Garden Cart

[Chip Hacket]

Happy Easter everyone! This is a project I've been working on forever it seems. My intent was to make this for my wife to use while gardening. I don't think she believes me.

The basic concept is for the wagon to follow you around as you pull the rope like any normal kids wagon. But this wagon has motors to do the heavy work for you. It has two motors for differential steering. It has two encoders, one for speed and the other for direction.

I quickly learned the wheels did not have enough traction out in the yard. What I wanted were some tiller tires which look like tractor tires. Unfortunately those cost more than I could justify and have larger diameter than I planned. So I pondered for quite a while until I saw a dual wheel baby buggy joke on TV. Ah Ha.

My initial plan was to use two drill motor batteries. They drain way to fast so my next purchase is going to be a deep cycle marine battery. My Dewalt batteries are 18 Volt, I haven't found an 18 Volt marine battery. I may have to go with a 12 Volt. Hopefully I can get enough speed at my current ratios.


It dumps as well.



This shows the speed and direction mechanism. I used a Briggs and Stratton recoil start spring for the speed. The idea is that it tries to keep a constant distance from the wife. So when the rope gets longer it speeds up. When it gets shorter it slows down. When it is the perfect length it stays at that constant speed.


Another view


I've been teaching myself machining while working on this project. I would do a better job I think now if I were to start over. But It needs to go to work this spring, so all the warts will stay for now.

I made a video some time ago but it is a .MOV , and the system wants another format. I don't know what format the system needs.

 

[MozamPete]

Like the idea, will be waiting to see the video of it in action

 

[kvt]

Nice, Something to consider for the wheels would b make a set of chains that you could put on the wheels, that helps with the grip.

 

[Chip Hacket]

Nice, Something to consider for the wheels would b make a set of chains that you could put on the wheels, that helps with the grip.

Yep I actually bought some chain at lowes for that reason. I had a heck of a time getting them on. I got frustrated and gave up. Probably was just a bad day.

 

[kvt]

two lengths of chain just long enough to sit on and go around the rim on each side, Some way to connect the ends as you need. Then put a piece just long enough to go over the tire to the rim on each side. Say 6 or 8 of these. Then evenly spaced out along the two outer chains. To help hold them on, use the small bungee cords to help take up the slack on the sides. Or at least that is how I have seen them. Since they are not going to be going fast you could even use a heavy wire to connect the cross lengths to the main ones.

 

[dlane]

Or go with a little smaller chains , put them on tires without air psi then air them up

 

[Chip Hacket]

The dual tires seem to have afforded me much better traction


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[kd4gij]

Now add RC to it and you can sit in the shade with a brew and follow her around with it.

 

[mzayd3]

I love it! Would you mind elaborating a little more on the electronics and control scheme?


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[Chip Hacket]

Maybe this wasn't the forum to post this but it's the only one I frequent. But since you asked. I used an atmel based micro controller which uses arduino. The two DC motors are driven by a regenerative motor driver. It gets speed signals from the micro controller. The controller tracks pulses from the 2 speed and direction encoders. Essentially it's programmed to stay straight and at a predefined distance. If you look carefully you can identify the two small encoders. One on top of the recoil spring assembly and the other under it. If I knew what format I would post a video


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