Izzy's Trail Board 2

DIY Builds
1

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Background

I ride mountain bike single track. I like the maneuverability, instability, and small footprint of one wheel self-balance boards. I write my own vesc package, Trick and Trail. To increase maneuverability and board control in the air I removed the battery from the board and put it in my backpack. I already run 20S1P on board and 20S2P in my backpack, so running 20S3P in my backpack isn’t a big change for me.

Parts

Parts

Comments

Comments

For this build I wanted to stick with the XR axle because many of the motors and motor accessories I want to use are based on the XR. I have my eye on the new Kiil Guard suspension system in particular.

I went with an 8 degree angle for the front and rear rails. I think this is a bit more angle than the TFL steep and deep rails. The footpads add another 3-4 degrees. I would say 8 degrees is probably the highest you want to go.

Board length is 28.5" from end of footpad to end of footpad. This is a bit shorter than my original WTF growler rails. The rear rail and footpad is 1/2" shorter than the front rail to accommodate my ride stance. The tire gap is 11" from bumper to bumper.

This board feels extremely stiff due to the simplified design. The stack of items bolted together is only the bumper rail and foot plate, making it very secure. The bends in the foot plates add to the rigidity. The stiffness feels extremely responsive but also bumps in the terrain are more readily transmitted to the rider. I had to reduce high current haptic buzz (foc play tone) from 10V, 180Hz to 5V because it was shaking me out of my shoes. I also had to implement some new code to handle feedback vibration that occurred because of the tighter coupling between the IMU and the motor.

The board weight and balance feels great, like I expected. Doing 180’s feels really balanced and agile. Less board weight in the air is noticeable. Tail clearance for drops is amazing.

There is minimal space on the front footpad due to the width of the controller. Right now it feels like there is just enough room, but my foot is 100% locked in like a snowboard. The front foot binding release interferes a bit with the control enclosure and just barely fits in the space created by the arch of my foot. Future improvements would focus on improving this layout.

I need to improve the heat sink because it is hitting high temp a little too easily. My old board had the foot plate in contact with the heat sink so it had more mass. In this case I will probably just increase the thickness of the heat sink from .09 to .18. I could add extruded fins to it but I think that is overkill. I have also found that since the heat sink is exposed I can smear a bit of water on it from my water bottle and it cools down like 10 degrees per minute. I bit of a gambit but I trust my enclosure design to keep water out.

This build was very cost effective. Most of the parts I had on hand (controller, battery, motor, center rail, wiring, jacketing, fuses, connectors, anti-spark). I had to buy material for the bumpers, rails, and the rail fasteners, about $200. The footplates I had made by sendcutsend which cost me $72, including shipping and tax. I can build a new set of rails for $50 if I wanted to try a different angle or accommodate a larger tire.

Glamor Shots

Glamor Shots

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More Pictures

More Pictures

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My first set of rails failed because of a design oversight.

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It was a pretty classic tensile stress failure

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First failed rails

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To solve this I added more material to the area that failed.

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Rail fit up before paint

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Rails after paint
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I used 3D printed templates to help make my rails.

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Front Foot Binding

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Control Enclosure Internals

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Foot pad switches feed under the foot plate and connect with 2mm bullets. There is a gap of 1/8" between the foot plate and the bumper because of the rails. I used 1/4" neoprene foam around the perimeter of the footplate to prevent dirt and water from filling the space.

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Battery harness with fuse and anti-spark loop key. XT30 connects to the voltmeter I keep on my backpack shoulder strap.

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On my backpack we have a carabiner attached to about a foot of bungee cord, which will stretch until we reach the extent of the paracord. Then we have the battery cable which is longer than the paracord.

14 Likes
2

Wild dude!!!

1 Like
3

This is awesome! Hey @TheBoardGarage check this ish out!

2 Likes
4

oh the trick and trail package. :slight_smile:

did that do something like eliminate pid control of current? or modify the settings drastically?

2 Likes
5

Very nice I love something as purpose built as that,

Since you have space with the battery in the backpack and you care about weight would it be worth the effort to use a smaller high kv motor and large gear reduction to keep at least as much power for around 4kg less weight?

1 Like
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I changed the control algorithm to be non-linear, similar to how remotes can be tuned. Beyond that I have mostly focused on traction control because that is the main limitation on trails.

1 Like
7

Definitely something I have looked into and I would love to pursue if I thought it was promising. So far what I have learned is super interesting but not super promising.

You need a very high gear ratio because the tire is big. It needs to be at least two stages. Low end torque is a major factor for trail riding and I wouldn’t want to end up with less torque. When doing this design I was looking at the peak torque of the motor I am currently using. I don’t have it on me currently.

Consider that a lot of rigidity is needed between the motor and the tire to prevent slip. The builds I have seen use a pretty beefy bracket. Stronger than standard rails.

Then there are clearance considerations for the transmission components and motor to mount on my rear footplate. Overall I think this would be a multi-$1000 build and like a year of build time. I would have to have a killer design. By comparison this build was a few hundred and 2 months.

I have my eye on a company out of china called Floatwheel that has been producing a competitive product to Onewheel. They are talking about making a smaller hub motor that uses ATF to stay cool. I was thinking that would be the most cost effective weight reduction.

2 Likes
8

You will love this thing @Soflo

3 Likes
9

Holy shit!!! This is right up my alley!!!
How does that tire handle?
Looks really square, but cool

If you are having heat problems, definitely increase the thickness of the heat sink, also some people carry a can of freeze spray and instantly cool down motors and controllers.
Really cool build

2 Likes
10

It’s funny you say that because it is the roundest tire on the market. Maybe jsut the pics. Everyone who tries my board talks about how nimble and responsive the tire is. You can roll it all the way over to the rim. Makes for a much more snowboard like feel.

3 Likes
11

Thinking of getting that tire for my plus… pretty sure it will work.