It works! It's not that impressive! It's kind of a dead end.
My original design had these structures that plugged into each side of the turbine and stretched out to the backsides of the wheels. The idea was they would support the axles, eliminate the need for the clip on the output shaft, and provide a mounting point for the car's body. In practice, they added too much drag to the axle and were way too flimsy. The axle spins much better without them, but it's easily dislocated.
The body was designed in a bit of a hurry, so the front axle design is basically the one I used on my version of the Bugatti balloon car, and it doesn't work that much better here. It's only attached to the front sockets of the turbine, so the car sort of bows in the middle when it runs (like a top fuel dragster! Demonstration of torque. Feature, not bug). The shape is inspired by the Lotus 56 turbine Indy car.
When I printed it all out, I hooked up a balloon and... it went 4 feet. Hmm.
I whipped up a set of lightweight drive wheels, which added maybe another 6 inches. On a few runs, the deflating balloon fell over onto a drive wheel, which brings the car to a stop. I'm thinking now that a gear-driven rear axle with smaller rear wheels might yield better results.
Print a version 2 balloon turbine, if you haven't already. You'll need everything from it except the center pin/output shaft.
From this page, print the body, the output shaft, and two of everything else. Well, not quite everything, you have your choice of rear wheels, and if the wheels fit the axles well enough you can skip the wheel clips.
I'd recommend printing everything with a fairly low infill (5%?) to keep weight down. You should be able to print it all raftless, the pins that plug the axles into the output shaft have built-in support that needs to be trimmed off.
Sand the output shaft on the side where it runs through the backside of the turbine housing.
It has to be very smooth.
Smooth out the front axle pins and the hubs of the front wheels too.
Fit the turbine rotor into the housing, then slide the new output shaft through. Clip it on the other side (I find putting the clip in with the pins facing out works best for this application). Slide the body over the sockets of the turbine housing, pop in the pins. Pin the front wheels to the body, then slide the axles through the rear wheels and attach them to the output shaft. Add balloon.