You know, a non radar-reflective one along the lines of stealth aircraft, and would enable the driver to slip past police radar guns. Is this feasible, and what kind of technology would be needed? {Note to Mods: in the event that this might be illegal, this question is purely hypothetical - I have neither the time, the money, nor the expertise required to build one. I’m just, you know, curious}
Probably not, since the wheels can’t be changed significantly. Even if you shroud the wheels you’ll have a body so low that it would be impractical.
And even if you do all that, unless you make it invisible you’ll never beat VASCAR, so it’s not particularly sensible to spend all the money on R&D. What’s more, DOT would never approve it and the cops would hassle you into next year.
YES! My old physics teacher while HE was in college was working on some sort of project and managed to come up with a certain brand and color of paint (an ‘otc’ paint if you will) that absorbed rather then reflected radar waves. He painted his entire car with it, and in his ‘experiments’ the police radar guns couldn’t see him. He said he regularly sped right past police officers, but never got pulled over since they had no way of telling how fast he was going.
The “radar signature of an unladen swallow” aircraft are more a matter of geometry and operational stealth than “non radar-reflective”. They work by reflecting as little as possible directly back to the ground station… I.E. they bounce it off in other directions. If you get them from a few narrow “bad” angles, the stealth geometry can actually make them a bigger target.
Radar absorbing materials were a big thing towards the end or WW2, but never really caught on. They mostly centered around wood laminates made with special types of glues. The performance advantages of metal aircraft were too great, though. You could probably built a car out of wood laminate, but I wouldn’t recommend getting in a wreck. Splinters, y’know?
The problem is, even if the car is invisible to radar it’s still, hey, visible… It would probably be easier and cheaper to just go to court and fight your speeding tickets.
Even if your car were completely invisible to radar, there are still several kinds of police speed traps you could fall victim to. For instance, sometimes two officers work in tandem – one sits in an unmarked vehicle and radios ahead to his partner whenever he sees a car go speeding by, passing on a description of the car. The other officer is a certain distance down the road, so that if you get there in less than X amount of time he knows you had to be speeding, and will pull you over. No radar necessary, just speed = distance / time.
I remember a program on Discovery or TLC regarding this very issue.
A car called the Stealth (NOT the Dodge Stealth, a re-badged Mitsubishi) was mage of carbon fiber, painted with matte black radar absorbing paint, and faceted like the F-117 stealth fighter.
An interesting note; the components of the car were not welded or riveted, but bonded together with glue!
Years ago Car and Driver magazine fitted a project car with “microwave shield,” as I recall. They found it did not register on the radar gun they were using. On one run, however, the radar did register over the speed limit. Turns out it was a big truck behind their test vehicle – so if you’re invisible to radar, it would be possible to get a ticket while going the speed limit if someone coming up behind you is speeding.
One of the letters in response to that article mentioned that a naval radar buoy, a small item designed to register on radar, looked just like the reflector of a standard sealed-beam automotive headlight. This may present a problem for maintaining radar stealth while driving at night.
I don’t necessarily doubt your physics teacher told you this, but if he did, he was bullshitting you. It would probably be possible to design a car to have a low radar signature, but you’re not going to get it by just painting it with some regular paint.
Technically it is quite possible to build a car that is nearly invisible to radar. Paints, mystery microwave gizmos, and other assorted nonsense isn’t going to do it though. When I worked at a defense contractor that made radar and flir systems, a bunch of us sat down at lunch one day and came up with our ideas for a “stealth toyota” (since one of our co-workers had recently purchased a toyota, and we started talking about speeding tickets, and one thing led to another…). It’s actually pretty tricky. You can’t have any flat surface that reflects radio waves facing directly forward or backward. This means lots of 45 degree angles. You want to reflect all of the energy to the sides or upward so that very little of it returns to the front or rear. This includes things like the radiator and the wheel rims. You can tilt the radiator, but the rims get tricky.
With all the proper radar absorbing materials and the mechanical modifications required, we figured we could pull it off for a couple hundred thousand.
“Much cheaper just to pay the tickets,” the new toyota owner noted, and sadly another fine engineering project was shoved into the waste basket.
IANAL, but as far as I know a car like this would be perfectly legal.
:rolleyes: :dubious: :smack:
Our cops use lidar so…
:eek: :eek: 
Discovery’s Mythbusters just did a show on beating radar guns. They covered the car in aluminum foil (didn’t work), painted it flat black (didn’t work), tried a bunch of infrared LEDs (didn’t work), put a wierd wheel of spinning mirrors on top (didn’t work), and fired a bunch of aluminum chaff from a PVC pipe using a fire extinguisher (didn’t work).
There are ways to defeat radar guns using electronic counter-measures. Many years ago, an amateur radio magazine published an article that described the design and construction of a system that allowed the operator to fool a radar gun into displaying a speed that was selected by the operator on a set of digiswitches. If you set the switches on the device to 55, the radar gun would display 55, regardless of the motion of the vehicle. I’m not going to describe how the system worked, but it isn’t hard to figure out if you are familiar with how radar guns operate.
[hijack=“rice”] Thank You!
I’ve been seeing a bunch of cars lately that are painted flat-black, but I haven’t been able to figure out why. The best guess I’d come up with was that it was some sort of primer coat for the pseudo-metallic paint these kids put on their hatchbacks to make them faster.
This makes more sense and fits into the mindset better.
[/hijack]
Similar to the moths which avoid echolocation by bats by emitting their own clicks?
Do all the various brands of radar gun produce the same basic pulse/frequency, or do they all have slightly different outputs (not unlike television remotes)?
Think continuous wave doppler radar.
I believe current models operate in the X, K and Ka bands.
For those who aren’t aware, when you actually transmit something back towards the radar gun, like electronic countermeasures, or the microwave oven stapped to the hood like they did on mythbusters (heh, that was funny), you cross the line and are now doing something illegal.
Magnetrons (the little guy inside the microwave that generates the radio waves) are also kinda dangerous. After all, they do cook your food rather quickly. Don’t try this at home, kids.
Oh, right. I forgot about that one. Didn’t work.
-
-
- Transmitting signals to confuse speed-monitoring devices is most likely illegal, at least in the US.
-
- I remember the Car and Driver article–they covered the car in paint that had a lot of powdered iron in it. I seem to remember they stripped off all the chrome parts as well, ended up painting the wheels and inside the wheelwells, and the radiator too. But the car still was detected, at distances ranging up to a 1/4 mile, so they took off the one thing they had left untouched until this point–they removed the front license plate. Then it was undetectable until it was within a few dozen feet.
- And now the US police often use laser instead of microwaves–which (being light) you could probably mix some kind of paint to absorb the laser light, if you knew the wavelength… but you’d still have the problem of the license plates, as they are designed to be very reflective of light anyway.
~
There are thin film coatings that act like optical notch filters, removing only the selected frequency. That might make the license plate non-reflective to the laser. It would probably be horribly expensive.
It’s a lot simpler, and cheaper, to just obey the speed limit.
Or you could give up on the car and try a different approach
I’ve been able to determine the veracity of this story. Anyone know more?