How I Made This Amazing PLA Spring Powered Car

by Jason King on February 21, 2015

3D Printed PLA Spring CarHaving realised the other day that I’d not used my 3D printer for a few days I decided it was time to take a look at some of the things I’d Liked (favourited) recently on Thingiverse.

Some of the things I’d Liked were RC car chassis, a bit like this 3D Printed RC Truggy we wrote about a while ago.

I used to race RC cars so making one of these would be pretty awesome, but I didn’t feel I was ready for this ambitious project quite yet. As I get more into 3D printing I’m liking the idea of building things from component parts more and more too, but I needed an easier project to start with.

The only things I’d printed in parts and built so far were the Velociraptor Business Card and the RoboSavvy Spool Holder Kit.

Naturally, the 3D printed PLA spring powered car I had found a few weeks ago looked like a great idea. Including my custom made NinjaFlex rubber tyres (more on these later) there were 16 parts to print and assemble. This looks like a fun little project to undertake.

Downloading and 3D Printing the Parts

First of all I downloaded all of the parts from Thingiverse Here, then I set about working out which parts I needed.

The reason I say this is because some parts needed two of them printing (front and rear wheels for example) and other parts had optional modified versions I could use.

An example of modified parts were rear wheels with grooves to fit tyres if required, which as you’ll see later I did use.

I decided on ColorFabb Dutch Orange for all of the moving parts, except for the spring, for which I decided to use RoboSavvy Green. The two sides to the rolling chassis were printed in ColorFabb Blue.

3D Printed Car PartsThere are some instructions on Thingiverse detailing some of the best settings to use for printing. Basically most parts should be printed in PLA plastic, at 0.2mm layer height (medium resolution) and at 10% infill.

The only exceptions are the spring and knob which need to be 100% infill for strength.

After printing the parts on my Glass Build Plate using lots of hairspray, all parts printed perfectly with no warping. Incidentally, I’m loving this glass build plate and hairspray combination, and haven’t used blue tape for months now.

NinjaFlex Black Rubber Tyres

Naturally when I saw the optional modified rear wheels for use with tyres (rubber bands I think) I thought of the NinjaFlex Rubber I hadn’t used for a little while and knew I could do better than boring old rubber bands.

Using Tinkercad and my vernia caliper I quickly took some wheel measurements and designed some custom tyres which would fit snugly onto the back wheels.

I’d seen YouTube videos of this car wheel spinning like crazy on smooth surfaces and I was having none of this, I wanted traction and I wanted my car to be 100% 3D printed.

The tyres printed first time with no dramas. I hadn’t forgotten how tricky NinjaFlex can be to print with, so I slowed down the extrusion to 30 mm/s and all was well. I used plenty of hairspray on the build plate again, even though warping is unlikely with such a flexible material. I was taking no chances.

That was it, for making the parts. I now had 16 parts all lined up and ready to assemble. It was now a little late in the evening though so I decided to leave the assembly until the next day.

Assembling the 3D Printed Spring Powered Car

The Thingiverse instructions on how to build the car included a Trimble Sketchup file showing the assembly, which to be honest I didn’t use. Although I used to use Sketchup a lot it no longer seems to be installed on my laptop.

Never mind, I figured that this thing must be easy enough to assemble from the images and a little common sense. It was easy to work out which parts fitted where, but lots of trimming of parts was required.

Some parts need to fit tightly together and others need to rotate smoothly. It’s simple to work out which are which so I set about putting this car together, with the help of a modelling knife and a little Teflon grease.

The spring (big green spiral) and the pawl (three armed orange wheel) were the trickiest parts to fit together as they were an extremely tight fit and lots of trimming was required. Fitting the wheels onto their respective axles required some trimming and so did the rear axle gear and winding knob.

It did take a little time to trim, grease and assemble but I had no worries as what’s the worst that could happen? Maybe I’d break a part or two, but I was safe in the knowledge that I could print replacement parts if I needed to.

Luckily nothing broke (PLA is surprisingly strong) and it fitted together pretty well.

The tyres were a good tight fit but worked really well. If you print this yourself and want my designs for the tyres feel free to let me know and I’ll make them available.

Just be careful with the modelling knife during assembly and don’t let children assemble this. You’ll be using the knife a lot for trimming so bear that in mind.

First Few Test Runs

The first couple of test runs were a bit shaky, with some adjustments required. The loop on the outside of the spring was too tight on the chassis, which I thought it needed to be.

Originally forgetting that the spring rotates a little, I realised that where the spring attaches to the chassis it needs to rotate a little for the best performance.

Out came the modelling knife and grease and that was solved. The rear wheels also scraped a little on the chassis but moving them out a little on the rear axle solved this too.

I made this YouTube video of my third or fourth run and as you can see it runs pretty well. There’s always room for improvement and I’m very tempted to make some wider dragster style rear wheels and tyres.

Part of the fun is pimping this little car up to the max and that’s what I intend to do. I wonder if I could make a meatier spring too and up the horsepower?

Anyway, please feel free to download this and make it for yourself. It really is fun to do and assembling all the parts and makes a change from the usual process of just downloading and printing a single item.

If you enjoyed reading this it’d be great if you could Like, Share and leave a Comment. Also, download my FREE Beginners Guide to 3D Printing at Home eBook if you’re interested in making cool stuff like this yourself.

Thanks for reading and happy 3D printing.

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