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Where can I find an .stl file to plug a printed part onto a Parallax CR Servo? — Parallax Forums

Where can I find an .stl file to plug a printed part onto a Parallax CR Servo?

Is the servo head connector universal? I am wanting to make a paddlewheel to put on a boat.


  • What servo are you going to use? I have a spline print for that. It shouldn't be to hard to design one.

    How big do you need it to be?

    Do you want it to look like this one: Paddle Wheel

  • The CR Servo and 360 Servos have a standard Futaba spline profile.

    A Google search for "Futaba spline .stl" brings up a lot of hits.
  • AwesomeCronkAwesomeCronk Posts: 1,046
    edited 2019-04-25 22:23
    Thanks! I think I may have found sort of what I want. It will take some tweaking, though.

    I need to get onto my computer and check how deep the hull rides in the water. Can I have a look at your spline print?

    EDIT: After getting the document loaded, I have found that I need a 80mm diameter paddlewheel. I also need a shaft extruding from the center on one side, 12mm long, 6-8mm diameter. If I can just get ahold of the portion connecting to the servo head, I can take care of the rest in FreeCAD.
  • AwesomeCronkAwesomeCronk Posts: 1,046
    edited 2019-04-26 00:22
    Wait, @iseries I think I may have found your file. Is this it?

    In any case, I have decided to use this one.
  • So AC what are you building? Is this an automated stern wheeler? Or something else entirely?
  • Hehe, twin hull, 53cm length boat. BOEBot style steering with a paddlewheel on either side. Will post design images later today
  • AwesomeCronkAwesomeCronk Posts: 1,046
    edited 2019-04-29 15:25
    Got it! Here is the CAD image of the boat without wheels. 21 inch length, 7 inch width. Hull is 1.4 inches, bottom to deck, and the computer casing is 1.9 inch tall. Has an antenna, which I don't plan to print, but there is a hole in the top to poke an antenna wire out there. Made sure to have enough room to stack a few PCBs, optimized to put an XBee in there.

    EDIT: Added a picture of the paddlewheel, which has a 5 inch diameter.
    518 x 452 - 20K
    352 x 340 - 23K
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 22,999
    edited 2019-04-29 16:39
    Very cool! This is very similar to a project I had my robotics students design and build a few years back. They ultimately raced their "paddlemarans" in the local harbor. Much fun!

    Here's a video of my initial prototype:


    A couple suggestions: we found that the fewer paddles the paddlewheel had, the better. Most students made theirs with three or four. (You can see how slow mine went at full speed in the video. I think the paddles interfered with each other, creating drag due to cavitation.) Also, adding a tail fin helped to stabilize the craft and made it easier to steer.

    Since the race was held in saltwater, the servos, the receiver, and the battery were sealed in a watertight box with glands on either side for the paddlewheel shafts. This also allowed for reduction gearing inside the box. If you're running it in freshwater, this might not be such a big factor, but be prepared for everything to get wet!

    Be sure to post a video of your craft in the water.

    Have fun, and good luck!
  • Thanks for sharing your project! I was planning for 16 paddle blades, and I had not thought of a tail fin. Incidentally, I am using the s-60 Katamaran example hull from FreeCAD. My paddles are 4.5mm wide, so they should gather plenty of power. I’ll likely print wheels with 16 and 4 paddle blades. My wheels are mounted almost directly to the servos, so I don’t know how to seal them.
  • For the ones that do enjoy a good reading about "Propellers" and are also a bit addicted to mechanics, there is enough food for thought available at:

    After choosing your preferred download format and grabbing a copy, go to page 638: "The Design of Miscellaneous Propulsion Devices"

    Hope it helps a bit.

  • Well, 24 hours into printing the front half of the hull. I am thinking that I will need to replace the filament roll here in about three hours
  • Went a little ways longer than three hours, walked into the room about 6 hours afterwards, found the print complete! Dropped $20 on filament because this roll had about 12 inches left on it!😬

    Here is the finished fore hull.
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