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  #1 (permalink)  
Old 12-11-2004, 10:19 AM
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fact or fiction?

This about the 10th time I've received this email warning Fact or fiction? I've done the search here, no results.
Subject: HYDROPLANING


I don't know if this is true, but it is something to think about anyway.



Subject: Fw: Hydroplaning
Something we may have never thought of.
A 36-year-old female had an accident several weeks ago and totaled her car.
>A resident of Kilgore, Texas, she was traveling between Gladewater &
>Kilgore. It was raining, though not excessively, when her car suddenly began to hydroplane and literally flew through the air. She was not seriously
injured, but very stunned at the sudden occurrence!
When she explained to the highway patrolman what had happened he told
her something that every driver should know --- NEVER DRIVE IN THE RAIN WITH YOUR CRUISE CONTROL ON!!.
She had thought she was being cautious by setting the cruise control
and maintaining a safe consistent speed in the rain, but the highway
patrolman told her that if the cruise control is on and your car begins to hydroplane -- when your tires lose contact with the pavement, your car will accelerate to a higher rate of speed and you take off like an airplane.She told the patrolman that was exactly what had occurred.
We all know you have little or no control over a car when it begins to
hydroplane. You are at the mercy of the Good Lord. The highway patrol
estimated her car was actually traveling through the air at 10 to 15
miles per hour faster than the speed set on the cruise control.
The patrolman said this warning should be listed, on the drivers seat
sun-visor - NEVER USE THE CRUISE CONTROL WHEN THE PAVEMENT IS WET OR
ICY!,along with the airbag warning. We tell our teenagers to set the cruise control and drive a safe speed--but we don't tell them to use the cruise control only when the pavement is dry.
The only person the accident victim found who knew this (besides the
patrolman) was a man who had a similar accident, totaled his car,and
sustained severe injuries.
If you send this to 15 people and only one of them doesn't know about
this, then it was all worth it. You might have saved a life.

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Old 12-11-2004, 11:31 AM
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True

A car will do this - this is especially dangerous in a turn.
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Old 12-11-2004, 11:55 AM
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Sounds bogus. Since most, if not all speed controls sense drive-shaft speed the worst that should happen if you lose traction is the engine speed should stay constant. Still not a good idea, cause when the rear end is loose and the front end hooks up - instant [color=yellow]end-o[/color] (don't ask how I know this, just trust me on this one!!). And there is no conceivable mechanism to cause a car to go airborne on a flat road unless it was in an accident on the TV show CHIPS where every car on the road eventually cleared 20' vertical w/ two twists.
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Old 12-11-2004, 12:39 PM
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I never experience this, drove many miles back and forth from Virginia Beach, Va to Jacksonville, Fla. I drove all the time with the cruise set and in the rain many of the times. When I felt anything different (mostly from almost falling a sleep and weaving), a little brake action put everything back into perspective.

Dutch
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Old 12-11-2004, 01:09 PM
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I am not saying that you can launch yourself airborne. I am only saying that CC can cause you to hydroplane or make the situation worse.

It is all based on circumstances:

Interstate, heavy rain, cruise set at 70mph, 4 cylinder front wheel drive car.

Car begins up a steady grade that is also in a curve to the right.

As the incline causes the car to slow, the CC adds in extra throttle to increase speed. This sudden increase causes front end to push to the outside of the turn and car begins to hydroplane.

Uncorrected (by hitting brakes or turning off cruise) car will attempt to maintain speed - this causes the car to hydroplane more and skid faster to outside of turn. Unskilled driver violently jerks wheel to counter skid and also locks brakes at same time - car will go right off the outside of the road, which in this case is elevated and turning away from car's new direction of travel.

Car goes soaring off the road and crashes into the median.

FL does a great job of grading their roads to keep water off the roadway. WV does not. It is not uncommon for the base of a bridge or the inside of the road to have standing water - on the highway. I was hydroplaning on the way to work and expect to do so on the way home from work.

As a general rule, not counting road surface, tire tread or water depth, a car will start to hydroplane at 9*sq root of the tire pressure.

For a normal car, figure about 50mph. Shows how important good tires are....
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Old 12-11-2004, 01:14 PM
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I'd have to say this is bogus...a flying car??

However, I did once have a problem driving a company car, a small/medium size Dodge. I was driving with the cruise engaged on the Interstate, in Winter. The roads were dry, but I crossed a bridge that had an icy film. Remember those "Bridge Could Be Icy" signs? Anyway, the car did break loose.
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Old 12-11-2004, 01:25 PM
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On our european highways itīs worse on the right hand lane as the big trucks groove the road and water lays in there.
German autobahns are bad as they are flat not cambered or tilted to aid drainage.
Itīs all in here, http://www.nap.edu/openbook/nch016/html/45.html click the page to move on.
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Old 12-11-2004, 02:55 PM
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If you look at how a cruise control works, you will see that it does not accelerate when the tires break traction.

The cruise control gets the vehicle speed from the speed of the tires, not the distance traveled across the pavement. They usually get the reading from the drive shaft, drive axle, wheel speed sensors, or speedometer. The older add-on systems that you could buy at places like Sears, simply had sensor that took a reading from pieces that were attached to the driveshaft. They were usually put on with something like strapping tape. When the tires break traction when the cruise control is on, they will spin faster momentarilly, until the cruise figures it out, then slow down. They spin faster, due to the reduced resistance, then the cruise gets a reading that the vehicle is going faster than the set speed, and slows it (the tire)down. With everything computer controlled, the time that the wheels speed up will be very short. Also a properly wired and operating CC system will loose power and disengage when the brake pedal is moved.

You can test this by raising a vehicle so the wheels are off the ground, and setting the cruise control. That would put the vehicle in a similar situation. The vehicle is not moving the speed that the cruise is set at. If it was going to accelerate in a skid, it sure would when the vehicle is on jack stands, cause it is not only going slower, it is stopped.
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Old 12-11-2004, 03:05 PM
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Quote:
Originally posted by paperairplane
I am not saying that you can launch yourself airborne. I am only saying that CC can cause you to hydroplane or make the situation worse.

It is all based on circumstances:

-----------------------------------
As a general rule, not counting road surface, tire tread or water depth, a car will start to hydroplane at 9*sq root of the tire pressure.

For a normal car, figure about 50mph. Shows how important good tires are....
I'm sure there are circumstances that cruise will exacerbate a traction problem. However the situation postulated in the original post is not likely. First, the cruise control is reading drive shaft speed so if you lose traction, the rear wheels will speed up to the theoretical car speed and stay there and not 'accelerate to a higher and higher speed. . .'. Second, if you lose rear wheel traction, even if the engine takes off uncontrolled, that would just spin the wheels faster with no affect on car speed - it takes traction to move a car forward so one that is hydroplaning is a victim of gravity but not of motive power; If it is heading upgrade it will slow down, if heading downgrade, it will speed up due only to gravity. Uncontrollable sliding is the biggest danger.

I am not familiar with the units '*sq root'. Is that a misprint?
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Old 12-11-2004, 03:21 PM
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Although I've never heard that formula...9 x sq root... the math is correct.

9 x sgrt32=
9x 5.65= 50.9 mph


It does seem to me that "hydroplane speed" would be more a factor of surface area, velocity and weight not to mention countless other factors.
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Old 12-11-2004, 03:48 PM
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I agree with paperairplane. Flying cars.......waaaait a minute. Now doing a helicopter spin well maybe. If you've never done a "louie" well I suppose it could triger the imagination.

As far as the cruise in slipery conditions...having lived a lot of life in Minn and farther north..it's not a good idea. Learn to feel the road and conditions with your foot and hands on the wheel and leave the cruise off. Why push your luck.

My diesel dually does not do well at all when it is slipery with the cruise on. Actually straight ahead.. not bad but as soon as you turn, it wants to lose it. Now part of this is the limited slip rear end but what really happens is that as you turn you tend to lose speed due to friction losses just like an airplane. With the cruise on, it senses speed loss and applies power. If it is slippery around you go. Same thing happens when you start going up hill...with cruise on if it is slippery as you start slowing down going up the hill it applies power. You may start fishtailing and the cruise tries to maintain speed and again around you go. Now nearly 4 tons of truck tries to go in a straight line even if it is turned sidways so it can be a handfull. Throttle management will save you most of the time but the cruise was not meant to do this.
Once again. the new and inexperienced drivers get in real trouble quickly due to lack of training. Drivers training doesn't prepare people for nasty weather conditions. Short of getting out and learing about it real time, there isn't too much you can do. Maybe all driver training classes should be done in the winter up north. Nothing like driving around on a frozen lake to teach you about driving when it is slippery.

For most of us hotrodders. The rod is life and we are acutely aware of our wheels. Doing smokie burnouts and sawing the wheel back and forth we learn to drive when the wheels are spinning and the car is slipping and sliding. Others who give a GGD about cars don't understand the effects of rain, snow, sleet, wind or anything else on the road and don't care. They step on the gas and expect to go regardles of conditions. Have a crash and " the .....car just took off and flew through the air like it had a mind of it's own".

Little do they know LOL

bentwings

I forgot,

Willys....sq root mathematical term square root. a number times itself is called "squared" for example 3 squared 3 x 3 =9 or 3^=9

sq root of 9 is the number times itself to make 9 thus 3 is called the sq root of 9.

In real life terms:
The "sq root" is the number of hours you quoted a job and were paid for. 9 is the number hours you took to do the job.


bentwings

Last edited by bentwings; 12-11-2004 at 03:48 PM.
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Old 12-11-2004, 05:36 PM
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I have an idea lets get the mythbuster guys to check this one out. Oh and by the way I am sure that willys knows what a square root is, kinda hard to get your engineering degree with out math 101.
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Old 12-11-2004, 07:04 PM
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True. I just wondered what the square was from which the root was to be extracted!
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Old 12-11-2004, 08:45 PM
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If you go to truthorfiction.com enter hydroplane.They have an explantion there.
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Old 12-11-2004, 11:23 PM
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The real reality is that I always thought "roots" had something to do with teeth...like root canal.. maybe there is a square root canal

speaking of math

I just went back and re-read some of the posts....hydroplane speed is 9* sq root of tire pressure.

so my dually has 64 psi in the tires (really) so sq root is 8. 8 x 9 =72 mph?? I wouldn't think of going 70mph in any rain or any wet road with it..loaded or not. It has good tires (Michelin load range E) all around and is a real handfull when it is slippery with trailer or not.

I much prefer to poke along at 50-55 under control and get there an hour later than rocket along at 70 and wind up in the ditch or cause and accident.

I gotta read the hydroplane story again.

bentwings

Last edited by bentwings; 12-11-2004 at 11:23 PM.
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