I’ve been thinking along similar lines, using wheels to move a farmbot around, replacing the y axis. One idea I had was to use ebike wheels as the drive/wheels. They cost about $130 each, but come with control system, wheels, etc. Could stick on a mountain bike tire for extra traction. Only issue is I don’t know how much precision you can get with them, especially at low speeds. Another issue is levelness. If one wheel is up on a bump, the platform is not going to be level, which will affect all of the other axes. The arm might be at the right x/y/z coordinates at the top of the frame, but it could fall off target as it lowers if the whole frame is tilted.
I’m super excited to see how your build goes @Josh
Ground clearance is an issue. I tested the wheels and mounts. The wheels need to be twice the size.
I plan to design a two piece wheel. I am not set on a hight yet. I was thinking 1 meter. Or 3 ft to start with. The height can very easily as the legs are pipe.
For a prototype PVC will be all right. http://www.jmeagle.com/pdfs/Technical%20Bulletins/TB10SunlightEffectsonPVC.pdf
Do remember PVC is not 100 percent UV sound “Impact Strength” will reduce over time if it not protected with paint, UV additive or some other UV blocking coating. Yes painting PVC pipe down pipes is totally recommended.
Impact Strength is kinda critical when the machine runs a wheel into a hole or the like.
Josh UV is a huge problem. Please also remember electrical wires most of them are not UV stable. UV will be one of the big bugs that will catch you down the track but are simple to design for and deal with now. Design choosing UV safe were possible and deal is coat/protect the parts that are not UV stable off the get go.
I should have said 10cm wheel min presumes you did not have motor directly connected to wheel the way did. But Motor inside wheel or some form of chain drive keeping the connection at wheel shaft as small as possible.
5cm of ground clearance or else fails I guess you found.
Yes UV is a big concern when using polymers. I plan to protect the frame. My brother inlaw works in wiring harness manufacturing. He will be a great resource for the wiring harnesses.
I thought about building drop box for the motors. A way of transferring the power down to the axle. This has two advantages.
Better ground clearance.
More gear reduction.
Disadvantages.
Increased backlash travel.
Increase in material.
The motors are still to fast. They could be slowed down by .5 I am still looking for suppyers for the motors. I hacked these from bad window regulators. The motors are inexpensive when purchased separately from the regulators.
I just am not able to find anything local. Everything is from oversea. I like the worm drive. I may need to look at other options for drive motors.
I did not think of having a brake on the wheels. This maybe an option if we were to use gear motors. It just adds more mechanisms. Steppers would work they would use energy when braking though. So my opinion is to use a mechanical brake. Aka worm drive or a spring brake of some kind.
For now the drive works. I just need a bigger wheel.
Advantages of bigger wheels.
1 better ground clearance.
2 less soil compaction.
Disadvantages
if printed, needs to be 2 parts
more plastic.
travel speed increased less torque
Its almost a draw. Anyone else have any pros or cons.