Mechanics and Construction > Mechanics and Construction

Do I stand a chance?

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JonHylands:
You won't have any success putting it right on the tracks - it is very runny. The place I got it from is in Toronto, btw.

What you might want to do is use silicone - run a bead across each link.

If you really want to use urethane, you have to have a mold. For your first mini-sumo, I personally wouldn't worry too much about it - there are so many other things to deal with to make a competitive robot.

- Jon

frank26080115:
well what i really wanted to do was this.
make a shallow and long mold, pour the urethane in it, and suspend the tank track right on top of it.
after it dries, simply epoxy it to the tank tracks.

we want to send our university applications with a picture of us holding up a shiny trophy (or whatever they give us) lol

SomeSaba:

--- Quote from: paulstreats on October 16, 2007, 05:31:56 PM ---erm.. i did think this also, the larger surface area the more friction.
also 203:1 is a large gear ratio, ive got one of these gear boxes also and they are very powerful, i would be impressed to see anything force it the wrong direction against the gearing (they have a LOT of resistance when the motors are turned off). which brings us back to the wheels. larger surface area more friction.
i would keep with the design personally, but get as close to the weight restrictions as possible

--- End quote ---

Im afraid, im going to have to disagree with the bolded text. Surface area does not affect friction. friction = uN = umg. Mass, gravity and the coefficient of friction between the two materials affect friction.

If you drag mass block 2 x 2 x 1 accross a table, the 2 x 2 face of the block will have same friction as the 2 x 1. :) i did a lab like that in my physics class lol <3

Pressure though is affected by area <3

if i am wrong plz correct me :O

paulstreats:
You are completely correct about friction and surface area.

The greater the surface area, the less pressure per metre there is pushing down. so the even though the surface area is larger, it is still supporting the same amount of weight overall as a small surface, but less weight per square cm than a small surface.

The way to improve friction is to alter the coefficient of the material, or to increase the weight/pressure down.

Larger tyres are usually thought of as giving better grip, this is either completely wrong or due to softer/stickier tyres are usually made larger and wider because they structurally have to be. Or of course the tyres themsekves are heavier.

maverick monk:
that gearbox is strong! i have the 203 ratio set up in my work in progress bot with the same tracks and it is nuts, it will actualy run into a wall, and crawl up it with a weighted load. no torque problem here!

the treds are nice, id make thin rectangular molds of urathane foam and epoxy them onto the lugs of the tracks. that should work well

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