Car experiment shows extent of flood danger

[wayno]

Car experiment shows extent of flood danger

http://www.abc.net.au/news/2016-06-18/research-shows-cars-deadly-in-floodwaters/7522798

A world-first experiment in Sydney has found just how easily cars can be carried away by shallow water, making the crossing of floodwaters by drivers a potentially life-threatening decision.

[Xplora]

I guess this is nothing new to those who have crossed rivers in a 4wd but those locked in the city just do not get it and still others who should know better take things too far. I have gone through many flooded causeways and know how dangerous they can be once the water is above the door line. Your car then becomes a sail for the water. Many crossings we would do on foot first. If you have trouble walking a straight line through the water then it is running too fast was my general rule and with that I have never had a problem but much depends on the weight of your vehicle as well. There is a U tube video of a 4wd crossing a flooded river (I have a recollection it may be the Cox's in Lidsdale state forest - done that crossing too) and it started floating downstream. He kept the power up and the tyres acted like a paddle wheel, even going into reverse to straighten up, and somehow he managed to make it to the other side of the crossing. His car was not watertight it seemed. You can watch it here. https://www.youtube.com/watch?v=LC5ld79joIA Also acting against the weight of your vehicle are 4 tyres filled with air.

[slparker]

He is not steering underwater. When floating and when the wheels are submerged above the axles the force provided by the forward rotation of the upper half of the wheel starts to match that of the lower half below the axle.
When fully submerged the forces exactly match- which is why a paddle steamer has half its wheel submerged.
I'd say that in the latter part of the vide his front wheels floated onto the rising slope of the river floor and the wheel could gain forward momentum by pushing against rocks. Until then he was drifting - although perhaps turning the wheels against the current might provide some crude steering, like sticking a paddle in running water. But I wouldn't rely on it.

[wayno]

wouldnt the wheel arches reduce the traction effect in water for the upper part of the wheels since they would be just washing the water round the arches rather than pushing it forward into the main water body?

[slparker]

I don't think so. The net result is still 0 longitudinally. If there is churn in the wheel well the force from Thad would be directed down towards the stream bed and up towards the vehicle. There is no possibility of a net force in one vector only along the plane of a submerged spinning wheel. Unless that force is directed.
There is along the axis, of course, which is how an impeller and propeller works.

[Giddy_up]

These vehicles float and the wheels provide the thrust.

http://www.argoatv.com.au/

Not sure about the science


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[slparker]

They don't fully submerge the tyres.

[GBW]

I don't think so. The net result is still 0 longitudinally. If there is churn in the wheel well the force from Thad would be directed down towards the stream bed and up towards the vehicle. There is no possibility of a net force in one vector only along the plane of a submerged spinning wheel. Unless that force is directed.
There is along the axis, of course, which is how an impeller and propeller works.

Doesn't water pressure increase with depth?

[michael_p]

Gentlemen and ladies:

[wayno]

yeah that video was posted several comments ago if you bothered to read the thread

[michael_p]

Bugger is was too. Sorry I missed the link.

[slparker]

We need mythbusters to clear this one up.

[GPSGuided]

Someone need to make some propellers.

[north-north-west]

I don't think so. The net result is still 0 longitudinally. If there is churn in the wheel well the force from Thad would be directed down towards the stream bed and up towards the vehicle. There is no possibility of a net force in one vector only along the plane of a submerged spinning wheel. Unless that force is directed.
There is along the axis, of course, which is how an impeller and propeller works.

Doesn't water pressure increase with depth?

Ambient pressure does, yeah, but the change in a metre is minimal compared to the flow.

[newhue]

If you own a Land Rover Defender they are designed to fill up as you enter the water to keep it grounded. Of course driving with the water level in your lap is not everyone's idea of a successful crossing.

[Xplora]

If you own a Land Rover Defender they are designed to fill up as you enter the water to keep it grounded. Of course driving with the water level in your lap is not everyone's idea of a successful crossing.

Love this. Was it designed that way or is it the excuse they came up with later because they could not build it tight? I have been in lots of water above the doors and am most happy for the good seal. Don't mind me dong some Rover bashing. Can't help it. I have some good friends with Rovers and we have done some pretty wild stuff together. We tried to get a Range Rover repaired in Porepunkah once and the mechanic yelled at us and most impolitely said 'get that British S#$% out of here.' He was a Ford man I think.

[stry]

If you own a Land Rover Defender they are designed to fill up as you enter the water to keep it grounded. Of course driving with the water level in your lap is not everyone's idea of a successful crossing.

Love this. Was it designed that way or is it the excuse they came up with later because they could not build it tight? I have been in lots of water above the doors and am most happy for the good seal. Don't mind me dong some Rover bashing. Can't help it. I have some good friends with Rovers and we have done some pretty wild stuff together. We tried to get a Range Rover repaired in Porepunkah once and the mechanic yelled at us and most impolitely said 'get that British S#$% out of here.' He was a Ford man I think.

Definitely someone's flight of fancy

To get enough water inside quickly enough, holes the size of the doors would be needed.

And being full of water does not address the "sail effect" mentioned earlier. Try holding a small, partly submerged boat in flowing water and you will very quickly get the picture. Or if that isn't convenient, hold a sheet of plywood face on into a gentle breeze. Underestimating the power of water kills a lot of people in all sorts of situations.

[newhue]

Xplora, hmmm, I think it was by design, but then again they leak so much the water has to get out somewhere. The new ones don't leak as much as the older ones, but they do fill reasonably quickly.

Back in the Camel Trophy days they had a few float off down the river, but they were often crossing fast flowing mountain streams. Somewhere in the archives there is a quick shot from within the cab of a driver crossing a river with water up to the bottom of the windscreen and half way over the steering wheel. Not that I am saying cross flooded rivers in Defenders, just they were capable of it through design. Partly why the army bought them.

[photohiker]

Partly why the army bought them.

lol. And spent millions keeping them going. Landies would be the most maintenance prone vehicle available, especially when they were owned and built in the UK.

Not saying they didn't work well when they were functional, but the Japanese wiped them with far better reliability.

[slparker]

The army ones had an Isuzu engine for good reason...

[newhue]

photohiker, yep. I know, I got one. Actually the ford motor in it works well, its all the UK engineered stuff around it falls apart. They are very good off road and quite comfy really, but yes the Japanese stuff does appear more reliable. Well with regards to oil leaks definitely.

ahh slparker...the scared Isuzu donk. The stuff legends are made of, just the legend forgot to mention it rattled and vibrated the rest of the car to pieces. And don't forget those ear muffs over 80km/h lol.

[stry]

The army ones had an Isuzu engine for good reason...

Only towards the end. For many, many years the army landies had only the landy 4 cylinder and the landy 6. The 4 was nicer (to me )

[Xplora]

ahh slparker...the scared Isuzu donk. The stuff legends are made of, just the legend forgot to mention it rattled and vibrated the rest of the car to pieces. And don't forget those ear muffs over 80km/h lol.

Now if they made it tight you would not hear the noise as much. The other thing is to turn the radio up. I do tend to agree that seepage into a car will not do a great deal to stop water washing you away. It needs to rush in like when the door is open. Maybe it encourages you to alight from the vehicle once stopped in the middle of the stream and sit on the roof to wave down the helicopter. There were other issues with the Army version due to modifications. The person in charge of their procurement has commented they should be retro fixed before sale as they are subject to roll over. Are we allowed to have some brief 4wd talk here? Do not want to upset the purists but I use my vehicle to get to tracks as well. Even drove a mates Landy yesterday to pick him up from a backcountry ski trip so I am not that prejudice.

[newhue]

Yes the army drove them faster with weights that Land Rover never designed them to d I think. Interesting though with the earlier series 3 type the army had did't seem to cause issues, but OH&S come in the rest is history. They Defenders were a 50K truck that costs 150K after modification. That's motor, chassis, spare wheel, fuel tank and trimmings. Not sure what OH&S was on top. Perhaps not bad for 25 years of service but who know the maintenance bill. They drive them hard, with many young testosterone filled young lads trying to break them. The Mercedes are a 90K truck which one can buy, however the army is paying 300 t 450K for model variants and trimming not released to the public. They are more refined and capable for the modern soldier, but sadly we live in a world where they are both too easily disposable.

anyway, back to the floods....

[jfullertonharvey]

I was able to experience this experiment! was presented by the UNSW Water research lab in Sydney. very interesting to show how easy it is to push the car