# Take and Make: Trammel Kit

12-28 Update.  We continue to iterate on the Trammel Project.  Dr. Sereveny’s students at Riverbend Community Math Center have updated the files with a larger hole for the pencil/pen and they are working on an adjustable arm so we can make multiple shapes (of Ellipses).

And they sent Links to the Hardware screws and filament:
Hardware:
We use a Prusa 3D printer.  The pink, blue, and black filaments are really nice — they are SpiderMaker 3D Matte PLA Filament.  I like that kind better than the official Prusa filaments because of the soft and smooth texture as opposed to the brittle and crystalline texture of the other kind.  Here is a link:

The latest STL files are here.

There may be adjustments to the scale needed.

New Trammel Files for 3d Printing!

Thank you to Dr. Amanda Sereveny and students at Riverbend Community Math Center who made files to make this in 3d print version and made us a quantity to use and distribute.

There are three parts — be sure to make two of the “inserts” if you print your own or order.  Files here.          Use Chicago Screws (M4 x 8mm.)

Take a look at this video to see it work. IMG_0237

We can relate the geometry of the trammel to the usual formula for an ellipse (see images below or click to the doc)

This formula progression is from MatematicaVisuales.           Our version in a google doc you can copy is here.

This Trammel is not adjustable, but you can make one on paper and try various combinations of axis length.

Specifics on 3d printing:

1. My students have been using the .stl file that I sent you at first.  We open each of the three files in the slicer for the 3D printer.  We have Prusa printers, and so we use the Prusa slicer.  When we open the file in our slicer, it asks whether you want to use the default units which are inches, and then click yes.
2. For the slicer, we choose the following options:  No supports.  Infill set to 15%.  Prusa PLA filament.  .20 mm quality.  We usually arrange the base, two of the inserts, and the arrow in a group close to each other so that they can be printed all at once.  Then we click Slice Now and save the GCode to the SD card.
3. When printing, our students have been using a temperature of 205 for the nozzle and 70 for the bed to avoid burning the models.
4. It is often necessary to use a screwdriver or other pointy tool to remove loose filaments from the inside of the track and from the holes in the pieces.  It can help to slide the inserts back and forth in the tracks to remove some of the stray pieces.  It can help to use the screws to help clean out the holes in the inserts.
5. Use one Chicago screw to attach one of the inserts to the last hole of the arrow.  You need to press gently on the arrow to get it to pop down into the screw base.
6. Next, we put the base of the other Chicago screw up through the bottom of the other insert and slide it in one side of the track.  The insert with the attached arrow slides into the perpendicular track.  Finally, we pop the arrow gently down onto the base of the other Chicago screw so that it comes through the second hole in the arrow.  Finally, we use a screwdriver to secure both screws, pressing firmly.

Original Wood design.

These are really fun!  This design could possibly be improved but it does work pretty well.

The newest version  files are here in AI, SVG and Corel formats.  It’s a pretty simple design.

Here are the parts.  Basically a larger square overhangs the smaller creating a channel with partial cover that the little “cars” can slide in, but not pop out.  Also there’s one more little square piece that goes on top of the little cars like a gasket to give the handle some space off the top so there’s less friction and catching.  That’s in the schematic, but not in the photo at the right.

Careful glueing and paraffin wax give good results, but there are multiple ways to get  problems.  This one is working smoothly and you can use the hole in the handle to draw an ellipse.  This is an early video, and the ellipse below came out even better with a better hole for the pen.

Update.  Riverbend Community Math Center is making their own version of the Trammel and also some other models!  We are so excited to have these students working on their own versions and ideas including this 3d printed Trammel.  Pythagorean puzzles are on the way.