Well, this thing is not very heavy, but it is about minimizing friction by using ball bearings. And it is Arduino realted, because I'm participating in a 3D print contest, where Arduino is to be used.
What I need is a plate, which freely moves in 2D (XY-plane), when pushed from any direction (in XY), while the plate itself remains in its orientation. The plate doesn't rotate around Z-axis. The plate lies on a fixed base.
The red plate is the fixed base. It has four grooves with four steel beads. A middle plate (transparent blue in the picture) has identical grooves on the bottom side and lies on top of the beads. The middle plate has identical grooves on the top side, but in perpendicular direction. And four beads lying in the grooves. The top plate (r̵e̵d̵ yellow) has matching grooves on the bottom side and lies on top of the four balls. With this I hope to get the top plate to freely slide in any direction in the XY-plane. I will add a soft spring for the r̵e̵d̵ yellow plate to return to its middle position.
Is there a better way to get the top plate to roll freely in 2D?
If this works, I will add sensors to measure in which direction the r̵e̵d̵ yellow plate is pushed. But that will be another thread.
But you are again constraining the movement direction, so why even ask about moving in any direction? If you want to move in any direction, use peanut butter or something that will allow what you want.
To keep it simple. Then again, if any other arrangement would work better, but would make the top plate also spin freely around the Z-axis, I guess it would be ok. The main idea is the XY-movement.
The blue plate moves back and forth in the direction of the grooves. The bearing balls in the grooves roll in the same direction. The balls prevent the blue plate from rotating. Sure, if you twist with little force, the grooves jump off the balls. Likewise the yellow plate moves according to the blue plate. And is prevented by the balls from rotating.
Probably not in this case, but CVT (continuously variable transmission) uses viscous oil at high pressure (similar to non-Newtonian fluid changing states) as the friction to transmit power from input to output. See 1:45 of this video.
No torque is involved here! I just want a plate to lie over a structure. And that plate to freely move horizontally about 30 mm in any direction. It's not about transmitting any rotation or any other movement, just a plate moving freely.
What I'm aiming at is a circular shaped robot car. When my dog pushes it from any direction, the car starts to move in the direction of the push. Without first rotating. Four mecanum wheels will take care of the movement, hidden completely under the circular shape. In my OP image, the wheels are attached to the red plate. The blue plate is hidden inside the structure and the yellow plate is the top plate, which can seemingly roll in any direction in relation to the red base plate.
You seem to know exactly what you want and dismiss every guess at your vague, imagined, goal. Try; (1) you build your project for your dog, and return here for Arduino coding issues and showcase the final project... or (2) stop being vague and work toward a solution in under 200 guesses.
I'm probably very bad at describing this. With "linear bearing in 2D", I mean that instead of an ordinary linear bearing, the ones we have in say 3D printers which travel in one direction or one dimension only, I want a bearing ball supported structure, where a plate can move in 2D, that is in all directions in an XY plane (horizontal plane). The movement can be as small as 30 by 30 mm. Or even smaller. My idea is that I stack two layers on top of each other, each moving in only 1D, but perpendicular to each other. This should let the top most plate move in any direction in the horizontal plane with lowest possible friction.
I am constraining one level to move only in 1D. And the next level to only in 1D, but perpendicular. A 3D printer moves the plate in 1D and the extruder in 1D, resulting in full 2D control at each layer.
Here is a free-hand drawing of something you can print using resilient plastic that will allow movement when pressed from any angle and will return because of the springiness of the plastic curves. The inner hub is fastened to one plate. The outside ring is fastened to the upper plate. Ball bearings or marbles are placed one per opening and restrained by using something like heavy grease just around the bottom of each ball. That is just so you can assembly the device.
More movement can be achieved by making the serpentine plastic coils having greater diameter or more curves.
That's a neat design, Paul. I might try that instead. The springs don't need to be 3D printed. I guess any springs could do. Like springs from ballpoint pens.
