Help out rookie/less experienced teams

[MrForbes]

We used fiberglass for the 1726 chassis last year and this year. But we did spend some time looking at the kit chassis, and noticed the lowered center holes.

The fiberglass works very well as a chassis material...it's tough, easy to work with if you don't have a machine shop, and the shapes we use work well for robots. The side rails which hold the wheels are I beams turned on their side, the ends are channel, and it's all held together with bolted on aluminum angles (similar to those you've shown above). We learned about this material from our mentor team 842. We use a different frame layout than they do, though.

[T3_1565]

wow what a thread to find! Being on a less experienced team myself and being one of the few that wish to prototype sweet design, we have decided to try a crab drive (to keep up with you vetren-like). I don't mean to be rude or anything and I understand this is a thread to posted ideas, not ask questions but is there any chance someone could ethier post or PM me on the simpliest way to start a crab drive. And before you ask I do understand it is complicated to do, thats why I am starting now

[Otaku]

Feel free to ask them to post it here!

This isn't just a thread for more experienced teams to help out less experienced ones, but a place where less experienced teams can come to ask for help. Remember, we're all gracious professionals here.


That being said, I don't know anything about Crab or Swerve drive. Sorry.

EDIT:

Oh, but I did find this article on Wiki Books...

http://en.wikibooks.org/wiki/Robotic...hysical_Design


Enjoy. =]

[AdamHeard]

Originally Posted by Tim Delles

Just want to clear this up.

You can have to much traction (depending on the gearing of your drive train) All teams should (after the drive train is complete) should bring the robot up to proper wieght (using paper wieghts or what not to load down the robot) and then push against the wall. If your wheels begin to slip you are good. However if your wheels do not move, thus forceing the motors to stall a course of action must be taken to keep the motors from stalling.

There are a number of ways, the most common is reducing the coefficent of friction of the wheels.

Yup, you're right.

...Sometimes you get so focused on something (traction affecting turning), you forget basic facts...

sorry about that.

[Otaku]

Originally Posted by squirrel

We used fiberglass for the 1726 chassis last year and this year. But we did spend some time looking at the kit chassis, and noticed the lowered center holes.

The fiberglass works very well as a chassis material...it's tough, easy to work with if you don't have a machine shop, and the shapes we use work well for robots. The side rails which hold the wheels are I beams turned on their side, the ends are channel, and it's all held together with bolted on aluminum angles (similar to those you've shown above). We learned about this material from our mentor team 842. We use a different frame layout than they do, though.

...Woah. Fiberglass?

I'll have to mess around with that after I get a job. I'd love to see it's potential.

[T3_1565]

Originally Posted by Otaku

Oh, but I did find this article on Wiki Books...

http://en.wikibooks.org/wiki/Robotic...hysical_Design


Enjoy. =]

Thanks for that! I have done some research on crab drives and thats why I want to make one! unfortnatly I'm not sure how to go about starting said crab drive so any team who has done a crab drive before, it would be great to know how you started lol!

[AdamHeard]

Originally Posted by T3_1565

Thanks for that! I have done some research on crab drives and thats why I want to make one! unfortnatly I'm not sure how to go about starting said crab drive so any team who has done a crab drive before, it would be great to know how you started lol!

71, 111, 114, 118, 16, 469 and 1625 have all done crabs.

71, 111, and 118 have been doing them for years, so I would talk to them.

[T3_1565]

cool thanks a lot. all I need now is there phone number!

[Otaku]

Originally Posted by T3_1565

cool thanks a lot. all I need now is there phone number!

Click "Members" at the orange bar here on CD (right next to "User CP"). Click "Search Members"

Insert Team Number.

That should help some.

[Chris Fultz]

to quote some famous FIRST personalities:

The three most important things on a FIRST robot are:

1. Drive
2. Drive
3. Drive

Spend time getting it right and making it faster than you really think you need - you won't regret the decision.

The best way to learn is to wander around at competitions and see what other teams are doing and what works and ask them how they do it.
Also, try to go to some off season forums or the forums at the Championships.

The last bit of advice - build prototypes and experiment, but don't decide in December what drive you want to use. Wait until the game is announced, decide how you want to play the game, and then decide what drive is best for that.

For example (these are general comments only - please don't blast me),

a swerve or mechanum drive lets you get all around the field quickly, but they don't push / play defense well for the very reason they work well getting around the field.

a tank drive is quick to turn and great for pushing and defending, but not very efficient so they consume a lot of battery power

a four wheel drive is easy, but can be tough to turn with traction wheels - or easy to push around with the wheelchair wheels or other rollers

a six wheel drive is easy to turn and can be a good defensive drive, but uses a lot of weight in sprockets and chain.

Bottom line, there is no "perfect" drive and each game strategy lends itself better to one particular type. several drive types have been successful this year - it depends on how the team wants to play the game.

[pyrome]

Team 852 has been with FIRST for several years, so maybe some aspects of its robot design can be used by rookies:

THE FRAME:
Our frame is made out of 80/20. This is amazing stuff because it can be bought in very large stock lengths and cut down to size, and there are plenty of different connectors one can buy that make it easy to build a very versatile chassis.

The bottom plate is simply 1/8in aluminum plate, cut out and attached to t-bolts in the 80/20. This allows the electronics people to do whatever they want with the bottom of the robot (drill holes and bolt things down, for example).

The plates we use to cover the sides of the robot are made out of Lexan. It is soft enough not to crack in the heat of a FIRST battle, but hard enough to protect your electronics.

THE DRIVE TRAIN:
This year, we changed our drive train a little bit. We used four CIM motors in our drive train, two per side. Each CIM has a small gear on its axle. Each pair meshes with a larger gear, which has two sprockets on the same shaft. Those two sprockets attach via chain and sprocket to the wheels adjacent to the gearbox. Then, since we have 6 wheels, the wheels in back of the gearbox attach via chain and sprocket to the rear wheels.

Our front four wheels are traction wheels. The rear two wheels are omniwheels. The 6-wheel drive train allowed us to put the traction wheels closer together, which allowed for better turning. The omniwheels keep us stable and allow us to pack our arm away (by making more room in the back of the bot).


GAME PLAY DEVICES:
You probably already know this, but whatever you do, keep it simple. It's easier to diagnose and fix problems that way, and you might win the GM industrial design award. Whenever you design a component, come back to it a day later and ask yourself the question: can I make this device in fewer parts? Some of the best engineers can turn a 5-part device into a single masterpiece.

If you got this far in my extremely long post, congratulations (I'm done).

Good luck rooks, I have respect for you guys.

[EricH]

Originally Posted by Chris Fultz

to quote some famous FIRST personalities:

The three most important things on a FIRST robot are:

1. Drive
2. Drive
3. Drive

Spend time getting it right and making it faster than you really think you need - you won't regret the decision.

The best way to learn is to wander around at competitions and see what other teams are doing and what works and ask them how they do it.
Also, try to go to some off season forums or the forums at the Championships.

The last bit of advice - build prototypes and experiment, but don't decide in December what drive you want to use. Wait until the game is announced, decide how you want to play the game, and then decide what drive is best for that.

If you can't drive, you can't play. Well, you can, but the last time non-driving robots could really play was 2001, and those spent the entire match on a stretcher. This year, even pure ramp/lift robots need drives to clear out their home zone, and that's assuming that they don't play defense.

If your drive is lousy, your arm will not be very effective, even if it is the best arm in the competition! How far would teams 234, 254, 1114, 67, 111, 330, 118, 45, and 217 have gotten without drivetrains? Not very far, I'll tell you that.

Prototyping is good. In 2005 we prototyped a mecanum drive. After analysis, we decided to go with a six-wheel dropped center. Why? The mecanum wasn't the best way to go for us. We felt it had disadvantages that were unacceptable to us. But in recent years, mecanums have become increaingly common. I'm not sure if that's because teams are deciding that they need them, advantages outweigh disadvantages, or just the cool factor. I also don't really care, because that's the team's choice.

Originally Posted by Chris Fultz

For example (these are general comments only - please don't blast me),

a swerve or mechanum drive lets you get all around the field quickly, but they don't push / play defense well for the very reason they work well getting around the field.

a tank drive is quick to turn and great for pushing and defending, but not very efficient so they consume a lot of battery power

a four wheel drive is easy, but can be tough to turn with traction wheels - or easy to push around with the wheelchair wheels or other rollers

a six wheel drive is easy to turn and can be a good defensive drive, but uses a lot of weight in sprockets and chain.

Bottom line, there is no "perfect" drive and each game strategy lends itself better to one particular type. several drive types have been successful this year - it depends on how the team wants to play the game.

Bingo. But in addition to the drivetrain capabilities, what can your driver handle? I mean, if the driver can't control the drive you give him/her, then you just wasted a lot of time. Does your team know how to use the drive you want effectively? (I've seen examples in recent years of good drives not being used to their full potential or not being used "right" for the game.) Do you want to innovate (e.g. 703's 14-wheel or 118's V-6)? If you can answer these questions, you are in a much better position than someone who can't. There is no one ideal drive solution, just as there is no one ideal any-other-aspect-of-robot-design solution.

[Kellen Hill]

Originally Posted by Chris Fultz

a swerve or mechanum drive lets you get all around the field quickly, but they don't push / play defense well for the very reason they work well getting around the field.

Just to fix a generalization, swerve drives can be very defensive like we were this year. One match we held Wildstang to one tube and in Quarterfinals we held the Beast to one tube in four matches. Mecanums are just a little different.


If anybody wants help with swerve drive stuff contact Gear from 1625 he is my brother and designer of our ever so amazing swerve drive this year.

[T3_1565]

thaats cool I may get in contact with this "Gear" I would really like to make a swerve / crab drive because our entire team seems to think in that sort of manner (that being to deak around people and not get caught in shoving matches)

[Smaug]

baker post our design that you were given today it is a exact size to our bot. one of our teams drew it so each of our groups can have a copy. it is a extremely simple design. through out the comp. we were at there were quite a bit of teams who like our drive train and chassis cause it was so simple and it is an awesome test plat form.