Posts Tagged ‘cruise control’

Hydroplaning And Cruise Control – Safety Concerns

Posted on: April 16th, 2013 by SilverStar

hydroplaning and cruise control Let me describe the problem when combining the use of cruise control under conditions that create hydroplaning.

Let me start with the cruise control,

Cruise control has two main functions:

To prevent fatigue on long trips and to help people with lead feet from getting speeding tickets. Especially here in Edmond.

There are 4 main parts to the operation of the cruise control:

  • You have a very sensitive speed sensor, usually on one of the front wheels or non-drive wheel.
  • It produces a voltage signal that is sent to the cruise computer
  • When you select the speed you want, the computer compares the speed of the auto and the requested speed and the computer then sends information to the actuator on the engine.
  • The actuator then has complete control of the throttle; it can increase or decrease the engine speed to help maintain the desired speed.

So, the speed sensor communicates to the computer, you select desired speed, the computer signals the actuator that is in complete control of the engine, WHICH controls the transmission, all the way to the tires on the road, which PUSH or PULL the car.

SO

Literally, this is where the rubber meets the road.

Let’s touch on hydroplaning

Tires maintain traction on the road by using a mechanism called BULK FRICTION.

This is where the rubber of the tire pushes down into tiny pits of irregularities of the road surface,

Example, put on a pair of shorts and go out in front of your house and kneel down on the pavement for about 15 seconds, get up and look at the skin on your knees. You now have an inside view of what your tires go thru all day long.

WHEN it rains, the little voids in the road fill with water. Then the rubber of the tire seals the edges and pits, because the water is not easily compressed – which in essence acts as a barrier preventing the rubber from pressing the tire, reducing traction and control of the vehicle.

Too much water, at to fast of speed causes the water not to disperse fast enough and the tires lift up off the payment and you have hydroplaning.

Example, summertime commercial with the silly slide, or super slide?

Plastic about 3 feet wide and 25 feet long, you connect a garden hose to it which produces a thin layer of water, the kids run as fast as they can, jump on it and for the duration of the slide they are completely out of control.

Bringing Hydroplaning And Cruise Control together

When the cruise is on and you run up on water, the front tires slow down because the Bulk Friction is reduced and will not turn them as fast, the slower speed causes the actuator to be signaled to accelerate, because the rear wheels lack traction, they speed up very fast spinning free, making the whole situation completely uncontrollable.

In conclusion

We now know the basic operation of a cruise control and that the car is totally in control of acceleration when it is applied.
We also know what conditions create hydroplaning.

Finally when the cruise and wet pavements are combined we have a recipe for disaster.

I hope I have impressed you well enough that you can relay this information to our children to help keep them safe.