Rotocasting Machine - Has Anyone Made One?

Discussion in 'Replica Props' started by RacerX45, Jun 20, 2006.

  1. RacerX45

    RacerX45 Well-Known Member

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    Does anyone know where I might finds plans and/or pictures I can use to make a simple rotocasting machine? Thanks.

    Randy
     
  2. Jimbo890

    Jimbo890 Well-Known Member

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    I once saw the innards of one of those vintage roto-cast vending machines they use to have at amusement parks and zoos, back in the 1970's. Anyways, the molds were held in a multi-axis chamber that reminded me a lot of a 2 axis globe stand. In fact, a large one would be perfect for a rotocast for small parts.
     
  3. RacerX45

    RacerX45 Well-Known Member

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    I've come up with a simple design for the machine (I need one that's big enough to accomodate helmet sized molds). What I'm struggling with is how do I get power to the motor on the inner frame without the wires wrapping up as it spins.

    Randy
     
  4. moffeaton

    moffeaton Master Member RPF PREMIUM MEMBER

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    I saw where someone converted an old centrifuge into one - it's a scary looking thing.
     
  5. WookieeGunner

    WookieeGunner Well-Known Member

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    <div class='quotetop'>(RacerX45 @ Jun 21 2006, 01:06 PM) [snapback]1265231[/snapback]</div>

    Couldn't you make the rotation joint of the outer ring hollow and then run it through there?
     
  6. RacerX45

    RacerX45 Well-Known Member

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    <div class='quotetop'>(WookieGunner @ Jun 21 2006, 02:23 PM) [snapback]1265241[/snapback]</div>

    Couldn't you make the rotation joint of the outer ring hollow and then run it through there?
    [/b][/quote]

    I thought about that but when you attach the wires to the motor on the frame the wire will need to be able to rotate. Once the frame starts rotating, that will cause the wire to spin and wrap around itself since it will be attached to a non-spinning plug on the other end.

    Randy
     
  7. 1138

    1138 Well-Known Member

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    I've always wanted to build one of these too but never got to it. I researched designs and remember seeing a pic of a table-top rotocaster in my local casting supplies shop. The desktop version IIRC relied on a weighted platform and gravity to turn the secondary axis. I can't remember how that thing worked, but it did.

    Obviously all the commercial machines have both axes motorized. These are the sites I used for research.

    http://www.plastermaster.com/rotation/mannetron/index.htm

    http://www.bentleychemicals.co.uk/rotacast-brochure.pdf

    http://mannetron.com/2x2.htm

    It might be worth contacting one of them to see how the secondary motor is wired. The only logical way to do it is for the wire to run through a hollow-tube frame and both the axles being hollow as well, being driven by geared or belted drivetrain versus the motor shaft directly driving the axles.

    Would love to see it if you discover a workable design :thumbsup

    Dan
     
  8. moffeaton

    moffeaton Master Member RPF PREMIUM MEMBER

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  9. RacerX45

    RacerX45 Well-Known Member

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    JACKPOT... Searching on slip ring led me to this sight:

    http://www.mercotac.com/

    They make a rotating electrical connector that should do the trick (costs about $60). Thanks.

    Randy
     
  10. clonesix

    clonesix Sr Member

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    Any helmet sized mold is small enough to rotate by hand, provided that the material kicks off fast enough. Your shoulders would give out if the material took 30 minutes to kick. I cast helmets by hand with resin that kicks in 3 minutes.

    I have been sitting here drawing this up,

    [​IMG]




    I think everyone can picture the two concentric frames that pivot on the X and Y axis. Let me say that the frames need to be strong enough to carry the weight of the mold + material. (up to 50 lbs) So they should be steel or aluminum box tubing. Anyone who is adventurous might try 2" plumbing. All the 90 deg angles and Ts are Off-the Shelf. If someone wants to try this, post pics.

    Does this need to be motorized? No, not if we are going to keep it simple.

    Starting with the outer frame that rotates about the X axis, the frame is supported at both ends by its axle rods that are supported by bearings supported by vertical supports*. connect one axle to a hand crank, and you have rotation on the X axis.

    The inner frame rotates on the Y axis. It also is supported at each end by axles that pass though bearings in the outer frame. One axle that passes through the outer frame is connected to a pulley wheel. (Size of pulley will determine the rotational speed of the inner frame with respect to the outer frame)

    What is that pulley connected to that spins the inner frame? (There is more than one answer to this)
    Answer: At the outside of the outer frame is a second bearing and shaft. On the shaft is another pulley, (in line with the first) and a wheel that rides on the vertical support*.

    As the handle is cranked, the outer frame rotates and the wheel riding on the vertical support turns, which causes the inner frame to rotate.

    *the vertical support mentioned above needs to be large enough to allow the wheel to make a complete revolution. It could be a piece of plywood, but it should be strong enough to support the frames and not lose contact with the drive wheel.

    I picture a wheel similar to a Razor Scooter wheel, but any type of rubber wheel work.

    Does that read well? I can't tell.
     
  11. RacerX45

    RacerX45 Well-Known Member

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    I totally agree that I could do this by hand or without the need for motors. This is definitely a want, not a need. I've wanted to try to build one of these for awhile and am just now getting started on it. Since I haven't welded anything in almost 20 years, I'm going to make the frame out of 2x4's. My molds are fairly light since they have fiberglass jackets so I hope this will work.

    Randy
     
  12. RacerX45

    RacerX45 Well-Known Member

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    Now that I found the part to allow me to use two motors, what size motors should I use? The professionally built machines use a 1/2HP DC, variable speed motor. The ones I have found so far are pretty expensive and rather large. Any suggestions? My design is pretty similar to the one clonesix drew up except with 2 motors instead of the pulleys and hand crank. The smaller the size of the motor the better. Thanks.

    Randy
     
  13. Anakin Starkiller

    Anakin Starkiller Master Member RPF PREMIUM MEMBER

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  14. 00MrNotWrong00

    00MrNotWrong00 Sr Member

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    3 foot by 3 foot. she's a big one. I plan on making some big molds soon and I'm going to want to rotocast my new phasers. So her she is I hope to have her finished with in the next two weeks.
    [​IMG]
    I've been watching videos of the home made rotocasters people have made on Youtube and it's killing me how many people have used the same gear on the main shaft as on the secondary shaft. You can watch the same side of the inner frame point up on each rotation. That's bad. I think I read somewhere that the ratio is supposed to be 15 to 1 but I don't remember, one thing is for sure you don't want it to be in the same position after each rotation of the main frame.
     
  15. franz bolo

    franz bolo Sr Member

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  16. Dimclay

    Dimclay Member

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