There's been some talk about the difference between tracks made in the dunes on foot vs. those made on machine.

Our friend BS insipred someone to make a comment regarding the low contact pressure a Manx buggy has with the ground over on the DUSA board. This got me thinking.

I measured the area my feet contact the ground. I rounded a little on the conservative side since after all it's not a perfectly square contact patch. I then divided this by my weight and got a figure of roughly 2.5 PSI pressure exerted on the ground by me just standing there.

I then measured the contact area on my buggies tires and divided that by it's estimated weight. The result was about 2.1 PSI. Again erring my measurements towards a smaller contact patch than it probably really is and more weight than it probably really is.

This could help explain why tracks left by vehicles normally only last a matter of hours in the dunes whereas footprints can last for days.

I wonder what the numbers would be like for quads and bikes. I was surprised a just how large of a contact patch my front tires had when I actually measured it. I knew the rears would be big from the paddles but never realized just how big implement tires are or how much can contact the sand.

Also, my measurements were made on concrete not sand - in the sand the terrain conforms and more contact area would probably be in use.

Far from scientific but it does get ya thinking.

you forgot to add the small consideration of power. Could the torque applied by an engine affect the impacts to the land done at the contact points?

What kind of power are we talking here for a bike or quad? from 20 to 50 hp? as opposed to a fraction of 1 hp for a healthy human.

even though you are "far from scientific", if you're going to do some thinking, you should include common sense.

"Common Sense"??????? come on Blu, that might ruin you arguement.

Ok, the horsepower of a vehicle can make a difference in the impact of the sand, so can weight and speed. But, a foot in motion actually looses half of it's contact with ground, while a wheel surface to the ground should remain unchanged. Thus the horsepower issue might be a mute point.

Probably the least amount of impact on the sand might be a person with snowshoes on???? Maybe Danny should hike the dunes with those?

Since we are dealing with a sand dune, we can assume that there is a huge percentage of sand particles. The thing about sand particles, which differs from clay and silt, is it's ability to be compacted. Sand particles can only be arranged, packed, and stacked in very few ways, so sand is not as compactable as other soils. So, with this in mind, there is going to be a maximum impact possible- at the maximum compaction allowed by sand. At some point, you can take the heaviest vehicles, with the thinnest tires and be making no more an impact than something smaller with balloon tires.

environmental effects on the dunes by vehicles would include impacts to plants and animals on and below the surface.

there's no way that someone using common sense would suggest that impacts from hiking have anywhere near the effects of the impacts from motorized vehicle rec.

I don't know, Blu... seems to make sense to me... A person walking will be applying torque to the equation also. Add to this the much smaller contact patch and you can start to see the issue.

With a buggy, add speed and you start to get what is normally called "floatation" which is where the tires just barely touch the surface, basicly touching the sand in the least amount allowed by physics.

Climb up a sand hill on foot and you'll sink into the sand as much as a foot!

...
Vor

It totally makes sense Blu. Also, lets say youre on dirt, not just sand... you have a hiking trail that is only about 3 feet wide, does not accomodate OHVs. You begin to start digging a little rut- as each hiker uses the trail. Then it rains. You have a perfect little rut for water to flow and erosion to happen. If the trail had been wider, perhaps if made by a large vehicle with tires bigger then a human foot, this may not have happened.