I'd like to have a strong metal spike, fired into the road by an explosive cartridge, attached to a metal cable with a brake on the cable reel. It should be manually operated.

It would only be for emergencies such as when a car is sliding out of control towards a cliff with no hope of stopping. It should be strong enough to hold the car after it goes off the cliff.

60 MPH is 88 ft/sec, so an 88 ft cable should allow for 3G deceleration (96 ft/sec/sec). I'd want the brake set for 6G in case of higher speeds or brick walls.

I realise it would damage roads, and I don't want the car in front of me to have one, but in a life or death situation it could help. Kind of like a parachute in a tall building - it might actually kill more people than it saves, but I'd like the chance to be in control.
-- tolly2, Feb 05 2002

Automotive aerobraking http://www.halfbake...otive_20aerobraking
Won't let you dangle from a cliff, but then who'd want to? [phoenix, Feb 05 2002, last modified Oct 17 2004]

"...I don't want the car in front of me to have one..."

Which, oddly enough, makes it sound like a 'me too'.

Check out my 'Automotive Aerobraking' idea.
-- phoenix, Feb 05 2002


I'm slightly wondering how well you could get this to stick in the ground or road surface. Looking at the damage a fast car crash can do to a car, an anchor is going to face horrendous forces as it impacts and catches. You seem to think you can spread the force over a few seconds, but if you want the anchor to do anything other than bump behind you, you're going to have to find a way to make it stick into the road surface.
-- pottedstu, Feb 05 2002


And asphalt is only a few inches thick anyway. An anchor would likely not hold.
-- StarChaser, Feb 08 2002


You want to make cars safer by putting more explosives in them?
-- bookworm, Feb 08 2002


The amount of explosive force necessary to drive the spink into the road would probably shoot the car up into the air and you'd be even worse off.
-- mlfnet, Apr 30 2003


springiness (is that a word?) of the cable.

I beleive "elasticity" is the word you were searching for. anyhoo... why are you so caught on this idea that you need and emergency, emergency brake. if you have decent tires, no hydralic leaks, good brake pads and a properly adjusted ebrake then you shouldn't have any trouble stopping your car, even in the "fell asleep at the wheel while street racing on the cliff" scenario. In addition, if you have enough of a reaction time to set this thing off then you probably have time to swerve away from the edge.
-- Mr Machine, May 19 2004


I saw one of these on the UK TV programme "Tomorrow's World", which used to show off shiny new tech. Anecdotally, this caused said tech to fail and disappear without a trace.

I think it must have been around 1990 I saw it, but possibly as a piece of archive footage they'd dragged out to show again: a Mini with an explosively powered bolt and a chain or cable attached to the back axle.

They took it for a test drive. Hit the brake hard, which triggers the bolt. It tore the back axle out and the rest of the car cheerfully carried on. Most amusing!

Quick search didn't show up anything linkable, sorry.
-- maffu, Dec 20 2008


//It tore the back axle out and the rest of the car cheerfully carried on//
More than likely - the Mini is front-wheel drive.
Might stop a rear-wheel drive car quicker, but having seen American Graffiti, this may not be the case.
-- coprocephalous, Dec 22 2008


The problem is that you're trying to stop the whole car, whereas it is really only essential to stop the driver, who is much lighter.

What you need is to replace the conventional seatbelt with a four-point harness. The harness is not connected to the car (as would usually be the case), but rather to the Spike-o-Matic device. Upon activation, the spike is deployed, harpoonesquely, through the rear window, and lodges in some fixed object. The driver is then extracted from the car via the back window, with only minimal load on the spike, tether and fixed object.
-- MaxwellBuchanan, Dec 22 2008


An additional plus, [MB], the flight through the back window is likely to remove arms and legs thus reducing the load further. I like it.
-- MechE, Dec 22 2008



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