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Ron Patrick's Street-Legal Jet Powered Volkswagen Beetle
This is 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 was 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 a street-legal jet 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 VW delivered 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 Roadster 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 wheel standing Barracuda "Hemi Under 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 particularly 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 anodized, and then the labels for the switches
were milled into the front using 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 required. 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 don't want 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 tied 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 pump. 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.
The engine is a General Electric Model T58-8F. This is a helicopter turboshaft
engine that was converted to a jet engine by some internal modifications and a
custom tailpipe. The engine spins up to 26,000 RPM (idle is 13,000 RPM), draws
air at 11,000 CFM, and is rated at 1350 hp. It weighs only 300 lbm. It grows as
it warms up so the engine mounts have to account for this. The mounts in the
front are rubber and the back are sliding mounts on rubber. The structure
holding the engine was designed using finite element analysis and is redundant.
Strong, damage tolerant, and light. Second battery and fuse/relay panel on the
right, halon fire system and 5 gallon dry sump tank on left. 24V starter motor
is in the nose of the engine. 700 A of current goes into that motor for 20
seconds during start-up. Due to heat, must limit starts to three in one hour.
Big screen is to avoid FOD (foreign object damage). Jet keeps sucking the rose
out of the bud vase on the dash!
A lot of attention to details in the car. Note the aluminum block
holding/protecting the halon gas line, pull line, harness to engine, and oil
pressure line. Rectangular tank under inlet screen is for various fuel drains.
Note temperature gauge and shutoff valve for dry sump tank. 3 gallons of turbine
oil at $25/quart (ouch!). Two-stage PPG paint matching exterior of car was used
inside the car. It is not easy to paint around a lot of bars, etc while crouched
in a car, in your dusty home garage, avoiding drips, and with your wife
screaming that the fumes will cause brain damage in the kids. Especially with
two-stage where you have multiple coats and critical drying times. Kids passed
their grades so I guess damage was minimal, but more importantly, the paint
turned out great!
Street racing action. The other guy wimped out after a few "big-fire"
demonstrations. What you see in the picture is about one-twentieth the full size
of the fireball. Guy standing beside car had never seen it run before and was
smiling ear-to-ear throughout the show. Had I launched, I would have burned him
to a crisp. Well, live and learn.
We get this a lot. A police officer picking at his nose while trying to figure
out what to charge me with. Notice the hopeful anticipation of us on the right.
We're rooting for him and offer suggestions but unfortunately, the California
Department of Motor Vehicles did not anticipate such a vehicle so he's out of
luck. Hmmm, the car has two engines making the car a hybrid so maybe we can
drive in the commuter lanes along with the Toyota Priuses.
*** Update 7/18/06 *** You have to give the California Department of Motor
Vehicles (the DMV) credit for creativity on this one. A DMV insider has
disclosed to me that the DMV has made a formal request to a federal agency to
rule if my Beetle constitutes a threat to national security based on what could
happen if it got into the wrong hands. This raises three questions in my mind:
#1 Does this mean I’m the right hands? #2 If someone with the name "b_laden13"
is the highest eBay bidder for my Beetle can I refuse his offer even if he has
the prestigious eBay Red Shooting Star feedback rating (the highest)? #3 Would
this affect my eBay rating?
The car was built in this garage. Paint, welding, everything except some mill
work. That's me standing beside the engine that is out of the car for some fuel
controller work. The orange line is for the afterburner. There's one on the
other side too. Here you can make out the four rows of variable inlets/stators
at the front of the engine. Their angle changes with engine speed and are used
to avoid compressor stall. There are 11 compressor stages and 2 turbine stages.
The engine's pressure ratio is 8.3:1. That's how you work on a jet engine. Stick
it on its end. Easy to store them that way too.
Here's my wife's Honda Metropolitan scooter. She wants it to go faster than 40
mph. So I have these two little JFS 100 jet engines and I am thinking how to put
them on the scooter. Engines are 50 lbm each so weight is an issue. Will
probably use air-start with a carbon fiber tank of compressed air. That saves
weight since batteries will then not be needed.
Looks cool from the top. Will want to make aluminum housings to go over the
engines just like on a DC-9.
Bitrom the back too. Should get the scooter going. On one jet engine alone, this
engine will get a kart up to 60 mph. Looks like I have a lot of spare wire left
over from the Beetle job to do the scooter.
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