UKC

Does it stick?

In reply to Dave Flanagan:

stick to what is the question?

wet grass = no
dog turds =oh yes

In reply to balti boy:

What I mean is, does it have the property of adhesion?
It is a science quesiton.

In reply to balti boy:
And anyway the shit sticks to it not the other way around.

In reply to Dave Flanagan: No it has the property of friction.

In reply to Dave Flanagan:

Do you want to argue high-friction vs. "sticky"? In which case I'd say that no, shoe rubber is not sticky (unless it hasn't been properly cured).

In reply to Richard Bradley:

Actually that is rubbish

In reply to Richard:

Thats exactly what I'm trying to get at. Why isn't it sticky and how is this defined?

In reply to Dave Flanagan:

I remember way back when I got my first sticky boots (SuperRats) you could rub them together and they stuck to each other fairly well.

Modern boots don't seem to do this as well

In reply to Richard Bradley:

Adhesion (stickyness) is the force needed to seperate two different contacting objects perpendiculary, like pulling bluetack
vertically up from a surface.

Friction is a velocity dependant property, defining the
reistanace to lateral translation of one object against the
other

I guess that high friction prevents the boot slipping when
pushed downwards by your weight against the rock.

High adhesion would prevent your foot moving vertically up from a flat surface e.g the floor.

Guess that in reality, climbing invovles a hybrid situation,
where the force between boot and rock would be at an angle were elements of both adhesion and friction would come into play?

Also, the rubbing boots togther thing is measuring cohesion, i.e adhesion between the same two materials.

In reply to Dave Flanagan:

I think if 10 years worth of fading memory serves me right.

It is to do with the microscopic roughness of the surface, and if you want to get really teachnical
the case of rubber. its to do with the long cahin hydrocarbon molecules, and their afinity to want to attach to other molecules as they are missing a few electons?

again I am sure a more up to date or learned poster will tell you other wise.

In reply to Dave Flanagan:
I have some mountain master 5:10 approach shoes and when I was walking over rocks in the lake district last summer you could hear them 'schlump' 'schlump'.... as they came unstuck from the rock with each step. As rockboots have even 'stickier' rubber, I'm sure there is significant adhension.

In reply to Dave Flanagan:

I wonder how many people know that one of the reasons 'sticky boots' work so well (and polish the rock) is that that contain carborundum as well as sythetic rubber?

In reply to Sankey:

No, it's not a velocity dependant property. Two materials in contact generally have two coefficients of friction: one for static contact and one for moving contact. The moving coefficient is invariably lower than the static one, which explains why things can be really hard to move but then go shooting away leaving you to fall over in a comedy manner once you do get them moving.

In reply to Gordon Stainforth: I didn't. But you would expect anything that generates that degree of friction to have polishing qualities.

In reply to Carless:

Fire's were excellant for the 'stick' test

It might have been then though that the two rubber soles smeared together into one instead of actually adhesively bonding

In reply to stevomcd:

Well, so friction differs between velocity = 0, and
higher velocities then? Sounds like a velocity dependant property!

Quote from a web page (poor source I know, but don't have time to find a better one, sorry)

"Finally, what about the velocity dependence of this and other types of friction? In the case of 'stick-slip' friction the velocity dependence is easily seen in
the case of the mass and spring. This same type idea applies to kinetic friction in general. The coefficient of kinetic friction for all materials shows some
dependece on velocity to a marked degree. Thus, kinetic friction and 'stick-slip' friction are, for the most part, velocity dependent forces."

In reply to Sankey:

I knew that was going to be the reply! []. Yes, if you like, having different frictional coefficients at v=0 and v>0 arguably makes it a velocity dependent property.

I personally felt that the distinction between static and non-static was a more important and better description.

I'm sure there are observable changes in frictional coefficient at higher velocities, but generally one value at any speed does the job fine. At least, that's what we were taught.

In reply to Sankey:

In terms of climbing we are only intersted in static friction as once it becomes dynamic our foot has slipped and we have falled off. Right?

In reply to Dave Flanagan:

Right! Unless you're on the Etive Slabs and you fall off. Then you're likely to become VERY interested in the dynamic frictional properties of skin and rock.

In reply to Dave Flanagan:

If you are a good climber! The way I climb, dynamic friction can be just as important, gives enough time to desperately lurch up to the next hold as the
feet slide off!

In reply to stevomcd:

Still no closer to the anwser though. If rubber was adhesive surely dust, chalk and such sticking to the sole would be than it is.
Can modern day climbing shoes stick together?

In reply to Dave Flanagan:

Adhesion will depend on the properties of both things contacting, boots only need to stick well to rock, so it may be possible to design their surfaces so that unwanted stuff does not stick. Likewise, the boots sticking to each other test is not that relevant as rock and rubber are pretty unlike!

In reply to Dave Flanagan:


Do you mean "worse than it is"? Soles get choked up with crap pretty quickly - if you actually clean your soles (spit and rub, say) before climbing you'll notice a dramatic improvement (except on polished grit).

In reply to Richard:

Yes sorry.

In reply to Sankey:

So is it far to say that if 2 shoes stick together this stickyness is non-transferable to rock?

Can anyone tell me if hysteresis is a factor in static friction or is it only relevant when the 2 materials are moving past each other?

In reply to Dave Flanagan:

It should be possible to design shoes that would not stick to each other at all, but do stick well to rock, in theory. Would say that boots sticking to each other well may be a by-product of a manufacture designing boots that stick well to rock, but I don't think that you could test boots by how well they stick to each other and expect it to correlate with peformance on rock.

In reply to Dave Flanagan:

Hysteresis is relvant in any situtaion where the rubber is experiencing a change in force applied to it. Example is the claim by some soles that they have a "memory". Idea is that if you are smearing around a grit pebble, the rubber
will deform around the shape, giving a good contact. If
you reduce the force through your foot (change body posistion, start to move up), the rubber will start to spring back into its orignal flat form, meaning that it will not contact the pebble as well, and you might slip off.
However, if the rubber has high hystersis, it will respond very slowly to the change in force, and so remain in the original snug fitting pebble shape for longer, keeping you on.

In reply to Sankey:

Nice on, thanks. Planetfear did an article about climbing in the cold and mention "memory"

In terms of climibng rubber is hystersis and 'softness' the same thing?

In reply to Dave Flanagan:

No, they are different properties, hysteresis is kind of springbackability. Remember a pair of red chillies had
this memory effect, and the guy in the shop demonstrated it by pushing something hard into the sole, you could see the
imprint for a few minutes afterwards. Obviously you
want the rubber to recover eventually or you would have a permanent record of every hold you had used!