Thread: Animatronic help

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Hey everyone I've got a question for all of you animatronic geniuses. I am making a set of demon wings that use the same principal as this video http://m.youtube.com/index?desktop_u...&v=julYWda9o3Q Obviously mine will be much bigger but the question I have is about servo motors. I would like to use two independent servos that can drive both clockwise and counter clockwise (if I understand it that's pretty much the definition of a servo) my idea is to have a thin steel cable connected to both the top and bottom portion of the wing and connect each to the servo so when the servo spins one way it opens the wing and when it turns the other way it will pull the wing tightly closed. The biggest question I have is how small of a servo do you think I could use. I don't know much about them yet but obviously as I will be wearing these for a long period I would like to keep the servos as light and low voltage as possible, so any recommendations for a physically small servo that can put at least 30 lbs of torque, and won't suck so much power that I have to plug myself into a wall? Forgive my lack of knowledge I have researched but the fact of the matter is I trust experience over spec sheets any day of the week. I will try to post a rendering of my design as soon as I can get back on my computer to give a better idea of what I'm trying to achieve.

Thanks in advance!

Here is hopefully a non mobile link of the video. http://www.youtube.com/watch?nomobile=1&v=julYWda9o3Q

"..a physically small servo that can put at least 30 lbs of torque, and won't suck so much power that I have to plug myself into a wall?"

These are pretty much mutually exclusive specs....there is no such thing as a small servo motor that can provide 30lbs of torque and if you find one that can provide that much torque it will require a bunch of current. How fast do you want the wings to move? If they do not have to move quickly then it might be it possible to make some kind of a "cam" and open it using a linear actuator. This actuator gets you 40lbs of torque and a 6" stroke. BUT its more than $100 and it sucks 3Amps. You might be able to run this from something like a motorcycle battery (12V) hanging on your belt.

Maybe I'm over estimating the 30lbs of torque, there is no way I'll need that much unless I make them out of steel lol.

you may be able to make it work...to make wings that you will wear you will want them to be exceedingly light, especially if you are going to be wearing them for an extended period of time.
You really need to design the wings themselves AROUND the actuator type you will be using.
A linear actuator (as above) might be your best bet, but once again, that adds to the expense. Until you have a solid design for the wings, or at least the materials that you will be using and you have physically opened and closed them yourself it may be difficult to guess at the actuator type and necessary strength. High torque servos with metal gears and such are also loud...linear actuators are a much quieter option.
I'd say your best bet is to make a model of what you are going for...a frame and basic "wing" material and they try out a servo...if that dosen't work then the linear actuator is your device of choice.
Sorry I couldn't give you a definitive answer, but I hope I've helped a little.

dK

OK- but you will still most likely need more torque than just a standard servo can manage by itself. My next suggestion would be that you look into this type of thing made by Servo City where they have taken a servo motor and mounted it in a gearhead type of housing. They have many choices of gear ratios and rotational options so you should be able to find what you need based on the design that you come up with. The advantage of this option is that since it is still a servo motor it is most likely easier to control than the linear actuator option.

with a little more searching I found this, you may want to go with something more like this if you are not too tech savvy when it comes to servos/stepper motoer/actuators...

just a thought.

dK

It seems like, for what you're doing, you don't necessarily need servo positioning, but rather just need full open or full retract. Is this fair to say?

If you just need the wings to open fully, or retract fully, a pneumatic cylinder is probably the best way to get this kind of force with low weight. Lowes or Home Depot sell small belt-mount tanks, or there's also paintball CO2 and N2 tanks. Then, you can use a flow control valve to control the speed with which the wings open.

If you did need huge force and servo operation, you'd probably end up needing to make your own servo from a wiper motor, position feedback pot, and servo controller from Pololu.

- Hook

I saw the vids for the manual operation and that would be really easy to do. Unfortunately I hate easy and enjoy a challenge and my back isn't what it used to be so the weight will be bad enough without the constant movement of the shoulders and arms. I like the idea of an actuator I just don't like the cost of a 12V or the added weight of an air tank. I guess I'm going to start by making a cardboard version, get that perfected then I can use it as a template for all of the pieces. Attached is the basic idea of what I'm going to build. I hope I can figure a way other than manual or this whole project will be a bust. Thanks for all the help guys!