# Help with a Corpse Prop



## Fetch (May 16, 2008)

I'm working on a prop similar to this scene from the movie "Shutter:

Other :: SHUTTER.flv video by Bucket-of-Terror - [email protected]@[email protected]@http://vid337.photobucket.com/player.swf?file=http://vid337.photobucket.com/albums/n368/Bucket-of-Terror/Other/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@n368/Bucket-of-Terror/Other/SHUTTER

My prop will be of a young girl, kneeling in front of a cemetery fence, apparently studying a tombstone or prop on the other side while humming softly to herself. When someone approaches her, there will be a brief delay, then her head will tilt backward with a scream to reveal the face of a decaying corpse.

What I'm trying to figure out is the simplest way to get the desired motion. At first glance it would appear to be pretty easy, but I'm wanting the head to tilt waaaaay back, at a freakishly-impossible angle. I also want to keep the mechanics as simple as possible. Here's a few pics of what I've knocked together so far:


























Not sure if that's the best way to hinge it, because the hinge is opening almost 180 degrees, and whatever method I use to push/pull it needs to be kept compact and below the neck line. I'd like it to move to position 1 when triggered, then return automatically to position 2 once the timer deactivates. I want to keep it simple and avoid pneumatics if possible, but not sure what else to do at this point. Any suggestions?


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## Fetch (May 16, 2008)

Hmmm...it left off part of my post for some reason. Here's the rest:

My prop will be of a young girl, kneeling in front of a cemetery fence, apparently studying a tombstone or prop on the other side while humming softly to herself. When someone approaches her, there will be a brief delay, then her head will tilt backward with a scream to reveal the face of a decaying corpse. 

What I'm trying to figure out is the simplest way to get the desired motion. At first glance it would appear to be pretty easy, but I'm wanting the head to tilt waaaaay back, at a freakishly-impossible angle. I also want to keep the mechanics as simple as possible.


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## Otaku (Dec 3, 2004)

That's a nice prop concept and a nice challenge. You may be able to do it with a beefy pull-type solenoid with ~1" travel. They come in AC and DC versions. You can look them up on www.McMaster.com. A long tension spring could be used to assist the return cycle. The soleniod would have to overcome the spring on the tilt-back cycle, so the spring will need to be fairly light tension. Is the skull the one you will be using?


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## Fetch (May 16, 2008)

Thanks. It's looking like more of a challenge than I had anticipated. A solenoid w/spring return is a good idea, but still not sure exactly how to attach it. It's definitely worth exploring. 
And yep, that's the skull I'll be using. It's styrofoam and hollow, so it's fairly light. Of course I will be adding weight once I corpsify it and add a wig.


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## Brckee1 (Feb 21, 2007)

Why avoid pneumatics? If you use pneumatics this would be simple as heck. If pneumatics is not an option, a motor and linkage would be my next choice but the electronics would be more complicated.


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## jabberwocky (Apr 30, 2008)

You might want to try a power door lock actuator.
Fast acting in extend and retracting movement, 12v powered.
Should work perfect for your prop with the right linkage.
Avoid the web and take a trip to your local wrecking yard to save some cash.
Bring a power-drill with a 1/4" bit for removal of the rivets.


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## Fetch (May 16, 2008)

Brckee, I'm not completely opposed to pneumatics, as I've successfully gone that route before. Just seems a little "much" for such a simple motion. Plus there's the noise factor, running air lines, etc. But it may end up that way in the end.

Jabberwocky, funny you should mention a door lock actuator, as that's exactly what my initial thoughts were! I already have a couple of surplus ones I could use, but I guess it all comes down to how to do the linkage.

Thanks for the input guys.


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## Dr Morbius (Sep 21, 2004)

I would spring load it from the BACK so when a catch is released the spring does the actuating.The cardoor solonoid could be used for that. A cord on a small motor could wind around a simple shaft to reset the head.


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## Otaku (Dec 3, 2004)

Doc, I think you're on the right track with the small motor idea. Kinda like how a Boris jaw works. The motor spins and pulls string until the skull hinge hits a hard stop, and when power is cut to the motor (use a R/C timer for this) the spring returns the skull to home position. Easy to do, and the motor will give you a fast, quiet action.


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## The_Caretaker (Mar 6, 2007)

A simple bell crank mechanism should work, you can tailor the movement by the length of the arms of the bell crank from the pivot point so a small movment on one end of the bell crank can give you a large movement on the other, you may need to counter balance the skull to help it retun to the starting position by a spring or weights


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## octoberist (Apr 3, 2007)

*Shutter*

I love the movie SHUTTER. It was hilarious. I especially loved the part where the ghost girl is sitting on Joshua Jackson's shoulders and he can't get her off. Good times.


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## Phil (Sep 2, 2007)

Happened to have a door lock actuator on my desk and it looks like a 1" throw. With the bell crank and slightly curved linkage this could work.


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## Terrormaster (Sep 27, 2007)

Between this and Haunted Bayou's $20 prop my brain is stewing on something really neat. Damnit, I don't need any more work this year - must resist urge to add another prop build to my plate... Must resist...

-TM


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## Fetch (May 16, 2008)

I'm really digging the bell crank idea right now. Gonna play around with that this weekend, and some of the other ideas as well. Thanks again everyone.

And Terrormaster, I feel your pain. There's 3 or 4 major props I want to build, but I'll be lucky to finish this one!


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## Terrormaster (Sep 27, 2007)

Only the cauldron and the hands are left on Agnes so I'll be ready to tackle some of my lesser characters. I've spent so much time working on her taking a break for something different is probably what I need to kill any burnout. My other three big projects are the shack, the columns, and the fence but won't start those till mid September. 

The bell crank definitely seems to be the right approach for what you're doing. I may be going on a different tangent though than what you've got. But still liking the pull string counter balanced by a spring like the Gemmy skulls. If I come up with something before you do I'll post pics.

-TM


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## HalloweenZombie (Jul 22, 2007)

Great concept for a prop. Now you've got me thinking...


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## Aelwyn (Jul 7, 2008)

Oooo---can't wait to see the finished product! I have no clue about moving props (technical stuff is beyond me), so it's interesting to see how you're doing this.

And now I SOOOOO have to see that movie!


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## joker (Sep 25, 2007)

Why not make it spring loaded. Might have to counter the weight on the skull so it falls back instead of forward. You might even get more of a natural looking fall that way too.

Something like this







+

When the cylinder is compressed it holds tension on the spring keeping the head in place, but when it's extended there's slack in the spring allowing the head to fall.

The only problem I see would be that it might not reset exactly facing forward but you might be able to make the base of the skull and top of the socket similar to a hood ornament setup so it resets itself upright properly.


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## Terrormaster (Sep 27, 2007)

I haven't done anything with actuators yet. But the ones I looked at require the voltage to be reversed to pull it back. Also didn't look like there was enough leverage in it to move the head a full 90deg tilt back. Those two are the reasons I'm leaning towards the Gemmy Skull concept with a bell crank. While the mechanics might get a little hairier the electronics stay simple. Not sure there's a way to do this and avoiding pneumatics that won't involve either complex mechanics or complex electronics... I'll probably experiment with the mechanics next week myself just because I've become curious about this concept.

-TM

-TM


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## joker (Sep 25, 2007)

Terrormaster said:


> I haven't done anything with actuators yet. But the ones I looked at require the voltage to be reversed to pull it back.


Could a flip-flop switch be used for reversing the polarity?


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## Terrormaster (Sep 27, 2007)

Possibly, not too familiar with those (i'm more mechanical oriented than electronics). My biggest concern with the actuators are whether or not the actuator arm can push the head back a full 90 degrees. Like I said, haven't worked with them yet but going by the research I've done I can't see the actuator arm having more than an inch or two range of motion in both directions tops.

The only way I can see that working is maybe the head is weighted towards the back. When the actuator is open/up it blocks the head from falling back. Then when it's down it clears a path for the head to fall backwards. 

That could work for what Fetch is doing. The variation I'm doing looks like the bell crank won't work for me. I'll need more of a leverage type setup. What I'm thinking is that when the head falls back another prop pops up from the front for a double scare - think see-saw.

-TM


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## Terrormaster (Sep 27, 2007)

Ok, was looking the lineup for this year's NEHG and saw they're doing a demo on using Linear Actuators in place of Pneumatics. So I thought "wow, that'd be great for this prop" and started looking up info on them. A pretty neat piece of technology but what I'm gathering so far is the components are not by any means cheap. I don't know if I just been looking in the wrong places or what but the lowest I seen is about $130 for a small linear actuator with only a 2" stroke. By all means that makes pneumatics (providing you already have access to a compressor) much cheaper.

-TM


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## Fetch (May 16, 2008)

From what I've seen so far, I'm running into a similar problem as Terrormaster, in that I'm finding it difficult to figure out how to use it effectively to provide the leverage I need. Somehow I've got to lift up the front of the skull and push it backward at the same time, which is difficult enough without having to also keep everything compact. But I will persevere.

And TM, I've looked into the linear actuators as well, and like you said, new ones are a little cost-prohibitive from what I've seen. So far I haven't been able to find anything less costly in the surplus market that has a decent throw.


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## Terrormaster (Sep 27, 2007)

Fetch, I think this is gonna be one of those props we have to think outside the box. And in this particular case we've been thinking with a pneumatics mind set.

Here's something I though of last night (needs to be fleshed out a bit more though). Instead of trying to spring load the head to say in place and pull it back with some sort of mechanism. Lets try the opposite - spring load the head to stay open and use a mechanical mechanism to keep it closed until triggered (like launching a rubberband off your finger). Don't know if you're familiar with The Flailer prop over at Allen's Halloween Page but thats the general idea I'm leaning towards.

Basically there's a cord attached to a crank arm and a slip disc that pulls the head up. The motor keeps turning until it hits a limit switch. The switch is positioned just before the slip point. When the PIR is engaged the motor is toggled back on and push the disc past the slip point springing the prop. You'll have to look at the info on the page to get a better idea of what's going. While he does it with an arm, I'm positive this could be applied to the neck.

I'll try and work up some details later today.

-TM


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## Terrormaster (Sep 27, 2007)

Okies, this is what I've got so far. Basically just the neck mechanism built with PVC:










The spring keeps the neck in position and will be connected to the motor slip disk. I think the perfect motor for this is the Valeo 15094704 which has an auto-park feature. The auto-park will ensure that the motor always returns to the trigger position without the complex relay and limit switch mechanism that they used on the Flailer (well complex for me since the site doesn't explain the circuit).

The slip disk works pretty simple. The rail that the string connects to spins freely on the motor shaft via some lock washers. Mounted underneath that rail is a disk or plate that's bolted to the shaft. A pin or screw sticks up out of the under plate. When the motor moves the pin around it catches the upper rail and push it around. When the rail reaches the center point where it's no longer pulling the string, the spring yanks the rail around the rest of the way (ie: throwing the head back). When the pin catches up with the rail it will pull the string back and reposition it (lifting the head at the speed of the motor). Just as long as the trigger point is setup just before the auto position the prop will be cocked and ready to spring again.

The motor is pretty inexpensive ($17 @ All Electronics) and the only remaining challenge is the circuit to pulse the motor from a PIR - perhaps Otaku, Doc Morbius, or one of the other electronic wizes can chime in on that.

And before SI comes along and comments on the jar of Petroleum Jelly - I use it on the prop eyes. That's my story and I'm sticking too it 

-TM


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## Otaku (Dec 3, 2004)

The function of the spring is to keep the head is "back" position, correct? I'd still go with a 12VDC pull solenoid to bring the head back and use the spring to return it to home position. I've used this 12VDC solenoid (McMaster-Carr p/n 70155K6) for other props (including precision automated fixtures at work) and had no problems. They're powerful and very reliable. Use a one-shot 555 timer to activate the solenoid when you want the head to fall backwards. Any momentary trigger will start the timer (PIR, button, mat switch). You'll need a 12VDC wall wart that can supply at least 1A - the solenoid draws ~800mA. You can also use a compression spring around the solenoid shaft to assist in returning the head to the upright position. If you need a quick drawing of the wiring let me know.
BTW, what's the approx. weight of the head?


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## Fetch (May 16, 2008)

TM, I can totally see your mechanism working for what I'm doing. Unexpected company kept me from spending a lot of time experimenting this weekend, but I hope to play with your idea a little this week. And oddly enough, I had already been eyeing the motor you mentioned, mainly for the auto-park feature! Looks like it would only need a brief jolt to kick it around a full revolution. I'm going to order a couple tonight.

And Otaku, I don't think the 1-inch pull from the solenoid will give enough travel, even with a funky linkage. But I'm not all that "up" on mechanical advantage, so I could be wrong.


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## Terrormaster (Sep 27, 2007)

From the experimentation I did with the amount of pull required on the string, 1"-2" just might very well cut it - at least with the design I've tried (ie: I measured the amount of string between the neck back and neck upright positions). 

Otaku, I too would like to know any mechanical advantages of the solenoid solution. Actually, my only familiarity with solenoids are in the sense of pneumatic solenoids and automotive solenoids. So lets pretend I'm a huge noob, and without getting into all the technical details from the wiki page, explain exactly how the type of solenoid you're speaking of works and how it would work with this prop. Are pull solenoids like linear actuators?

Thanks,
-TM


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## Otaku (Dec 3, 2004)

This solenoid has an 80 in/oz pull, so can handle some pretty good loads. Remember that the point at which the solenoid, or its extension rod/bar, connects to the pivoting part determines the travel. I use this solenoid on an oscillating prop, and I use probably 3/4" of the stroke but due to the connector location on the turntable (near the center of the radius) I get about 5" of travel. The load is a "Burnt Bob" foam prop mounted on an 18" round of 1/2" plywood. That's mounted to a 12" lazy susan bearing, and the solenoid has no trouble moving this load at all. I have a spare unit at work - I can try to set up a prototype linkage to demonstrate the system. Give me a few days to scare up some spare time.
Question - will this prop have some sort of torso in which to hide the moving parts?

I see that Sickie hasn't commented on the Vaseline yet...


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## Terrormaster (Sep 27, 2007)

Otaku said:


> This solenoid has an 80 in/oz pull, so can handle some pretty good loads. Remember that the point at which the solenoid, or its extension rod/bar, connects to the pivoting part determines the travel. I use this solenoid on an oscillating prop, and I use probably 3/4" of the stroke but due to the connector location on the turntable (near the center of the radius) I get about 5" of travel. The load is a "Burnt Bob" foam prop mounted on an 18" round of 1/2" plywood. That's mounted to a 12" lazy susan bearing, and the solenoid has no trouble moving this load at all. I have a spare unit at work - I can try to set up a prototype linkage to demonstrate the system. Give me a few days to scare up some spare time.
> Question - will this prop have some sort of torso in which to hide the moving parts?
> 
> I see that Sickie hasn't commented on the Vaseline yet...


Ahhh, that makes sense Otaku. So you're increasing the range of motion by transferring it to another device much like gears on a bike (there's a mechanical name for this but escapes me at present) - sorta. Connecting the solenoid to the outer edge of the bell crank gives you the short 1" range; connecting it closer to the center pivot point increases your range. I haven't worked with solenoids on a prop before so this is new ground for me.

I can't vouch for Fetch but the design I was tinkering with would fit into a prop similar in concept to Haunted Bayou's prop challenge entry. So to answer your question - yes, the mechanics can be placed into the torso.

The PVC prototype I whipped up was more to help Fetch. My overall design is slightly different in that it would work more like a see-saw. Basically opposite of the head would be another small prop (most likely a stuffed crow) that would be hidden in the chest cavity when the head is upright. Then pop up and out as the head falls back. The head would be a corpsed blucky with some hair and a black widows veil - general pretty light weight.

Not sure mechanically, except maybe simplicity, what advantage that the solenoid would give - but again, I'm new to solenoids used in this manner. I know for what I am designing, the slow return to upright might be more effective than a quick snap back - my concern would be the crow slipping back into the chest. I'd presume there's no way to control the speed of the solenoid - it's in or out right?

-TM


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## Otaku (Dec 3, 2004)

Actually, you can control the action of an electrical solenoid to a degree by using a light compression spring on the plunger. This will slow the retraction of a pull solenoid and the reverse can be used to control the return. Otherwise, you're correct, the solenoid will retract very quickly. I'm trying to find some pics of the solenoid as used in the groundbreaker prop I mentioned - I'll post an example when I find the pics.


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## Fetch (May 16, 2008)

I would definitely be interested in seeing those pics, Otaku. I plan on putting whatever mechanism I end up using inside the chest cavity, but the prop will be the size of a young girl, so the more compact the mechanism, the better. Her head will be a corpsed styrofoam skull, so it should end up being fairly light.

TM, I'm anticipating your prop almost as much as my own!


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## Otaku (Dec 3, 2004)

Fetch,
Here's a pic of the 12VDC solenoid on the groundbreaker prop I built a few years ago:

http://halloweengallery.com/displayimage.php?pos=-3806

You can see that the attachment point is near the center of the disk. This translates to greater movement at the rim, of course. The spring around the solenoid shaft acts as the return.

This is a short video of the prop in action:

GDBRKR.flv video by Otaku1031 - [email protected]@[email protected]@http://vid73.photobucket.com/player.swf?file=http://vid73.photobucket.com/albums/i231/Otaku1031/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@i231/Otaku1031/GDBRKR


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## Fetch (May 16, 2008)

Thanks Otaku...that makes perfect sense. Nice prop, too.


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## Terrormaster (Sep 27, 2007)

Noice! I wonder, I've did a little digging around over at AllElectronic at solenoids but I couldn't get a feel for actual size. The PVC frame I built was done mostly with 3/4" PVC (except the neck component which was 1/2" so it'd spin freely inside the 3/4".










I was thinking of changing the T at the bottom to an X connector and mounting the solenoid on the inside facing up and connect a crank arm to the neck piece. Is there a solenoid that would fit nicely inside a 3/4" connector (which is actually more like 1" diameter) and still have enough pull to do the job?

-TM


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## Otaku (Dec 3, 2004)

The solenoid I used in the groundbreaker is available at:
http://www.mcmaster.com/
Search for "solenoid" (no quotes) in the Find Products list. Click on "Linear Motion Solenoids" in the list. Check out the cylindrical "pull" solenoids, they should fit in the pipe with room to spare. You'll want to use a continuous duty solenoid to prevent overheating.


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## Fetch (May 16, 2008)

OK, I FINALLY had time to start working on this again over the weekend. I ended up using the crank arm/slip-disc idea that Terrormaster described, and it works pretty well. Here are a some clips of the mechanism in action:

video :: MVI_1683.flv video by Bucket-of-Terror - [email protected]@[email protected]@http://vid337.photobucket.com/player.swf?file=http://vid337.photobucket.com/albums/n368/Bucket-of-Terror/video/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@n368/Bucket-of-Terror/video/MVI_1683
video :: MVI_1684.flv video by Bucket-of-Terror - [email protected]@[email protected]@http://vid337.photobucket.com/player.swf?file=http://vid337.photobucket.com/albums/n368/Bucket-of-Terror/video/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@n368/Bucket-of-Terror/video/MVI_1684
video :: MVI_1685.flv video by Bucket-of-Terror - [email protected]@[email protected]@http://vid337.photobucket.com/player.swf?file=http://vid337.photobucket.com/albums/n368/Bucket-of-Terror/video/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@n368/Bucket-of-Terror/video/MVI_1685
video :: MVI_1686.flv video by Bucket-of-Terror - [email protected]@[email protected]@http://vid337.photobucket.com/player.swf?file=http://vid337.photobucket.com/albums/n368/Bucket-of-Terror/video/[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@n368/Bucket-of-Terror/video/MVI_1686
I used the Valeo 15094704 wiper motor that has the auto-park feature, and a PicoBoo to set the timing. Took some trial-and-error (mainly error) but I think I finally got the timing right. Please let me know what you think so far.


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## Terrormaster (Sep 27, 2007)

Wow - that worked a lot better than I imagined. I like the way it kinda falls back and bounces like the head actually fell loose. Gonna have a few ToTs going home to change their wet costumes.

-TM


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## Fetch (May 16, 2008)

Yes...thanks to your idea, TM, I'm quite happy with the results so far. I've got mixed feelings about the bounce, though. But it may not matter- once I get the head corpsed, the wig on, and the body built and dressed, I think a lot of that motion will be lost.


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## Otaku (Dec 3, 2004)

Hey, that works very well! I think you have the timing spot on, and as you said, the bounce should go away once the corpse is dressed. Nice prop!


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## Phil (Sep 2, 2007)

That looks awesome! At what voltage are you running the wiper motor?


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## Fetch (May 16, 2008)

Thanks Otaku. The picoBoo controller made the difference. The best part about using the pico is I can extend the time the head is back for as long as I want.


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## Fetch (May 16, 2008)

Phil said:


> That looks awesome! At what voltage are you running the wiper motor?


12v. The speed of the wiper motor is not so much reliant on the voltage for this prop, as I use it's auto-park feature instead of just letting the motor run.

Basically I programmed the picoBoo to start the motor, then almost immediately stop it... just enough to tap the lever arm over its "catch point" so the spring tension will pull the head back. I found that if the jolt is brief enough, it won't activate the auto-park, and the arm will remain in place. Then, after a measured pause, the picoBoo will start the motor again, long enough this time to activate the auto-park. Then the power is cut once more and the motor resets itself to the trigger position again, pulling the head upright.

The speed of that particular motor is affected by lowering the voltage, but anything below about 7.5v won't move it. And lowering the voltage makes no difference to the rotation speed when it is auto-parking.


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## Devils Chariot (May 23, 2007)

Hey Fetch, that mechanism is genius. I had to watch it like ten times to get it, and then I scr4olled down a bit and you explained it. I have ditched this motor for my cauldron prop and will use it for something else, and this make me think! Good work.


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## Fetch (May 16, 2008)

Thanks DC, but I can't take all the credit. Terrormaster and Otaku, among others, helped me tremendously. 

The prop it about 90% complete... I just need to find something suitable to dress her in. Hope to post pics and a vid within the next couple of weeks, so stay tuned for the unveiling.


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## joker (Sep 25, 2007)

Trying to understand this. 
The skull is hinged and has springs attached to keep the skull in the down position. The motor has an additional arm with a slip disc (washer) attached that is connected to the skull. Slightly off set the arm with the slip disc is held in place by the tension of the spring and a slight nudge from the wiper arm allows the springs to pull the head back. Using the autopark feature the motor makes a turn and resets the arm pulling the head back up?


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## Fetch (May 16, 2008)

Exactly. I'm using a timer to kick the motor into action twice: once for the nudge, then again to engage the autopark feature.


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## Fetch (May 16, 2008)

FINALLY...here she is:

http://www.hauntforum.com/showthread.php?p=253595#post253595


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