4wd Wheelchair Motor Skid Steer

Maxg · December 18, 2020, 8:52pm

To start, I am very new to the robotics/electronic motors space. I am trying to learn as much as possible. I have read lots information and watched lots of videos, but I still have lots of questions. This is a lengthy post, so thanks to anyone who reads it!

I am looking to build a mini skid steer/electric loader to help with yardwork, specifically mulch moving. I would like to make this a rideable machine. I have a very steep yard, so whatever I build will need to be able to handle sloped and off-road terrain.

I plan on powering it with 4 electric wheelchair motors. I have a Quantum 1650 base—a large bariatric wheelchair. The base has two large 24v motors and I also have the wheelchair controller module and joystick.

I also have two motors (brakes removed) from a disassembled Jazzy 1113 wheelchairs. I have the controller, although it was not working to control the motors—I believe it is simply a ribbon connector issue in the joystick.

I have a few key decisions/questions which is what brings me here:

Question #1: Does anyone have any build plans or suggestions? I have thought about getting some welding work to extend the front of the Quantum 1650 frame, add lift arms, and add sheet metal to the frame to protect electronics. Additional disclaimer: I cannot weld, so any work I would have to pay for.

Another thought I had was modifying a zero-turn mower frame (ie: strip engine and mount wheelchair motors) to use the 4 motors/wheelchair wheels. My intention is to use mower wheels (or similar), but I am aware I will need to either use couplers or get a hub conversion fabricated as well. I would also consider a normal riding mower stripped down and modified to support 4 wheels. My concern with both of these approaches is if these platforms would be too heavy.

I have also thought about track drive, but I did not know how well that would work with 4 motors as most tracks (for purchase) I have seen use single drive sprockets. Additionally, to buy these tracks seems quite expensive—even if I go with the cheap ones from Alibaba.

Question #2: I have read that the best way to control the motors is to use a Sabretooth 2x60 controller. Does this seem like the best approach, or would anyone recommend any other controller? Additionally, since I am looking to make it a ride on machine, does anyone have any ideas for the best controls? I have seen the sabretooth can support analog controls but have no idea what type of analog controls are available to be used.

Question #3: I am thinking of powering the lift arms with either strong electric linear actuators, or with an electric hydraulic pump (like used on a dump trailer). Does anyone have an thoughts on which one is better?

Any other comments/feedbacks/criticisms are welcome. Thanks for any help!

o_lampe · December 19, 2020, 9:35am

Hi @Maxg
are you sure these 4 motors are identical? Otherwise you create avoidable problems.
How would you place them?
Quantum motors on one side, the Jazzys on the other? Probably the least problematic option.
As long as their motor specs are similar.

Maxg · December 19, 2020, 10:45pm

Thanks @o_lampe. The motors are not identical, but I believe they are similar as they are both 24v DC motors. For convenience, I had been planning to add one Jazzy to each side if I kept the existing frame, but I will take your advice.

msotis · January 14, 2021, 8:36pm

there is a real market for something similar . . Basically need an RC midi size electric towing vehicle for many gardners/ smallholders . allotments etc To tow a lawn mower / wheel barrow whatever else . Not ride on.
Amusing little project on this site Robots . Guy has acquired a crashed petrol snow mobile Caterpillar mechanics intact . Taken from there for two motor skid turn lawnmower Some useful ideas for you motor couplings etc. There is another 4 wheel project on p int Fascinating.
A rare find Crashed snow mobile with caterpillar mechanics intact !!.

tried to make one myself Cycle tyre to caterpillar track Reckon I would go the wheel chair route For its frame Just put larger knobbly tyres on it Two motors/ skid turn . probably ok for a fairly level rugged surface towing vehicle

BigfootAKADaryl · November 14, 2021, 7:11pm

I have 4 wheel chair motors on my skid steer 4x4 RC mower I am building for mowing steep slopes. They are different motors. I have them wired to a sabertooth 2x32 without any problems although have not driven it a lot. Did drive it up a 45 degree ramp with 100 pounds in it, its only limitation seems to be traction. All together it was about 200 pounds for my test and it did not strain at all. I did put the wheels on the motors and put it off the ground and made sure the wheels rotated at the same speed. I disconnected the brakes on the front motors because they were not releasing and the rear brakes are more then enough to hold it on a 45 degree angle. The power these motors have is pretty incredible. Here is what I have so far, working on the electronics now and the mower electric start. I used parts from the two wheel chair bases, some bed frames I had around and some steel plate that was rusting in the shed. I had seen others use 4 motors in the 2x32 without issues so that is what I am doing. If your motors did spin at a slightly different speed, you could put the same motors on one side and the other on the other side and adjust the speed in the sabertooth programing I think.

Maxg · May 6, 2022, 6:41pm

Sorry for the very late reply - haven’t been on here in quite a while. Very impressed with your build. And thank you for the information – it is very helpful.
I decided to scrap the idea of the skid steer. Building a skid loader was going to be too much for my first project, so I am building an RC mower too. Saw so many on Youtube that I figured it might be an easier route. And coincidentally mine also will have the John Deere look - I acquired a cheap John Deere RX73 for the project.
At one point I thought I came up with alright plans, so I got a quote from a welder. Quote was too pricey and my plans weren’t well thought out enough, so I decided instead to by myself a cheap harbor freight welder and teach myself enough about welding to do this project.

I built a steel tube frame to mount all motors. Ended up picking up a free Jazzy Select base and getting two motors from it that I am using in place of the two Quantum 1650 motors. The select motors are closer in RPM and I think should work fine from some testing I did with a previous design.

I got the mower deck from an old black and decker that someone was giving away because they couldn’t fix. I wired the motor directly to a cheap PWM and it works great. I also added a linear actuator to raise and lower the deck. Currently lifts from one side (which I reinforced with some flat bar bolted through). Design wise I realize this might not be the best way of lifting the deck, but it works for now. I realize I can continue to upgrade/tweak the design as I go.

I will use the frame from the RX73 which I have stripped down to basically nothing. It’s fairly light and will sit on top of my steel tube frame to give me a platform to mount the batteries and electronics.

I did get the Sabretooth 2x60. At one point I wanted it to be a riding mower and had a joystick communicating through and Arduino/simplified serial signals. Now, I will use a Flysky FS-I6s. Hoping to finish final assembly, wiring, paint this weekend.

I do still have a few outstanding questions regarding the electronics. The mower will use a separate 24v battery than the drive motors. For the drive motors I have 2 12v 35ah SLA batteries and am wondering if this will be enough. In terms of fuses/breakers, I also am curious if any are necessary. Found a post from Dimension Engineering (linked below) seeming to imply they aren’t, but not sure if my build is big enough that they will be. Also found a post from SuperDroid Robots (linked below) showing a breaker between the battery, which conflicts with the Dimension engineering article. Any advice on this part is appreciated.

https://help.dimensionengineering.com/knowledgebase.php?article=2

Maxg · May 6, 2022, 6:42pm

Superdave · May 24, 2022, 7:27am

Hey Maxg & Fellas,
I am in process of building one myself,… definatly a challenge sorting through all the info (and lack of) out there.
You didn’t specify your motor size…Or the brake amperage.
The batteries should have enough power on flat ground…But you are on the low end if you are using the brakes and powering the blade too.
Any reason you wanted 4wd vs coupling the wheels with a chain and using two motors?
I have seen others do 4 motors…Only problem i saw , was if they weren’t the same motor, seems they’d fight each other if you didn’t have feedback of some sort.

You DEFINITELY want fuses and disconnects!!! To NOT have them is a HUGE risk!!!
And I recommend an E-STOP of some sort . In mine the e-stop kills the 24V main contactor.
There is Arduino failsafe RC code which works with the Flysky i6 for what your doing…I have tested it.
Seems like “Elliotmade” quoted and linked it in his build. If you need it…I can look around for it.
What do you lack? Do you have code for your Arduino completed?
I’m not complete with mine…As I mechanically “over engineered” mine and parts have been a PIA to get made…
(It will be a much simpler design for the next one.)
If you need something specific and I’ve already dealt with it…Be glad to help if I can.
Good Luck,

Eric_Wu · September 13, 2022, 10:11am

@Maxg Hello Maxg, I am wondering have you finished your project? Maybe we could offer some help, we have hub motors and adapted driver for such a platform. And we have made a one like yours successfully. If you want to get more, feel free to contact me.

Maxg · September 13, 2022, 9:03pm

Hi all,

Once again been a while since I have been back on here, but I greatly appreciate all the feedback!

I did finish building it with my 4wd setup. It drove fine forward/backward, but I had issues with turning. I have read lots since then about issues with 4wd and turning.

I think there were a few contributing factors:

Think I encountered issues described here - 4WD Turning Difficulties - Technical Discussion - Chief Delphi
@Superdave may have been right that my motors may have been fighting each other.
The way I fabricated the front wheels may have been an issue. I welded half of the original wheelchair wheel hub onto the back of the 16" mower wheel. I put bolts through the hub to act as studs. I then connected the motor hub to these studs. My placement was slightly off on one wheel, so when I drove it slowly I realized it didn’t roll completely straight which caused it to struggle when trying to turn. The back wheels I used conversion flanges and they roll straight and it’s a seemingly much better method. (Pics included)

I decided to cut the front wheel assembly off and I went ahead and welded some punched tube and threw casters on it. I’m encountering all kinds of issues now with the electronics. I rewired some, but I think the welding is off so the casters are sitting poorly and causing the motors to draw more amperage than they should. I assume this is the issue because the Sabretooth keeps restarting. This doesn’t happen on level surface or jacks though. Just happens on a slope.

Overall some other issues were the entire thing was too big for such a small mower cut deck. I did this because I wanted to build something big and cool, but it was definitely overkill and led to more challenges along the way. Still been an awesome learning experience even though this thing has struggled to ever run.

I’ll keep chopping and rebuilding until I have something that works.

Also picked up a Ryobi 40v mower that a friend found in a dumpster. Assume it had a bad switch in the bail handle, but I got it working. Might use parts from the 4wd one to try again, but this time with more planning up front and more importantly this time I have more knowledge than before.

Again thanks for all the responses and I’m happy to answer any questions.