Instructables
Picture of Magnetic Key
The goal of this project was to make a wind-up doll key for a Halloween costume, which would rotate at a reasonable speed. I also wanted to make it so that the key could be attached to an hidden harness without damaging or altering the back of a costume. In the end I ran out of time and encountered some major technical hurdles, namely the fact that no matter how light you make the key you will need an absurdly strong magnet to attach it, and the motor I chose was not nearly strong enough. Meh, it makes an interesting Steam Punk artifact.

Over all, I spent about $100 on this project, but it would have been less than half that cost if I had gotten the brass at someplace besides McMaster-Carr. That place is EXPENSIVE!



... and yes Virginia, The Dresden Dolls rock.
 
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Step 1: Tools and Materials:

- brass plate
0.010" thick 8"x12" brass
mcmaster.com 9011K7 $5.59 (x2)

- brass sheet
0.010" thick brass shim stock 6"x60"
mcmaster.com 9504K24 $10.96

- brass tube
2" outer diameter 0.032" wall 3' length
mcmaster.com 8950K842 $52.37 (seriously WTF?)

- 1/2" balsa
3"x36"x1/2" balsa
pearl art $5.00ish

- magnet
k&j magnetics $7.00
http://kjmagnetics.com/proddetail.asp?prod=MM%2DB%2D42

- nut + bolt
scrounged

- disco ball spinner
amazon $9.95
http://www.amazon.com/gp/product/B000HZJXCE

- toggle switch
scrounged

- 2 cell AA battery box
scrounged

- epoxy
- dremel/ drill
- band saw
- disc, belt, drum sander
- soldering iron + solder
- pliers
hengle2 years ago
Funny you should mention VWs.... I was looking for a way to make one for my VW (roof mount, since it's a Baja Bug) to use for a parade. The theme is Toyland, so a toy VW makes perfect sense.
Thanks for the great how-to!
Awesome idea! Now to go wide up some giant clockwork..... robots? Big Ben? hmm....
Patrik6 years ago
If you could make the shaft of the key shorter, you wouldn't need as much magnet power to keep it sticking to the surface. Is that entire second cylinder the "obscenely powerful magnet"? I assume it's a large electromagnet - a rare earth magnet of the same strength would probably be much smaller and not use up your battery...
roye.zhu Patrik4 years ago
yes ,you r right
mydian_nightshade (author)  Patrik6 years ago
Nope, the rare earth magnet is only a 1/4" tall. Sorry I don't have better pictures of the process. The big cylinder you're talking about is the disco spinner battery bucket - for a D cell battery. Also, the length of the key shaft is due to the length of the disco spinner assembly.
This is really amazing!! Wow!
___5 years ago
u can use wood and paint brass
that is so cool!
hammer98765 years ago
Aw. I wanted to see the key on the Halloween costume! Was it a doll (key in back) or a wind up clock (key in the face of the clock)? VERY nice looking key.
Sandisk1duo5 years ago
awesome!
jc8176 years ago
I saw a huge key like this on the back of a vw beetle the other day. Horrific, but funny.
I think it might go a bit better if you make the "wings" on the end of it turn instead of the entire thing. Other than that it is very good.
How do you do that?
crapflinger6 years ago
looks nifty on the fridgie! hehe i wonder if, because of the strength of the magnet, if it would just end up twisting up your costume when you tried to wear it with your steel plate idea?
I don't think the magnet turns, the key turns around the magnet. That's how I see it working anyway. Cool idea. Good instructable.
AH! yes that does make sense!
jongscx6 years ago
If you ever do make that costume, could you post a video of the wearer doing the robot... PLEASE...
mydian_nightshade (author)  jongscx6 years ago
YES! XD
darkmuskrat6 years ago
Nice!!! Is all I can say.... For some reason I want to go play kingdom hearts now, hmm.
cool :)