Peter Wallers Robot Ramblings

[peterwaller]

If my memory serves me right, and that is by no means a certainty, the best grip you can get with smooth serfaces would be 150gms.
Any over that are due to stickyness or grip caused by surface iregularities.
The maximum grip occurs just before the tyre loses traction and starts to slip so as soon as it does start to slip it tends to break away suddenly and jump slightly.
It was hardly noticable on the cricket bat handle tyre but does occur on the lint roller and HP roller tyres.
This does not happen when they are just driving only when traction is lost when trying to push somthing with an effective weight greater than the grip.
I think the skating around on a spinner is due to vibration causing the weight to be lifted off the tyres for part of the spin cycle.
Anyway that is my theory so far, any further thought on the subject would be greatly appreciated.

[Andrew_Hibberd]

I agree completly, the grip should peak at 150g on a smooth surface. However I have no idea whats best just below this coeficient or just above or just on it.

[peterwaller]

I would go for as high as possible.
If you are pushing a 150gm weight with a 250gm push unless it has extremely good grip you should never reach the point where your grip starts to slip.
Even if you do the jumping will probably help to dislodge the opponents grip.

[peterwaller]

It looks like I might need to rethink my testing methods a bit.
I have today received one of the rolls of egrips tape and got some unexpected results.
With the egrips on 48mm diam 11mm wide wheels I got max 110 gms dipping to 90gms when traction was lost.
I placed some polystyrene plastic sheet under the wheels and the push went up to 210 gms dipping to 150 gms when traction was lost.
It looks as though the surface is going to have a much greater effect than I had previously thought so I need to think this through a bit more.
Although I used a wood surface originally painted with the paint I use on my arena I only put on one coat and the finish is rougher than normal.

[razerdave]

After changing Divinity's grip with the cricket bat you gave us, it worked great on those plastic sheets in your 'office' but not so great in your arena or on mine. You should coat your arena in those plastic sheets

[peterwaller]

I have revisited my testing procedure and come up with the following.
First I rubbed down the painted suface and applied another coat giving a smoother finish.
Secondly I cut a rectangle of hardboard and plastic so each test is now carried out on Painted Surface, Hardboard Smooth Side, Hardboard Rough Side and Smooth Plastic.
To show the variation in traction during slipping I now note the max and min of the traction value.
The chart on my website has now been updated.
http://www.antweightwars.co.uk/TyreTraction.pdf

[EpicentrE]

I really am bemused by the egrips results. I've had Void running around tables pushing keyboards, cups, and other heavy objects around without any issue whatsoever, and I don't recall losing grip once during the AWS, even in the melees and fun multi-way fights I did in the secondary arena. Could there be a factor we're missing?

[earthwormjim]

Do I feel a Tug-of-war competition brewing at the next AWS???

[peterwaller]

I would have to agree these results do not seem to reflect what we saw at the AWS.
In fairness The sticky Lint Tyres I tested were all new rubber or well cleaned and I don't think many people were using it at the event.
All of mine were using the cricket bat rubber which I think was a big mistake.
Also this is a flat push as soon as one robot gets under another the weight on its tyres increases where that on the opponents decreases.
I tried Dominant on the rig and it pushed off the scale at over 500gms just because the slopeing front was forced under the arm greatly increasing the downforce on the tyres.
Actually Jim you might have something there maybe it would be better to pull the scales rather than push them that way there is less chance of the chassis experiencing changes of downforce against the end of the scales.
Having said that it was the same for each tyre material.

[knightrous]

I really am bemused by the egrips results. I've had Void running around tables pushing keyboards, cups, and other heavy objects around without any issue whatsoever, and I don't recall losing grip once during the AWS, even in the melees and fun multi-way fights I did in the secondary arena. Could there be a factor we're missing?

Weight Distribution.