Tyres on the wrong way for over two years

[winjim]

you're nearly there. The mechanical effect is providing a mating, the chemical effect is what seals the deal.

That chemical effect that you couldn't bring yourself to explain?

 

[Yellow Saddle]

Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?

Perhaps the best visible manifestation of VdW's that one can see and feel and comprehend is that of Gauge Blocks (Gage Blocks in the US).

These are pretty incredible. They are perfectly-machined steel blocks of a given dimension (usually one-inch or similar sizes and abut 15mm thick). They are used to calibrate engineering measurement tools. Their sides are optically perfect in smoothness but much smoother than the wavelengh of visible light. Visible light's wavelength is in the order of 700nm but these blocks are smooth in the single-digit nm scale. In other words, if you wring two of them together, they make such good contact that VdW's kicks in and sticks them together. You can stick enough of them together that way to make a stick of about 300mm long. It takes quite a force to break them apart - a force I'd estimate similar to breaking a very hard biscuit.

Lots of people say there's a trick and that because it is steel, there's some sort of magnetism involved. Enter the ceramic gauge block. Same thing.

Then people say yes but it is air pressure that keeps them together: Enter the vacuum chamber.

They stick entirely through van der Waals. And if anyone tells you VdW only works between like molecules: Enter the ceramic/steel combo.

If ever you can play with them, try it. Most precision engineering shops will have a set. They have an interesting story too. They were first manufacturerd to sort out Ford's accuracy and callibration problems in the 1940s, IIRC. 60 year old gauge blocks sell on 3-bay for as much as a brand new set, if they were looked after.

If you can't get your hands on a set, there's always YouTube. Plenty of rednecks there fooling around with them.

 

[winjim]

Perhaps the best visible manifestation of VdW's that one can see and feel and comprehend is that of Gauge Blocks (Gage Blocks in the US).

These are pretty incredible. They are perfectly-machined steel blocks of a given dimension (usually one-inch or similar sizes and abut 15mm thick). They are used to calibrate engineering measurement tools. Their sides are optically perfect in smoothness but much smoother than the wavelengh of visible light. Visible light's wavelength is in the order of 700nm but these blocks are smooth in the single-digit nm scale. In other words, if you wring two of them together, they make such good contact that VdW's kicks in and sticks them together. You can stick enough of them together that way to make a stick of about 300mm long. It takes quite a force to break them apart - a force I'd estimate similar to breaking a very hard biscuit.

Lots of people say there's a trick and that because it is steel, there's some sort of magnetism involved. Enter the ceramic gauge block. Same thing.

Then people say yes but it is air pressure that keeps them together: Enter the vacuum chamber.

They stick entirely through van der Waals. And if anyone tells you VdW only works between like molecules: Enter the ceramic/steel combo.

If ever you can play with them, try it. Most precision engineering shops will have a set. They have an interesting story too. They were first manufacturerd to sort out Ford's accuracy and callibration problems in the 1940s, IIRC. 60 year old gauge blocks sell on 3-bay for as much as a brand new set, if they were looked after.

If you can't get your hands on a set, there's always YouTube. Plenty of rednecks there fooling around with them.

That's going on the list of things to show my kid when she's a bit older.

 

[ufkacbln]

Coriolis effect is a macro effect ( extremely large volumes of fluid are needed ) hence the stuff you sometimes hear about toilet flushes and sink draining being effected differently in either hemisphere aren't right.

Also affects weather formations

 

[winjim]

No. Imagine a perfectly soft (conforms to every nook and cranny) but perfectly frictionless material. Now imagine whether or not it will "hook and mesh" with road irregularities and resist them enough to create friction.

What I'm imagining is something like a leopard using its claws to climb a tree, with the sharp road surface digging in to the soft tyre. But I guess that would depend on the roughness of a particular piece of road.

 

[Tanis8472]

Thats roads around here perfectly described LOL

 

[Yellow Saddle]

What I'm imagining is something like a leopard using its claws to climb a tree, with the sharp road surface digging in to the soft tyre. But I guess that would depend on the roughness of a particular piece of road.

That's not what happens but most people find it difficult to comprehend. It is a bit of a mind bender. We've been brainwashed by (car) tyre adverts and the (psychologically chosen) shapes of treadblocks on car tyres and also to an extent of tractor tyres and their V-grooves. It is easy to get imaginary views of traction from that. You have to dismiss what you think you know and start from ground zero.

I find it useful to at first just examine just how how much friction a piece of rubber on something really smooth, like glass has. Take a pencil eraser and draw it over a window with a bit of downforce. You'll see there's plenty of friction already, no need for tiger claws. There's enough friction to break the rubber bonds and leave a streak of rubber behind. Now think about the enormous traction a train locomotive generates by rolling smooth wheels on smooth tracks. It is pure VdW amplified by massive downforce.

Now progress to my example in the post above. A (very) soft tyre on very rough road but zero friction between the two. Forget about physical penetration of the rough surface on the soft surface. That's clearly not what happens. Just think of the deformation of rubber on road micro roughness but with the complete absence of friction (adhesion). Imagine how the tyre will just spin over the roughness as it is torqued because it cannot grip.

Now progress to a view of the above example where the rubber conforms to all the nano-scopic irregularities in the road but with adherent forces between the two. The irregularities increase the surface area in a fractal manner, VdW builds up and voila! Traction. The beauty of VdW is that it is cumulative and unlimited. Press harder and more VdW points switch on.

The argument presented above is only for one case of traction: A smooth tyre on asphalt. Once we ride on gravel, mud, ice and vegetation, the mode of traction changes. Then we rely on penetration of a (hard) tyre on a (soft) surface and the shear strength of the substrate. In other words, tread and something like your tiger-up-a-tree example.

 

[GuyBoden]

14 pages and not a sign of the OP since the first post........

 

[winjim]

 

[Smokin Joe]

Well Guy, what have you learned?

 

[ChrisEyles]

There was a thread in the touring section about what tyres to use for JOGLE... I was tempted to say use the same tyres you would for LEJOG, just reverse them

Refrained, but couldn't resist posting it here.

 

[winjim]

That's not what happens but most people find it difficult to comprehend. It is a bit of a mind bender. We've been brainwashed by (car) tyre adverts and the (psychologically chosen) shapes of treadblocks on car tyres and also to an extent of tractor tyres and their V-grooves. It is easy to get imaginary views of traction from that. You have to dismiss what you think you know and start from ground zero.

I find it useful to at first just examine just how how much friction a piece of rubber on something really smooth, like glass has. Take a pencil eraser and draw it over a window with a bit of downforce. You'll see there's plenty of friction already, no need for tiger claws. There's enough friction to break the rubber bonds and leave a streak of rubber behind. Now think about the enormous traction a train locomotive generates by rolling smooth wheels on smooth tracks. It is pure VdW amplified by massive downforce.

Now progress to my example in the post above. A (very) soft tyre on very rough road but zero friction between the two. Forget about physical penetration of the rough surface on the soft surface. That's clearly not what happens. Just think of the deformation of rubber on road micro roughness but with the complete absence of friction (adhesion). Imagine how the tyre will just spin over the roughness as it is torqued because it cannot grip.

Now progress to a view of the above example where the rubber conforms to all the nano-scopic irregularities in the road but with adherent forces between the two. The irregularities increase the surface area in a fractal manner, VdW builds up and voila! Traction. The beauty of VdW is that it is cumulative and unlimited. Press harder and more VdW points switch on.

The argument presented above is only for one case of traction: A smooth tyre on asphalt. Once we ride on gravel, mud, ice and vegetation, the mode of traction changes. Then we rely on penetration of a (hard) tyre on a (soft) surface and the shear strength of the substrate. In other words, tread and something like your tiger-up-a-tree example.

OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.

 

[raleighnut]

OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.

View: https://youtu.be/Bt4rCWZp6zk

 

[Yellow Saddle]

OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.

I don't agree with your conclusion. Either we are riding on spikes or we are not. If you are riding on spikes, the fact that there is a VdW between the spike and the rubber is kinda irrelevant, or at most superflous. If the spikes are just denting the rubber, then we are relying on VdW. There could even be a hybrid scenario where the two are balanced so finely that traction is reliant on both.

I cannot envisage such as scenario since we never ride on stuff that routinely and cyclically penetrate our tyres.

Reverse the scenario where the tyre's spikes penetrate the road, then we have a real scenario. Here we are talking about knobbly tyres punching into the substrate and relying on the shear strength of the substrate for traction. Similar with ice and carbide spike tyres. The spikes enter the ice and we rely on the ice's shear strength to provide traction. The fact that there is a teensy bit of VdW between tyre and ice is kinda irrelevant.

Imaginary scenarios however, are not the reason for tread in tyres or, the pattern direction of tread in tyres. There is no known scenario where tyres have to have penetrating devices to ride on asphalt.

Van der Waal's is all around us, you just have to open your eyes to it. I don't know why the poor Dutchman doesn't get the recognition for his work that he deserves. They treat friction in high school physics like religion: it is because it is. Just shut up and say f-r-i-c-t-i-o-n. At university physics its gets the same glanced-over treatment Only in some specialist courses do they delve into it. Typically specialised branches of mechanical engineering.

I urge you to have a good look at gauge blocks. They're the most eye-opening scenario I can think of. Even if you just look at it on You Tube.

I once had the opportunity to live in a country where geckos were a plague. They used to shoot everywhere in the house, get in the toaster and make your toast smell like bacon, short out the television set by walking across wires, lay eggs in PC fans etc etc. I watched them for hours and hours walking on all sorts of surfaces I would fashion for them surfaces to hang from (vertical and inverted) that you can only imagine. Only if the surface was not strong (powdery, siliconised etc) could they not walk upside down. I had one clinging to a gauge block's polished surface in any orientation - no problem. They use VdW to their advantage, yet us humans still fart around with treads in tyres. They are not like an octopus wit suckers, they cling with little other than soft, good-contact hairs on their feet. All VdW.

I realise that science is not everyone's cup of tea but dammit man, how do you get people to take an interest in why and how things behave all around us like they do?

Go put a flat aluminium pan on your ceramic stove hob and pick it up. Feel the force. It is with you.

Rant (to no-one in particular) off.

 

[winjim]

I don't agree with your conclusion. Either we are riding or spikes or we are not. If you are riding on spikes, the fact that there is a VdW between the spike and the rubber is kinda irrelevant, or at most superflous. If the spikes are just denting the rubber, then we are relying on VdW. There could even be a hybrid scenario where the two are balanced so finely that traction is reliant on both.

I cannot envisage such as scenario since we never ride on stuff that routinely and cyclically penetrate our tyres.

Reverse the scenario where the tyre's spikes penetrate the road, then we have a real scenario. Here we are talking about knobbly tyres punching into the substrate and relying on the shear strength of the substrate for traction. Similar with ice and carbide spike tyres. The spikes enter the ice and we rely on the ice's shear strength to provide traction. The fact that there is a teensy bit of VdW between tyre and ice is kinda irrelevant.

Imaginary scenarios however, are not the reason for tread in tyres or, the pattern direction of tread in tyres. There is no known scenario where tyres have to have penetrating devices to ride on asphalt.

Van der Waal's is all around us, you just have to open your eyes to it. I don't know why the poor Dutchman doesn't get the recognition for his work that he deserves. They treat friction in high school physics like religion: it is because it is. Just shut up and say f-r-i-c-t-i-o-n. At university physics its gets the same glanced-over treatment Only in some specialist courses do they delve into it. Typically specialised branches of mechanical engineering.

I urge you to have a good look at gauge blocks. They're the most eye-opening scenario I can think of. Even if you just look at it on You Tube.

I once had the opportunity to live in a country where geckos were a plague. They used to shoot everywhere in the house, get in the toaster and make your toast smell like bacon, short out the television set by walking across wires, lay eggs in PC fans etc etc. I watched them for hours and hours walking on all sorts of surfaces I would fashion for them surfaces to hang from (vertical and inverted) that you can only imagine. Only if the surface was not strong (powdery, siliconised etc) could they not walk upside down. I had one clinging to a gauge block's polished surface in any orientation - no problem. They use VdW to their advantage, yet us humans still fart around with treads in tyres. They are not like an octopus wit suckers, they cling with little of good-contact hairs on their feet.

I realise that science is not everyone's cup of tea but dammit man, how do you get people to take an interest in why and how things behave all around us like they do?

Go put a flat aluminium pan on your ceramic stove hob and pick it up. Feel the force. It is with you.

Rant (to no-one in particular) off.

VdW forces do seem to be taught more in chemistry than in physics, mainly to explain what liquids and solutions are.

As for the science education bit, you know how people get annoyed with their kids constantly asking "why"? I have resolved never to do that. It is the most important question of all. Children are natural scientists, I intend to try and keep that enthusiasm going for as long as possible.

For what it's worth, I am not suggesting that the mechanical interlocking / spiky effect is, in road conditions, dominant or even particularly large compared to the VdW forces, just that it makes some, however minor, contribution. With you on the tread, although I still can't bring myself to put those little arrows on the wrong way. Maybe one day I should, it might be quite a liberating experience.