Full disclosure, I’ve never built any kind of board at all. I’m going to be learning as I go. I’m also going to ask some questions so I hope I don’t get to annoying. I feel I’m capable of doing this or I wouldn’t be attempting it at all. All of that said, let’s get into it.
So the style is bikeboard, speedboard, casterboard, or something like that. It’s based off of a steering linkage used by Bimoto motorcycles and others. It’s also similar to other boards shown on this site in the past.
The motor will be 6368-63100 I’m looking for recommendations.
I’m thinking 12S-4P.
I have no clue what ESC to use so looking for recommendations on that also.
My area for batteries and ESC is about 5.5X1X24. It’s the area circled in red below.
Been thinking about something with two wheels for my next project, maybe something like this. I like kart wheels though, so something like this that doesn’t tilt the wheels, maybe
I’m curious where you get your parts machined? I’ve used Weerg for my current project, and while the parts came back fantastic, it was an expensive process.
Were there any design considerations when choosing the steering geometry? It’s a virtual pivot point, but I’d think the basics like rake, trail, and offset still apply. I’ve always thought of these as motorcycles, just without the handlebars. Although maybe with the spring between those arms you don’t need ‘baked in’ return to center characteristics.
What is your bearing surface? Metal on metal? If so, the handling won’t be great. Static friction in the hinges prevents the steering geometry from tracking straight at small angles, which puts a much heavier load on the rider to keep the vehicle balanced. I started off with steel shafts and greased bronze bushings, it really tired out my legs and the handling was just kind of shit tbh. Rulon J is really good for this, but be aware that the short structural depth of your linkage will overload the rear pivots, and squish them out of shape in short order.
You won’t be disappointed if you go big, since inline boards feel effortless at high speed, you’ll be able to handle a good deal of power.
MakerX has a few different single ESC models, I know spintend has a couple as well
Rake angle makes the steering response more tippy, the same as a conventional bike.
I think that bikeboards are trail agnostic though, to some degree. Because, while forces generated by the trail will center the wheel, the trail is also the lever arm that generates steering moments, so there will be some terms that cancel out there. I have 100 mm of trail on mine, but it doesn’t feel any different from my old bicycle with 70 mm. Increasing the trail does increase the amount that the front end dives sideways when leaned over, which influences the ground clearance requirements.
The stationary point of the four bar linkage creates a natural steering lockout. It doesn’t exactly occur at the stationary point, the steering geometry affects it, but it’s a decent approximation.
The spring creates static stability in the steering of the front wheel, which is beneficial for ease of balancing at low speeds, but is not strictly necessary and can be compensated for with practice. The trail of the steering geometry creates dynamic stability, which is a completely different effect, that increases with speed. Having dynamically stable steering geometry is not optional for these boards.
I did all of the machining myself. That helps keep the cost per part pretty low.
The way the steering system is designed the axle is in trail of the focal point of the two arms. That distance changes both in offset and trail distance as the tire pivots. This causes a self dampening effect in the system.
I’ll probably end up going with the 63100 then. I have a lot of room to work as far as motors go.
The bearings are all oilite bronze. I ran all the numbers for shaft size and and coefficient of friction. It should work enough for this test article. I’ll know when I roll down the road for the first time.
In my experience the difference in friction was only clear in comparison, the increased difficulty in balancing is difficult to distinguish from having the ride height be too tall.
I threw what I have for the board together for a couple of quick photos. With a little weight on it and rolling it across the floor, it seem to respond pretty good to lean input. Still a few other parts to make. Back to work!
The machining looks nice but there’s something about the laws of physics that makes me feel like something isn’t gonna work! I hope I’m wrong and wish you the best! Projects like this make this forum fun!
The trail is about 43mm right now with the spacers I have on the front axle. Thicker or thinner washers can be used to adjust the trail.
Here are a few pictures for those not familiar with the twin link steering system. As you can see in the pictures, the theoretical pivot point of the steerings links ofset opposite the direction of turn. At slower speeds centripetal (not centrifugal) forces are low and tight turns, due to the side loading from bank angle, are easy. As speed increases and centripetal forces increase, these forces try to push the center of the axle in line with the pivot point. This makes turning require more force and stability increase as speed increases. By changing the geometry of the entire system you can control turn force and stability in the system.
What makes sense to me is when the board leans over the weight makes the wheel want to move to the high side but that steering linkage self-corrects said input.
Seems so convoluted compared to the simplicity of a bicycle style caster front wheel. Yet elegant at the same time.
Yes, they are for a spring. A spring helps with the low speed steering of the system. It will inproove the board tracking at anything below a fast walk. As speed increases the board gets more stable. It may not be needed though.
The main arms are slimmed down for wheel tire clearance and weight savings. They could be beefed up a little and still have good clearance. The parts are made from 7075 aluminum. I’ve run FEA on them and they should handle everything i plan on doing with the board. I will probably beef up the arms on the next board though.
The steering is one of those solutions to a problem that isn’t there. It sure looks good though.
