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Psychomaniac
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623 Posts
Discussion Starter #1
My wife is planning a corpse bride using a wedding dress we picked up at a swap meet and a Bargain Basement Barney skeleton we just ordered. It was originally going to be a static prop with her holding a bunch of black roses or a watering can. Now she wants to animate it and have her tamping down a grave (of her groom) with a shovel.

I've been thinking about how to do this. If we place her next to one of our large palm trees then I was thinking I could use an AC motor mounted above (blocked off the tree) with heavy fishing line running down to a screweye in the shovel. I can mount a disc to the motor shaft and the line on a swivel and it'll slowly move the shovel up and down.

I've love to hear a critique on this plan and also feed back on what kind of motor. I'm thinking a rotisserie motor but I'm not sure if if can lift a shovel attached at the edge of a three inch disc.

Thanks!
 

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Psychomaniac
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623 Posts
Discussion Starter #2
I looked at wiper motors and the torque is perfect but the RPMs are too high, even on low speed. The rotisserie motor at 6 RPM or so is actually too slow. I've also been thinking about some kind of sliding setup where the shovel is lifted slowly and then drops to the ground.

I feel like Goldilocks with this one!
 

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Psychomaniac
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623 Posts
Discussion Starter #4
I'm trying to decide if the wiper motor at 5v (15 RPM) will give me enough torque to do the job. I might just get one to mess with since they're so cheap. The quick return linkage might work but I think I'd like more downward speed. I'll try and make a drawing of what I have in mind and post it. It's basically two discs, one which turns with the motor and one that freewheels and is attached to the shovel. The freewheel disc has a slot in it for 180 degrees which engages a pin on the motor disc. As the assembly gets to the top the prop disc is free to rotate 180 degrees where it stays until the pin travels around and engages it again. I can fabricate the discs out of acrylic on my laser cutter/engraver so making it is easy (as long as it'll take the torque) but getting the discs to slide past each other smoothly will take a little bit of work.
 

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Funeral Crasher
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7,435 Posts
I would make a cam for the motor similar to a round circle with about 1/4 of the "pie" cut out.
As it turns it pushes down on a "see-saw" lever. The opposite end of the see-saw would have the string tied to it that lifts the shovel. As the cam rotates around to the cut-out section the lever will drop, along with the shovel.
Similar to this chicken animation (at the bottom):
Cams and cam followers

www.surpluscenter.com has a lot of inexpensive, low RPM gear motors to choose from.
 

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393 Posts
I recommend that you also build a fake shovel to make it much lighter weight so you won't need quite so much torque. A real fullsize shovel is really heavy. You could build a lighter one using PVC pipe for the shaft. Encase it in a block of styrofoam and sand it to shape. The shovel head could probably be made a variety of ways. Just a thought.
 

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Psychomaniac
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623 Posts
Discussion Starter #8
My wife came through on the shovel. She found a small beach shovel that has a realistic shape for the blade and handle. Those parts are plastic and the short shaft if wood. As is it weighs less than a pound.



We'll replace the shaft with PVC, paint the whole thing and we're in business. The wiper motor at 5v should have no problem with this.
 

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Psychomaniac
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623 Posts
Discussion Starter #9
Got the wiper motor today. The possibilities with this little gem seem endless! I hooked it up with a simple metal arm and fishing line going down through a hole and onto the shovel. At 9v on low speed it's just about perfect. I think I'm going to drop my plans for any kind of linkage. The motor has plenty or torque and the speed is good.
 

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Everyone missed the most important thing. Open Track Racer said he has a laser cutter/ engraver! How cool is that. Racer, can it cut metal or is is just for woodburning and light cutting of plastic? Tools are cool and you can never have too many!!
 

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Psychomaniac
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623 Posts
Discussion Starter #11
Bringing this back from the dead! Just finished the bare mechanism for the bride. I'm testing it for a while before painting. So far so good.

YouTube - Corpse bridge animated shovel mechanism

Believe it or not, that's the same blue plastic shovel I posted before. It has a longer shaft and a new paint job.

The bride is ready too. She's a corpsed bucky with long blond hair, a wedding dress and veil. We'll attach her hands to the shovel and let her tamp down on her freshly buried groom (who's arms will be sticking out of the ground).
 
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