I know, but it’s going to be close. The deck is going to be in the neighborhood of 2kg. And ergonomically, the big advantage of the narrow center section is that I can grab it with one hand and hoist it on to my shoulder, which is a great way for me to carry things.
Yep. I’m going to do everything I know how to eliminate failure modes, but this will still be more risky than a conventional remote and I’ll be wearing a full suit of armor for it.
-I’m going to be using old school 1-2ms PWM throttle signals, since that communication method has a very long track record for resisting interference in the RC world. Additionally, the failure mode for analog signals is gradual, compared to digital signals suddenly becoming gibberish.
-The plan for loss of signal is to make sure the ESC freewheels, then foot brake. And pull the loopkey if the throttle is stuck for some reason.
-The plan for loss of power is to figure out how to make a redundant power supply for the Arduino, but I’ll get to that after I know that it works and finish low-speed testing of the board.
-The control system requires 1 sensor set at each end, but I’m putting in groups of 3 so that a “voting” process can take place to reject a bad sensor value. This triple redundancy strategy is how aircraft control systems are set up.
-The plan for interference is to cover all components of the control system in grounded, shielded wires and aluminum foil Faraday cages. I will also be keeping the Arduino far away from as much of the power electronics as I can.
I will be running everything through a low pass filter to smooth out the influence of bumps, yes. And I will be operating on the ratio between the front and back sensor values instead of the difference between them, so that the throttle signal is independent of the changes in G loading that occur when you go over a bump.
However, that’s the only limiting factor on ramp time. My control logic will make it impossible for the board to generate enough thrust to tip me over in normal operation. And hopefully, my really wide stance will make that quite difficult in a fault condition.
Yeeeah might have been a mistake in hidsight. Routing the balance wires through that narrow space made them get crushed together anyway, so I figured I should at least keep it neat and uniform with a loose braid that prevented instances of a single wire crossing (they cross is a 3x3 grid, so its more distributed? Idk). I immobilized the braid every few centimeters with big globs of construction adhesive.
It’s a neat idea, but I won’t be using PID to control the board. Reason being that using a large I term like you suggest would create throttle inputs that persist after my weight distribution has changed, so for example it would allow a situation where the board is producing high thrust but my center of gravity is towards the rear. Not a good combo.
@mr.shiteside I opened up the tube core and redid the balance wires, what do you think? The original problem I was trying to solve with the braids was that a flat ribbon of disconnected wires will want to loosen up and get tangled as soon as it’s not strapped down to a flat surface. So my idea now was to embed the wires in glue, sandwich them between layers of paper to promote flatness and wrap them in fiberglass tape. To fit through tight spaces, I waited until the glue was halfway cured and still flexible, and just bent to the entire package into a U shape, so the wires still didn’t cross each other. The ribbon is still immobilized along its length with glue.
Did the tube layup last night, it came out with a couple defects on the tension side of the structure so we’ll see how it goes. If it fails the jump test I’ll have to see about replacing it.
All of the sandwich panels will need a bit of sanding to fit them up before I can tack them in place with filler, but hopefully I can get that done today after I get back from work. Reinforcing all the joints with carbon will take at least another day after that.
All I got done this afternoon was cleaning up the ends and cutting out the drop through slots with my rotary tool. As usual, I forgot to factor in how little skill I have in using a rotary tool.
I’m glad I took all the time I needed though, because carbon dust and splinters are no joke.
Following with great interest! It’s refreshing to see some true and innovative DIY here and I appreciate the lengths you’re going to to make the process accessible for the rest of us mugs. Were you as nervous as I was when you first aidstood on the Tüüb?
…and will the cocaine feature in later episodes then?
No visible progress today, but I deburred and fit up all of the panels for the foot pads, which hopefully should be pretty much the last sucky part of the build. Joinery begins tomorrow.
It finally looks like the finished product! Got the panels glued up today. None of the joints are structural yet, but it will be ready for carbon reinforcement tomorrow when the epoxy is cured. For reference, that is a 37-in long cutting mat.
After a breif intermission caused by me not realizing I was running out of epoxy because the container was heavy so I thought that I had more…
I finished the main structure of the deck last night and took it out for a spin at my local park in analog mode today, did a few miles and took it up to around 20 mph downhill (EDIT: GPS says 27mph ). It was my first time ever seriously riding a board, but I think I picked it up pretty okay. I got relatively comfortable doing gentle carves and foot braking. I’m still not super steady in turns and especially not in low speed ones, but I love the handling of the board. Super smooth and predictable.
I think I got the width of the foot pads spot on, I can just hang either side of my foot over the edge a little bit if I want to. The concave was okay I think, I wasn’t pushing it very hard in the turns but I still never felt like I was in danger of slipping off, even though there isn’t any grip on the deck yet. No complaints about the wheelbase, it’s a little long for analog pushing but feels super steady while coasting, and the foot placement feels totally natural to me when going downhill in a tuck.
The trucks have a lot of lean in them right now, which is definitely going to result in motor bite. I have a lot of headroom in the tail of the board to carve out clearance for the motors, and I can also look at flush mounting the rear truck. Plus I can just get bushings that limit the lean more, so I’m optimistic.
It is responsive to my weight, but even with the gain turned all the way up the response is only a few millivolts, so I have to figure out why that’s happening.
). It was my first time ever seriously riding a board, but I think I picked it up pretty okay. I got relatively comfortable doing gentle carves and foot braking. I’m still not super steady in turns and especially not in low speed ones, but I love the handling of the board. Super smooth and predictable.
