Watch those water crossings

[Geoffury Find all posts View Profile Close Geoffury]

You have to be carefully crossing water ways, as these cops found out



Story here. They did well to winch it up to the banks
http://www.ntnews.com.au/news/northe...3ddc77094bec90

[Symo Advanced Member Find all posts View Profile Close Symo]

Aren't the Police behind the "If its flooded, forget it" campaign that been doing the rounds the last two years?

[Snaga Wishing I was lost Find all posts View Profile Close Snaga]

wow... you can see the amount of water flow in that aerial shot!!

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

It's okay, they're NT coppers - expendable.

[KIMBOPRADO Senior Member Find all posts View Profile Close KIMBOPRADO]

See they have done tests recently on actual vehicles to see how much water before a car floats in river crossings - interesting read

http://www.abc.net.au/news/2016-06-1...waters/7522798

[DGW Senior Member Find all posts View Profile Close DGW]

I was reading this article before coming back to the forum.

I loved this quote "New cars in particular have really been made airtight because of the climate control systems that they have to keep the air conditioning temperature at the setting you'd like. Because they are airtight they are also water tight". I am sure many of us know this is not quite correct but they do appear to be using a stationary vehicles in their test.

If you can't or won't walk a water crossing, you shouldn't drive it.

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

Basically it's the moving water that causes the most issue. The pressure exerted by moving water is the square of its velocity. As velocity increases so does pressure. Once this pressure exceeds the frictional force of your tires, your car will float. Pressure becomes a force, and as depth increases so does area, therefore so does force. Also Bigger tires = more bouancy too. Archimedes principle applies: the buoyant force of an object is equal to the weight of water it displaces. Each 30cm the water rises increases your cars buoyancy by 680kg and the lateral force applied to you car increases by 225kgs. (Assuming average flow speed of 9-20km/h).

Basically, your car can cross deeper static water than when the water is moving. Movement of the vehicle has little effect but does reduce frictional force if it's a bumpy crossing. 60cm of moving water can make most vehicles float.

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

I noticed they were doing their tests with empty cars. If the results were true, no one would get across Nolans.

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

I noticed they were doing their tests with empty cars. If the results were true, no one would get across Nolans.

I was wondering if the fuel tanks were full too, because that's a nice big floaty if it is. But yes, a loaded vehicle would be heavier so the bouyant force would need to be greater, i.e. the water level would need to be higher to float a car. The vehicles going through Nolans are going to be 500kg to 1000kg heavier.

Nolan's never looks to be flowing that fast. The main issue with floods though is the speed of the water. If the water flow rate is lowthen its unlikely, or much harder, to overcome the frictional force of the tires. That's why we can all stand in a pool with water up to our waists and not float, yet get swept away by 6 inches of water in a flood.

[Snowy FNQ Member Find all posts View Profile Close Snowy FNQ]

This was a couple of weeks ago near Mossman FNQ, bonus points if you can identify make and model. To be fair these back roads are fairly hairy, you can be on a one lane bridge really quickly, but I believe this was a local and quite probably should have known better.

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

I'm jealous of your bush up there, Snowy. Makes me feel like I'm on holidays, just looking at it.

...and yes you are right R4dll. There's little current at Nolans, but traction is an issue in the deeper spots.