Police cars?

[davereid]

My 2007 3.6 VZ Commodore goes like a rocket to 160. From 160 to an indicated 220 it still goes well. At 220 speedo its actually going 200 GPS. At that speed its still accelerating but not with much titty, might reach 240 speedo (215 GPS). My 2002 AU2 Falcon was a V8 - not actually much faster, but better acceleration.

That ranks right up there with 'CDs will deflect the radar' myth as THE most stupid urban myth.

CDs of course wont have any effect on Radar.

But if they are on a steep angle they may cause problems for laser.

Consider how laser works...

The laser sends a pulse towards the target. The time for the beam to hit the target and be reflected tells you the distance to the target. A short time later (say 1/100 sec) you send another pulse. The time tells you the new distance to target.

So, at 100 km/hr or 27m/s, the target should be 270mm closer between your two measurements.

But what if the first pulse is from (for example) the back of the headlight reflector, and the second pulse reflects elsewhere - say the front of the headlight reflector ?

You might get 270mm closer due to your speed, plus another 100mm due to the curve of the headlight reflector.

This would exaggerate your speed. Of course, the reverse could apply !

The laser has software to sort this out - at its simplest it takes several readings, and won't lock until it gets several the same.

If the best reflector on your car is the flat number plate, the laser will get a reading easily.

But, if the best reflector is a CD - which is of course a device specifically designed to be a great reflector of laser, and that CD is on a very steep angle on the dash board, then the laser has a big challenge.

If the first reflection is from the bottom of the CD, and then 1/100 sec later, the beam is 20mm higher and reflects off the back of the CD, the laser unit will reject the reading.

[cs363]

According to a mate that works for a leading automotive publication, the SV6's are good for around 230km/h +/- 10km/h flat out, though after about 190 they take a while to get there. SV8's are apparently good for around 250 and will obviously get there a tad quicker than the V6.

Many of the Police cars aren't SV6's though (I believe they are used by the HWP), vast majority of them are the base model Omega.

As previously mentioned, no doubt the extra equipment carried would have some effect on the power/weight calculation as would the drag of the lights and aerials, though the newer style lights are considerably lower drag then the bulky old units.

Interesting comment that was made is that the new VE Commodore runs the new 3.6L V6 with variable cam timing on exhaust and inlet and make 195Kw - that's 10Kw more than an HSV Clubsport from a few years ago!

Whilst trying to verify the above info I came across this: http://www.autozine.org/html/Holden/Commodore.html on the interweb, and it seems to back up the above figures and also gives other performance info for those planning to outrun their local rozzer....

Regardless, even if they were using Porsche Turbo's or whatever the comments regarding the speed of radio transmission and helicopters should be a cautionary advisory for any of you with anarchistic tendencies....

[cs363]

A bit of additional info: Obviously magazines etc are testing relatively fresh cars under controlled conditions - real world (attainable) speeds are probably more in line with davereid's comments above.

It's also interesting to note that one of the issues experienced with the new VE shape over the old VZ when it comes to Supercar racing was that the VE was actually slower because of the drag created by the wider frontal area.

And like anything, outright performance figures should be taken with a grain of salt - as many of us have experienced there can be big differences between cars or bikes of the same model for no apparent reason, maybe the difference between being built on a Friday or a Monday, different conditions or a whole bunch of other variables.

[FJRider]

My 2007 3.6 VZ Commodore goes like a rocket to 160. From 160 to an indicated 220 it still goes well. At 220 speedo its actually going 200 GPS. At that speed its still accelerating but not with much titty, might reach 240 speedo (215 GPS). My 2002 AU2 Falcon was a V8 - not actually much faster, but better acceleration.



CDs of course wont have any effect on Radar.

But if they are on a steep angle they may cause problems for laser.

Consider how laser works...

The laser sends a pulse towards the target. The time for the beam to hit the target and be reflected tells you the distance to the target. A short time later (say 1/100 sec) you send another pulse. The time tells you the new distance to target.

So, at 100 km/hr or 27m/s, the target should be 270mm closer between your two measurements.

But what if the first pulse is from (for example) the back of the headlight reflector, and the second pulse reflects elsewhere - say the front of the headlight reflector ?

You might get 270mm closer due to your speed, plus another 100mm due to the curve of the headlight reflector.

This would exaggerate your speed. Of course, the reverse could apply !

The laser has software to sort this out - at its simplest it takes several readings, and won't lock until it gets several the same.

If the best reflector on your car is the flat number plate, the laser will get a reading easily.

But, if the best reflector is a CD - which is of course a device specifically designed to be a great reflector of laser, and that CD is on a very steep angle on the dash board, then the laser has a big challenge.

If the first reflection is from the bottom of the CD, and then 1/100 sec later, the beam is 20mm higher and reflects off the back of the CD, the laser unit will reject the reading.

And the .000345th's of a km/hr that the two readings might indicate, will have 5/8th's of fuck all difference on the claimed speed written on the ticket, the nice officer gives you.... but feel free to challenge it in court... good luck...

[davereid]

And the .000345th's of a km/hr that the two readings might indicate, will have 5/8th's of fuck all difference on the claimed speed written on the ticket, the nice officer gives you.... but feel free to challenge it in court... good luck...

Actually, the difference is massive - a 150 mm difference in reflection source is an inflation, or deflation of speed of more than 50%.

To simplify it for the simpletons that surround us, your actual speed of 100km/h could be recorded as 150, or 45, depending on your luck.

But, its not something you routinely defend in court.

The clever blokes who designed the laser were aware of this problem, they called it slippage.

They put software in the laser to detect if slippage had occured, and if they detected it, the laser simply took another reading.

This means, that given a very slippage prone surface like a steeply angled CD, the laser has to take a lot of readings before it gets one that is stable.

Will laser eventually "get a lock" ?

Of course ! Its just a matter of time, until a good operator, with a tripod or stable point of balance can get a series of accurate reflections from your number plate, r other reflective surface, without accidently getting a reflection off a different object.

Just maybe, if you have the MK1 eyeball going, it might give you the extra 5 seconds to slow down.

[scumdog]

I've heard it a whole heap of times. 180 always. i've even heard it on the news so it must be true. They have to have some standard practice for you power trippin twats or it'd be mayhem with big headed cops with big cars giving big tickets to suffice their tiny cocks

Us power-tripping twats with big heads and small cocks can go as fast as we like, like even faster than 180.

What d'ya think's gonna happen if we go faster than 180? - the boss will flick a big switch that slows us down or something??

Sheesh, some people!

[peasea]

Us power-tripping twats with big heads and small cocks

I know, I've seen them both! Mate, tiny doesn't cum into it!

In fact, they're so tiny they don't even cum! Go figure.

[FJRider]

To simplify it for the simpletons that surround us, your actual speed of 100km/h could be recorded as 150, or 45, depending on your luck.

But, its not something you routinely defend in court.

If it is unreliable as you suggest... it should be, by the simpletons that surround us that choose to exceed the posted speed limits...

The clever blokes who designed the laser were aware of this problem, they called it slippage.

They put software in the laser to detect if slippage had occured, and if they detected it, the laser simply took another reading.

Not nearly as clever as the governing authorities that allow the Lasers to be used with the limited legislation and policy, concerning their rules of use...

Will laser eventually "get a lock" ?

Of course ! Its just a matter of time, until a good operator, with a tripod or stable point of balance can get a series of accurate reflections from your number plate, r other reflective surface, without accidently getting a reflection off a different object.

OR... if the "target" motorists speed flucuates enough, so no accurate reading can be achieved...

Just maybe, if you have the MK1 eyeball going, it might give you the extra 5 seconds to slow down.

Might be safer and cheaper to just slow down...

Considering the Laser range, and noted abilitys (and inabilitys) of said MK1 eyeball...

[scumdog]

I know, I've seen them both! Mate, tiny doesn't cum into it!

In fact, they're so tiny they don't even cum! Go figure.

So it's a win-win.

YOU know they have small dicks

THEY know they've screwed you out of $170 and 20 demerits.(or more - and maybe not for the first time!)

Happiness all round.

[peasea]

So it's a win-win.

YOU know they have small dicks

THEY know they've screwed you out of $170 and 20 demerits.(or more - and maybe not for the first time!)

Happiness all round.

You can't see me, so I'm happy.

Me and Jim gonna keep a lookout, sharing shifts, glancing here and there...

[FJRider]

So it's a win-win.

YOU know they have small dicks

THEY know they've screwed you out of $170 and 20 demerits.(or more - and maybe not for the first time!)

Happiness all round.

Is that why they say thankyou when you give them the ticket... ???

[cs363]

Is that why they say thankyou when you give them the ticket... ???

You're not hearing it right....

[JacksColdSweat]

The laser sends a pulse towards the target. The time for the beam to hit the target and be reflected tells you the distance to the target. A short time later (say 1/100 sec) you send another pulse. The time tells you the new distance to target.

...

The laser has software to sort this out - at its simplest it takes several readings, and won't lock until it gets several the same.

...

If the first reflection is from the bottom of the CD, and then 1/100 sec later, the beam is 20mm higher and reflects off the back of the CD, the laser unit will reject the reading.

... and no doubt these "multiple readings until lock" can all be achieved in pretty much under a second?

I'm picking you pull the trigger and before you even release it the laser unit has taken several dozen readings until it is happy... all in the space of a second or less...

I once got a positive laser reading on my Bell Escort X50 - freaked me out cos I had never heard the laser warning go off

I think it must have been bounced readings off another vehicle

I saw the gun when I got close to the cop so it was legit and I wasn't speeding so it didn't matter...

...much like this post...

[davereid]

... and no doubt these "multiple readings until lock" can all be achieved in pretty much under a second?

I'm picking you pull the trigger and before you even release it the laser unit has taken several dozen readings until it is happy... all in the space of a second or less...

Was my explaination of how it works that crappy !

Laser cant measure speed directly, it can only measure distance to target.

It has to take two distance measurements a known time apart and then use math to calculate the distance changed, in the time.

That time is 1/100 sec.

Even a tiny fraction of a mm rise or fall in the operators aim will move the reflection point up or down by 50-100mm if the target is 100m away.

If that reflection is coming off a perfectly flat surface then there is no problem.

But, if the refection is coming off a sloped surface, say a CD at 45 degrees from the vertical, each 100mm of vertical "wobble" by the operator, will change the distance to target by 100mm.

This makes it very hard for the laser to get a series of identical readings and thus achieve lock.

ie.. two measurments of distance to a flat surface will give the same result, even if one is a few mm higher or lower than the other.

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But two measurements of a sloped surface wont work.


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Pretty clearly, even if the target was stationary, laser would have measured a change in distance even though none had occured.

So the laser takes a series of measurements, each 1/100 sec apart. Only when it has a whole lot the same indicating a high probability that it is getting reflections off a flat surface does it process the data and give the operator a speed reading.

Thats why CDs work at blinding laser.

[peasea]

I want to be a Stealth Bomber when I grow up. It seems the technology is there but I still refuse to grow up.

Rock and a hard place..........