Trammel of Archimedes - 4 Pass

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Introduction: Trammel of Archimedes - 4 Pass

About: I like to design and build random things.

I've always been fascinated by the trammel of Archimedes. This version consists of a base with four slots intersecting at the middle of the circle. Four sliders are confined within the slots and are attached to a handle by pivots (screws) at fixed positions along the handle. The mechanism can be used for drawing a perfect ellipse. This is done by positioning a writing utensil at the end of the handle while making a full revolution. For more information/history, see here.

With that said, it is often sold in novelty shops with interesting names like Bullsh*t Grinder, Bullsh*t Masher or Do-Nothing Machine. Once you have it in your hand, you will notice that it turns into a nice fidget toy and a definite time waster :).

This is actually my third iteration of the the trammel. The first one (two pass) was built from wood. As part of the same instructable, I included a 3D print. I then took it up a notch and made 3 pass version. This one was beyond my woodworking skills so I took the 3D print route. The one shown in this instructable is my most advanced yet at four passes. With each build, I've taken lessons learned and made improvements. For this build, it actually took me 3 prints to get all the bugs worked out.

As an added feature, I was able to convince my son to animate the CAD files in Blender. Besides showing how it works, I feel the results are pretty mesmerizing.

The actual part in motion is shown here:

Supplies

Tools:

  • 3D Printer

Materials:

  • Filament: PLA used - 3 colors
  • Sand paper (optional)

Step 1: Base

The base is 100 mm in diameter and 20 mm tall. The 4 passes on the trammel are centered equally spaced around the circle. For the paths, I chose a dovetail groove. This groove was based off a lesson learned on my initial 2 pass print (T-Slot) where I had to remove the supporting structure above the slot. I added rounds to the center edges which help keep the slides on track if they enter to the middle section at an angle. The pockets around the perimeter are mostly cosmetic even though they do add a nice place to grab the trammel from underneath as you are spinning it.

Step 2: Slide

The slides were designed to match the grooves in the base with a 0.5 mm of clearance. I added chamfers and rounds on the slides to allow for cleaner movement. For each slide piece, the hole is centered on the top and is sized for a small wood screw.

Step 3: Handle

Being sort of lazy, I used the CAD tool to work out the dimensions for the pivot points. For the overall length, I just wanted something to clear the base while spinning. The hole in the end is for your finger.

Step 4: Parts

These are the three colors I had on hand. I suggest using contrasting colors if you print your own. Besides the print, you will need four screws. I used eye hooks to in lieu of screws to allow for quick adjustment. I also added flat washers but they aren't really needed.

Step 5: Assembly

The build is pretty straight forward. Place the sliders in the base. Line up the holes and attach the handle with the screws.

Step 6: Pictures

A few inside pictures. Banana for size reference.

Step 7: More Pictures

Here are the final pictures. It has been passed around the house quite a bit and will be a desk toy at the office once the Covid19 pandemic is over.

Step 8: STL Files

All files are included to build your own. You will need to purchase screws or hooks. Note that I can provide STP files if anyone would like to modify the design.

Thanks for viewing!

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    15 Comments

    0
    bvermeulen
    bvermeulen

    1 year ago on Step 8

    This is a really cool 3D printed example for my classroom.
    What are the Round and Chamfer Sizes on the slide?
    Also the STL files are not exported in mm just thought you should know.

    0
    mtairymd
    mtairymd

    Reply 1 year ago

    Thanks. The rounds on the sliders are 2.5 mm. Everything was modeled in mm. I know I had to scale the parts up or down by a factor of 10 in Cura. If that doesn't work, convert from inches to mm. Use the 100 mm base diameter for a reference.

    0
    bruce.desertrat
    bruce.desertrat

    1 year ago

    Neat! Love the 'banana for scale' :-)

    0
    DavidR885
    DavidR885

    Reply 1 year ago

    Yeah, but how big is the banana. Maybe it is a really big banana, like at Coffs Harbour. There needs to be something to scale the banana......like a ruler.

    0
    DavidR885
    DavidR885

    Reply 1 year ago

    Just WOW!

    0
    mtairymd
    mtairymd

    Reply 1 year ago

    So true!

    banana.jpgBanana_Size.jpg
    0
    mtairymd
    mtairymd

    Reply 1 year ago

    I once posted something on imgur and someone asked about the size. The next thing I know, 50 people responded with banana. I had no clue about the reference. One google search later - here you go.

    https://knowyourmeme.com/memes/banana-for-scale

    0
    mbovaan
    mbovaan

    1 year ago

    Neat Cant wait to try make it once lockdown is over and I can get to my workshop. Was it a big or small banana ;-)

    0
    mtairymd
    mtairymd

    Reply 1 year ago

    Normal size banana :)

    0
    TheFireMan
    TheFireMan

    1 year ago

    Fascinating piece of kit.
    I am teaching myself to use 3D printers.
    I purchased an "open-box" Creality CR10 which needed some minor parts replaced,
    and a non-working MonoPrice Mini Delta that (luckily for me) just needed proper re-assembly.

    I would find the STP files very useful.

    Thank you.

    0
    mtairymd
    mtairymd

    Reply 1 year ago

    Thank you. Don't worry - 3D printing is pretty straight forward once you get the bugs worked out. I have a low end machine that works fine. PM me when you are ready for the STP files and I will email them to you. I would have uploaded them to instructables but that feature is currently down.

    0
    KarimS30
    KarimS30

    1 year ago

    Hi, great work on this one! Well documented / videographed and explained. That blender video is mesmerizing... This looks like a great lockdown project. If the slides were magnets, and the trammel tracks were wire wrapped tubes (shaped for the slides, of course) then this possibly could generate enough electricity to light up some LEDs one could embed in the pockets... but I guess it wouldn't be the Bull**** Masher then... Great work!

    0
    mtairymd
    mtairymd

    Reply 1 year ago

    Thanks! Generating electricity sounds too complicated for my simple mind :).