Question, Aluminum for Wings

[Vickibrownies]

Hello all,

I'm making a new costume at the moment, a Demon for myself, from World of Warcraft to go along with a Warlock costume I'm making for a friend.
We've been mocking up set of wings for this costume, the mechanics, Arduino controlled servos and all that.

This is the design we're finalised on, mocked up in cardboard.

The plan is to make these wings up using aluminium and chunkier servo controls, but I have never done anything using aluminium so have little frame of reference for how strong it is and my only option is order it on-line so I can't get a feel for how strong it is and what to order.

My intention is to use 1" Bar, that is 1/8" thick (roughly 3-4mm thick) and was wondering from anyone with experience is this is thick enough for this entire structure to hold itself up, support the rest of the wing design and then the costume bits. Do I need thicker, wider bar, would this be too heavy? All of that.

Any advice would be great!

Thanks

 

[OldSkoolEffects]

I don't think servos will have the torque you need when they are actually vertical, given the associated moment arms of the assembled parts. I could be wrong, but I would suspect you'd be eating them up unless you're using super high-torque, metal geared, ball bearing servos, and at that point, why not just use a stepper motor?

 

[Vickibrownies]

I don't think servos will have the torque you need when they are actually vertical, given the associated moment arms of the assembled parts. I could be wrong, but I would suspect you'd be eating them up unless you're using super high-torque, metal geared, ball bearing servos, and at that point, why not just use a stepper motor?

I've never done any project with either Servos or Stepper Motors before, so I couldn't tell you the difference in function between them, nor how to control stepper motors in the same way we could control servos digitally.
Either way, the test servo we picked up seemed to have strength to spare, lifting a 2ltr bottle of water with ease, when we where testing it out or am I missing something more technical to it? Would you suggest a better place to mount them, if not where they are, or directions on suggestions on stepper motors instead?

Thanks

 

[JPH]

You may want to consider linear actuators. Also, the heavier a set up the more battery you are going to carry. 1/8 (0.125) inch aluminum is strong but will bow. If you use a right angle of 1/8 inch, you could prolly stand on it. For cosmetic aluminum use 1/16th or even 1 mm.

Thicker aluminum = more weight = more battery = more powerful motors = more weight on your spine

Your setup looks neat, but will it work against gravity, not laying on the floor? Will it hold when closed or extended?

If you are bending aluminum use 3000 or 5000 grade

 

[Vickibrownies]

You may want to consider linear actuators. Also, the heavier a set up the more battery you are going to carry. 1/8 (0.125) inch aluminum is strong but will bow. If you use a right angle of 1/8 inch, you could prolly stand on it. For cosmetic aluminum use 1/16th or even 1 mm.

Thicker aluminum = more weight = more battery = more powerful motors = more weight on your spine

Your setup looks neat, but will it work against gravity, not laying on the floor? Will it hold when closed or extended?

If you are bending aluminum use 3000 or 5000 grade

Thanks, that's awesome information! I didn't know linear actuators where a thing, they sound far too sci-fi, hah.

I'm not massively worried about weight of it on me, I have a long history is large costume pieces, but of course I'm worried about the working load of the wings, but that's great, sounds like for this use 1/8 alu would be good, probably going to get inch thick bars, since it's not going to have sort of lateral load.

Our intention is to build the frame, then use our test servo to see how well it moves it (It was a good £10 one, metal geared that has a torque listed as '13.00 kg-cm' not that it means much to us), and then we'll see if that needs stronger servos, or just more of the same, then once it's all together we'll see how much spare strength we have to work with that'll then define what the dressing on the wing skeleton can be.

That set up in the video is made of card board and buckled too easily under it's own weight after we cut holes to put the servos in, that and the wires to drive the servos aren't very long and totally awkward, which wasn't smart on my point.
As I say, this is my first time trying anything this ambitious, but I have a local MakerSpace worth of tools and an Internet worth of ideas, so hopefully it'll all come together!

-Vicki

 

[Heroic Replicas]

I'm a metals guy - if want solid structure, you could use angles, extrusions or tube, and set it up in triangles.

If you're looking for CNC cut profiles (steel or aluminum), drop me a line and I can get you a quote. I can get really fancy.

For reference, steel takes twice as much force to deform than aluminum, but weighs 2.5 times as much and is a bit cheaper.

The torque on your motor means how much weight it can overcome times distance you're applying it. From the motor, the first bolt it's connected to looks to be about 10-15 cm away. This means your motor can overcome about 1 kg worth of force from that position. It looks like a fair bit of weight will be handled by the stationary bar, and you have two motors, but you'll need to test it to make sure it'll work.

 

[OldSkoolEffects]

Torque is Force times Distance, so T=F*d. What that means is that if you have a 13kg*cm servo is that you could theoretically hang a 1kg weight on from a bar 13cm long, and have it stay in place; the trick there is that you may not have the ability to move it from that position, so it's best to stay below those ratings.

If you're using linkages, you'd have to do some kinematics analysis to see what forces the servos are actually trying to counteract.

Also, different cross-sectional shapes will react forces differently, i.e, flat bar will twist more easily than channel or tubing, so it's not just a question of material.

Also, if you only paid 10 pounds for a servo, it can't be that good.

 

[DragonSew]

Some small Ideas from a Graduate Engineer (Mechanical Engineering):
- Use small L-Profiles. They are lightwhight but loadable.
- For the Linkings: Don't use simple screws... use plain bearings, made of plastic like the iglidur plain bearings from Igus. Lightwight and smooth.

Other general idea: Why do you want to use actuators? Use springs and a bowden for actuating.

Just my short ideas