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Mekon
Starting Member

1 Posts

Posted - 26 Sep 2009 :  12:27:22  Show Profile  Visit Mekon's Homepage  Reply with Quote
I want to build a 7 foot tall humanoid weight bearing skeleton with adjustable poseable joints.

I’m new to this kind of project so I may not be using the best terminology yet.

The joints also need to be capable of bring ‘locked’ into position without collapsing or moving due to the structure’s own weight or external forces.

I’d be thinking of something along these lines:

Neck Ball Joint
Shoulders Ball Joint
Elbows Hinge Joint
Wrists Ball Joint
Hips Ball Joint
Knees Hinge Joint
Ankles Hinge Joint

The frame will be covered by a shell probably made of resin or fibreglass so the mechanism for adjusting and locking the joints must be fairly simple and accessible. The movement wouldn’t have to be smooth as a ratcheted type action would be adequate. A lockable universal joint might also do.

I don’t have welding skills or access to welding equipment so I’d be thinking about a wooden structure with the joints screwed or bolted on. Plastic tubing also a possibility I suppose.

I’ve looked at various areas and have so far determined the following:

Animatronics and robotics use motors, pneumatics and other electrics but that’s well beyond my requirements let alone my capabilities and budget.

Model making and sculpture armatures tend to be for fixed or limited movement structures.

Animation armatures provide good movement but tend to be small and they don’t usually need to support larger weights or be lockable

I’ve considered a home made ball joint with tension provided by bungee cord, but I don’t think this would be very easy or effective and wouldn’t fulfil the ability to be lockable.

I’m willing to spend some money, but not loads. Making each joint myself or adjusting cheap existing objects would be preferable here.

So, your ideas please!

Cheers.


Bob
Serious Geek!

United Kingdom
1217 Posts

Posted - 26 Sep 2009 :  18:10:36  Show Profile  Reply with Quote
quote:
Originally posted by Mekon

I want to build a 7 foot tall humanoid weight bearing skeleton with adjustable poseable joints.

I’m new to this kind of project so I may not be using the best terminology yet.

The joints also need to be capable of bring ‘locked’ into position without collapsing or moving due to the structure’s own weight or external forces.

I’d be thinking of something along these lines:

Neck Ball Joint
Shoulders Ball Joint
Elbows Hinge Joint
Wrists Ball Joint
Hips Ball Joint
Knees Hinge Joint
Ankles Hinge Joint

The frame will be covered by a shell probably made of resin or fibreglass so the mechanism for adjusting and locking the joints must be fairly simple and accessible. The movement wouldn’t have to be smooth as a ratcheted type action would be adequate. A lockable universal joint might also do.

I don’t have welding skills or access to welding equipment so I’d be thinking about a wooden structure with the joints screwed or bolted on. Plastic tubing also a possibility I suppose.

I’ve looked at various areas and have so far determined the following:

Animatronics and robotics use motors, pneumatics and other electrics but that’s well beyond my requirements let alone my capabilities and budget.

Model making and sculpture armatures tend to be for fixed or limited movement structures.

Animation armatures provide good movement but tend to be small and they don’t usually need to support larger weights or be lockable

I’ve considered a home made ball joint with tension provided by bungee cord, but I don’t think this would be very easy or effective and wouldn’t fulfil the ability to be lockable.

I’m willing to spend some money, but not loads. Making each joint myself or adjusting cheap existing objects would be preferable here.

So, your ideas please!

Cheers.






Hi Steve and Welcome to RobotBuilder

You will need some tough joints to cope with the sorts of loads you might expect in this situation. The hinge joints could be simply two pieces of wood bolted together, just slack the bolt of to pose the limb and then tighten it up to lock it in place. Trend (The Router people) make screwed inserts that would fit into one piece of wood and simple locking levers threaded to suit the inserts. That would save using a spanner each time you needed to move a joint.

The ball and sockets are more difficult. I would guess the ball would need to be between 1.5 and 2 inch diameter. If you thank about the hip joint consider a ring of steel about 2 1/2" outside diameter screwed with countersunk screws to the wooden pelvis. The inside diameter of the ring should be bored about 1 3/4" and the outer face chamfered about 1/4" to provide a seating for the ball. A second similar ring with three M6 clear holes bored through the ring to line up with three similarly spaced M6 threaded holes in the fixed ring would allow a 2" diameter ball to be locked in any position. I would suggest using a solid nylon ball to make the joint, but as a second thought you might find car 50 mm tow balls could be pressed into service here.

I hope this is helpful. I would post some sketches, but I seem to be having some difficulty uploading to the site at present.

Bob
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mike23
Average Member

United Kingdom
129 Posts

Posted - 27 Sep 2009 :  11:07:29  Show Profile  Reply with Quote
Maybe I'm missing the point completely about what you are trying to achieve, but it sounds like a tailors dummy to me. Why not find a shop that's closing down and make an offer on a manikin ? If you can't use it as is, then surely the joints should be salvagable.
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peter Lovell
Starting Member

2 Posts

Posted - 03 Mar 2010 :  16:40:49  Show Profile  Visit peter Lovell's Homepage  Reply with Quote
Right there are many new and amasing materials around
One of these is call Polymorph Its a plasic in pellet form that you put in a bowl pour boiling water on, after a few mins you take it out and mould to what ever shape you want. As for joints first make the ball wait for 20 mins for it to cool down the put a thin layer of greese/or what ever you have to hand over it, then mould the plastic and you will end up with a perfect joint which you can attach the rest of the skeleton to and the plasic when hard will more than strong enouth for the job and polymorph is not that expensive. You find at maplins ,ebay etc but just enter it and search you will find it
regards Peter

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