Painted the frame to keep it from continuing to rust, and for STYLE, obviously.

Added these 1/16″ thick HDPE strips to the middle bottom of the frame to reduce metal scraping when it bottoms out over curbs and stuff (long wheelbase, low clearance, it happens)

Cut out and attached a full-size solid deck out of this crappy shipping-crate plywood

Then stained it to reduce the show-uppiness of shoe marks, to the state in the first picture. I also reworked some of the component mounting strategy, extended and tidied the potbox-controller wire and adjusted the potbox lever. I have ordered a 4QD VTX40-24 controller to replace the Curtis 1208C, for the sake of being able to adjust the acceleration/deceleration ramp rates. Unfortunately that controller will not drop right in with the potbox setup, so I will have to set something up to make it work. I would like some sort of neat-o pistol grip style controller but I’ll probably just slap something together for now.

I have largely realized the concept I started out with. Pretty nicely indeed, if I say so myself.

The question I’m thinking about now is really where I need to take the concept- I don’t think what it is now is really there. I need to pick a direction for the project, and see if I can get something that really makes sense. In short, I don’t really like riding this thing. Sure, I’ve probably only put in maybe 20 minutes of “board time”, and I’m not a skateboarder by nature or history, but for me the design doesn’t really feel quite “there” or “right”.

This line of thinking can be expanded to address the state of “stand-up” personal vehicles in general.

• Scooters
• Skateboards
• Self-balancing 2-wheel Scooters (Segway-style)

Both Segways and Scooters have handlebars. Segways go 12mph, (non-seated) Scooters usually top out around 10-30mph, some of the electric skateboards on the market can hit speeds above 20. My machine doesn’t manage more than a tepid 6-8mph (estimated, limited by the voltage and gearing of wheelchair transaxle). Fast jogging speed. It steers like a skateboard but has a form-factor unlike any electric skateboard I am aware of. It’s taller, longer, wider. I think it could feel secure and stable at 15-25 mph. Not sure if I’ll be able to test that assertion with this motor transaxle I’m running now. It’s got more than enough power but is geared wrong. I really can’t put any bigger wheels on it.

Benefits of stand-up vehicles:

• Can be awesome
• Good visibility in traffic
• Hop-on, Hop-0ffness
• Generally reasonably compact, efficient nature

Downsides of stand-up vehicles

• High likelihood of falling on your ass
• Practically limited top speed

I don’t think you can safely go much faster than 25 or 30 mph on something without Butt-Support. The Segway is freaky enough at 12, not to mention the ever present “if this thing pukes I am going to be on my ass, hard” factor.

Despite the issues with this prototype, and stand-up vehicles in general, my concept has some things going for it.

• Big pneumatic wheels soak up little bumps pretty well
• Big enough deck for two people (untested, I won’t be the one testing it), or stuff
• Massive undercarriage- you could put enough battery to go 40-80 miles on a charge in it, easily

That’s assuming you are comfortable enough riding it to want to go 80 miles on it. So far, for me, I don’t think that’s so much the case. It’s a pretty good ankle/knee workout.

The other big benefit of my concept in its scale/implementation is its nearly boundless versatility with permutations of design. Some big possibilities that have come up:

• Put toe hooks/clips onboard for better steering and stability leverage- this was independantly suggested by two skateboard afficianados who rode it.
• Put a handlebar on the (non-tiling) axle assembly- would take much of the trickiness and uncertainty out of riding it.
• Put a bucket seat on it. Particularly if you had your hands free I think you could generate plenty of tilting force to ride it sitting down

I’ve got an idea for a more elegant, reliable and adjustable axle-pivot/damper setup, and indeed it would be a good idea to get a powertrain setup that allows for more speed. These transaxle motors are built sturdily, and could be run over-volt, maybe even double voltage at the expense of brush life. I don’t think the windings themselves are at great risk of frying given the light weight of the vehicle. I haven’t monitored the cruising current draw of my motor at 24v, I suspect it is quite low.

I don’t envision trying to produce these things, or have them built. I think that I may just work on a second prototype to develop the things I just mentioned, then I might just make documentation and plans available. That would suit the flexibility of this design well, so that anyone can build it the way they would like it.

So- there is still potential and promise here, as well as a few issues keeping me from hopping on and cruising around town more. I’m still scared of the super-quick accel/decel from the current motor controller after getting pitched off of it. I’m still just not comfortable with the stability of the board (I think that’s more my problem rather than an issue with the machine). The top speed is boring. Also, while in some road situations it’s clear where to ride a thing like this, be it the bike lane, or in the street- on other streets it’s a bit more difficult to work out. I’m not sure how a vehicle like this is supposed to be allowed or prohibited. It’s too wide and slow to really play that nicely on bike paths or sidewalks, it shouldn’t be duking it out with cars on bigger roads though.

Indeed, my most imminent job is just to get it out and ride it more. I tend to avoid opportunities to hurt myself. Suppose that’s why this is not really such a good project for me… but I’m this far into it already, right?

If you are in the bay area and are interested in riding this thing and telling me what you think I would appreciate your input. Drop me a line.

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If you didn’t see it, take a look at the previous skateboard post for an idea what this is all about-

For now I’ll let the pictures tell the story:

Since the last post I finished welding up the frame, made a front axle on the lathe, acquired batteries and wired up the controls, assembled all the parts, and designed and implemented a return-to-center damper system.

The batteries can be seen on each end of the frame with the motor controller (beige) and charger (black) in the center. The deck is an old kitchen cabinet shelf out of the house my folks are currently renovating.

The “potbox” hand controller. One way on the black levers is forward, the other reverse. The E-Stop button cuts power and shorts the motor leads, slowing the vehicle down very fast.

The return-to-center damping action (provided in a skateboard truck by a doughnut-shaped rubber bushing) is here accomplished through the unconventional use of two rubber exhaust bushings, these were sourced on eBay, and are apparently designed for use with some models of Land Rover. I’m not sure how well they’ll last but at present they are very effective, they have about the right amount of resistance and are smooth through the entire travel. They are only placed on the rear axle presently, to double the resistance another set could be placed on the front axle.

So, how does it ride? Really nicely, in fact! The biggest problems right now are with the non-intuitiveness of the throttle control, and the excessive aggressiveness of the acceleration and deceleration ramps programmed into the Curtis 1208C controller that is in use. I was showing it to a few people at school, in a bit of a rush and hastily popped the throttle and was thrown right off the back of it as it lurched forward, fell on my wrist and sprained it pretty good. The steering and balancing action however is quite nice. A skateboarder at school gave it a test drive, he picked it up instantly with no hesitation and said it was really awesome. So there’s potential. I need to make sure I can’t adjust the accel/decel ramp on the 1208, if not I may shop for an adjustable controller (4QD VTX-40 maybe, something from Kelly maybe).

I made this video last weekend before the exhaust hangers arrived- My friends and I just bungee-corded some places on the frame and gave it a try.

My dad rolls it his own way:

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Moving along, I decided that building a skateboard-steering car was not a reasonable project for me, but maybe building a maxi-magnum-electric skateboard could be. I already have an electric transaxle that I found in an abandoned and screwed up electric scooter wheelchair, along with its controller and some junk PbA batteries. And thus the plan was hatched.

The concept: mount the transaxle to the frame with a pivot axle at a 45˚ angle to the ground, with that pivot axle intersecting the wheel axle. Mount another axle in the same way. If you continue the lines made by the pivot axles they will make a right-side up V when the whole assembly is viewed from the side. So, the pivot axles point up and out from the front and back of the vehicle. That’s how it is in skateboards, as well as the BOB car linked above. Build it. Put batteries and motor controller in the frame, drive it, see what happens.

The first step was attaching wheels to the transaxle- the wheelchair wheels were shot long ago and I wanted bigger diameter wheels for more speed. I ordered a set of these wheels from the Surplus Center. I was expecting to be able to unbolt the rim and take the hub/bearing cartridge off, but it turned out it was pressed into the rim. So I popped it onto the lathe and took care of that – then I made wheel hubs to adapt the .750 double-keyed transaxle shafts to the 2.75″ bolt circle on the rims. The hubs are solid aluminum. Thanks to the Laney machine shop program for that. That stock alone is probably worth more than I’ve spent on the whole project so far.

I then did a bunch of planning and working out triangles and measurements for the frame- I made a rough mockup out of wood that gave me some useful insight to the way the clearances would work out for the steering setup. I decided to mostly use 1″x .063″ mild steel square tubing because I already had about 13 ft. of it, picked up another 20 ft at a local steel dealer. There’s some 1″x1″x.125″ angle iron also, and just a bit of 1/4″ plate. So, this morning I set about building it.

A chopsaw is essential. I have an old delta mitre saw outfitted with an abrasive blade.

Starting to take shape.

Even with many parts still missing, you can start to see how this is going to come togetherI made this hardware in the machine shop on Thursday

So, it got dark and I stopped taking photos, but I did infact get the frame welded up and the transaxle assembly completed and attached to the frame. I will need to do some more work to set up the front axle, and get ahold of (make) a front axle- but that’s going to have to wait for next week in the machine shop.

The deal is, it works. It’s going to work. As soon as I get a chance I will take photos (and video!) of the completed axle assembly. It’s actually pretty sweet how it swings back and forth with the tilting of the deck. The delrin bushings pictured above are the key part of that swivel assembly. I’m not sure how well they’ll hold up, I know that skateboard trucks often use ball bearings- but they’ll work for now. The assembly feels tight, secure and smooth in this initial testing.

I’m pretty excited about this project. I could see this vehicle being a pretty good little around-town runnabout. I also designed the frame to be able to accomodate several battery options- you’d get really impressive range with a 24v x 40AH LiFePO4 pack! I’m definitely hopeful and looking forward to giving it a ride to see if it’s something I want to invest further in.

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