Building prosthetic feet for my robot

[kolleamm]

I came up with the idea today of using a prosthetic feet for my robot. The problem is that hardly anyone sells them online. What materials would I use to build one? The size is a regular shoe size.
Something that looks like this. I'd like to make a very good quality one.

Thanks in advance

 

[Nidum]

Carbon Fibre

 

[kolleamm]

Carbon Fibre

I'm confused on why they are made of carbon fiber. Isn't Carbon fiber supposed to be very sensitive to shocks?

 

[billy_joule]

Define "sensitive to shock".
Main reason CF is used for prosthetics is because it has a high specific modulus (stiffness to weight).

 

[kolleamm]

Someone told me that if you were to hit carbon fiber with a hammer it would break. Wouldn't each step be like a hammer hit?

 

[billy_joule]

No, not really. A hammer has a small surface area and high hardness, quite different to a foot.

Carbon fibre (well, CFRP to be precise) is widely used in prosthetics.

 

[256bits]

You could try some plastic material, such as
http://www.dupont.com/products-and-...tics/case-studies/prosthetic-foot-design.html
http://www.niagarafoot.com/niagarafoot/index.html

 

[gjonesy]

You could try layers of fiberglass cloth and impregnate that with epoxy resin. Of course you with have to design and build a mold. Then cut the finished product to size. My understanding is you could cut it with an ordinary band saw, (I would ware protective clothing and a face mask with air filtration.) It would be the same process as making it out of carbon fiber. I haven't worked with either material but it is available at most hardware stores. I contemplated building a wooden boat once and was told I should skin it with a fiberglass shell.

 

[kolleamm]

You could try layers of fiberglass cloth and impregnate that with epoxy resin. Of course you with have to design and build a mold. Then cut the finished product to size. My understanding is you could cut it with an ordinary band saw, (I would ware protective clothing and a face mask with air filtration.) It would be the same process as making it out of carbon fiber. I haven't worked with either material but it is available at most hardware stores. I contemplated building a wooden boat once and was told I should skin it with a fiberglass shell.

Interesting, do you know what kind of epoxy I would use? And would I need to create vacuum pressure on the piece during hardening? Also why use fiberglass cloth instead of carbon fiber cloth?

 

[gjonesy]

To answer your first question...no ive never worked with it but id assume they would sell it in the same section as the fiberglass cloth. As far as vacuum forming im sure the answer is no. You would just have to build a mold of a foot that you could break away, layer it with fiber cloth to desired thickness. You would probably have to use a puddy knife to smooth out the layers in the mold as you added them but then just break the mold after it dries. Smooth out or cut off the rough edges

 

[gjonesy]

Also why use fiberglass cloth instead of carbon fiber cloth?

Cost.....i know you can buy enough to cover a boat fairly reasonably. I have no idea where you could get carbon fiber or what to use as a hardener. You can get fiberglass anywhere.

 

[kolleamm]

Cost.....i know you can buy enough to cover a boat fairly reasonably. I have no idea where you could get carbon fiber or what to use as a hardener. You can get fiberglass anywhere.

Thank you! I will try to find some tutorials on YouTube.

 

[256bits]

Thank you! I will try to find some tutorials on YouTube.

An idea to make a prototype is to get a pair of old skis, cross country or downhill, and cut and assemble to your desire.
There already is a curved pointy bit at the front for the toe part.
It is laminated and flexible.

I think it might be possible to heat and press between a mold, though you would have to investigate that aspect.

It could be made to look more like this,

 

[gjonesy]

Thank you! I will try to find some tutorials on YouTube.

You are welcome, BTW still toying with the idea of building a boat and I am also interested in learning to work with fiberglass also...so if you find something interesting or a good educational tutorial on working with the stuff let me know. I do wood work as a hobby and the boat would be a cool project. As far as mold material id say plaster would be your best bet. Unless the make a releasing agent that you could coat your mold with or a material that epoxy resin wouldn't adhere to.

Good luck

 

[kolleamm]

An idea to make a prototype is to get a pair of old skis, cross country or downhill, and cut and assemble to your desire.
There already is a curved pointy bit at the front for the toe part.
It is laminated and flexible.

I think it might be possible to heat and press between a mold, though you would have to investigate that aspect.

It could be made to look more like this,

That's a brilliant idea! I will seriously consider it. Thank you!

 

[kolleamm]

You are welcome, BTW still toying with the idea of building a boat and I am also interested in learning to work with fiberglass also...so if you find something interesting or a good educational tutorial on working with the stuff let me know. I do wood work as a hobby and the boat would be a cool project. As far as mold material id say plaster would be your best bet. Unless the make a releasing agent that you could coat your mold with or a material that epoxy resin wouldn't adhere to.

Good luck

Sure thing! I will post some links on here to the best videos I can find. I remember watching one for carbon fiber. It really wasn't all that complicated. I'm curious though why the strength is so high in fiber glass and CF.