Yet Another Cycling Forum

General Category => Freewheeling => Topic started by: Tim Hall on September 11, 2019, 09:29:51 pm

Title: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 09:29:51 pm
Would it be ever so wrong to fashion a gilet type garment using a space blanket and velcro so as to increase the radar cross section of the average cyclist and thus increase the chances of triggering a speed camera?

The facts that (a) there's a handily placed speed camera on the hill down to Brighton, (2) there's a Friday Night Ride going past it this weekend and (iii)  I'm going on the ride are all mere coincidences.

(Did I ever tell you of my plans to make a speed camera chaff rocket by repacking a party popper with strips of tin foul?).
Title: Re: Radar reflective gilet
Post by: LittleWheelsandBig on September 11, 2019, 09:42:39 pm
It might be more efficient to fashion a corner radar reflector and mount it to your handlebars or whatever. Otherwise the wrong body position might create a radar-stealthy cyclist.
Title: Re: Radar reflective gilet
Post by: IanN on September 11, 2019, 09:46:22 pm
Or get a £20 compact radar reflector for a RIB and mount it to your rack...

https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version (https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version)
Title: Re: Radar reflective gilet
Post by: Ham on September 11, 2019, 09:48:32 pm


(Did I ever tell you of my plans to make a speed camera chaff rocket by repacking a party popper with strips of tin foul?).

Did you chicken out?
Title: Re: Radar reflective gilet
Post by: Kim on September 11, 2019, 10:53:05 pm
The Brighton speed camera detects recumbents just fine (DAHIKT), so an average cyclist shouldn't be a problem, unless employing carbon bling stealth bomber tactics.
Title: Re: Radar reflective gilet
Post by: Wobbly John on September 11, 2019, 10:55:33 pm
A speed camera (can't remember where - Wisbech?) was picking us up on the last FNRTTC...
Title: Re: Radar reflective gilet
Post by: Kim on September 11, 2019, 10:59:38 pm
A speed camera (can't remember where - Wisbech?) was picking us up on the last FNRTTC...

Did I miss an Opportunity?

That said, even on the Red Baron, I'd struggle to exceed 33mph on the flat for more than a few seconds.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 11:00:21 pm


(Did I ever tell you of my plans to make a speed camera chaff rocket by repacking a party popper with strips of tin foul?).

Did you chicken out?
Curse these stubby pheasant fingers.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 11:02:23 pm
It might be more efficient to fashion a corner radar reflector and mount it to your handlebars or whatever. Otherwise the wrong body position might create a radar-stealthy cyclist.
The camera in question detects the rear of the passing vehicle, so I'd need to hang it off my saddle.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 11:05:25 pm
Or get a £20 compact radar reflector for a RIB and mount it to your rack...

https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version (https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version)
I used to sell navigation buoys, as you do, so have a passing familiarity with those sort of gadgets. That one doesn't look very good. In a fit of enthusiasm, I've downloaded a Qinetiq report into radar reflectors, which confirms my suspicions.
Title: Re: Radar reflective gilet
Post by: phil w on September 11, 2019, 11:06:39 pm
I set off a 30 mph speed camera on my Brompton tonight. I can now rest happy.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 11:08:15 pm
The Brighton speed camera detects recumbents just fine (DAHIKT), so an average cyclist shouldn't be a problem, unless employing carbon bling stealth bomber tactics.
Steel frame, 36 spoke 3 cross wheels, as God intended.

I've set it off before, but I was riding next to Adrian, so our combined RCS may have been a factor.
Title: Re: Radar reflective gilet
Post by: Kim on September 11, 2019, 11:20:38 pm
Or get a £20 compact radar reflector for a RIB and mount it to your rack...

https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version (https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version)
I used to sell navigation buoys, as you do, so have a passing familiarity with those sort of gadgets. That one doesn't look very good. In a fit of enthusiasm, I've downloaded a Qinetiq report into radar reflectors, which confirms my suspicions.

Looks a bit on the small side for S-band?  Does marine radar use S-band?  I'm guessing...

ETA: According to a speed-camara-detectorist site, Gatsos use K-band radar.  But a small target is still a small target, and like the traffic lights, it's probably tuned for cars.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 11, 2019, 11:27:35 pm
Or get a £20 compact radar reflector for a RIB and mount it to your rack...

https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version (https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version)
I used to sell navigation buoys, as you do, so have a passing familiarity with those sort of gadgets. That one doesn't look very good. In a fit of enthusiasm, I've downloaded a Qinetiq report into radar reflectors, which confirms my suspicions.

Looks a bit on the small side for S-band?  Does marine radar use S-band?  I'm guessing...

ETA: According to a speed-camara-detectorist site, Gatsos use K-band radar.  But a small target is still a small target, and like the traffic lights, it's probably tuned for cars.
All merchant vessels above x size must carry X band. Bigger ones will have S band too. Thus passive reflectors are designed to work with X band.

I couldn't find the Gatso band due to poor Google fu, so thanks for that. Hmm, will an X band passive reflector do anything with K band?
Title: Re: Radar reflective gilet
Post by: Kim on September 11, 2019, 11:31:42 pm
I expect so, a corner reflector still works if it's much bigger than the wavelength (consider BS6102 bicycle reflectors, where the cubes are a couple of mm across).
Title: Re: Radar reflective gilet
Post by: Kim on September 11, 2019, 11:40:49 pm
Further thought, speed camera chaff devices are probably available off the shelf from Le Maitre's craft herpes glitter range.

(Can you fire a pyro with the current from a hub dynamo?  Paging Big Clive.  Big Clive to the PINK courtesy phone please...)
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 12, 2019, 12:07:19 am
Wiki says Ku band is used, 12-18GHz, so a wave length of 2.5cm to 1.67cm. Half a wavelength is therefore 1.25cm to 0.8cm, which is a bit bigger than your standard glitter.
Title: Re: Radar reflective gilet
Post by: Kim on September 12, 2019, 12:11:12 am
I dunno, looks about right...

http://www.youtube.com/watch?v=b1wXzLDW4Tw
https://youtu.be/b1wXzLDW4Tw


Here you go, Ku-band chaff:  https://www.lemaitreltd.com/products/special-effects/special-effects/glitter-confetti-streamers/
Quote
Glitter pieces measure approximately 20mm x 55mm


And a CO2 cartridge powered launching device:
https://www.lemaitreltd.com/products/special-effects/special-effects/pocket-air-cannon/
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 12, 2019, 12:15:27 am
Ooh. File that under "what could possibly go wrong? "
Title: Re: Radar reflective gilet
Post by: T42 on September 12, 2019, 08:11:16 am
A good bunch of riders can trigger a speed camera. Our 25-strong Audax pack once triggered one on a stretch limited to 90 kph.

I'd love to have seen the picture.
Title: Re: Radar reflective gilet
Post by: quixoticgeek on September 12, 2019, 12:29:56 pm

Note to self, check darwin award site on Monday... :p

J
Title: Re: Radar reflective gilet
Post by: T42 on September 12, 2019, 01:37:10 pm
Alas, according to the GPX we were only doing about 25 kph.  I think the poor darling got confused by all those shiny spokes.
Title: Re: Radar reflective gilet
Post by: JohnL on September 12, 2019, 04:39:14 pm
Would chaff work? I can see it rapidly decelerating from air resistance. I would have thought a fixed reflector would work better...
ETA: it would look super cool though...
Title: Re: Radar reflective gilet
Post by: hatler on September 12, 2019, 08:22:55 pm
Further thought, speed camera chaff devices are probably available off the shelf from Le Maitre's craft herpes glitter range.

(Can you fire a pyro with the current from a hub dynamo?  Paging Big Clive.  Big Clive to the PINK courtesy phone please...)
You'd probably need to chuck a capacitor into that one to ensure there was a big enough kick. That used to be my line but for the life of me I can't remember the Vs or As required to set a puffer off.
Title: Re: Radar reflective gilet
Post by: hatler on September 12, 2019, 08:25:00 pm
Or get a £20 compact radar reflector for a RIB and mount it to your rack...

https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version (https://www.marinescene.co.uk/product/1835/tube-type-radar-reflector-powerboat-version)
Those tube reflectors are, I believe, quite sensitive to orientation. When applied to the mast of a sailing yacht they apparently become invisible in a big enough breeze that results in the boat heeling more than a bit.
Title: Re: Radar reflective gilet
Post by: hatler on September 12, 2019, 08:28:38 pm
The only time I've got that camera to fire we were two abreast (matthew) and doing 46mph. I've subsequently been past it on my own a number of times in the 35 - 40 range and never got it to fire.
Title: Re: Radar reflective gilet
Post by: Kim on September 12, 2019, 08:30:23 pm
When I set it off I was doing about 35.
Title: Re: Radar reflective gilet
Post by: Jurek on September 12, 2019, 09:00:39 pm
I've made it go off whilst doing 49mph on the Bianchi.
( I think I must've really been giving it beans).
In the early days of FNRttC.
Title: Re: Radar reflective gilet
Post by: Basil on September 12, 2019, 09:10:05 pm
Some years ago i heard about yoofs setting off the speed camera on the Pershore Road by swinging a paint tin round on a piece of string.
Title: Re: Radar reflective gilet
Post by: Kim on September 12, 2019, 09:15:05 pm
Some years ago i heard about yoofs setting off the speed camera on the Pershore Road by swinging a paint tin round on a piece of string.

I set the speed camera on the Bristol Road off by annoying an Audi driver (by existing) into flooring it past the speed camera.  Sadly it was pointing the wrong way to capture my massive grin.
Title: Re: Radar reflective gilet
Post by: Cudzoziemiec on September 12, 2019, 09:39:08 pm
Some years ago i heard about yoofs setting off the speed camera on the Pershore Road by swinging a paint tin round on a piece of string.

I set the speed camera on the Bristol Road off by annoying an Audi driver (by existing) into flooring it past the speed camera.  Sadly it was pointing the wrong way to capture my massive grin.
;D
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 12, 2019, 09:42:00 pm
I've made it go off whilst doing 49mph on the Bianchi.
( I think I must've really been giving it beans).
In the early days of FNRttC.
Didn't Leggy and Adrian (perhaps you as well) set it off then apologise/explain to a grumpy motorcyclist that it was them, not he  that caused the flash?
Title: Re: Radar reflective gilet
Post by: hatler on September 13, 2019, 08:25:00 am
Matthew and I overtook a car just before setting it off. There was no subsequent conversation however.
Title: Re: Radar reflective gilet
Post by: Greenbank on September 13, 2019, 10:10:05 am
Would chaff work? I can see it rapidly decelerating from air resistance. I would have thought a fixed reflector would work better...
ETA: it would look super cool though...

Yay! Litter!
Title: Re: Radar reflective gilet
Post by: matthew on September 13, 2019, 10:58:04 am
Matthew and I overtook a car just before setting it off. There was no subsequent conversation however.

I am not sure we triggered the camera but we were either side of one of the large scooters. Mini Hatler was driving you down the hill at a fair lick but the camera didn't fire which was why the rider had a joke with us. If you set it off at a different time I wasn't involved.
Title: Re: Radar reflective gilet
Post by: JohnL on September 13, 2019, 04:13:55 pm
Would chaff work? I can see it rapidly decelerating from air resistance. I would have thought a fixed reflector would work better...
ETA: it would look super cool though...

Yay! Litter!
And that....
Title: Re: Radar reflective gilet
Post by: Kim on September 13, 2019, 04:48:26 pm
Would chaff work? I can see it rapidly decelerating from air resistance. I would have thought a fixed reflector would work better...
ETA: it would look super cool though...

Yay! Litter!

Said anyone working in the dark corners of a theatre where the stuff was used for a panto umpty years previously.
Title: Re: Radar reflective gilet
Post by: Tim Hall on September 14, 2019, 04:56:37 pm
Reporting back. I didn't get my arse in gear to molish the previously described gilet, although I did have a space blanket in my first aid kit. This remained unused.

The route was the "proper route" taking in a speed camera in a 20mph zone in Coulsdon  a camera at the foot of Reigate Hill in a 30 mph zone and the o e just past the golf course on the descent to Brighton.

Anecdota said that no one had ever set off the Coulsdon camera, suggesting perhaps it wasn't switched on. I gave it beans anyway, but no flash.

Reigate Hill had a lot of motorised traffic, due to the southbound M23 being closed for roadworks. I waited for a suitable break and sound the bike up to R17. While the lower stretch of the hill has been resurfaced,  the initial part was as rough as a fence post,  with filling shaking corrugations. I was lined up for possible success but when I rounded the final corner there was a sea of brake lights, as I'd caught the motorised traffic. Applied the brakes and coursed my luck.

The run into Brighton was at about 0830 so again lots of motorised traffic, the drivers of which braking as the went past the camera. No flash here either.

Summary: No flashes, no one died.
Title: Re: Radar reflective gilet
Post by: hatler on September 14, 2019, 06:44:48 pm
I was at 39mph through the Brighton camera but wasn't aware of any flash.
Title: Re: Radar reflective gilet
Post by: McWheels on September 14, 2019, 09:41:08 pm
Sadly I don't think chaff will help you. The piggy-banks appear to operate by Doppler, and thus most likely to be continuous wave rather than pulsed.

The radar cross-section of your average oik onna bike won't be much compared to the metal back end of a Q8, so don't be surprised. A bit of corrugated tin facing said camera would probably be sufficient though, and anecdotally it appears a second rider is sufficient.

Given the choice I'd go more active jamming, albeit illegal, so this is strictly a think-piece.  :demon:
Provided one can determine the base frequency of the camera, which is a box of tricks in its own right, then there are 2 things one could do.
1. False inject a ludicrously high speed into it, say 240mph. v= df/f*c/2, so 240mph difference to 10Ghz is only 16kHz. Incidentally 35mph comes out at about 2.3kHz. This is also why you can't outrun a speed camera. Compared to c, your pedestrian dawdling at anything less than Mach 3 is too easy to set a receiver for. However the Beak is unlikely to agree the camera was operating correctly when 240mph comes before him from a 10yr old Citroen. Potential drawback that if this is the 3rd time, your car might get Heavily Investigated. And this might be a bad thing.
2. Overload the base frequency, so it can't detect the higher Doppler against the noise floor. Bit harder as you have to be really precise when capturing the base frequency, and correct your apparent speed to the stationary device, and hope they're not doing FMCW, but the payback is that you don't get flashed at all.

I'd recommend against barrage jamming, simply because it's much easier to spot that Something Is Going On when SkyTv, AirWaves and who know what else get all fuzzy when that Honda CRV goes past. You also might be actually interfering with Something Important, and that wouldn't be right.
Title: Re: Radar reflective gilet
Post by: matthew on September 19, 2019, 11:08:56 am
Sadly I don't think chaff will help you. The piggy-banks appear to operate by Doppler, and thus most likely to be continuous wave rather than pulsed.

The radar cross-section of your average oik onna bike won't be much compared to the metal back end of a Q8, so don't be surprised. A bit of corrugated tin facing said camera would probably be sufficient though, and anecdotally it appears a second rider is sufficient.

Given the choice I'd go more active jamming, albeit illegal, so this is strictly a think-piece.  :demon:
Provided one can determine the base frequency of the camera, which is a box of tricks in its own right, then there are 2 things one could do.
1. False inject a ludicrously high speed into it, say 240mph. v= df/f*c/2, so 240mph difference to 10Ghz is only 16kHz. Incidentally 35mph comes out at about 2.3kHz. This is also why you can't outrun a speed camera. Compared to c, your pedestrian dawdling at anything less than Mach 3 is too easy to set a receiver for. However the Beak is unlikely to agree the camera was operating correctly when 240mph comes before him from a 10yr old Citroen. Potential drawback that if this is the 3rd time, your car might get Heavily Investigated. And this might be a bad thing.
2. Overload the base frequency, so it can't detect the higher Doppler against the noise floor. Bit harder as you have to be really precise when capturing the base frequency, and correct your apparent speed to the stationary device, and hope they're not doing FMCW, but the payback is that you don't get flashed at all.

I'd recommend against barrage jamming, simply because it's much easier to spot that Something Is Going On when SkyTv, AirWaves and who know what else get all fuzzy when that Honda CRV goes past. You also might be actually interfering with Something Important, and that wouldn't be right.

I think you may have misinterpreted the intent of this thread, the aim here is to trigger the camera to flash whilst you cycle past at circa 35mph on a decent. Being on a bike and only being there once every three to four months the likelihood of the local constabulary tracing you to charge you with furious cycling is limited so it is primarily about the Kudos points in the peleton.
Title: Re: Radar reflective gilet
Post by: McWheels on September 19, 2019, 04:39:15 pm
Setting it off? The conversation had drifted away from that, but it's far easier. In fact the yoofs wiv a paint pot onna string had the right idea. A decent metal target going fast enough.

Or a corner relfector at least quarter wavelength in size. Ideally a flat metal plate is best, but its directionality is poor. Metal mudguards would help, or plastic with tin tape. Humans have a rubbish RCS, and a bike is very thin. Panniers would help, but not aerodynamically.