4-wheel skid steer fruit bin mover

[jclason23]

Hi All,

I'm new to the EV world and this will be my first build. My intent is to build an electric 4-wheel skid steer vehicle to transport bins of fruit around an orchard (see attached CAD images). In terms of functionality, the vehicle is sort of a cross between an e-bike, fork lift, and a stand-up skid steer. The steel frame and fork lift designs are mostly complete, but I need some help specifying the optimal hub motors, controllers, braking components, batteries, and throttles. Here are the specs for the vehicle:

1. Total load is 2000 lbs (750 lb vehicle, 1000 lb fruit bin, 250 lb vehicle operator)
2. Operator stands on the back deck of the vehicle, with controls attached to bicycle handlebars (or similar)
3. One hub motor in each of the four wheels
4. Motors need to be high torque with relatively low speeds (max speed would be 7-10 mph, and most of the time the operating speed would be 1-3 mph).
5. Terrain is mild with mostly grass, hard pack dirt, and some concrete/asphalt with a max slope grade of 20%.
6. Vehicle must be able to spin 360 degrees on a single axis when fully loaded, hence the skid steer configuration
7. Motors and throttles must have foward and reverse functionality
8. Right side motors must be controlled separately from left side motors
9. Approximately 16" tire size
10. Ideally I'd like just one controller to handle both right wheels, and a second controller to handle both left wheels. Or if there was a controller that could handle all four wheels and still achieve the desired functionality, that would be even better.
11. Ideally the throttles would be dual-function twist throttles where you twist forward to go forward, and twist backward to go in reverse. If such throttles aren't available, I'm OK with thumb throttles with a second button or switch on each throttle for reverse.
12. Braking system must include a parking brake to prevent movement when parked on a slope.
13. I'm thinking the batteries would either be 36V or 48V.....something that is readily available and commonly used in similar-sized vehicles like golf carts. I need enough power storage to accommodate a full day of use without having to recharge, so anywhere from 2 to 6 batteries will probably be necessary.
14. Clearance between bottom of frame and ground (when forks are fully raised) would be 5-6 inches.

Thanks in advance for any help, guidance, and recommendations!

 

[marty]

There are other ones. Here is one.

| Toro

www.toro.com

Most things are easier and cheaper to buy instead of building.

 

[Hillhater]

I need some help specifying the optimal hub motors, controllers, braking components, batteries, and throttles

very unlikely you will find hub motors , controllers, etc , capable of providing the high torque, low rpm, drive on a 2000lb vehicle .
If possible at all, They would be very specialised custom components with high costs involved.

 

[jclason23]

There are other ones. Here is one.

| Toro

www.toro.com

Most things are easier and cheaper to buy instead of building.

Yes, I agree that it's usually easier and cheaper to buy instead of build, assuming you can buy something that meets your needs. Unfortunately the dingo and others like it meet some of my specs but not all of them. For example, the rated operating capacity of the dingo you referenced is only 515 lbs and the tip capacity is 1251 lbs which is dangerously close to the 1000 lb bins of fruit that need to be moved around. But thank you for your response.

 

[jclason23]

very unlikely you will find hub motors , controllers, etc , capable of providing the high torque, low rpm, drive on a 2000lb vehicle .
If possible at all, They would be very specialised custom components with high costs involved.

What do you think about these?

100nm electric golf cart motor with 16X6.50-8 Turf Rider Lawn Garden tire - UU Motor
80a dual drive controller for electric scooters - UU Motor

I'm not sure about the quality of these components or the reputation of the vendor, but the specs seem to check the boxes for what I need.

 

[amberwolf]

QSmotors also makes single-sided-mount motors, even ones big enough for cars. All the QSmotors I've seen so far have been much better build quality than the typical stuff. Actual designs are about the same.

 

[bengxe]

You need more gear reduction than you can fit inside a hub motor. If I were somehow convinced to try something like this I'd probably have 1 large motor on each side with chains to the front and rear and the highest ratios I can fit. Letting it go any faster than 2-3 mph sounds dangerous and impractical.
That toro weighs 2342lbs and you think you're going to build something 1/3 of that weight, has more load capacity, and goes 3x faster.

 

[marty]

What kind of fruit? This question makes no difference but I like to eat fruit.
How you moving the fruit now?
Why do you want the operator to stand? Most skid steers and fork lifts the operator sits.

I have very little knowledge of construction equipment. If I wanted to move 1000 lb fruit bins I would go talk to local construction equipment sales people for ideas.

Neighbor has a pear tree that's getting bigger. Branch is now on my side of the fence. Researched when to harvest pears. Picked one. Put it on kitchen counter to get ripe. Ate it. Pear was way toooo ripe. Took a few bites and threw it in the trash.

Silly neighbor works to make money. She buys food with money. She does not eat the pears. Now she is talking about having the pear tree cut down

 

[Chalo]

With the proportions shown in the drawing, skid steering will surely be inefficient, not very effective, and damaging to the ground surface especially when loaded. I reckon it would be tons better to have two powered wheels straddling the bin plus a single castered wheel right behind the driver's platform. Using worm gear reduction motors with fixed chain drive to the wheels would allow the thing to remain securely parked when not being propelled.

I don't think the vehicle weight/payload weight ratio is impracticable, but I think it's a bad compromise to give the thing a top speed several times its working speed. You'll give up too much oomph in exchange for road speed that may not be important to its role.

Are you going to reverse engineer a pallet jack for the forks, or fab something entirely from scratch?

 

[nicobie]

Can't you just stick some forks on the front of a small tractor that has a bucket? A used tractor will cost less that fabing what you have drawn. Is this going it the fields or on concrete?

 

[Hillhater]

Can't you just stick some forks on the front of a small tractor

Good suggestion, …but maybe forks on the rear lift linkage would be better, even cheaper, and give better manouverability which is what a skid steer has.
if the desire is to avoid ICE engines, then an simple electric conversion of a compact tractor is much easier than a scratch build EV.

 

[keithwins]

Just found this thread. I'm heading in to a somewhat similar project. How high do you need to lift the fruit bins? Are they always the same size, or are you trying to develop a more general-purpose forked solution? Can you include a pic of a bin? What kind of fruit?
What is the terrain like? How far do you need to move them?
I've got a mini-skidsteer that I may convert, but the V1 is going to be a cargo trike conversion, essentially this:

The end result will probably be stand-on vs. bike rear end, much more like a MSS.
I would also like to do it with hub motors, I don't want chains or other mechanical systems if I can avoid them.
I have some ideas about how to do this that I'm hoping to develop, I'm just a little too busy with other things right now.

 

[keithwins]

I see 1000W 48V motors that can be set to low-speed ranges, like say 11mph top speed. That's pretty much the right range. Even if it were very inefficient in that range, say 100W/wheel... that would likely be enough for my basic idea (which is quite similar to yours: I didn't quite assume 1000 lbs capacity, I was thinking around 600 lbs at least).
When someone says "the torque drops off", it seems to me that in most cases, discounting a stall condition, most motors will produce more than 10% of their torque pretty far down the curve. But I don't have a lot of hands-on in this world, I could be missing something.
I'm curious about how easy it will be to include a reverse in all this... it seems like it probably comes down to the controller, maybe?

 

[amberwolf]

I recommend that we move your project to it's own thread, with all the various posts about it from any thread they're in now moved to just that thread. That way it won't confuse others helping with this project, or yours, and keep all the info in one place for you and any other readers or helpers.

I see 1000W 48V motors that can be set to low-speed ranges, like say 11mph top speed.

You can't "set" a motor to a speed (range).

They are built with a specific kV (RPM/volt), so that for a given voltage they spin a certain speed.

To change that you have to cut the original windings off and rewind all the coils to whatever turn count is needed for the kV you require.

 

[amberwolf]

When someone says "the torque drops off", it seems to me that in most cases, discounting a stall condition, most motors will produce more than 10% of their torque pretty far down the curve. But I don't have a lot of hands-on in this world, I could be missing something.

I recommend experimenting with the simulator at ebikes.ca to see how various conditions affect a particular setup, or several setups in general; you'll get a better idea of how the interactions work.

 

[amberwolf]

I'm curious about how easy it will be to include a reverse in all this... it seems like it probably comes down to the controller, maybe?

Depends on what you want from the reverse, and the physical control mechanism you prefer.

If you want a system that goes backwards exactly the same way it goes forwards, with exactly the same controllability, use some form of non-freewheeling / clutchless motor/drivetrain, and an FOC controller (the Phaserunner/etc series from ebikes.ca as one example), since those just "change the sign" of the current waveform they apply to the motor for reversing it's rotation--all control methods by the user are the same, just changing to reverse mode with a switch or button.

Given the right throttle mechanism, or the right intermediate electronics, you could even have one that goes forwards for half the throttle, and reverse for hte ohter half, with a center-off position (some systems use this form for braking controls); the disadvantage is decreased resolution for both (less movement of control input for the same output).

If you want a system that has a single backwards speed, you could use a button that both changes the mode to reverse and provides a specific amount of control input, or a controller that is built to do this or programmable to do this via the single button.

Etc.

 

[Reid_in_QC]

Hi JClason23. I just found your thread while looking for an answer to a build puzzle I'm facing on another small agricultural machine. I spent a fair bit of time looking for wheel motor solutions similar to your needs. Something small but robust with high torque and load handling. I just thought I'd drop a reply here to say:
1) sorry you got so many not-very-helpful suggestions about your design. I'm a farmer and EV fan/builder and your machine, for orchard work, makes sense and seems worth pursuing.
2) are you still working on this and looking for solutions/ideas? I don't want to waste your time if you've solved this and completed the build.