Custom 3D Printed Parts for the DonkeyCar

A 3D printed part for mounting a battery and Nvidia Nano on the Exceed Magnet RC car chassis.

Yesterday I spent a day with a friend that had a new 3D printer. Although he only had the printer for a few weeks, he has spent many hours learning how to use it. Despite the low-cost of his printer, the printer created very precisely fitting parts. He purchased an Ender Pro for about $220 with about $100 of add-ons and upgrades. I asked him if he could help us print some 3D parts for the DonkeyCar. Rather than just printing a flat platform and roll-bar, he wanted to optimize the design for all our cars. We use the Exceed Magnet and the Nvidia Nano at our events and he decided to optimize the design in several ways. The new chassis is shown in the image above. This part replaces the Radio Tray part 28017). Here are the design changes he made:

1. He lowered the battery so the design and placed it under the Nano so we would have a lower center of gravity — this would allow the car to go faster around corners. We use an Anker 6800mAh LiPo batteries which typically last for an entire day.
2. He replaced the existing RC car Radio Tray new frame that holds all the new parts (battery, nano, ESC and servo board). This approach allowed us to even reuse the screws!
3. He created a precise holder for the Nvidia Nano using four supporting pillars above the battery. Although the legs look narrow, they work together and provide plenty of support. He used standard M2.5 X 6mm machine screws to mount the Nano. You can get these screws from Pololu for 99 cents for a package of 25 screws.
4. He created a slotted attachment for the electronic speed controller (ESC) which required no screws and no tape.
5. He created a mounting location for the servo controller using a single M2.5 X 6mm screw.
6. He created a separate low profile mounting point for the camera. This design allowed the entire camera to be “hidden” under the plastic car or truck body. The enclosure snapped directly over the camera without any screws. Although the camera is a bit to low to win any races, it is a nice design. Because it is modular a new mount could be swapped in for an actual race. The one we worked on was designed so that the angle of the camera could be adjusted.

His design also is optimized for printing speed. Instead of the roughly 12 hour print time for the standard DonekyCar chassis, his new design prints in about 4 hours.

His parts are now publically available on the OnShape site. Here is a link to the main chassis in the program OnShape. There are three other parts to mount the camera here, here and here. You will need 5 M2.5 X 6mm screws and four cable ties. One large cable tie goes around the battery and three small cable ties are for the wire management.

Here is a photo album of the assembly process.

The main advantages of this design are faster print time and lower-profile placement of the heavy parts. The cost of the black PLA (which seems the best material) is also under one dollar. It is a bit harder to view the battery charge level and replace the LiPo battery without unscrewing the Nano. And finally, this design will only work with the same Nano, battery and Exceed Magnet RC car chassis.

We also plan to work on a part that would raise the camera up to be a fixed standard 15-degree angle at a height of 15cm. We also will need to modify the camera mount to allow for a wide-angle lens. This would allow all our cars to use a similar model for the training events.