Transforming a $156 scooter into a 20mph wheelchair

[pfcs49]

I'd seen several articles on wheelying onto a slightly modified electric scooter-board and riding it, and wanted to try it out.
Also, in my head from the gitgo was the possibility of making an economical and lightweight power wheelchair attachment.
Here is a preliminary view of the scooter as it arrived with the neck loosely attached to the deck and rear wheels:

[pfcs49]

And, before you loose interest, here is the endpoint............at least temporarily!


Oh! And that Volvos From Hell deal? Ted S photoshopped my last decal onto the scooter. It looks kind of dumb in bare aluminum!
PS: Ted/MrSporto here, has moved to Florida. His semi-automatic 911 Carrera with hand controls is for sale!

[pfcs49]

Actually, there's already a V1.1 I modified the mechanism to lock the cycle to the foot-plate tubing/foot-plate differently. The first, seen here, has a black knob on a shaft over threads to cinch down the over-center lineage that is swung into position by the 1"x 5" x 1/4" aluminum control lever seen in the 2nd photo. The knob was about impossible to tighten (and it only required one turn = .028"!). The second iteration uses a second lever. Once the over-center limiter is fully down, the second lever is pulled up and an eccentric cam type lobe (in fact, a pair of 3" washers mounted eccentrically and bolted to the lever) forces the over-center device fully down against the foot-plate, pulling the "U" shaped couplings under the foot-plate tightly into position, creating the lower of 3 connections.
The other connections are two rod-ended 1/4" steel rods. They are permanently attached at the cycle and once the footplate is connected, I push the steering column forward about 4". This lifts the casters off the ground. Then using 1/4" pip pins in the free ends of the links, I attach them to a pair of mounts you can see just above the castor tubes on the wheelchair frame down-tubes.

Below is the current eccentric lock and the former screw-down cincher.
The lower mounting consists of the two "U"s that pick up the tubing of the chair footrest when the handlebar is pushed forward, lifting the castors off the ground. Then the upper lever is pulled down (as in the photo). It swings down across the footplate, and is stopped by the green metal tab. It's a repurposed hinge with a section of 1/2" rod welded to it.
The former iteration was accident proof. Once the knob deal was preadjusted, the shoe of the device (1/2" rod) would brush the footplate and snap into position against the green stop. The linkage would then be a little over-center so it wouldn't come out but, because as it moves past center, it loosens a bit. A full turn of the knob which runs on 1/4 28 hardware brings it into a clamped state (so, 1/28" to tighten) But accusing and turning the knob was very difficult, so I dabbed the current deal which depends on the considerable "stiction" of the eccentric, clamped inside the mounting yoke. I'm not real sanguine about it yet, but so far it's proved satisfactory-it stays tight when I run it. I need to further improve on it, but in this configuration, I can attach the machine in very short order! It' s very satisfying to clip and go! I need to do a video.

[pfcs49]

Here are all the basic parts I fabricated before assembling them to the scooter wheel/handlebars/neck assembly. I also cut down the deck plate around the battery/control box under it and moved it up, in front of the steering column. I also shortened the steering column 7 1/2 inches before mounting the battery/controller box to it.

[pfcs49]

As you see, there's nothing very complicated here! Just a few pieces of mild steel sheet cut with a 4" angle grinder with a cutoff wheel mounted, some 1/4" steel rod, 6 1/4" rod ends, a couple 1/4" pip pins (your wheelchair axles are 1/2" pip pins), a 1x2 piece of steel box tubing. I helps that I have mig welder (~$400), but that can be outsourced.

What you end up with is marvelous! It's unbelievable that this scooter pulls a wheelchair @~20mph on smooth level pavement for such little money. I haven't weighed my rig, but I think it's about 30-35 lbs. It is very easy to throw in the back of my car, go somewhere, and be self propelled. We went to Brooklyn the Sunday after the election and it was so great to run around in the city, whether on sidewalk or street! The advertised range with provided 36v 4Ah LiPO battery is 6mi. Another nice thing: I have a ZX1 which is great within it's limits. It's much too heavy for I or my wife to load into our vehicles (~75lbs). It's SLOW. And it has a joystick.
I didn't realize how much freer a hand throttle and handlebars would make it seem, but it's like moving from a fork lift truck to a sports car. The acceleration is palpable and very satisfying.

[pfcs49]

In the background note my spiffy MIG welder that will run off a 110V outlet! It's quite cheap to buy with a roll of coated wire which is terrible to weld with. I opted to immediately add a bottle of CO2/Argon and a regulator to it which brought my outlay to less than $400 total. I run it on 220V and I'm amazed at it's capability! When I had my car business, I had a Lincoln 150 (Amp). This bugger 1/8 the weight and size and almost as powerful!
Also note that detached, the device is happy and stable standing on it's own. The neck still folds if you need a smaller package in your vehicle.
Note, as well, the use of a catheter tray for small parts! I have many on compartmental shelves. Very handy!

[pfcs49]

I forgot! The supplied electric brake is fine for holding your speed downhill (and this rig REALLY coasts!) but hopeless in an emergency. I made a rudimentary "disc" brake setup out of two gate-hasps (for padlocks) bolted to the forks and pulled together by a bicycle brake handle and cable. The gold anodized 1/4" cap screws on the rear edge of the fork adjusts the attitude of the hasp so it's nearly touching the tire sidewall and is parallel. Works great! Stops from 15mph in ~10 feet.
The scooter display with thumb-throttle on right handlebar displays speed (MPH or KPH) battery voltage, gear (1, 2, 3) as well as trouble-codes and stuff you can reprogram (tire dia, motor poles, etc) It has a trip and overall odometer as well.

I already have a second scooter apart on my bench. FRANKENSCOOTER lives!
I got a four new motor controllers in both 36 and 48 volt iterations, all with a reverse from a switch. They are cheap! $11-$24 from China of all places!
Also, a 10Ah 48V LiPO battery which should liven things up!
20mph in a wheelchair is more than enough for me!! Believe me, it's exciting, especially on these shitty roads! But these shitty roads also feature shitty hills, real steep ones. One I couldn't get up without tacking back and forth on, just around a curve! Exciting stuff.

Traction is poor and limited by the weight on the front tire. I could have skimped on weight but figured I wanted as much as possible so I included steel in my build including a piece of 1/2" x2" x 5" plate to space out the lower mount. On these real steep pitches, I can get just sufficient traction by sitting forward on my chair and leaning over the handlebars, but motor torque is clearly not sufficient. As delivered, the machine is 36V 4Ah 350W.
I will see how well the original motor-wheel deals with a 500W controller and possibly also 48V 500W controller.
I expect to be buying a 10" pneumatic tired motor and extending the forks a little for it and also shimming the lower mount to match the new geometry.
Hopefully this will result in a deal the can rip around in my hilly yard. If it does, bye-bye heavy old ZX1

[ChesBay]

Excellent project Phil!!

[juniorsenior]

You did something I’ve been dreaming about for a while now on my firefly gen 2. I’m wondering if you might have any insight to the firefly - is the speed electronically limited, and how could I turn off it’s limiter? Would I need a new controller?

if I did do that, would I burn up the motor?

Thanks!

[pfcs49]

Can you post a picture of the Firefly? How big is the tire? Pretty sure you could change the speed by changing the controller or swapping the motor but that would depend on how it's implemented.

[Gordy1]

You did something I’ve been dreaming about for a while now on my firefly gen 2. I’m wondering if you might have any insight to the firefly - is the speed electronically limited, and how could I turn off it’s limiter? Would I need a new controller?

if I did do that, would I burn up the motor?

Thanks!

I know that the gen 1 Firefly had two speed limits which could be changed via the controller if you knew how (ie it involved some special sequence of buttons, it wasn’t an obvious selection on a menu). What speed are you currently limited to?

Gen 1 was 250W, and the wheel diameter was pretty small. Having now played around with larger wattage hub motors (which includes a 500W 36V set-up that can go at about 35km/h), I’m not convinced that the Firefly one could have gone much faster than the higher factory setting. Although I admit that I don’t actually know what ends up being the limiting factor in hub motor speed. Chinese controllers don’t seem to specify a speed limit, but that may be because they don’t know what diameter of wheel the controller will be used on, and that obviously affects the speed (but not the hub rotation speed).

[pfcs49]

Your questions are mine as well! The little display/thumb throttle assembly has a main menu, which mostly makes the display show various info like battery voltage, trip odo, overall odo, whl RPM,etc, but there's a sub-menu which you can edit with the buttons which has wheel diameter (8") and motor pole pairs (15) as well as %total speed (80 is default). Also non zero starting/zero starting, hard starting/soft starting. I have raised %total speed to 100 but I think it returns to the default when I shut the scooter off. I haven't really played much with this sub-menu because as-is the machine is perfect for my needs. It's top speed is clearly a danger on my bumpy streets.

That said, all your questions are pertinent. What happens when I swap a motor? Will the top speed be the same if the wheel diameter is 8"? For that matter, what if I program in a different diameter? Can I change my limit that way. Or if I vary the number of motor poles? I should play with this on the original deal, but the environment here is not good for going on the roads! (why I only rode my Freedom Rider a couple of times before passing it on!) And so I haven't ridden this thing much.

But these will all be front and center questions when I start swapping controllers around OR jump the original up from 36>48V.
I have the 2nd scooter essentials on my bench (motor/battery/controls/control box) and made up a test jumper for the 6 terminal ribbon wire that goes to the handlebar/controls so I can hopefully figure out exactly what is going on and how to use the original display/throttle/controller to command anothers control box.
The boxes, which are quite cheap (~$9-28 from China) are pathetic in terms of instructions! Then theres the potential problem of synchronizing the 2x3pairs of wires to the 3 Halls generators (position/direction) AND the 3 pairs to the motor "phases" (poles) to get them happy. Theres a pair of wires termed "learning" that may or may not facilitate this.
I just need to commit to spending hours figuring out exactly what each of the circuits for the throttle controller and brake controller do on the KDX scooter so I can apply that to integrating other controllers. I don't want too give up the features that the original controller provides like bar display of battery, numeric voltage of battery, speed, distance, etc.

More than speed, I want to find torque for hill-climbing and I don't know if higher voltage alone will change that? I have a pyrometer to watch motor temperature; the KDX has no temp sensor in it's motor. I suppose that will be answered as soon as I plug the 48V 10Ah battery onto the KDX chair-motor!
I also have 500W controllers in both voltages. I'm not too concerned with burning out the KDX motor on the second scooter; I expect I'll need a 500W motor for the second more capable chair-scooter but would be happy to be wrong!



PS: If anybody needs, I purchased a bunch of wiring supplies including pairs of 3, 5, and 6 terminal plugs with ~4" wires in as well as a set of housings and terminals to make up any of the larger connectors that seem to come with all the Chinese aftermarket controllers. The test rig ia just a pair of 6 terminal male and female plugs soldered together with the wires numbered. Not that the colors of the new wires are not in the same order as the KDX wiring, but I also go a set of terminal removing tools so I can make things coherent if/when I make up harnesses to mate new motor-boxes to KDX controls.

You may think I'm loose with my money, but all the wiring stuff (including a lot of high current plugs for phases, etc and battery connections) was much less than a Franklin!

[Gordy1]

I think I can answer some of your questions, but definitely not all!

If you increase your motor power (Watts) you will definitely be able to increase your speed (provided the controller doesn’t limit the speed). Torque will also be increased, but by how much, I’m not sure.

Programming in a different wheel diameter on the controller will not change the physical speed. It will change the speed that is registered on the controller screen (so if your programmed wheel diameter doesn’t match the physical diameter of your front wheel, your speed reading will be incorrect).

Having just upgraded an electric off-road go-kart (which doesn’t use a hub motor, just a “normal” 1000W motor) from 36v SLA to 48v Lithium, including a change in controller, I can say:
- speed has increased, which was the result I was after.
- torque seems to be the same (presumably as the motor hasn’t changed). But the torque was always good. I think a bigger powered motor would be required to increase torque.

Unfortunately I can’t help out with halls/phases, as none of the motors that I’ve played with have these options. (Is that brushed vs brushless, or am I making that up?!?!).

You are definitely right about the useless controller instructions. I made sure that the most recent controller that I purchased had a large label on the top of the controller that states which wires do what. But when it arrived, the label didn’t match the wires coming from the controller! Thankfully I find that the important connections (battery, motor, and throttle) are usually easy enough to identify. But I did blow a fuse in the new lithium battery (and possibly blew the controller) when I was trying to work out one of the other functions. (A little hint - don’t short-circuit the small red and black wires, which I thought might be an on/off function but definitely isn’t!).

Some of the control wires have labels on them. Some in English and Chinese, and some in Chinese only. My son’s google phone was able to translate the Chinese symbols quite well, but then you just need to work out what they are trying to say. For example one translation was “turn”. That was the throttle, so I guess it was saying that the motor will “turn” using these wires....

[pfcs49]

Theoretically, Watts is the same as horsepower and horsepower is a function of torque and RPM. Perhaps an electric motor produces a constant torque at all RPMs? (IC motors, torque falls off as RPM increases BUT horsepower is a function of RPM so it peaks after torque has fallen a good bit)
I know there's some factor with these brushless motors that there's an inherent speed limit on them, perhaps dependent on AC frequency? I should do some reading but having too much fun still!
I DO know that horsepower is in some ways irrelevant; speed of a motor vehicle is always a direct function of available torque at that speed. Watts when dealing with AC motors is V x A= W (roughly-AC is not DC!), so it implies that "you can't have one without the other" (love & marriage) They do go together like an electric carriage I guess.


Brushless motors are 3 phase and have 3 power wires/no ground, and use alternating current. The Halls generators, which are a kind of electronic position sensing switching device, inform the controller of rotor position and hence when to turn on or off the next phase legs to rotate the motor, which leaves you with 36! possible combinations of sensor and phase pairings, only 2 of which work!
Apparently some brushless/3 phase motors will work without sensors but none I've seen so far.

Brushed DC motors are easy to control and reverse-just reverse the poplarity. I think you can reverse a brushless 3 phase motor by finding the right timing for the phases and the sensors, but that would require 8 wires to a 4 pole double position switch with 4 wires being heavy enough to handle high current, something not at all practical! I'm counting on these new controllers to do that with two wires.

The Chinese aren't terribly helpful with their info. We are supposed to be electrical engineers! I dread to have to go through the drudgery of trying 36 combinations of wires! The Halls and phase wires are mostly color coded the same; but my reading informs me that there's no agreement about the timing of them and many will need to just do trial and error
Of course, the KDX wiring uses much more compact MPCs (Multi Plug Connectors) than the aftermarket ones. That's why I got myself both kinds of kit so I can make adapter harnesses OR change one set of connectors to unify, but first I need to get one swapped, then (hopefully) the other controllers will be identical in their color coding. I may be dreaming.

PS: I've enjoyed your projects and videos. Great stuff and I hope I can get to your level! (there's STILL a 15 year old in me that wants to fly!)

[Gordy1]

I think I’ll stick to brushed motors...my brain hurts just thinking about all the wiring combinations you could have!

Some day I’ll get my son to do a video of all the electric “toys” that he has, most of which I’ve made or modified. There are pros and cons for each, with no perfect solution for every scenario unfortunately.

If he didn’t already have a SmartDrive, I’d definitely be modifying a scooter like you have. To me, having handlebars in front is a better option than being pushed from behind/under the chair (safer and something to hold onto), but my son doesn’t seem to agree!