Self Reversing Screw Mechanism, Walking!

"Self Reversing Screw Mechanism, Walking!" utilizes the self reversing screw mechanism from my "Marblevator, Self Reversing Screw Lift" model to create a walking mechanism.

Instead of raising and lowering bucks as in the Marblevator model, two "bogies" are slid forward and rearward along the mechanism tracks. The wheel wells, wheels and axles are design such that when the bogie slides forward, the wheels rotate, and when the bogie slides rearward, the wheels lock. Thus as one bogie rolls forward, the remaining locks in position to allow the mechanism to move forward.

As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.

Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1, and 3D printed in PLA, Tough PLA and TPU on Ultimaker S5s and an Ultimaker 3e.

Soldering iron and solder.

Thick double sided tape.

Thick cyanoacrylate glue.

I acquired the following parts:

• One N20 60RPM gear motor.
• One 3.7VDC 100MA lipo battery with matching JST wired connector.
• One 100mm length of 1.85mm diameter music wire.

I 3D printed the following parts at .15mm layer height, 20% infill, PLA and no supports unless noted otherwise:

• Two "Cap.stl".
• Two "Leg.stl", Tough PLA.
• One "Motor Mount and Traveler Pin Guide.stl".
• One "Screw.stl", .1mm layer height, 20% infill, .25mm nozzle, Tough PLA.
• One "Traveler Pin Guide.stl".
• Two "Traveler.stl", .1mm layer height, 20% infill, Tough PLA, supports.
• One "Wheel Well Left.stl", .15mm layer height, 20% infill, Tough PLA.
• One "Wheel Well Right.stl", .15mm layer height, 20% infill, Tough PLA.
• Four "Wheel.stl", .1mm layer height, 20% infill, TPU.

This is a high precision 3D print and assembly model using at times very small precision parts in very tight spaces. Prior to assembly, test fit and trim, file, sand, polish, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing, sanding and/or polishing may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step.

To assemble the self reversing screw mechanism, I performed the following steps:

• Temporarily adhered one "Traveler.stl" to "Motor Mount and Traveler Pin Guide.stl" using petroleum jelly as shown.
• Positioned "Screw.stl" into the assembly, sliding the axle into the round hole in the top of the assembly, and making certain the traveler was properly positioned in the screw upper turn around.
• Slid the motor into the assembly with the motor shaft fully inserted into the screw.
• Temporarily adhered the remaining "Traveler.stl" to the screw lower turn around using petroleum jelly.
• Pressed "Traveler Pin Guide.stl" onto the assembly.
• Pressed on "Cap.stl" onto the top of the assembly.
• Soldered the JST wired connector to the motor, red to "+", black to "-".
• Pressed the remaining "Cap.stl" onto the motor end of the assembly.

To assemble the bogies, I performed the following steps:

• Cut four 10mm lengths of music wire.
• Glued one "Leg.stl" to "Wheel Well Right.stl".
• Positioned one "Wheel.stl" into the one of the wheel wells and secured into position using one 10mm length music wire, making certain the wheel rotated easily when slid forward, and locked when slid backward.
• Repeated the previous step for the remaining wheel and wheel well.
• Repeated the previous two steps for the left wheel well.

For final assembly, I performed the following steps:

• Snapped the right bogie to the frame over the traveler pin.
• Snapped the left bogie to the opposite frame over the remaining traveler pin.
• Secured the battery to the mechanism using double sided tape.

With assembly complete, I plugged the battery into the motor JST connector, set the model on a somewhat rough surface, and off it walked!

And that is how I 3D printed and assembled "Self Reversing Screw Mechanism, Walking!"

I hope you enjoyed it!