2005 Drivetrains

So what’s most important in a drivetrain for the new game?

I would guess … speed? Since you have a limited amount of time to be capping/etc, you want to cut down the amount of time it takes to do certain things … like getting to the goal from the scoring object or something.

But say you have your one or two rows in place and the other team is going to block that or create their own rows…one could argue that a speedy robot who can’t really push another robot around would do terrible in defending their score and stopping another team from scoring.

Hm… true.

So… a good transmission? So you can change from being speedy to being powerful whenever you need?

I don’t know too, too much about drive trains and transmissions, but is there a way to build something where the amount of force you’re experiencing from an object (or another robot or something) can help the robot automatically adjust its transmission from speed to power? Sort of like from D to 1 (that’s the most “powerful” one right?) or something in a car with automatic transmission.

Don’t know if I made sense there, but I hope I did :slight_smile:

i would say matters on driving skill. since there are going to be much more robots on the field, and the field has not expanded to 1.5 times as big as before, there will be lots of contact and manuevering will be top priority. so i would say as fast as your driver can comfortably drive around. and for pushing… well if you wanna go defensive robot type, id put in a 2 speed. if its all about offense id stick with a lighter highspeed and work more on the arm or w.e you wanna use for the scoring

I think that this year is the first year i am going to consider a 2 speed gearbox. the resoning is you need to have an extremely fast robot being able speed aroud to keep the stacks owned by your team but at the same time with so many robots on the field you will get into a pushing match every round. so for those 2 reasons i will say that you need both a powerful and fast drive.

the one interesting thing is that first gave a very powerful drivetrain this year and i think that my drive will be designed to be faster in high gear and more powerful in low then that because i see many teams using that stock gearbox this year

I think people are going to vote for something they dont believe in, trying to throw off other teams from their super secret strategy.

I think you need not a “happy medium” but a good performance in both areas. Something like the HexaMax R2. If only you knew what the heck that was. hehehe

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.

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.

Although not as large point wise as capping the goals was last year, your gonna want to be able to push bots out of the way to finish your 10 point rows.

You need to be able to go fast at times to get to the goals you need to, especially at the end, but but more importantly is controllability and power since the field will be very crowded and everyone will be getting in everyone else’s way.

I think that the combination of speed and torque will be a factor this year. there will be fights over getting the 10 points at the end, and prossibably one team trying to prevent someone from using their tetrahedrons.

i think its going to be hard to get all three robots behind that line it looks like such a small area.

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

It is important to be able to control your speed to help maneuverability, however you do need some pushing power. One of the biggest things is for the drivers to be able to control the robot well.

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.

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

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)

Go look at a scaled drawing of the field, and put 28" by 38" into that scale, and then compare the size of the robot to the space between the “endzone” goals.