h a l f b a k e r yWhat was the question again?
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“Black” ice, freezing drizzle, and sleet are some of the most dangerous driving conditions to be found. My proposal is to have infrared laser beams mounted on the front bumper to melt the ice before the tires reach it. The control will be tied into a thermometer, a hydrometer, and the windshield wipers.
When the right weather combination exists, the lasers will turn on and aim down and slightly ahead of the vehicle. As vehicle speed increases, the lasers will have to be aimed further ahead and the power increased (due to the more oblique angle). I don’t think that the lasers will have to be aimed further than the headlights. A manual switch will also be available for those times when you don’t trust the sensors. I imagine that the ice will be vaporized into a cloud of steam. Note: this system is not intended for heavy snow.
The thermal properties of ice.
http://www.engineer...box.com/24_162.html
[AbsintheWithoutLeave, Jan 11 2005]
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It's cold here some would say. I almost lost the car a few hours ago, I have to go and start it every eight hours. The water froze in the pump house and I had to raise the temp and insulate the door. It's too cold to touch the floor with shoes on I notice. Yeah, I need a laser in this cold snap. |
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A 2 metre wide car moving at just 16 km/h (10 mph) over 3mm thick ice would have to boil over 26 litres of water a second! That is about five and a half imperial gallons of water from 0 degrees to > 100 degrees in a second. I've forgotten the exact latent heat and specific heat figures for water, but I remember they're pretty big. I guess you could save energy by just aiming the beams at where the tyres are going to be, but that is still a lot of energy.
I suppose the advantage is that the weight of the car's bolt-on nuclear power pack would give better traction. |
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Under the right conditions ice can reflect like a mirror. I would not want to be on-coming traffic. |
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Main advantage: roadkill sauté. |
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Would there be a setting for nailing the oncoming idiot who refuses to dim his brights? Imagine ...the the result of fried retinas on the bastard careering into oblivion in your rear view mirror. Sign me up! |
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Yeah, permanently blind the oncoming traffic... [JF], bake this and I'll recommend you for a Darwin award. |
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<rubbing it in> All this talk about ice: It must be winter somewhere. Actually, it did go down to 25C last night. |
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[Absenthe], what about the energy requirements to just melt the ice? Even though [Coal Drag] mentions vaporizing, the main thing is just to melt the ice. |
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[robinism] I looked it up - the latent heat of melting of ice is 334 kJ/kg - that is to get one kg of ice at 0 degrees to 1 kg of water (about a litre) at 0 degrees takes 334kJ.
So, to melt those 26 litres (assuming it is *just* about to melt anyway) requires334*26= 8684 kJ/sec. That's a required output of almost 9MW (cf. my 2 litre petrol engine's 95-100kW output) just to drive along at a little more than jogging pace. And that is assuming all the laser radiation is absorbed by the ice. Anyone have figures for laser efficiency? |
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So in that scenario, melting the ice requires about 100 times the total power output of the engine? |
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Maybe the goal could be, not to melt all the ice, but just to pock-mark it, so it isn't so slick. Have the lasers fire in bursts to put little pock marks in the ice, and also fire them just where the tires will be, as [Absenthe] suggested. |
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If a succession of laser-equipped cars went over the same patch of ice, it eventually would be melted. |
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