While visitng from Germany, my nephew wanted me to print something for him to play with using my Lulzbot AO-100 3D printer. Naturally I went straight to Thingiverse and found a cool Balloon Powered Jet Car that I could print up in about two hours with everything on a single plate. The video below is a timelapse of the print which was sped up about 1500%.
I sliced the model at a .40 layer height, 25% infill, and speeds were around 70mm/sec on Peremiters, Small Peremiters, and Infill. With such a thick print, I decided to squish the first layer a little more than normal. I chose 70% over the usual 90%. This turned out to be an issue with the wheels as it made one side of the wheels a little wider than the other 99%. A quick sanding took care of this though.
I used finishing nails to mount the wheels and used a drill bit to clean up the car axel holes, then a slightly larger drill bit to open up the wheel axel holes a little. Unfortunately the balloons I had on hand were just not powerful enough to push the car across the floor. Still, my nephew had a blast watching the car form infront of his eyes. I honestly think that he sat and watch the entire print.
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One reason why the balloon power is insufficient is the exaust is effectivly a straight pipe — which means the speed (or lack thereof) of the car scales directly with the pressure in the balloon. Changing the exaust pipe to a De Laval nozzle (https://en.wikipedia.org/wiki/De_Laval_nozzle) would help a little (such nozzles work best with heated and pressurized streams of gas; but pressurized ambient temperature streams of gas still see some benefit).