nine Continent stator and lock it from rotating.
UV Aluminum Stator Support.jpg
Completed stator support,
UV Aluminum Stator Support.jpg (33.61 KiB) Viewed 10494 times
Need wire slots for phase and hall cables too, so these are milled into the 45mm bearing support:
UW Wire Slots.jpg
Milling of slots for wires
UW Wire Slots.jpg (45.11 KiB) Viewed 10401 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Rotor

Post by justin_le » May 21 2010 5:52pm

The metal rotor ring and magnets were also made from a returned Nine Continent motor, in this case one that had suffered water damage.
UW1 Water Damaged Rotor.jpg
UW1 Water Damaged Rotor.jpg (55.8 KiB) Viewed 10491 times
The stock Nine Continent rotors are a little heavy, with a 7mm thick steel ring for the side cover bolts, and a pretty thick aluminum casting over top of that for the spoke flange. Since I had the spokes coming off the side plate, none of this was needed and I could shave off a lot of superfluous metal:
NC Rotor being machined.jpg
NC Rotor being machined.jpg (68.23 KiB) Viewed 10400 times
In the end, I took the steel ring down to about 2.5mm thick, reducing the original rotor weight of 1.78 kg down to just 830 grams:
UW2 Rotor Ring Weight.jpg
UW2 Rotor Ring Weight.jpg (61.35 KiB) Viewed 10491 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Re: Electric Assist Uniycle Build

Post by vanilla ice » May 21 2010 5:58pm

Hardcore work there.. put some gyros on it!

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All the pieces, and assembly

Post by justin_le » May 21 2010 6:16pm

Here is what all the bits and pieces looked like after quite a few late nights in the shop:
UX All the Pieces.jpg
Finished parts for electric unicycle build
UX All the Pieces.jpg (80.46 KiB) Viewed 10392 times
Stator is pressed on and bolted to the machined stator support:
UX2 Stator Pieces Bolted, end view.jpg
UX2 Stator Pieces Bolted, end view.jpg (73.27 KiB) Viewed 10483 times
Spindle is inserted into the right hand side plate, and original spoke flange bolts to a small aluminum spacer ring so that turning the cranks turns the hub in 1:1 ratio:
UX3 Spindle in Side Plate.jpg
UX3 Spindle in Side Plate.jpg (46.32 KiB) Viewed 10483 times
Steel rotor ring with the magnets is snapped onto this side cover and then held snugly down with 9 bolts clamping the edge. This is needed to hold it secure against the magnetic forces with the steel stator is inserted. Otherwise the 2.5mm steel ring isn't strong enough to stay round, and the force of attraction causes it to wrap around the stator and deforming into an oval shape.
UX4 Rotor RIng Secured.jpg
UX4 Rotor RIng Secured.jpg (45.58 KiB) Viewed 10392 times
Even then, it was a bit tricky to get the stator in:
UX5 Rotor and Stator Inserted.jpg
UX5 Rotor and Stator Inserted.jpg (88.12 KiB) Viewed 10392 times
After that, remaining side cover plate with the 45mm ball bearing is pressed in place over the wires.
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Finished Wheel

Post by justin_le » May 21 2010 6:28pm

Here's a couple shots of the built up wheel, after lacing into a wide 700c rim:
UZ Wheel Build Complete.jpg
Edge view of completed electric unicycle hub
UZ Wheel Build Complete.jpg (43.36 KiB) Viewed 10482 times
UZA Side view of 29 inch wheel.jpg
UZA Side view of 29 inch wheel.jpg (80.52 KiB) Viewed 10391 times
I've got the wheel mounted in a Kris Holm 29" Frame with a big apple tire. The little battery rack at the back was made from angle aluminum and holds a pair of Hobbyking 5Ah LiPoly packs and an infineon 25A controller. Handlebar off the seat is home-made and has the CA, a throttle, lumenator light, and ebrake lever all attached to it:
UZB Complete KH 29 Electric.jpg
UZB Complete KH 29 Electric.jpg (108.57 KiB) Viewed 10391 times
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Re: Electric Assist Uniycle Build

Post by dequinox » May 21 2010 6:34pm

WOW... Thats amazing Justin, quite a post after what seems like a long-time-no-see!
How does it ride so far?

Brilliant design, and I can't wait to see how the stabilizer circuits you are probably about to design for it turn out :D
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Re: Electric Assist Uniycle Build

Post by liveforphysics » May 21 2010 7:27pm

So nicely done and so cool! I can't wait to see the videos!
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Re: Electric Assist Uniycle Build

Post by grindz145 » May 21 2010 9:03pm

Ebikes.CA for the win.

It's so great to see people that are THIS passionate :mrgreen: :mrgreen: :mrgreen:

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Re: Electric Assist Uniycle Build

Post by liveforphysics » May 21 2010 9:12pm

Was the Honda electric unicycle a source of any inspirations for your project?


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Each engine start sprays them into a shared atmosphere which includes beings not offered an opportunity to consent accepting these cancer experiences and defective genetics life experiences.

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Re: Electric Assist Uniycle Build

Post by Toorbough ULL-Zeveigh » May 21 2010 10:26pm

nah, bet it stems all the way back to wishing for one of these when he was a kid.
bc2.gif
B.C. Transit
bc2.gif (14.6 KiB) Viewed 5938 times
be careful or u might get sued.


correct me if i'm wrong, but it looks like ur doing all the machining by hand, no cnc.
i found every step useful & directly applicable to various projects, none of which are a unicycle.
it'll save me a lot of frustration having ur pictoral roadmap for a guide, it's greatly appreciated.
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Re: Electric Assist Uniycle Build

Post by amberwolf » May 22 2010 12:21am

What, no panniers? :lol: Just kidding--every time I think I'm creative I see stuff like this. :)

Those mountain passes are gonna be easier without the rest of all that bike weight this time around, right Justin? :P

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Re: Electric Assist Uniycle Build

Post by Drunkskunk » May 22 2010 12:45pm

Wow. Thats Amazing!
Buy the ticket, take the ride.
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Re: Electric Assist Uniycle Build

Post by dbaker » May 22 2010 2:41pm

Very nice job, Justin! Amazing what you can do with a 9C! It would be so easy to enlarge phase wires with that large bearing!

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Re: Electric Assist Uniycle Build

Post by etard » May 23 2010 1:33am

Super sick man!! Video with burnout please!! :twisted:

I've gotta make it to one of the Maker Faires sometime, great to have someone like you representing the ES scene. Thanks for sharing.
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Re: Electric Assist Uniycle Build

Post by nicobie » May 23 2010 12:43pm

That's neat! Can't wait to see the video.

I'd probably kill myself trying to ride one of those.
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Re: Electric Assist Uniycle Build

Post by bzhwindtalker » May 24 2010 6:18am

unicycles are cool, ebikes are cool.
electro unicycle is cool² :mrgreen:

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Re: Electric Assist Uniycle Build

Post by justin_le » Jun 10 2010 2:02am

Toorbough ULL-Zeveigh wrote: correct me if i'm wrong, but it looks like ur doing all the machining by hand, no cnc.
That's correct, there wasn't any CNC used here, just a standard milling machine with a rotary table. I installed a digital readout system on it a few months ago though which was invaluable though, especially for getting all the ball bearing fits on the first pass. The first few side covers I experimented with by turning them on a lathe, but for something of this large in diameter it was a bit tricky and the rotary table with large milling bits was faster and perfectly accurate.
i found every step useful & directly applicable to various projects, none of which are a unicycle.
it'll save me a lot of frustration having ur pictoral roadmap for a guide, it's greatly appreciated.
Well glad it could be of use. Will be curious to see what these various projects up your sleeve are!

Justin
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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Re: Electric Assist Uniycle Build

Post by justin_le » Jun 10 2010 3:56am

dequinox wrote:WOW... Thats amazing Justin, quite a post after what seems like a long-time-no-see!
How does it ride so far?
So far, with just a throttle and an ebrake for regen this one works surprisingly well! You don't go especially fast on a 29" unicycle, my cadence tops out around 20-22kph, so with the electric assist I am only averaging just over 1 Wh/km, and for every amp-hour I use going up hill, about 0.5 Ah goes back into the pack on regen from the downhill. So that little 36V 5Ah LiPoly battery is good for over 150km at this rate. I'm at 70km right now and haven't charged it yet.

The control loop with a thumb throttle controller PWM isn't ideal though, and it will be much better when I finish a custom controller that is motor phase current regulated. That way between the throttle and the brake you can dial in the exact torque on the hub which will stay constant regardless of speed, rather than always adjusting up and down on the throttle as your speed changes in order to maintain the same torque. On a unicycle, you have other things to think about, and so having to hold and focus on the throttle for every change in the road or change in speed is a bit consuming.
Brilliant design, and I can't wait to see how the stabilizer circuits you are probably about to design for it turn out :D
So, you are right about this too. In the original plan, I thought it would be great to have self balancing circuitry on the electric assist uni - no throttle and you lean and pedal to accelerate or brake. I also thought you could use it as a 'trainer' device, to make it easier to learn, and then gradually turn down the amount of electronic balancing as you get more comfortable riding. That was the idea at least.

The circuitboard was made to fit in the same enclosure box we use for the CA production, running a PIC18F series chip to take the signals from a rate gyro and accelerometer and then use that to drive a 4 quadrant controller:
Tilt Circuit.jpg
Inside the self balancing circuitry
Tilt Circuit.jpg (101.04 KiB) Viewed 5825 times
I struggled for several days with the code trying to get this to work, but found that to have both human operated pedals AND a balancing control circuit running at the same time resulted in the two always fighting each other. The harder you pedaled, the more you injected a disturbance that the motor would correct by braking, and if you tried to stop or pedal backwards then the motor would kick in high gear going forwards. It was a really strange experience, like riding through a viscous fluid where the harder you worked the more resistance you faced.

As somebody who rides a unicycle, the only way I could make it work was either to turn the self balancing gain way down, so that I was basically able to overcome the motor and keep it steady with my legs, or I could turn the balancing gain way up, remove the pedals and just rest my feet and let the electronics do everything. As soon as you had pedals, and the motor, and the balancing circuitry, it was chaos.

I did bring a 2nd orange 24" electric unicycle down to the Maker Faire which had the balancing circuitry to show people though and to see if maybe someone else could figure out the right human/electric mix with it.
Mark on euni.jpg
Mark having a go on the electric uni after the pedals are removed.
Mark on euni.jpg (88.84 KiB) Viewed 5825 times
But again it was most rideable with the pedals removed, and since my intent was electric assist this wasn't the end that I wanted. That's why in the larger 29" uni, I left the balancing purely to the rider, and the motor is purely there as an assist and a brake, and that seems to work much better. At least for now, there is still a lot to explore here. -Justin
Currently recovering from the Suntrip race on a back to back tandem solar powered row/cycle trike. 550 watt solar roof, dual Grin All Axle hub motors, dual Phaserunner controllers, 12 LiGo batteries, and a whole wack of gear.

Now back in Vancouver with my Big Dummy Frame (yes This One, thanks ES!) with Grin all-axle front hub, Phaserunner controller, and 52V 19Ah Cellman triangle pack
My website: http://www.ebikes.ca
Please contact via email, info@ebikes.ca, rather than PMs, which are disabled

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