tire selection

[ddmx]

From the pictures drawn and description it seems phathry could care less about tired deformation. Seems he just wants more traction while the bike is upright and then some sort of linear decrease as the bike leans due to the fact that the tires aren't of a true circular cross section by nature.

[DJ99X]

Which would go back to this:

I could make different traction depending on where the tire is touching, but I can't see a good rationale for it. I'm pretty sure less traction when leaning would not be popular at all.

If you bumped up the track friction, then the side traction would be just like it is now, but with more traction when you're upright

Not that I agree with any of this. I have no problem with how it is now. At full power, the rear tyre is bound to slip in dirt

[jlv]

I get what he's saying. The question is how much does the traction change. You'd need a rig like I described to measure it. You could do separate runs at each angle and speed to find out how much the traction should really change at different angles. Anything else would just be making crap up.

[DJ99X]

In saying that, we have been making up friction figures as well

[jlv]

We're working on guesses, but I don't know if the varying traction by lean theory should happen at all. It's not like hardpack vs sand where you know hardpack has a high static and low viscous friction and sand is the opposite. If the lean theory is correct it's going to be too subtle to guess on.

[cpt_Slow]

I can definitely see how Phathry's suggestion would make the game much easier but don't know if it's realistic. If I understand right he's saying the friction of the rear tire should decrease with lean angle but the friction of the front tire should stay fairly constant.....thefore if the traction is increased we could still slide the back end but not wash out the front.

[cpt_Slow]

Also, I might as well post this even though I've only skimmed over it so not sure how relevant it is. There seems to be a lot of empirical data which might be useful?

[cpt_Slow]

Might help if I gave the link....sorry http://scholar.lib.vt.edu/theses/availa ... J_Chan.pdf

[Phathry25]

The setup I have in mind would be a weighted wheel and a scale. You'd tie one end of the scale to the wheel and drag it at various speeds while reading the force from the scale. The force divided by the weight will give you the coefficient of friction.

While driving around at work today I was finally able to visualize what you were saying here.

How much weight are the talking here? What should I drag the tire across? At this point in time loose dirt or sand isn't an option. A smooth, or rough concrete garage floor is an option though.

[jlv]

I guess you'd want to start with 1/2 of the rider + bike weight. It would be interesting to try different weights though. It's likely that the tileinfo file should cover both slip speed and pressure instead of just slip speed. But that will be easy enough to fix.

For the speed you'd want to cover the range used in the tileinfo file. You'd also want to pay special attention to how much force it takes to break the static friction when it's stopped.

You should get around 1 for static and .8 for sliding with rubber on concrete.

There were some tables in the pdf cpt_slow posted, but they weren't plotting exactly what I'd be interested in. I might have misunderstood them since I just skimmed it though.

[Phathry25]

You expect me to drag 200lbs around my garage? That is like me sitting on top of my wheel and having someone drag me around... Ugh, looks like I'll be hooking the John Deer up to the wheel... Not to mention it's only 24X30 and has way too many bikes in it.

Would it still be acceptable if I did it with smaller weights, and was able to graph it for you? At least then we could determine if the friction increase with weight is linear and go from there, right?

Are the slip speeds in the tileinfo in feet per second?

[jlv]

Actually, concrete isn't that interesting anyway. Could you till part of your lawn and use that instead?

Seriously, I'm going to have to do that experiment myself. Smaller scale would work for a hard surface like concrete. You'd have to estimate the contact patch area and then use a weight that would create the same PSI as the full scale. For dirt I expect full scale will be required.

The slip speeds are feet per second.