Sheer luck brings a Halloween themed project for this Fail of the Week post. [Stryker] wrote in to the tips line to share a link to what is an extremely awesome hack. He carved four three different faces on the sides of his pumpkin, then sliced the eyes, nose, and mouth into different sections. Couple this with an internal skeleton made of wood and PVC and he’s got himself a nice hack which lets trick-or-treaters spin the sections to select one of up to 27 different faces.
The sections do spin rather well and the finished project looks fantastic. So what is it that failed? We’ll cover that after the break.
Check out the support structure on the right. Did you already notice that each of the sections has a hobby servo motor attached to it? These were meant to mechanize the jack-o’-lantern. Each uses a belt to interface with the PVC fittings, and an Arduino is used to control the motors. [Stryker] shows this off in his video description. He says his “servo pulleys broke”. We assume this means either the plastic wheels themselves or the belts and hopefully not the motors. He plans to try again next year.
Can we help brain-storm an easy improvement? There was mention of gears and chain-drive. Is that the easiest way to salvage the concept and where should he source the gears and chains? Leave your helpful ideas in the comments section.
Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.
Why not use a friction drive with a rubber wheel instead of a belt or a chain?
cool project but 4 faces would give 64 different combinations. 27 combinations would be the result of 3 different faces.
It is 3 different faces per level: the description in the article is wrong there.
Thanks, fixed.
If the pulleys broke, there’s a friction problem. I couldn’t get the video to play, but it appears that there’s not much of a mechanical advantage in the pulleys (maybe 2:1?) and that there could be a lot of friction between the pumpkin slices as they sag.
How about trying a larger diameter pulley on the rotating tree, and putting some kind of low-friction layer between the pumpkin slices?
I was thinking along the same lines, only I thought you could do an easy friction reduction addition by fixing a laminant between pumpkin layers to reduce adhesion between moist pumpkin layers.
Maybe try some clear lacquer between the layers?
I was thinking along these lines. Reduce adhesion between pumpkin layers with a laminant.
They’re not touching. It seems the PVC-tube-around-wooden-dowel rotating tree has too much friction in itself because there’s no bearings whatsoever.
He’s also using LEGO pulleys with rubber bands in a slot cut in the PVC, which is a sure way to make them break against the serrated edges.
Why not try some worm drive with a gear on each platform ? Of course this implies some modifications to the motors orientation
those look like lego nxt parts possibly. Anyway IMHO this hack requires nema 17’s, a few stepsticks or easy drivers and real pulleys, but hey overkill is always fun isn’t it.
Using a faux pumpkin like funkins might be a good choice. Much lighter than a regular pumpkin and will last for years. You can find them at Michael’s or funkins.com
Hi, Stryker here. I tried the faux pumpkin last year but didn’t cut it straight enough. Also it didn’t seem right not using a real pumpkin. But if I can’t solve the friction problem I might try the faux route again.
Yea I agree fake pumpkin, the real things just weigh to much, and as for cutting it, if the pumpkin in plastic why not just melt instead of cut it, a cheap soldering iron you don’t care about should do a good job, file the rough edges off and Bob’s your pumpkin!
^ this guy has the right idea. also, I would make sure that whatever you decide to use, it should allow for slipping without breaking something if kids are going to be playing with it.
It’s too bad it didn’t work out, because that is a really cool idea.
Thanks for the helpful comments. I did try some different dividers between the slices but they either got too wet or were too thick. I’ll get it working for next year and repost.
I give multiple ‘kudos’ to the project, and project maker.
I thought this was an excellent application of minimal robotic adaptations, to make a very well appreciated (and seasonal) decoration.
Smiles and good cheer on your accomplishment!!!
For others that felt that too ‘stuffy’
Hey, dude! rad candle holder.dataodo@hawaii.rr.com
I think to make it work, all you would need is a lazy Susanne with the servo driving on top of another lazy Susanne. Somewhat like a friction drive driving on top of a friction drive.
Or, you could have a stationary central shaft, use a lazy sussane with a hollow center. The stationary side of the lazy susanne would be attached to the shaft, the other side to a platform allowed to rotate independent of the central shaft. Then each of the platforms would have a servo on it driving against the inner stationary shaft, via gear or timing belt.
If only I had some digital napkins to doodle, it may make sense.
My thoughts too – too much friction will be unhelpful, especially when weighted down with pumpkin.
Also – gear it down, lubricate it, use black marks on the PVC with an optical sensor (or lumps/bumps/rivets and a microswitch) so it stops in the right place each time.
To keep the real pumpkin idea why not try adding wheels to each layer to help with the weight? Similar to this picture.http://www.wired.com/images_blogs/gadgetlab/2010/02/ringpiece.jpg You could print that off with a 3d printer as well. The pulleys would take less effort to move it.
Why not get a plastic pumpkin and do the same thing. Just leave a small gap in between the slices. To hide the light from inside shining through the gaps, just hot glue some cloth (thick enough to not let light through of course) to hang down on the inside of each slice and cover the gap.
As far as turning the pieces, someone hit the nail on the head for me. I would just use a rubber wheel with some kind of spring tension on the rotating slices. You could find all this at the big chain home improvement stores.
Overall, neat idea. I might try my hand at making one next year.