Ron Patrick's Street-Legal Jet Powered VW Beetle
This is a my street-legal jet car on full afterburner. The car has two engines: the production gasoline engine in the front driving the front wheels and the jet engine in the back. The idea is that you drive around legally on the gasoline engine and when you want to have some fun, you spin up the jet and get on the burner (you can start the jet while driving along on the gasoline engine). The car was built because I wanted the wildest street-legal ride possible. With this project, I w as able to use some stuff I learned while getting my fancy engineering degree (I have a PhD in Mechanical Engineering from Stanford University) to design the car without the distraction of how other people have done it in the past - because no one has. I don't know how fast the car will go and probably never will. The car was built to thrill me, not kill me. That doesn't stop me from the occasional blast on the highway though.
The car is licensed here in California. In California, new cars have bi-annual smog inspections so if you modify the engine, it is likely to fail the inspection and you won't be able to drive it on the street. There are some exempt engine modifications (ex. after-cat mufflers - big deal) but none that will allow you to add 1350 hp to a new car.
Car was built to look as if V W de livered the car this way. It handles fine and is safe. I was thinking of putting it into an import car show but the promoter told me that it looked too plain and recommended that I put some decals on it, lower it, and put on some aftermarket wheels. Sure kid, put on some flimsy wheels won't take a curb and don't center on the hubs, lower the car so the tires rub and get cut by the body using springs that bounce me all over the road, and advertise for companies that couldn't engineer themselves out of a paper bag. I would have thought the 14" diameter tailpipe was enough for him but I guess it wasn't. Response from the hot rod magazines has been slow. One editor told me that is because I didn't use anything they advertise. But the response to driving it on the street and going to the hot rod shows (San Francisco Custom Car Show, Grand National Show in Pomona, and the Detroit Autorama) has been fantastic. This car attracts crowds better than any '32 Ford, '69 Camaro, or decaled Honda.
The Beetle was chosen because it looks cool with the jet and it shows it off well. Remember the Hurst wheelstanding Barracuda "Hemi U nder Glass"? Well, this is "Jet Under Glass". Air for the jet enters the car through the two side windows and the sunroof. It's a little windy inside but not unbearable.
The production hatch release switch on the driver's door activates two new latches (one on each side) and the hatch pops open just like a production car. The "hatch not closed" warning light works too.
Here you can see the split in the tailpipe after a particularily rude burner pop. All fixed and reinforced now. The heat blanket keeps the plastic bumper from melting when the jet is operating.
The back of the gauge panel was kept open to give the car a techie look. Something to talk about. The car's an engineering device, let's see some engineering thingies. The aluminum panel was designed in SolidWorks and cut out of billet, bead blasted, clear annodized, and then the labels for the switches were milled into the front u sing a font matching the VW cluster. Little details like the holes having flat sides so the switches don't spin and exactly matching the contour of the dash added time to the project. Several versions were made out of styrofoam first to get the layout and lighting right. From the back, the panel reminds me of the 1970s McLaren CanAm cars.
The first thing I did when I got the car was to cut the hole in the back for the engine. Made a fancy jig out of a tripod, a rod, and a lawnmower wheel to mark out the cut and went at it with a pneumatic saw. Then finished it off with jeweler's files. No paint requir ed.&nbs p; Didn't even chip. The hole was tricky because it goes through 3 layers (bumper and two layers of metal) and it's a circle projected onto angled surfaces. Just finding the centerline of the car wasn't trivial. Worrying what my neighbors would say if I ruined the back of a brand-new car made me REAL careful. I believe the hole is within 2 mm.
There are three gauges for the jet: %RPM, Oil Pressure, and Turbine Inlet Temperature. The most important is turbine inlet temperature. If you exceed about 650 degrees C for very long, you damage the engine. This is critical on start-up. You do n't wa nt a "hot-start". The throttle for the jet engine is located next to the gear selector. It is a lever and has three buttons: Cool, Big-Fire, and Afterburner. "Cool" leans out the engine and is used to lower the turbine inlet temperature if you get a hot-start. To light big-fire or the afterburner, you hold a button down and 1/2 second later, press the hot-streak button on the floor. Then things happen! Notice the kerosene level gauge in front of the gear selector (jet fuel is mostly kerosene) and the bud vase missing a rose. Where did it go?
Lotsa stuff back here. The force from the jet is tie d to the vehicle through sandwich plates inside the car bolted to contoured aluminum billets that were slid into the frame rails. You can see the billet on the left side with a hole in its center, welded to the plate with 4 bolts. Used helium as the inert gas and a lot of current to weld that chunk of aluminum. To return the car to its production height, adjustable spring perches were used. Same spring rate, just corrected the ride height. Drives and handles fine. Kerosene is stored in a custom 14 gallon, baffled, foam-filled kevlar fuel cell in the spare tire well. Two fuel exits in the back: a -12 on the left side and a -10 on the right. The -10 goes to a shutoff, then a Barry Grant pump (one of the few hot rod parts on the car), then up into the car where it sees a filter, a regulator, and an electrical shutoff valve before feeding the engine. The -12 goes into a shutoff, then a 1.5 hp, 11,000 rpm, 24V custom electric p ump.& nbsp; Pump is magnesium and can maintain 100 psi at 550 gph. >From the pump it goes into the car to a filter, then a large regulator, and then to the afterburner solenoid and the big-fire solenoid (to left of pump and feeding bottom of tailpipe through orange covered hose). Fuel system was tested for flow capability. Above the big pump you can see the relocated gasoline cap actuator and all that black stuff on the right side is the stock fuel evaporative control equipment. All circuits feeding solenoids and pumps have fuses, relays, kick-back diodes to minimize contact arcing, sealed connectors, and use automotive wires of a gauge giving a maximum of 1V drop over the circuit loop.