Ron Patrick's
Street-Legal
Jet Powered VW Beetle & Honda Metropolitan Scooter
Think how much fun this would be to deal with tailgaters.
All you would need is a sign that says, “Not Responsible
for Damage From Jet Exhaust, Keep Back 200 Feet.” and
then light it up and melt their front end off of their
car.
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 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 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 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 after market 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 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 turbo shaft engine that was converted
to a jet 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.
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 is 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.
Bitchin' from 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. |
