2005 Drivetrains

[Ianworld]

This year there isn't any room for tradeoff. Its going to be a bloodbath out on the field. 6 robots in that tight an area all lunging for the same stack is going to send so many parts flying. The strongest robot is the one that gets a row and stops other teams from making rows. The fastest robot though will stack tetras quicker, they'll end up with more tetras on top as the endgame approaches. Obviously both of these are key elements to control. Your robot will need the speed and the strength this year.

[Xufer]

Im sitting arround here crunching some numbers and it looks like we will be all speed in high and all torque in low if we do a 3 speed we will have a happy medium.

i figured about 340 ft-lbs and 2 fps in low and about 95 ft-lbs and 9 fps in high.

[Greg Needel]

Originally Posted by Xufer

Im sitting arround here crunching some numbers and it looks like we will be all speed in high and all torque in low if we do a 3 speed we will have a happy medium.

i figured about 340 ft-lbs and 2 fps in low and about 95 ft-lbs and 9 fps in high.

this is not possible because you wont have the traction to transfer that force to the floor.... kinetic force = (coefficient of friction)*(the normal force)

since the coefficient of friction can;t be more then 1 and your normal force is essentially the weight of your robot (force that acts perpendicular to the surface)

therefore your max force can not reach 340 ft-lbs


i would recommend recalculating your theoretical force to a more reasonable value around the max weight of your robot but even that will be overkill and you will just end up spinning your tires

[Tristan Lall]

Originally Posted by Greg Needel

this is not possible because you wont have the traction to transfer that force to the floor.... kinetic force = (coefficient of friction)*(the normal force)

since the coefficient of friction can;t be more then 1 and your normal force is essentially the weight of your robot (force that acts perpendicular to the surface)

therefore your max force can not reach 340 ft-lbs


i would recommend recalculating your theoretical force to a more reasonable value around the max weight of your robot but even that will be overkill and you will just end up spinning your tires

Greg, you're right about the wheel slip being the limiting factor, but with interlocking surfaces or certain combinations of materials, μ can exceed 1; it's a convenient approximate upper bound, but it isn't a physical limit. (See here.) Some FIRST teams have empirically determined the coefficient of friction of rubber tread on carpet to be around 1.2; it all depends on your particular wheels.

[Greg Needel]

Originally Posted by Tristan Lall

Greg, you're right about the wheel slip being the limiting factor, but with interlocking surfaces or certain combinations of materials, μ can exceed 1; it's a convenient approximate upper bound, but it isn't a physical limit. (See here.) Some FIRST teams have empirically determined the coefficient of friction of rubber tread on carpet to be around 1.2; it all depends on your particular wheels.

wow....i guess this just goes along with the saying "you never stop learning" all of my professors always just told us 1 was the max and while you can get a coefficient higher then 1 it still wouldn;t constitute a drive train with theoretical torque of 320 ft-lbs... thanks Tristan for the education

[Max Lobovsky]

Additionally, that is probably the torque at stall. You should not be able to stall your motors (or even get close) in low gear.

[Jizvonius]

Just a thought perhaps the only factors aren't speed and torque, but say... manueverability? I think the 'strategy on the fly' aspect of the game will reqire a large amount of agility(not the same as speed) and reliability from the robots to be able to adapt with the strategy.

Going pusher won't guarantee that you'll hold an area against a fast bot, and being fast won't mean that you'll outfox the pusher bots. Having a transmission doesn't guarantee the best of both worlds. The great thing about this years game I think is that with three-team alliances and 9 goals strategy becomes a lot more dynamic. Pushers and nimble bots both seem to have their place and use this year.

Just make sure that your particular strategy does not require more speed or torque than your bot can handle.


(btw i'd like to point out that speed and manueverability are not the same)