Building an articulated tail.

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Building an articulated tail.

Postby Dragonwim » January 30th, 2013, 12:31 pm

I'm building a tail for a costume and I want it to be able to swing back and forth. I know I could use servos and servo drivers to build it but that would take up too much space. What I plan to use art nitonol expansion springs, but I'm a bit out of practice building circuits. What I need is a circuit that will tell one spring to contract then after a few seconds the other contracts. I think this would be some sort of timer circuit but its been so long that I can't think of any circuit diagrams that would do the job. Does anyone have any recommendations?
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Re: Building an articulated tail.

Postby UAirLtd » January 30th, 2013, 5:36 pm

RC timer circuits, 555 timer circuits, and possibly look up slow oscillator circuits. Alternatively use microcontrollers, pick your poison.

But are you sure you want to be using Nitinol springs? Several amps, and high temperatures attached to your ass sounds like a REALLY bad idea to me. Perhaps you might be interested in the options chosen by other animatronic tail builders?

http://emilyryuu.blogspot.co.uk/2012/02 ... pdate.html
http://blog.makezine.com/2011/11/15/pri ... onic-tail/
http://www.wolftronix.com/tail/spine.htm
http://forums.furaffinity.net/threads/1 ... ronic-Tail
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Re: Building an articulated tail.

Postby Dragonwim » January 30th, 2013, 7:01 pm

Thank you for the links, and thank you for the suggestions. The nitinol springs will work on a 9v battery, the way they will be mounted is actually similar to the tail on the furafinity link. I know I could use servos but I don't want to, 1) because of price for the servos and controllers, 2) size, and 3) I don't know how to program. Another option would use a gear drive, this would spin an arm that would rotate around pushing the sides of a disk down which would pull on the 2 wires that will control which way the tail will swing.
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Re: Building an articulated tail.

Postby caleb » January 31st, 2013, 12:31 pm

Not sure that the nitonol would be strong enough once you get some structure and fur weight on it. They could be really cool though.

If you don't know how to program enough to use servos, how do you plan on alternating the nitonol wire? Don't be afraid of programming, you have us here to help!
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Re: Building an articulated tail.

Postby Dragonwim » January 31st, 2013, 3:09 pm

No fur actually, the costume I'm make ing is broadway from disney's gargoyles, so the only weight will be a few pieces of 1/4" thick wood strung along a hose, and most of the weight would be on the wire that is static. It'll have a layer of craft foam to help define shape and will be skined in spandex. It's not that I'm afraid to learn to program, I just don't have time to learn right now. I work 10 hour days as a machinist, and try to use my few hours to take care of other stuff. I do intend to get a raspberry pi soon, so I know I'll have to sit down and learn Linux for it. I figure that if I use some sort of timer circuit, such as the 555 timer that was recommended, I can tell one side to contract then the other, it'll just be a case of figuring the right setup.
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Re: Building an articulated tail.

Postby caleb » January 31st, 2013, 3:54 pm

I see!

Well, you could have one side spring loaded so you only have one timer circuit to figure out. Alternatively, you could also rig the whole thing with fishing wire and have a line go down their leg that pulls one side of the tail tight. Unfortunately, this would only work while they were walking but would be very low tech.

Another idea is to have a constantly rotating disk with a cable mounted off center (like a cam). this would make the tail wag without any circuit knowledge whatsoever!
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Re: Building an articulated tail.

Postby Dragonwim » January 31st, 2013, 8:32 pm

I had thought about doing something along those lines, and the wings will be built to work that way, but I wanted to do something difrent for the tail, the suggestion of only rigging one side and havering the other counterbalanced is something that didn't occur to me, and would be much simpler to do. Thank you for that digestion I think I will do that. The disk idea had occurred to me, and I may do that if I need to but I'd rather try the nitinol first. I will post pics of the finished tail if I get it done in time, I'm hopeing to debut the costume at a benefit photoshoot in Birmingham in march.
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