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What you are not going to be working on it for a whole month, now what do I do, I look forward to updates on this one every week. waiting to see the final version all lit up and working at night.
 

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Discussion Starter #25
Post-Halloween Assessment:

Well...the unicycle skelly worked, but it required constant attention. The unicycle was clamped to a cart that ran along a wooden track. The cart was pulled by non-stretch, super strong fishing line. The line was wound and unwound on two small wheelbarrow wheel rims bolted to a Frightprops motor. A Frightprops Picovolt controller set the speed and direction of the motor.

The motor-string setup was the prop's weakness. I had used a coupling nut to attach a threaded rod extension to the motor, but the back-and-forth motion of the motor loosened the coupling nut, causing the extension rod and rims to fall off the motor. I solved that problem with a dose of JB Weld nut lock liquid. A more reliable choice would have been to weld the parts together.

The Picovolt is an amazing little gadget with its ability to record and execute a series of movements continuously or when triggered. However, because the conditions of the track, cart and string varied from run to run, the cart's starting and stopping points would drift with each run. I had to check the rig about every 10 minutes to reset the cart's starting point. I forgot at the end of the evening while taking pictures, allowing the cart to deadend on the track while the motor was still running. The motor was strong enough to pull the string off the cart and firmly wrap the string around various parts of the motor setup.

It's funny--I'm never going to recreate this prop, but I keep mentally rebuilding it. I'd need a more predictable, automated way to move the cart--that or have someone operate the controller "live." I'd ditch the motor-string rig. This might work: putting the motor on the cart, with a gear attach to the motor's shaft. That gear could pull the cart back and forth along gear teeth bordering the track (assuming you can buy linear lengths of gear track). I think this arrangement would greatly reduce the run-to-run variation allowed by the string-motor rig or even by a motor-driven wheel on the cart itself. Some people had suggested using gadgets at each end of the track to cut power and halt movement, but I don't know how those work.

On the plus side, the cart-unicycle-skeleton combo worked okay. No one could see supports on the unicycle thanks to the use of blacklight. I wish it could have moved faster, but the prop combo (with a few bricks added to the cart as counterweight) was very heavy. I'm impressed the motor had enough power to move it.

Thanks to all who offered encouragement during the build. - Jay

In case you didn't see final video of all the circus-themed props, here's the link:
Halloween Circus
 

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What I saw in the video was an amazing prop that pretty much did what you wanted. To even get as far as you did in building it and getting it to work the way it did still blows my mind. I hope that you don't abandon the prop entirely and that it will see it's return in some future haunt. Maybe you can find someone who builds robots (like the ones in the video linked below) who could help you design a different way to move the cart the skellie rides on.

 

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Using a limit or reed switch isn't that hard. You wouldn't even need the Picovolt with a reversible 2 relay. You could use a PWM for the speed of the motor adjust.

The limit switch can be a simple momentary switch that either is activated by weight when the string hits a point. The Reed switch is magnetic and you can attach a magnet to the line, when the magnet gets close to the Reed it switches. I think the Reed is a better choice. You would set the relay to be Interruptible from each side making a barrier so it wouldn't pass your set distance.
 

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I was wondering if you had limit switches in your setup as running the system "open loop" usually isn't viable for more than a couple of operations. Using limit switches to activate forward / reverse on the motor would automate it, but having the speed ramp up and down would be best.

A lot of CNC machines have two limit switches for each end of each axis. The first (inner) is the "soft limit" that signals to the controller that it should go no further. The second (outer) ones activate the E-stop and should never be reached in normal operation. When one of these activates it can cut the power as the controller possibly has lost control (damaged output driver), locked up or one of the soft limit switches has failed.

Probably more than you wanted to know, but it may give ideas to someone else that goes down the path. :)
 

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Discussion Starter #30
I was wondering if you had limit switches in your setup as running the system "open loop" usually isn't viable for more than a couple of operations. Using limit switches to activate forward / reverse on the motor would automate it, but having the speed ramp up and down would be best.

A lot of CNC machines have two limit switches for each end of each axis. The first (inner) is the "soft limit" that signals to the controller that it should go no further. The second (outer) ones activate the E-stop and should never be reached in normal operation. When one of these activates it can cut the power as the controller possibly has lost control (damaged output driver), locked up or one of the soft limit switches has failed.

Probably more than you wanted to know, but it may give ideas to someone else that goes down the path. :)
No...no limit switches. If I were to do it again--extremely doubtful--I'd take your and Industen's advice and learn about them.
 

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Discussion Starter #31
What I saw in the video was an amazing prop that pretty much did what you wanted. To even get as far as you did in building it and getting it to work the way it did still blows my mind. I hope that you don't abandon the prop entirely and that it will see it's return in some future haunt. Maybe you can find someone who builds robots (like the ones in the video linked below) who could help you design a different way to move the cart the skellie rides on.

Thanks. I appreciate the kind words.
 

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Discussion Starter #32
Very impressive setup! The lighting on the unicycle skelly is perfect!
Thanks. I used Wildfire blacklight paint. The optical white paint is a standout, but the orange, blue and green didn't have nearly as much brilliance. I had to mix some of the white with the others to make the prop more visible.
 

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I think I would do it again. It looks great. The changes I would make would to use chain to drive the platform and also use limit switches as suggested by others. The chain would eliminate the stretch and other problems associated with rope/ string/fishing line. I am talking about something like bicycle chain. Again you have done a great job. It would be a shame not to do it again.
 

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It has had me pondering how I would do such a project. I doubt I'll ever make it, but it's fun to work out the details in your head sometimes.

For the track I was thinking of maybe a T bar like a bit like a monorail. The platform would roll on wheels across the base of the track like a skateboard, being kept on course by another set of wheels mounted sideways that almost contact the vertical bar.

How to propel the platform over such a distance if something I don't know yet. It has to deal with rain and some debris I guess.
 
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