Materials for a Lightweight, Sturdy Mechanical Chair

[Goggles]

Hello I am building a chair that will mechanically open itself remotely from a folded form. I decided to make this chair mobile I already have the electronics planned but i need help on the chairs easy mobility.

My first question what materials are sturdy enough to hold a person that is lighter than a Pine Wood chair. A list of materials lighter than Pine would be nice to suggest that is sturdy. I have checked Google already but yet to find the solution. Also the density of the overall material suggested if possible.

I want something within 10 lbs of carry weight. If not possible give me possible suggestions that could be light weight and sturdy or a combination of different materials.

Thank you , Also this is my first time on this forum site :=D

 

[etudiant]

Hi goggles and welcome to PF.

You believe you need a wood that is lighter than pine.
Pine wood density is about 0.5, bamboo about 0.3 and balsa about 0.2.
My guess is bamboo would be a better chair material than balsa, simply because balsa is so soft.
Good luck with your design. Please keep us posted.

 

[Goggles]

Thank you for your suggestion, and an introduction etudiant

I will experiment with bamboo, and hope to have my mechanical chair easy to move. :+D

 

[Bobbywhy]

Is using wood a mandantory requirement? Is it possible some other material might fall within your carry weight of 10 lbs. and weigh less than pine wood? Have you looked at aluminum?

 

[Straw_Cat]

Try using a laminated spruce/ balsa wood lay-up. (or spruce-cedar) Spruce is very strong for its weight, which is why it's used for guitar tops and home-built aircraft construction. (It has the highest strength to weight ratio of all woods, except perhaps pitch pine, which is nearly impossible to get now.)
You'd glue thin spruce veneer/ strips on to a core of balsa-spruce-balsa, and if you want, the balsa wood can be honey-combed to reduce weight.
Or you can go for the slightly heavier and much stronger cedar...
The spruce strips/ veneer can be quite thin, say 3/32", or glue up 2 1/16th inch strips on each side.
Use a vacuum bag to form the laminations, if you can arrange that. By going this route, you can also fabricate curved pieces.

A a rule of thumb, the more layers your laminations have, the stronger it gets. a piece made from 6 layers will be about 6 times as strong as a 1-piece layer. (rule of thumb number there...) because the glue makes it a lot harder for the layers to slip past each other when in compression.
I have a 5/8" square piece out in my shop made from 5 1/8" pine layers, and I can't bend it, let alone break it...

For an ordinary-sized chair, I'm fairly confident that one can bring the weight down below 6 lbs, not counting the mechanical elements. [ nb: I have built a lot of chairs ].

 

[Goggles]

Is using wood a mandantory requirement? Is it possible some other material might fall within your carry weight of 10 lbs. and weigh less than pine wood? Have you looked at aluminum?

I have thought about the aluminum idea, however I live in a dry hot area and would not like the metal to heat up when i am sitting in the sun , plus i worry about the material warping.Technically i would like something wood mandatory to insulate the heat I should have inserted this information in the beginning post to be specific. I apologize for such and thank you for your advice.

 

[Goggles]

Try using a laminated spruce/ balsa wood lay-up. (or spruce-cedar) Spruce is very strong for its weight, which is why it's used for guitar tops and home-built aircraft construction. (It has the highest strength to weight ratio of all woods, except perhaps pitch pine, which is nearly impossible to get now.)
You'd glue thin spruce veneer/ strips on to a core of balsa-spruce-balsa, and if you want, the balsa wood can be honey-combed to reduce weight.
Or you can go for the slightly heavier and much stronger cedar...
The spruce strips/ veneer can be quite thin, say 3/32", or glue up 2 1/16th inch strips on each side.
Use a vacuum bag to form the laminations, if you can arrange that. By going this route, you can also fabricate curved pieces.

A a rule of thumb, the more layers your laminations have, the stronger it gets. a piece made from 6 layers will be about 6 times as strong as a 1-piece layer. (rule of thumb number there...) because the glue makes it a lot harder for the layers to slip past each other when in compression.
I have a 5/8" square piece out in my shop made from 5 1/8" pine layers, and I can't bend it, let alone break it...

For an ordinary-sized chair, I'm fairly confident that one can bring the weight down below 6 lbs, not counting the mechanical elements. [ nb: I have built a lot of chairs ].

A very interesting idea indeed, I will experiment with the Spruce laminations for I can understand the strength in the supports and the amount of light weight in it all.
Thank you for the suggestive material.
I will experiment soon :+D