DIY

I am not sure if this will pique your interest but I find kinetic sand tables really fascinating. Sisyphus came up with it first and there have been a number of open source implementations in due course. One way is to implement it using a scara arm mechanism but they have the problem of load weight in the case of long arms.

I came across this design that rethinks the design using an elegant rack and pinion arm but still needs a belt that may go out of calibration over time. This looks to be improved further using [two, concentric rings] (https://frew.io/work/sisyphish) but this design is not available to explore/copy.

I have no idea about 3D designing, but I would love to create a table one day: something that will not need constant adjustment. If you get around to taking this up, I would love to see what design improvements you can come up with.

I've been pondering a gear cutter setup. This is usually done with a mill and a rotary table, but I was thinking of something simpler.

The blank would sit on a rotating table, that spins about the Z axis. The shaft for the cutter sits parallel to the Y axis, and moves along the X axis to contact the blank.

So I'm not sure this would qualify, it may be too simple. I'd been thinking about trying to build a solar forge (I got to learn forging from a really good blacksmith who worked with coal for a couple years, though I am very much an amateur). I've seen videos of people using old fresnel lenses from rear projection TVs to burn through skillsaw blades and if you can melt steel, you can certainly forge it. It might just be slow, or too focused on one spot, requiring some movement to distribute the heat, something I'd have to mess with. It'd also be a bit of a safety hazard overall, but at least it'd be outside on a paved driveway instead of of inside a shed like my old coal forge.

I was picturing something similar to this smelter but with a reused TV lens, and a fire pot where his crucible is. The mechanical parts would be for rotating it to keep the sun shining through the lens, and possibly for adjusting the focus. Stability and safety would be a big consideration, don't want the wind blowing it around too much.

Again, not sure if it's what you're looking for, but I'd like you to get some usable answers here. Best of luck with your project, thank you for reaching out to involve the community!

What kind of material and size limitations are there?

For work in Malawi I am thinking of introducing a bricket press to make brickets from biomass. One person must pull a lever and a piston is pressing biomass into a cylinder and compresses it. The end of the stroke should be stronger and less fast. And with returning of the lever the pressed bricket or pellet is pushed out and new biomass is inserted. It can be an interesting design from scratch and nice context? It would be challenging to make it convenient for the person while large pressing forces are reached (5000n)