Prototyping RC parts: which material survives which crash
How to iterate RC car and boat chassis, bumpers, mounts and bodies without overspending, and why the stiffest part is not the toughest.
RC is probably the best application a printer has, for an unromantic reason: parts break. Constantly. And a part that breaks every other outing is a part you want to redesign and hold again the same day, not order from Hong Kong and wait three weeks for.
The material mistake everybody makes
Intuition says: the part breaks, I need something stronger, I will go to carbon fibre. That is exactly the wrong direction. Carbon fibre raises stiffness and lowers toughness: the part deflects less and breaks sooner, and it breaks suddenly, with no warning. In an RC car that is going to roll, you want the opposite — a material that absorbs the hit by deforming and comes back. That is PETG, and for the parts taking the direct impact, TPU.
| Part | Material | Why |
|---|---|---|
| Bumpers and guards | TPU | Absorbs the hit and returns. It is what saves everything else. |
| Chassis and structural plates | PETG | Tough. It bends before breaking, which is what you want. |
| Towers, servo and electronics mounts | PETG or carbon fibre PLA | Fibre only where stiffness matters more than impact. |
| Bodywork and cosmetic parts | PLA | Cheap, good detail, paints well. It will break; that is fine. |
| Gears and drivetrain | Carbon fibre PLA, with caveats | Handles wear; does not handle sustained high torque. |
| Parts near the motor or exhaust | ABS | The only thing that holds there. An electric setup runs hotter than you think. |
| Boat and outdoor parts | PETG | Water, sun and salt. PLA does not last a season. |
How to iterate without going broke
- 1Design the part to break where you choose. A TPU bumper, or a tower with a deliberately weaker zone, is a mechanical fuse: a two-euro part gets sacrificed instead of the chassis.
- 2Print the first version in cheap PLA at a thick layer. It is not the final part: it is to check it fits and the holes land where they should.
- 3Only once the fit is right, switch to the proper material. Discovering in PETG that a hole is three millimetres out wastes the money twice.
- 4Order the parts you already know break in pairs. The second brings in the volume discount and saves losing a whole weekend.
- 5Keep the order reference. When you break the same part again in six months, repeating it is a matter of the reference and the quantity.
Will a printed part survive a nitro or large-scale RC car?
Cosmetic parts and guards, yes. Structural parts on a large scale, with the mass and speeds involved, sit at the edge of what printed plastic can reasonably do: there the sensible route is using the printed part to prove the geometry and having the final one machined in aluminium.
Can you reproduce a part from an old RC kit?
Yes, it is one of the commonest jobs in modelling: older kits whose maker dropped support years ago. We need the broken part or a good one to measure, and if you have the one from the other side of the car, better still.
What infill should an RC part have?
More perimeters before more infill. A part with four or five walls at 25% infill takes more impacts than the same one with two walls at 60%, and it weighs less, which counts in RC.