Last year, I purchased a 3000W Cyclone mid-drive e-bike motor and mounted it on a unicycle to make a powerful machine that can easily move 500 lbs around the yard for about $450. I thought it was pretty heavy and complicated, and thought if I could make a lightweight unicycle that was about 1/2 the price, 8 lbs lighter, and would use a geared hub motor as a lower powered e-bike. After a few months and some tricks, I finally got it built. Feel the power of a wheelbarrow that even your grandma would love.
I don’t know why no one in the US started making these things. As far as I know, Makita is the only company that makes a reasonably priced electric unicycle for the US market, and it only runs on 18 volts peak. The cart costs a whopping $859 without any battery pack (here at zorro). It’s rated at 287 lbs (total load), weighs 88 lbs, has a max speed of 2.5 mph, and runs on 2 batteries rated at 16 volts (but it doesn’t run in series, only one at a time)
My unicycle goes as fast as it can go, has a 56 volt peak (52 volt nominal) Ego battery powering it, and weighs about 30 lbs. I feel pretty safe running it with a load of 200lbs, although loads above that may end up damaging the hollow steel shaft. A geared hub unicycle has a reduction ratio of 5:1, but the 3000W Cyclone has a much larger reduction ratio because the gear system inside the motor has a reduction ratio of 5:1, and then the large gear and chain have a reduction ratio of about 8:1.
My price breakdown for this version is as follows
- Unicycle $95 here from Home Depot
- Aliexpress offers a $142 e-bike motor (at here) shipped from China to my door
- I have a cheap 17 amp controller.Shipped from China for about $20
- I also have a 1/2 twist throttle in my bunch of e-bike parts, usually around $10
- I bought an Ego 56v charging dock for $19 on eBay
- I have a couple of cheap little torque arms that I welded to the cart
- This doesn’t include the batteries, I have Ego 56v batteries in various sizes but I usually use the 2Ah ones and this setup seems to last close to an hour of light use
So if I had to buy all the parts, it would cost me a total of $286. It took me about 4 hours to assemble this machine and get it working. You will need to use a welder to mount the torque arm to the shaft mount.
If I did this build again, I’d probably get a controller and throttle that matched the motor, because putting all of that together was the biggest pain. What you’re looking for is any e-bike motor with gears and a very low top speed (<15 mph). Look for a low turns count (preferably 6T or lower), this will give you the most torque. Smaller wheels are better in this application because they have a shorter distance per rotation. Don't use DD motors, they don't have enough torque to move very heavy loads without overheating quickly.
To connect the controller to the battery charging unit, you just need to disassemble the charger and solder some wires directly to the + and – connectors inside the charger. Then screw the charger base onto the cart, making sure the screw holes to attach it back are exposed, and screw the charger back in place. You can still use a battery charger as a charger if you’re careful (I’ve never done that), but if you’re worried about a problem, just cut the wires and remove all the boards inside the charger. For DIY beginners, this is probably the safest course of action.
The unicycle runs better with lower tire pressure because you won’t be bogged down by every little rock and bump. I removed the flat free front end and used it on another cart, which saved me about $20 on this version. Don’t skimp on a donation wheelbarrow, buy something with steel arms that will last you for many years.
Both torque arms were torn off the first time I used the wheelbarrow a lot, so I re-soldered them better the second time around. It’s important to use a lot of rods and really get the metal hot so that it’s all in one piece.
You also don’t have to use an Ego battery pack for this build, any lithium battery pack will work with this build as long as the battery’s voltage range matches your controller. Most controllers provide a wide range of support. For example, the controller I used in this build can handle anything from 30v to 60v.
Alibaba and AliExpress are great ways to buy cheap Chinese junk and ship it to the US without paying huge tariffs. I bought the 48v 350W version of the hub motor, even though I’m running 17Amps x 56v nominal, which is 952 watts peak. As long as you don’t do this continuously, you can get away with it. The phase wires of this hub motor are very fragile, so I wouldn’t run it with any controller that puts out more than 17 amps.
In the end, I ended up getting what I wanted for the price I wanted to pay (< $300). Had a fun time building this wheelbarrow with the spare parts I had lying around, and it's perfect for moving lots of wood chip mulch, which seems to be my main task on my wheelbarrow. tree farm. I still use a 3000W Cyclone monster dolly when moving dirt and rocks, but the gear hub dolly is almost 10 lbs lighter and has no chain to handle it. Building things is fun, and sometimes you just have to build these crazy ideas in your head. Five years from now, electric unicycles and garden carts will be everywhere, but now if you want one, you have to build it yourself.