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Just completed my Rotocasting machine!!

 
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Stomper
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Joined: 01 Oct 2005
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Location: Woodburn, Oregon USA

PostPosted: Sun Feb 21, 2010 8:03 pm    Post subject: Just completed my Rotocasting machine!! Reply with quote

Heya Folks,

Last SundayI got a wild hair and started on a rotocasting machine. I basically just built the thing from the ideas I got off of Youtube, with the premise of a 2'x2' inner frame and built the thing outwards from there with no set dimensions. I plugged away on it a few hours every night after work, and now have it operational one week later in "manual mode". I bought a motor for it, but it didn't have enough grunt to turn it... should have gone bigger than a 1/4-HP!! I'm thinking I'll go with a DC motor, chain drive, and a variable speed controller for a finer rotational speed control when I recoup my expenses.

Anyway here's the embedded link, click on the picture and check it out!




If that doesn't work, click on this link and it'll take you to my photobucket page so you can watch it there: http://s29.photobucket.com/albums/c291/TK4063/Videos/?action=view&current=RotocastDemo.flv
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coffeehedake
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PostPosted: Sun Feb 21, 2010 8:17 pm    Post subject: Rotocasting Machine Reply with quote

Excellent work!
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clonesix
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PostPosted: Sun Feb 21, 2010 10:00 pm    Post subject: Reply with quote

Nice work. Let us know how the new motor works for you. I am building one of these myself.
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jdougn
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PostPosted: Mon Feb 22, 2010 9:40 am    Post subject: Change to RPMs Reply with quote

Nice looking rotational caster. The motor you've got may be big enough. It needs some way to decrease the overall RPM.

What are the calculations on the RPM of the rotational caster with the current motor & pulley setup in the video? How fast does the rotational caster need to turn?

If I'm looking at the setup correctly, the rotational caster would be spinning at a crazy fast speed. It looks like a straight pulley set up with both pulleys being similar in size and the motor is probably turning at 1725+rpm.

Regardless, nice looking caster. What do intend to make with it now?

DougN
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Stomper
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PostPosted: Mon Feb 22, 2010 10:08 pm    Post subject: Reply with quote

Thanks for all the input! I plan to make copies of a Mandolorian helmet I have been working on over the last (almost) two years.


As for the existing setup, what you don't see is the wiring and motor speed controller I stripped off of it, so NO... it wouldn't be going crazy-fast! Laughing The drive pulley is an adjustable sheave opened up as far as it will go before the belt rides on the axle part of it, with a diameter of about 1.5"-2" (can't get much smaller than that!)... the other pulley is a fixed groove and is approx 7"dia. Even with the motor on "full speed" and giving it a helping hand, it still doesn't have enough grunt to overcome the needed torque to rotate the thing. I figure that if I go with a 1-hp DC motor coupled with an A/C input-D/C ouput motor speed controller I'll be good to go, plus I'll get finer speed control that way... buy alas, its more money to invest!!
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jdougn
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PostPosted: Tue Feb 23, 2010 9:09 am    Post subject: Reply with quote

Obviously, I don't know what your exact setup is with the motor and pulleys. But here's a theory of what's happening with the motor right now. At full power the motor is probably trying to turn the rotational caster at hundreds of RPMs.

At "full speed" what is the rated rpm of the motor? Is it the standard 1725 RPM at full speed or less? Also, I suspect that as the speed of the motor is lowered the horse power of the motor decreases accordingly.

Here's what I think the math might be:
2" pulley on the motor at 1725rpm = 3450
3450 / 7" pulley on caster = 492 rpm

Here's an online pulley/rpm calculator that helps with the math:
http://www.temecularodrun.com/ref/rpm_calc.asp
You can enter any 3 values and it will calculate for the fourth.

To reverse this formula, if a rotational caster were set up like the Stelter Rotational Caster that CloneSix posted it would rotate at 1rpm to 36 rpm. In your setup, the motor RPM would have to be from something like 4 rpm to maybe 126 rpm. That would be difficult for most motors to handle for very long.

hth, DougN
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jegner
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PostPosted: Tue Feb 23, 2010 11:39 am    Post subject: Reply with quote

Hey Tony!

Cool! That sure looks the business! you might try a really big pully on one end to see if the motor will turn it. Does not look like a lot of force to hand-crank it.

I have a couple of questions though. How will you hold your mold on the inner frame? What sort of resin do you plan to use? Slower setting stuff than 'normal'? How do you 'cap' off your molds so that the resin won't slosh out?

This is really neat, something I should do too!

Thanks for sharing!

Jim
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stormtrooperguy
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PostPosted: Tue Feb 23, 2010 3:56 pm    Post subject: Reply with quote

nice! you know, i never thought about it, but a manual rotocaster wouldn't be all that bad...

i'm thinking in terms of using it in the basement part of my shop rather than the garage... i try to keep noise to a minimum in there, but turning a hand crank would be easier than slushing, and probably would look better too!

hrm, something to think about there.

any choice youtube clips that inspired you?
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Stomper
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PostPosted: Sun Feb 28, 2010 5:19 pm    Post subject: Reply with quote

jegner wrote:
Hey Tony!

Cool! That sure looks the business! you might try a really big pully on one end to see if the motor will turn it. Does not look like a lot of force to hand-crank it.

I have a couple of questions though. How will you hold your mold on the inner frame? What sort of resin do you plan to use? Slower setting stuff than 'normal'? How do you 'cap' off your molds so that the resin won't slosh out?

This is really neat, something I should do too!

Thanks for sharing!

Jim



I have since installed a 26" bicycle wheel in place of the larger pulley (I know its ghetto, but it works and looks half-way OK... LOL), the motor will now turn it WITH EASE! The only problem is that to reduce the RPMs to a usable rate, the motor gets overheated and cuts out on thermal overload... so a DC motor and controller will be the order of the day I rekon...

As to how to mount the mold in the frame work this is how I do it (for now), it seems to work quite well.




To "cap" the mold, I traced out the opening profile on a piece of plywood, made a "fence" around it by wrapping duct tape around the edge, and poured silicon into it while setting on a level floor. The silicon is bonded to the plywood quite nicely, and I just cinch it down with a "ratchety strap" after the batter goes in:




I'm thinking I'll use TASK-15 from Smooth-On, I'm still researching on resin, may even go with epoxy or polyester (fiberglass) resin... dunno yet.

Here's the very first helmet I made last night using some left over polyester resin... not the greatest results (I suspect the resin "snaps" to fast and ruins the finished texture), but I could work this helmet into a usable article if I wanted to...






Here's the VERY FIRST copy I attempted from this mold hand laying all the resin and fiberglass matting... it was just... awfull... LOL!!!





Here's some photos of the mother mold and inner jacket:






stormtrooperguy wrote:
any choice youtube clips that inspired you?



Here's a few to look at, I loosely based mine on the yellow rig in the first two links, but elected to make my frame work from wood for speed of construction and costs...

http://www.youtube.com/watch?v=ofzg_Hjukzg

http://www.youtube.com/watch?v=ArnzK6d6ugk&feature=related

http://www.youtube.com/watch?v=uTzvMg2cel0&feature=related

http://www.youtube.com/watch?v=2JhLoYk3HGY&feature=related
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jegner
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PostPosted: Sun Feb 28, 2010 6:00 pm    Post subject: Reply with quote

Very cool!

Thanks Tony, for sharing. Now, I gotta try one!

LOL!

Jim
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CHRISTOPHERSIM



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PostPosted: Thu Jun 03, 2010 5:41 pm    Post subject: rotoational casting Reply with quote

i hastily built a roto-caster a while ago in college but haven't tested it out because i was waiting until resources became available to buy a motor and variable speed control (still haven't). I'm wondering if anyone can comment on the uniformity of the cast's wall. I'm hoping to cast platsil gel 10 silicone rubber from polytek (extremely viscous) and uniformity is a must because the product is an exterior shell going over a plastic housing. Any insght or observations would be appreciated thanks? also would a stepper motor work for slower curing plastics?
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CJanssen
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PostPosted: Thu Jun 03, 2010 6:37 pm    Post subject: Reply with quote

Man I miss some great threads.....NICE work Tony. I agree with Jim, I need to make one of these myself.
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TK 109
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PostPosted: Mon Jun 07, 2010 9:28 am    Post subject: Reply with quote

Yeah, Tony. This is REALLY cool stuff! Wink Cool
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stormtrooperguy
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PostPosted: Mon Jun 07, 2010 9:13 pm    Post subject: Reply with quote

well, i just bought a FCAW welder last night, so i guess i'm ready to start on my rotocaster! Smile
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PARATECH1
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PostPosted: Thu Oct 27, 2011 8:06 pm    Post subject: Reply with quote

Your machine looks really cool. Your mother mold looks really nice and clean.
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