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Evel Knievel Intersections

Who needs an overpass, anyway?
  (+13, -6)
(+13, -6)
  [vote for,
against]

As a solution to traffic jams at intersections, it is often proposed that an overpass be built for, say the east/west traffic, thereby reducing the need for lights. Of course this is a pretty expensive proposition, and so is implemented only at the very busiest of intersections.

BUT! Evel Knievel has shown the way! Driving up a ramp and leaping across a bunch of cars has GOT to be equivalent to driving across an overpass at an intersection! Vastly less expensive to build! Just two ramps and some Minimum Speed Limit signs, that's all we need. At every significant intersection, of course!

Vernon, Jun 17 2005

My mistake - a related idea elevated_20stop_20lights
[gnomethang, Jun 17 2005]

Take Your Chance Railroad Crossing Take_20Your_20Chanc...Railroad_20Crossing
As mentioned in an annotation here. [Vernon, Jun 17 2005]

Stunt-By-Wire Stunt-by-wire
Shameless self promotion [david_scothern, Jun 21 2005]

Evil Knievel Highway Evil_20Knievel_20Highway
Shameless theft! [ldischler, Jun 22 2005]

[link]






       Some cars just can't hit a ramp very well. But, maybe put magnets somewhere???
daseva, Jun 17 2005
  

       Didn't we do this already? I seem to recall a cool [Bz] piccy as illustration.
*Edit - My mistake, it was the piccy of the car in the air that got me thinking! m(Linky)
gnomethang, Jun 17 2005
  

       The closest thing I could find was an annotation in "Take Your Chance Railroad Crossing" (linked).
Vernon, Jun 17 2005
  

       Heavier cars would find it a lot more difficult to cross this, there would need to be something that could weigh the car before it arrives at the ramp and gives ample warning as to exactly how fast they should be going.
fridge duck, Jun 17 2005
  

       I just know I'm going to spill my coffee.
Worldgineer, Jun 17 2005
  

       I used to drive over a railroad levy (a steep ramp up to the track on each side), where the speed limit was 50, but the up and over was a slow to 30. It sucked to slow down, and the tracks on top were extra bumpy. One night, late getting home, I said screw it, I'm not slowing down, hit it at about 62 mph, and it was perfect. No bumpy tracks, smooth landing.
oxen crossing, Jun 17 2005
  

       I'm all for it as long as they put a loop somewhere also. +
sartep, Jun 18 2005
  

       "Vehicle factory warranty void for residents of Pittsburgh, Cleveland, Toronto, Chicago, New York..."
RayfordSteele, Jun 18 2005
  

       Tractor trailers?
omegatron, Jun 18 2005
  

       [fridge duck] why weigh the cars? Would the heavier vehicles fall faster? Would they need to go faster than a lighter vehicle?
bristolz, Jun 18 2005
  

       yes, I suspect. Not the falling faster, but the lift.   

       Octopus intersections? I've thinking about flexible wheel guides that would drop to allow those who face a red to merry on at their own skill. Quite dangerous, though, thought I.   

       With my trademark horrible writing style I proposed a 3d intersection that would allow for momentum to loop you through a left/right turn. It was boned of course.   

       In the event of a traffic backup, being stuck on the high side of the loop turn would not be a great thing, I must admit.
Zimmy, Jun 18 2005
  

       [fridge duck], [bristolz], and others, the Minimum Speed Limit would be sufficient for all weights of vehicles. HOWEVER, **LENGTHS** of vehicles is another matter. Longer vehicles need to go faster, due to a kind of "lever arm" effect of the front end going off the ramp not-fast-enough before the back end goes off the ramp (the front end starts to fall while the back end is still supported against gravity by the ramp).
Vernon, Jun 18 2005
  

       [gnomethang] we have done this one already (see link)
david_scothern, Jun 21 2005
  

       [david scothern], yes, I see the similiarities. But a couple of differences are here, too. A Minimum Speed Limit sign means that the needed speed to jump a gap, for average-length vehicles (with average coefficient of drag), has been pre-computed, so this Idea does not depend on every car being able to autocompute the needed speed. I'm pretty sure some standard formulas can be devised for vehicles that have significantly different length and drag parameters, such that they need to go some X amount faster than the minimum speed. This does not mean the car needs anything fancier than a calculator with X fixed as a Constant (driver enters Minimum Speed and calculator displays the speed needed for that vehicle to make the jump).
Vernon, Jun 21 2005
  

       I disagree. There's not just a minimum speed, there's an optimum and a maximum as well. If you hit the ramp at just the right speed, you'll land on the landing ramp with no vertical motion relative to the ramp. Take off too fast and you'll fly over most of the ramp and come down with a massive crash as your suspension fails. You also need some way of ensuring that there isn't someone braking hard/stationary on the landing ramp. Leaving it to the skill of the average 17-year-old driver, or stressed guy coming home from work, is a recipe for disaster. You need some centralised control to make this work.
david_scothern, Jun 22 2005
  

       Here at the HalfBakery we don't usually have to worry too much about specific-case problems with a wild Idea. The "fun" aspect gives us leeway to play. :)   

       Nevertheless, you are at least a little mistaken about flying over most of the landing ramp, unless you go a LOT too fast. A ballistic object (which is what the vehicle becomes once fully airborne) always travels in a parabolic route. A landing ramp is a wedge, and a fair range of speeds will yield parabolas that intersect that wedge in various places (depends on angle of wedge). Remember the trick question, "If you use a gun to shoot a bullet horizontally, and drop another bullet from the height of the gun at the moment the first is fired, which will hit the ground first?" Discounting curvature of the Earth, the answer is that they land at the same time. Sure, a setup involving ramps is not the same as shooting horizontally, but the rate of gravitational ACCELERATION is what intersects parabola and wedge across a range of speeds. AND I suspect the shape of the landing wedge could be modified to better accommodate a range of landing points (all of which are speed-dependent), such that the car hits at a shallow enough angle to not ruin the suspension. The landing ramp would likely have to extend below ground-level for this to work, but if it increases safety (and the trench provides dirt for the above-ground ramps), then such a design might well be worthwhile.   

       I do agree that you COULD go fast enough to go too far before touchdown, but should something like this ever be implemented, you can be sure that Driver's Education will have special cars that give people a chance to learn why they need to go the Minimum Speed (for the vehicle) and not much faster. (I can also envision a special "training jump" in which the gap between the ramps is solid glass, looking like its not there but giving people the chance to go too slow and survive to see by-how-far they missed the landing ramp.) I think you'll be surprised by how many people could get accustomed to an Idea like this (and use it correctly in the Real World, not braking too quickly after landing) if they had a way to practice safely.
Vernon, Jun 22 2005
  

       Maybe, invent a "smart wedge" that rests on two guiderails and pneumatically shifts position based on IR readings form the approaching objects in flight.
daseva, Jun 22 2005
  

       Hmm... you've still not told me how you're gonna avoid Uncle Fred's battered old pickup that's broken down (again) and is stationary on the landing ramp (Yeah, I know, it must have stopped quickly - well, the engine seized during the jump and it stopped almost immediately on landing). With its parabolic shape, there's no way you can see the landing slope until you're committed to the jump.
david_scothern, Jun 22 2005
  

       Accidents happen. Your suggested automatic electronic system will have its own failure modes, will it not? Could Uncle Fred's vehicle have been put into neutral and allowed to coast to the side of the rampway?
Vernon, Jun 22 2005
  

       In general, [Vernon], adding a degree of freedom to any system makes it all the more vulnerable to error. In the case of your idea, the verticle motion of the automobile can be considered an added degree of freedom. A big one that might just be a little too dangerous if not, at least partially, corrected with some stabilizing mechanism, such as my electronic wedges.   

       Hmm, what about very strong tarpaulinish landing wedges that will give to the landing vehicle. This might ease the stress of decent. I like your idea, I just think the landing wedge needs modified.
daseva, Jun 22 2005
  

       [daseva], I was responding to [david scothern]'s Idea which is linked above. I do not think ill of your suggested improvements of this Idea. Thanks!   

       [ldischler], no, I did not know about your Highway when I posted this. If you think this should be given the m-f-d, then do so and I won't object.
Vernon, Jun 22 2005
  

       /(the front end starts to fall while the back end is still supported against gravity by the ramp)./   

       Come on, Vernon, haven't you seen Speed?   

       As someone who designs the rubber bits that hold suspension and transmission into cars, I can say with confidence that designing systems to withstand this sort of treatment regularly would result in very expensive vehicles. Even Land Rovers wouldn't be able to do it currently, and they're designed to withstand parachute landings!
egbert, Jun 22 2005
  

       [egbert], I've seen enough movies to be pretty confident about what I wrote. Remember "Groundhog Day"? The truck is driven straight over the edge of a quarry, but still lands upside down. The reason is that as soon as the front wheels clear the edge, gravity starts pulling it down. Since the back wheels haven't cleared the cliff, the net result is some slight forward pitching of the vehicle. Conservation of that initial small Angular Momentum results in the upside-down orientation at impact. (You can see something similar happening at the end of another movie, I think it was "Thelma and Louise".)   

       When going off a ramp you have the same phenomenon only a little less obvious. How many ramp-jumps have you seen where the rear wheels of the vehicle hit the landing ramp before the front wheels? Almost always the front is pitched-down when the vehicle arrives at the landing ramp! This was true even in that James Bond movie "Man with the Golden Gun" where the car did a barrel roll while jumping between ramps. (Don't count motorcycles because the rider's relatively significant body mass and ability to change postion can influence the overall vehicle orientation. Think cars and trucks only!)   

       So, my point is simply that the longer a vehicle takes to get entirely off the ramp (due to being a long vehicle!), the more forward-pitching and overall angular rotation will occur during the jump. And that's why a longer vehicle must go faster.
Vernon, Jun 22 2005
  

       It wouldn't... to prove this, imagine driving off slowly. There will come a point where gravity is pulling your front wheels down, while your rears are still supported on the ramp. How much rotation occurs just depends on how long this condition lasts. Shorter vehicles, or faster ones, will thus rotate less.
david_scothern, Jun 22 2005
  

       [david scothern], you're mostly repeating what I've already written here.   

       [fqhwgads], the movies I mentioned didn't use computer tricks to manipulate what those cars did; they were real cars doing real things. And the problem with your suggested extra lip designed to help longer vehicles (by giving the nose an extra upward push as it goes off the edge of the ramp) is that when the BACK wheels go over the edge, they will be boosted too, and meanwhile the front will STILL have had time to begin pitching! The solution really is a faster speed for longer vehicles -- which in turn means a more-special landing-ramp, because as has been pointed out above, a faster vehicle can jump too far. I tend to think the longer curving-down ramp I suggested, that extends below groundlevel (and of course then curves upward back toward the surface) would be optimal.
Vernon, Jun 22 2005
  

       Stubborn [fqhwgads], the only way to keep the car's orientation perfectly still whilst flying through the air would be to drop the entire ramp from under the car as it was crusing over it, BEFORE the front tires left the lip. Otherwise, say 'allo to my little friend!   

       Uhh... I mean, otherwise GRAVITY WILL TILT THE FRONT END. Enough! You like redundant debates, [fqhwgads]. I do to, to an extent. Now, if you look at the first anno, I hint at a way around the problem. Have a electromagnetic awning over the end of the ramp that turns on when the car's front tires leave the ramp, and stays on until the car's back tires leave the ramp. This will simulate my "dropping the ramp from underneath" method mentioned above.
daseva, Jun 22 2005
  

       this was kinda cool until it got overanalyzed.
sophocles, Jun 22 2005
  

       what sop said. can I call you sop?   

       //As someone who designs the rubber bits that hold suspension and transmission into cars// <snigger> someone has to do it! hey, its about time I fed you again!   

       bless him (evel) couldn't he spell Evil?
po, Jun 22 2005
  

       [po] you can call me anything you wish. I'd shorten your name, but I wouldn't want you getting P.O.'d.
sophocles, Jun 22 2005
  
      
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