Roto-Caster First Attempt


Well, as you all know, the big hold up on the backpack and cannon is the building of a rotocaster large enough to get the job done. Suffice to say the mold is approximately 24" sq x 12' H weighing in at a hefty 50 lbs! Since engineering is not my strongest skill set, I tapped into a bunch of people in that area, including a guy from work who convinced my that a pair of 50-inch lbs lift @ 4 rpm AC gear motors would work ( 1 for each axle ). These two motors were the key to making this an easy job, no special gearing/ no mathematical equations to work out pulley ratios, etc. etc.

Guess again. For not being an electrician, I got the who thing wired correctly (thanks Jerome!) and at long last plugged it in today and wa-la..........NAFT! The cooling fans spun on the motors, but that's about it. The motor driving the inner frame spun about 6" and stopped. The outer motor just sat there. I checked all the mechanical and electrical connections, nothing. The motors apparently didn't have enough power to turn the weight of the 2" x 3" frames, never mind adding the weight of the mold.

So, it's back to the drawing board. I'm thinking a single high torque motor, which means the pain in the ass trial and error of figuring out what size pulleys vs. what rpm AC motor I need to get. I can get the inner frame to spin with a different set up, one that uses two nylon gears that engage each other at a 90 degree angle. Then of course, I need a belt, and.......I can already feel my brain aching and my eyes rolling back into my head.

If there's anyone out there that can assist me with this, your help will mean more to me and half the people on this board than you know. Please contact me with a pm and I'll bring you up to speed. Meanwhile Jerome's reviewing a set of plans I found on the internet which can work..........AHHHHHHHHH!!!!!






Rotocaster Schems.jpg
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My brain is hurting just thinking of the motor nightmare your about to embark on.. I rotocast most of my props by hand. My suggestion, is ditch the motor all together and manually rotate the frames. With a several thin coats of resin, like Smooth Cast 65d, you will be able get an nice even overall coverage. I use several thin coats to ensure that I don't get a thick glob in any spots. Once the resin starts to set and change color start mixing the second coat and pour it in. Rinse and repeat until the desired thickness is achieved. The key is to get the resin coating while the previous one is setting or else the layers won't bond together and peel apart.

I know it's not a solution to the mechanical problems but I hope the info at least helps in some way.

Awesome work Carl!


Thanks for the input. The plan is to use the 65D, and may come to using a manual hand crank. But, once you've used a motorized roto-caster as I have, it's pretty darn convenient. Especially if you set it up with a timer knob, you can walk away and get some other things done, which is big deal, when free time is at a premium in my case.

Ya know, I've have to's posts like these that exemplify how necessity being the mother of invention is what transforms us artists into something more, part time engineers, part time electricians, you name it. Sure, these other disciplines are hard, but once done, my goal is to turn this nightmare into an easy to follow tutorial on how to build one, that anyone can do. This place can unlock the hidden talent in all of us, it's why it's so awesome, folks.

And don't worry-----the backpacks and cannons are coming! I WILL find a solution to this. Can I hear an amen brothers and sisters? :rolleyes:


Amen Brother! The wealth of creativity, knowledge and willingness to help, is what makes the lair such special place. "Artist" in my opinion is a blanket term for a Engineer/electrician/plumber/carpenter/designer . A little bit of everything is needed to make ours and others dreams a reality.

Can't wait for the tutorial on how to make one of these motorized casters. I love the workout I'm getting right now but like you said the time is more valuable.

Good luck Carl! Can't wait to see her rotating a mold!


Ill put up some pics of mine when I get to my computer- I dont have the motor installed as of yet-- you have to have a high torque low RPM motor to run these things. I have burned up a drill, a power window motor for a car and other motors dont seem to power it right or spin it so freaking fast that it looks like an amusement park ride that has gone haywire.
I am considering a winch motor as it has high torque but runs pretty slow. Im sure I will have to screw with the pulleys to get the ratio right, but not an issue as its pretty easy to change the size with the way i did it.

Most of the time I dont need to worry about a motor as I installed a hand crank on it and the resin I use sets in a couple of minutes so its not an issue. Most of the time I use the rotocast resin (Smooth Cast 65) .I do have some resins that take a lot longer and I want a motor for those so I can put them in and just let it run, but not at this point. Ill get it dialed in soon.


That is the cleanest place I have ever seen. Where is the white snow of cabosil. The pungent odor of parts A and B Resin and Foam. The crusted mixing Bowls.

Where Where Damn You!!!!!!!!!!!

Cary :p

Guan Thwei

Elite Hunter
Confused how?????  Its a rotocast machine
Oh I know I was confused if you were showing Carl your attempts with the same technique to try to help or a project you were working on and showing everyone. That is all just getting clarification.


Carl and I have been discussing the construction techniques, etc. Just wanted to show him mine-- he has had a few problems.