I am seeing a lightweight mobility scooter, but they are very expensive. However, I have purchased a lightweight folding 3-wheel E-bike. (see attached picture).

I want to make some changes to it, by adding two motors to the back, that taken from a hoverboard. But, I am having difficulty with adapting a controller. I want to just put an unpowered wheel in the front, and then two powered wheels in the back. These are BLDC hub motors with Hall effect sensors. I can use a speed controller like the $16 ones on Ebay BLDC Motor controller
I imagine I could purchase two of these, and give input for speed from one potentiometer. However, I need the wheels to have some freedom as they spin, so that a tight turn is possible. I am wondering if these BLDC motors will behave like stepper motors with these types of controllers. If so, the pair will tend to want to stay in sync. So, they will fight against a tight turn. Am I correct? I somehow need it to function like it had a physical differential gear. Perhaps one of the wheels to behave more like a DC motor. If it experiences a heavier load, it just slows down.

Here is my current strategy. Set one of them to be the master wheel. It is controlled normally. But the other wheel needs to be just a helper. Perhaps it is controlled to apply a similar amount of traction that is being applied to the master wheel. If I were to try using an Arduino (which I am trying to avoid), I imagine I might monitor the current draw of the master motor, and then run the speed of the slave motor however fast it needs to be, to equal that same current draw. Though, perhaps it should be more complex. If it knows I am at a higher speed, then keep the two wheels at near the same speed. At low speeds, a permit greater speed difference.

Any other ideas or advice about creating this virtual differential gear?

For a bit more background, here are the issues I have with the stock e-trike

1. It does not have the ability to change speed ranges. It is difficult to keep it at a slow walking speed.
2. It doesn't go up hills well, because the front drive wheel loses most of its traction on even a gentle slope.
3. It really is difficult to control in many situations. The spread of the back wheels is so narrow, that it really wants to be handled like a bicycle. But, you can't lean into a turn because of the 3 wheels. Nor are the wheels apart enough to be treated like a trike. Even a very slight side slope makes it difficult to stay upright.

 

The trike in the photo is a TOY! And a rather poor excuse for one as well. The lack of foot rests immediately disqualifies it as anything but a toy. To adapt it for actual use the frame will need to be extended rearward by at least three feet, and the back end will need larger wheels spaced farther apart. Then the seat can put more than half the rider weight on the front wheel. That will provide better traction for hill climbing. But still the motor power will probably not be adequate, so the two rear wheels from a powered hover-board would be a benefit.
But after the time and expense to do all of that it will make more sense to purchase a rather used actual mobility scooter and rebuild it.

 

What kind of terrain do you intend using on?
If general outdoors, including trails, you can get the Zoome for US$800.00
Hardly worth converting one that is not ideally equipped!
e.g. Zoome can be used in stand or sit mode.

 

Thank you for the reply. My main two usages would be shopping malls, and county fairs. I was surprised at how well the TomTop one does in the grass, as long as it is not up hill. The main issue with the ZooMe is that it weighs 97 Lbs. There is no way I can lift it in-out of my car. The TomTop one is around 37 Lbs.

 

But after the time and expense to do all of that it will make more sense to purchase a rather used actual mobility scooter and rebuild it.

It does have little foot rests just above the front wheel. Though, it would be nice if they were larger. The motivation I had to purchase it, is that all the other mobility scooters in this weight category cost $2,000+. And I have no idea if they could handle grass at all. I found a few other "toy" category ones. Here is one... https://superhandyus.com/products/superhandy-mobility-scooter-gut112-fba. But, it only has one powered wheel in the back. When I tested one, it could not handle grass at all, even very low grass, on flat ground.

 

I had a "duh" moment, and realized that adapting the throttle would be very easy. The Hall-effect device is designed to output a voltage, based on the throttle position. Simply using a voltage divider would allow me to cut the top speed by as much as I wanted.

 

That one in post #3 looks like the CG is way to close to the back axle. Dump over backward and it might ruin your whole day.
Stretch the frame of that one in post #1 about two feet and put six inch tires on the back spaced about 18 inches apart, move the seat back a few inches and a bit lower and it could work much better.

 

I am seeing a lightweight mobility scooter, but they are very expensive. However, I have purchased a lightweight folding 3-wheel E-bike. (see attached picture).

Rather than one that small I would consider modifying something like this, US$80. Amazon. 10lb weight .
Take a little engineering but possible.
The one in pic does not appear to be electrified, i.e. (E-Bike)?

 

I was considering one of these. There are 3-wheel and 4-wheel versions that can handle some outside usage because of their larger wheels.

There are also transporters, which are more like wheelchairs, but without the big wheels. I've even seen people take a transporter and mount a hoverboard as-is in place of the two non-swiveling wheels. The user would control it by tilting the foot pads, as it was intended to be used. Though in my case, I have one ankle that is 100% fused, so I cannot control things using my feet.

However, both of these lack shock absorbers. They would be viable for inside use, and there are ones on the market for low cost that can do that. I was seeking an affordable one viable for outside.