RepRaTS 3D Printable E-Scooter

An electric scooter that can be made entirely from printed parts and off the shelf components without any power tools!

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RepRaTS (Replicable Rapid prototyper Transportation Systems), inspired by the RepRap project, aims to build fully user-upgradable and user-repairable transportation with FDM 3D printing. Modular plastic beams are the core of a RepRaTS vehicle, which allow virtually unlimited adjustability and provide a huge amount of mounting options. RepRaTS require no power tools to build and assemble other than your 3D printer. The RepRaTS scooter was designed and built entirely in a small NYC apartment. Testing is currently ongoing on this prototype.

The Challenge

FDM 3D printing is one of the most affordable and accessible ways to start working with rapid prototyping and 3d design/modeling.  FDM printers can create a huge number of parts with great utility.  FDM printers require little dust collection or ventilation, so they can be used in residential settings, unlike many manufacturing methods.

While the price and quality of printers on the market is steadily improving, there are a number of challenges presented when trying to produce large and/or load bearing parts with FDM printers.  As printers stack layer upon layer of molten plastic, the strength of the adhesion between these layers is usually a weak link in a printed part.  This means that printed parts are strongest in compression, but in shear or tension can be severed along a part’s layer lines.  Furthermore, overhangs can be difficult to print, requiring supports which can be difficult to remove and negatively affect print quality.  Finally, the maximum build volume of a printer (with the exception of “infinite-z”  printers, which present their own unique challenges) caps the largest size a printed part can be.  All of these challenges make it difficult to use FDM to create large load bearing structures.

My Approach

Using electric transportation as a benchmark, the RepRaTS project seeks to expand the types of objects that can be considered “printable”.  Tensioned threaded rods connecting a series of printed plastic spacers create the structure of the RepRaTS scooter prototype.  This accomplishes two things: first, the tension in the threaded rods gives the scooter its strength and rigidity, and second, the rods force the printed parts into compression to compensate for weakness between layer lines.

The spacers used in the RepRaTS scooter have mounting holes that are printed perpendicularly to the body of the spacer and glued in after printing.  This allows high tension fastening both longitudinally along the beams and laterally across them.  As a result, it is relatively easy to mount components to the printed frame in any direction or orientation.  This is demonstrated by the scooter prototype, which has to accommodate many parts with arbitrary sizes and mounting patterns/orientations.  The battery, motor controller, throttle, brake, hub motors, and handlebar all need to be mounted to the plastic frame and accommodate large loads often in multiple directions.

The second prototype uses very large (13” tire) hub motors to demonstrate an upper limit of the design. If a scooter can be designed to use such large and powerful (1000W) motors, then a designer can comfortably build a smaller vehicle.

The third prototype is designed to be practical for daily use, therefore the motor size has been reduced to 350W 8" hub motors.  This greatly reduces the overall weight of the scooter and allows for much simpler packaging of the electronics.

The goal of the RepRaTS prototype is to serve as a demonstration of what types of structures can be produced with FDM rather than as an end goal.  Using the same technique, one can make other vehicles, furniture, storage, or many other modular load bearing structures.

I am continuing to design and iterate on the RepRaTS scooter and have a number of improvements in the pipeline, namely splash and impact resistant housing for the battery and electronics, a stiffer and stronger headset connection, end caps for the threaded rods, and an integrated lighting system.

McMaster-Carr parts in the OnShape assembly must be used in accordance with their terms and conditions, available here:

Quick demonstration video:

  • Acknowledgement

    James Dietz10/27/2021 at 11:33 0 comments

    Through the Hackaday Mentor Session I, was fortunate enough to be able to speak with Kliment Yanev about RepRaTS.  He gave me some really great ideas on how to improve and iterate on the RepRaTS concept.  Many of those ideas were incorporated in the current version of the scooter, and some I am working to include on future updates.  Thank you for all of your help, Kliment.

  • Future Work

    James Dietz10/27/2021 at 11:19 0 comments

    There are a number of improvements to the scooter that I would still like to make. Most importantly, the steering axis needs to be stiffened. I want to move from the current three bolt design to a larger single bolt with more effective interlocking features. Second, cable management needs to be addressed. I want to build channels into the body and forks to allow for simple and tidy cable management. I also would like to integrate the scooter battery into the deck. This would improve the handling of the scooter and reduce the overall footprint. 

  • New Scooter Update

    James Dietz10/27/2021 at 11:18 0 comments

    I have now built a third iteration of the 3d printable e-scooter.  My main goals for this design were to: improve torsional rigidity in the printed beams, decrease overall weight, improve on the percentage of printed parts, and improve safety. To improve rigidity, I moved from a “flat bar” beam with two threaded rods as reinforcement to a “hollow triangular” beam with three rods. I also added registration features so the individual spacers that stack together to create the scooter’s beams interlock, stopping the spacers from sliding against each other and improving rigidity.  The hub motors have been reduced in size and power to two 350W 8” airless hub motors. The smaller wheel size allows for smaller forks and the reduced power allows for smaller controllers and battery, contributing to an overall reduction in size and weight.  The total weight of the scooter is now approximately 40 lbs and the top speed is around 17mph.  The battery is a 13Ah 48V removable e-bike battery.

View all 3 project logs

  • 1

    There are some safety issues with the current iteration of the RepRaTS scooter.  There are a number of exposed threaded rods which present a hazard, especially on a motorized vehicle.  The lack of steering rigidity can make the scooter difficult to handle at times, and the exposed wiring presents some safety concerns.  I am in the process of fixing these issues.

  • 2
    Accessing CAD files and printing/assembly instructions

    All of the cad files for the scooter are available in the linked OnShape assembly.  All of the prints were printed in PETG with a 0.8mm nozzle at 0.4mm layer height with a 30% grid infill.  No parts require supports.  If you need supports, check your print orientation.  The parts labelled "plug" are meant to be glued in place.  To do this, first align the plug and spacer against a reasonably flat surface, and then glue with a wicking superglue.  I like to use Loctite 408 because it dries clear, but any superglue should work fine.  Also, the part labeled "steerer_tube" is meant to be superglued to the forks using the same procedure described above, to improve rigidity.  The motor controllers are placed in the housing and then zip-tied using the empty mounting holes on the scooter's neck above and below the controllers.

  • 3
    Proper Bolt Tension

    The key to this build is using tension in the threaded rods to give the beams strength and to keep the printed parts in compression.  The printed parts should not deform up to the max recommended torque for 3/8" low strength threaded rod, so do not be afraid to tighten aggressively.  Make sure to evenly and slowly build up to the max torque to avoid warping the beams as you are tightening.  If you find warping the frame to be an issue, simply back the nut out until the warping goes away and try again to tighten evenly.

    The steering spacer height may need to be tuned to allow adequate tension in the three threaded rods without seizing the steering bearings. Ideally the bearings rotate freely with minimal slop when the threaded rods are fully tightened. 

View all 3 instructions

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