# Help! Transferring circular motion to back and forth motion



## forbiddenforest (Sep 11, 2013)

Hey all! So this is our first attempt at an animated prop and we are having some trouble. At a local Menards a few weeks ago, my husband and I saw this animated Halloween dog inflatible. Hate inflatibles but loved the motion - it looked left, paused, then quickly looked right, paused, and continued. My husband has been trying to figure out how to transfer the circular motion of a ceiling fan motor to the back and forth with pause motion we saw. I'd love to turn this into a realistic wolf for the forbidden forest section of our haunt, but I am dumb as a box of rocks when it comes to motors and gears and all things mechanical. Any help or suggestions for how to websites would be greatly appreciated!


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## Runfromron (Sep 22, 2006)

FF,

For what you are trying to accomplish, a ceiling fan motor is not what you need. They have very little starting torque. It would be very difficult to adapt them to this application. For linear action, using pneumatics would probably be better, since they work in a straight line to begin with, but you are starting off with a very complex action prop, which I don't recommend for beginners. It could end up being very frustrating! That kind of multiple reverse and stop action really needs some sort of computer integration, in my opinion. Someone out there into programmables might be able to help more than I. Sorry to throw a wet blanket on your idea, but I really recommend starting out with a simpler prop.

Good luck!

Ron


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## RoxyBlue (Oct 6, 2008)

Agree with RFR about the ceiling fan I'm thinking a deer motor might be a better choice, but the tech gurus will be able to give good advice.

Here's a wolf build thread that will show you the deer motor. The head motion is up and down rather than side to side, but I would think you should be able to change the orientation of the motor to get lateral motion:

http://www.hauntforum.com/showthread.php?t=28802

Here's where you can buy a deer motor if you don't already have a Christmas deer to gut:

http://www.kindys.com/products/deco...ent-motors/replacement-motor-48-animated-buck

The description of the motor says it can be mounted to give either up and down or side to side motion.


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## Hippofeet (Nov 26, 2012)

As far as strictly the motion, from circular to straight, you would need a circular plate with a hole on the center, and a hole near the edge. The distance from edge hole center to where the hole would be on the opposite edge is the distance of left-right throw you will have, depending on the next step. Now you will have a linkage arm (I would just make one from flatstock) that is bolted to the edge hole on the circular plate, and the other end will be bolted to what comes next. That being, a straight captured shaft (or flatstock), captured meaning it can only move left or right, I would have it sliding in brackets. Now your middle shaft will bolt to that, when the plate is spun it will transfer the circular motion to and angular motion, and then to a straight motion. Look at old pictures of steam engines, this is how the steam driven pistons drove the circular wheels. You may need to play with the diameter of the disk to get the distance of throw you want.

All that said, thats a rough way to go, and it would be my last resort. when I do left-right head movements on props, I use a pneumatic cylinder, connected to a very short tab welded to a tube, to which the head is attached. This tube slides over another (lubricated) tube, which is welded (part of) the body armature. The cylinder will be horizontal, and mounted with a pivot bracket in the rear, on the same level as the welded tab. I use very short throw (1 to 3, depending) cylinders, and a one or two channel controller will run this. I would (with a push button controller) run as long a program as possible, to avoid obvious repeating. Looks more random. With speed control mufflers or fittings, you can set the speed of the movement at the solenoid, or at the cylinder. To get two speeds requires two setups, so 2 cylinders, two solenoids (5 port 4 way) and could be run from the same controller, depending on the make.

The pneumatic setup is actually easier, tab length and cylinder throw determine degree's of left-right movement of the head.

Another way would be with a circular plate on the motor, and a wire rope running around a pulley. You would need two mounting points on the circular plate, and two cables, or some sort of spring return if using one. So the cable would go around a small diameter pulley and pull on a tab to move the head left, as the motor finished that single rotation the spring would take up the cable slack and pull the head back to the right. That would be a cheap and easy to do it, depending on how much fabrication of parts you can do.

You could also (not easily, but I have done it) mount the head directly to a wiper motor shaft, in this case the shaft would be pointing up in the middle of the neck, with the body of the motor horizontal and to one side, and using at least a two channel controller, would wire it up to run forward and reverse (easy with DC voltage) and then use the buttons to time it and determine the degree of movement, and randomization.

I'm sure there are other ways.


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## halstaff (Nov 18, 2009)

There are certainly many ways to accomplish this but if it was me, I'd just adapt what I did for my werewolf and add fur instead of the clothing.




Check out these threads - http://www.hauntforum.com/showthread.php?t=18405&highlight=wolf and http://www.dreadnight.com/makingofthewolf.html


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## bfjou812 (Aug 15, 2008)

This might be of help for beginning automated props.http://www.robives.com/mechs


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## daddywoofdawg (Oct 3, 2008)

a deer motor would work for back and forth,connect the neck to the motor and put stop blocks on each side the motor will run one way till it is stopped,then change directions till it stops again.and repeat. you can do it other ways with cams or bars,but takes drawings to explain.


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## forbiddenforest (Sep 11, 2013)

Awesome advice everyone! I am thinking I may hack a deer prop for next year - but I am going to have my better half read these posts. I had suggested that before, but he thought that the deer motor or the wiper motor wouldn't have enough power for the weight of the head (although I was going to work with Styrofoam, so how heavy can it get?). 

Hippofeet - from what I can tell - it looks like he was trying what you suggested but couldn't get the pause timing right - hopefully your hints can help him out a little more.

Runfromron - the hubby kind of saw the inspiration prop at the store and ran with it, so who am I to stop him, lol. He's not a complete beginner - we do sets/ props/ effects/etc. for a local community theater group here, him for the last 15 years, so he's actually gotten pretty far on the mechanism. It's just me that's the idiot when it comes to the motorized stuff - so I can't help him or give him any suggestions. That being said - he got pretty far the first day he worked on it but then got really frustrated after not being able to get the timing right and worrying that his build would be too big for the prop. Me- I'm just thinking I'll build a bigger wolf, lol. That being said, we may use his build for a hanging spider above the door that raises and lowers on a web - either way- I'll try and post some pics/video soon and let you know which way we are going...

PS- sorry to the moderator - originally posted this to prop how to instead of technological terror - rookie mistake.


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## HomeyDaClown (Oct 3, 2009)

For rotary to linear ( back and forth ) two ideas come to mind.

The Scotch Yoke:









and this:


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## Runfromron (Sep 22, 2006)

The biggest problem that I saw was the fact that you not only wanted the back-and-forth motion, but also stop-hesitate-reverse motion too--which would much more realistic than just 'head-shaking'. That's why I suggested some sort of programmable chip or computer controlled 'intelligent' sequencing, which is beyond my ken. I hope that you are able to realize your dream! Patience and perseverance pay off!

Again, good luck!

Ron


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## Joe_31st (Aug 20, 2013)

Okay, I was looking up that "Scotch Yoke" mechanism because it seemed cool and I'm always interested in mechanisms for props. I found this that might fit the bill exactly:






It's called a "WhitWorth Quick Return Mechanism". It does what you want. It's rotary motion that goes slow, then returns quickly. The only thing, it probably doesn't give you that long enough pause that you want. But, at least we're getting closer.


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## Retroplayer (Feb 22, 2013)

Look up quick-return mechanisms:





There are several different designs to do it. For the pause, you will need to have a mechanical "stop" on the motion near the end of the travel which allows the full travel, but without moving the prop further.

A slotted cam could also do it with a loop path near the top of the travel. Once it exits the loop, the quick return phase starts.

Rinse and repeat and the motor only needs to move in one direction.

The magic of the quick return is that the cam is not centered, so it requires more travel in one direction than the other. A pause would just mean a point where the rotation of the motor is not translated into linear (back and forth) motion runing the pin through a loop at that point would accompliash that.

You'd be amazed at how simple the mechanisms are in these things. It just takes some thinking.


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## Retroplayer (Feb 22, 2013)

oops. Missed that last reply. My apologies, Joe


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## Joe_31st (Aug 20, 2013)

Retroplayer said:


> oops. Missed that last reply. My apologies, Joe


No worries. That was probably an even better animation. The whole mechanism is pretty slick. Just seems hard to make for a garage tinker'er.


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