Best Drivetrain

[RobJ]

Originally Posted by mrs. p

i saw that fight

Cory has to go in for surgery next week.

[vivek16]

One recommendation for any type of drive train: make sure you can accomodate for unforseen problems in the future regarding weight. Try to make it as light as possible. Budget out your weight strictly.

We had to remove a wheel from our omniwheel drivetrain. This is why we were fishtailing so badly during the MN regional.

-Vivek

[sgreco]

From my experiences I would recommend that most teams build 6 wheel skid steers with slightly dropped centers.

On another note, swerve has the most capability because it has full power in all directions and can instantly change direction.
My advice would be to try to develope a swerve drive in the offseason and if you aren't comfortable with the swerve drive by the build season then go with six wheel skid and finish developing your swerve drive for the next year.

[Lil' Lavery]

Originally Posted by Sgreco27

On another note, swerve has the most capability because it has full power in all directions and can instantly change direction.
My advice would be to try to develope a swerve drive in the offseason and if you aren't comfortable with the swerve drive by the build season then go with six wheel skid and finish developing your swerve drive for the next year.

Swerve cannot "instantly change directions", it has to allow for the wheels to be re-oriented. Holonomic and Mecanum systems are as close as any FIRST team has come to instantly changing directions, but even they still have to overcome momentum and interia.
Additionally, while you retain essentially full power from your drive motors, you don't apply any of the power from your steering motor into your drive (in any swerve system yet implemented in FIRST), so it never really has "full power". However, it still can apply equal force to a scrub steered (4WD, 6WD, etc) system, something that holonomic and mecanum systems cannot do (assuming the same motor configurations).
Swerve has a great deal of capabilities and potential, and allows you a lot of strategic options. Some methods, however, do reduce (or eliminate) certain functionalities while enhancing others. 118 and 148, for example, could not rotate their robot's frames. 148 had no reason to, though, and 118 overcame it by placing their manipulator on a turret. Both were able to save weight and increase power by centralizing their drive motors though. It is also the most resource intensive drive system.

[R.C.]

What about the crab and tank drive trannies?

[EricH]

Originally Posted by rc_cola1323

What about the crab and tank drive trannies?

What about them? What do you want to know? We can answer, but you'll need to be a little more specific than that.

[R.C.]

For starters how to build one. The pros and cons. Also the weight comparison and some pics of the best ones

[EricH]

I think the team to look at (or teams) are 118, 16, and 148. Those three raise the bar/push the limit every time they do a crab/swerve. 111 as well. (Two championships and a finalist on crab/swerve, plus regional wins/finalists, isn't bad.) Weight comparison--can be heavy compared to tank drive.

Now, how to build...Coaxial? Crab? Swerve? (There is a difference between crab and swerve.)

Pros: maneuverability and power and speed in one package to a greater extent than skid/mecanum/omni drive

Cons: may take time to turn, may require a turret, heavier, more complex.

If you're going to do one, start prototyping now.

[Jetweb]

Originally Posted by rc_cola1323

For starters how to build one. The pros and cons. Also the weight comparison and some pics of the best ones

In addition to the teams who have already been posted, I would add 1625. There swerve drive was up there with the best of them and they published a lot of info about it on this site that a simple search should find.

[hillale]

Originally Posted by EricH

Cons: may take time to turn, may require a turret, heavier, more complex.

If you're going to do one, start prototyping now.

Turning is definitely something to look into, either programming a way for the wheels to turn a certain direction when told to go to a specific point (if doing a coaxial, they may take the longer way around). As far as the turret goes, we powered the front/back wheels separately and were able to tank drive sideways at the start of the season to reorient (slow/painful). However during/after our 2nd regional we developed "drift" buttons. Pressing one of these buttons would cut power to either the front or rear gear box, allowing the robot, while moving sideways, arc in orientation. Once our drivers figured out how to best optimize these buttons, reorientation was much easier and a whole lot less painful (we still used tank steer, but not nearly as much).

Originally Posted by Jetweb

In addition to the teams who have already been posted, I would add 1625. There swerve drive was up there with the best of them and they published a lot of info about it on this site that a simple search should find.

Thank you for the recognition. Our team is very proud of our third iteration swerve drive, which handled 3 regionals and champs without any throwing of chains or any mishaps at all, actually. Being able to drive a swerve is something else, but the control system this year takes a lot of practice.

[Kellen Hill]

Yeah, just ask my brother, Aren Hill, if you have any questions about our swerve or just swerves in general. He has done our drive train the past 2 years and made our swerve a beautiful thing to watch. If you want to know how good our swerve was, you can take a look at his signature which has a quote from JVN.

[R.C.]

Are the banebot gearboxes any good? In 07 the teeth kept chipping and it locked up 6 times in 2 regionals and the championships. Also any personal experiences?

[AdamHeard]

Originally Posted by rc_cola1323

Are the banebot gearboxes any good? In 07 the teeth kept chipping and it locked up 6 times in 2 regionals and the championships. Also any personal experiences?

I don't have the most experience with them, but I am very familiar with the AndyMark line of gearboxes. No matter what good experiences people have had with the 56mm banebots, I've heard far too many horror stories for me to ever consider using them. The AM gearboxes are a far superior option in most situations.

[Smaug]

Drive train: simplicity is key. keep your center of gravity low.we have used the same chassis for three years and it will except about anything you through at it. the past couple of years we have use a 4 wheel drive because it is simple and so versital.

also our programmer and figured out how to get crab to rotate so we dont need a turret.

[vivek16]

I have actually been thinking about that. Couldn't you lock the wheels of a crab in a 4wd orientation and (if you have each side independently driven) just turn like a 4wd bot?

Has anyone attempted this?

-Vivek