this post was submitted on 02 Oct 2024
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Mechanical engineering uni project (self.diy)
submitted 1 month ago by ComplexMoth to c/diy
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I'm a mechanical engineering student with a fairly open brief for a short project. Have to draw a 3D cad model of a mechanism and do some motion analysis. So i thought i'd ask the fine folk of slrpnk if they had any projects that need a bit of ironing out.

Probably best suited if you have an idea and want see how the parts might move in 3 dimensions. I'd be able to tell you stuff like how much force/torque is in a particular part, letting you know how strong bits need to be.

Has to be a mechanism of some sort that i draw from scratch - let me know what dimensions i need to accomodate. And i have to present it to the class.

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[–] DontNoodles@discuss.tchncs.de 4 points 1 month ago

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.

[–] poVoq 4 points 1 month ago (2 children)

What kind of material and size limitations are there?

[–] Zachariah@lemmy.world 4 points 1 month ago (1 children)

Well, there are regulations governing the materials they can be made of.

[–] Kolie@lemmy.world 4 points 1 month ago (1 children)

What materials?

[–] Zachariah@lemmy.world 4 points 1 month ago (1 children)

Well, cardboard's out.

[–] Kolie@lemmy.world 2 points 1 month ago (2 children)

And?

[–] Zachariah@lemmy.world 2 points 1 month ago (1 children)

No cardboard derivatives.

[–] Kolie@lemmy.world 2 points 1 month ago (1 children)

Like paper?

[–] Zachariah@lemmy.world 1 points 1 month ago (1 children)

No paper. No string. No sellotape.

[–] Kolie@lemmy.world 2 points 1 month ago (1 children)

Rubber?

[–] Zachariah@lemmy.world 1 points 1 month ago

No, rubber's out. Umm, they've got to have a steering wheel.

[–] ComplexMoth 4 points 1 month ago

Any material, the software i'll be using has some basic material properties built-in, but theres room for customisation.

Size limitations - any sort of dimensions. Complexity - i could probably do a few mechanisms that are less than maybe 5-10 parts. Or else one large, say less than 50.

[–] Cybermatrix1 3 points 1 month ago (1 children)

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)

[–] ComplexMoth 2 points 1 month ago (2 children)

I think I'll see what I can do with this, Does something like this look suitable? From my back-of-envelope calculations, this gives 17000N force (about 1750kg-force like they've said).

And then the challenge is to release the pellet, and refill from a hopper containing more biomass material. Can you tell me what biomass material you would be using?

[–] Cybermatrix1 2 points 1 month ago

A cool. That is a known wide spread design. This is a very high force, I'm impressed. But it will come at a cost of displacement correct? We aim to make brickets for cooking fuels and we have a lot of groundnut shells. These groundnut or peanut shells have a a lot lignin so it is possible with wetted mass (softening)and perhaps heating with fire (lignine becomes like a glue at 200degC). After that the brickets are sundried. The bricket shape could be like icehocky pucks or at least the shape to cook with.

I think the wooden design is not that interesting to generate, but with a pellet release and refilling in one lever go (or two steps). That would be an interesting puzzle, yes?

[–] Cybermatrix1 1 points 1 month ago

Only I would expect the design would not be 3 dimensions as you asked but mostly all forces in one plane 😁

[–] JacobCoffinWrites 2 points 1 month ago* (last edited 1 month ago) (1 children)

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!

[–] ComplexMoth 2 points 1 month ago (1 children)

Very cool stuff. I might have to look a bit more into this. There's a chap melting copper here with a 13 square foot lens - looks like a pretty small beam, not sure if usable for your purposes. But cool idea, have you got some lens dimensions in mind?

Also, definitely not guaranteeing any safety, but think i'll give it a shot.

[–] JacobCoffinWrites 2 points 1 month ago (1 children)

That's great! I don't have specific dimensions in mind (only because I haven't sourced a lens yet). I'm not sure about the beam width. I think no matter what, it'll be a narrower heat than you normally get with a coal fire or propane forge, so the blacksmith would probably have to adjust beam and shift the position of the piece to distribute the heat. But people make all kinds of things using little coffee can forges so if it allows for even that scale of project it'd be very useful.

It might not be a drop-in replacement for a traditional forge, but it could be a really cool way to preserve a lot of the practice without burning coal or gas. Let me know if I can help at all!

[–] ComplexMoth 1 points 1 month ago (1 children)

Sure, I'll work off that copper coin lad's dimensions and try and make it adjustable like the smelter. Could you point me towards an example of the little coffee can forge?

[–] JacobCoffinWrites 1 points 1 month ago (1 children)

Sure! Generally they're just an old coffee can with a thick layer of plaster of Paris and sand or firebox cement on the inside. They cement in some torch parts so they can attach a can from a burnzomatic torch and blow fire into the small, contained space from the side while having a hole on the front (usually with some loose firebrick for a door) to insert the work.

https://makezine.com/article/workshop/making-your-own-tin-can-forge/

https://m.youtube.com/watch?v=xv9nnEhgfuY

I don't know that the design itself is actually applicable here, just that they're a good demonstration that even with a small forge, you can do some pretty cool blacksmithing.

In practice I think a solar forge would have to be open from the top, and couldn't really benefit from the tight space confining the heat, so it'd probably be closer to using a portable ferrier's anvil like you might see reenactors use at the fair, or something like this:

Though it'd look more like that artist's smelting rig with the big lens and all.

Thanks! I'm really excited to see what you come up with

[–] JacobCoffinWrites 1 points 1 month ago

Just to add, the way I pictured this working was to set up a basic smithee, probably a three sided shed so I'd have a dark place to work (helps to gauge the temp of the metal by color). I'd get some of those gas welder's goggles with the flip up flip down lens (or use my electronic welder's hood) so I could safely look at the work in the firepot (solarpot?) then take it inside to quickly work on it. I'd stow the forge inside the smithee (or in an attached lean-to) when not using it. One feature that might be good would be a way to cover the lens and unclip it from the forge so it can be stored in a box or wrapped up, to reduce the risks of it starting a fire.

[–] gazter@aussie.zone 2 points 1 month ago

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.