Re: Best Drivetrain
 

Wow i didnt meen this to come off like this..
First of all, i am truely sorry i've accused 118 for bending the rules. It was based on nothing and it was a false accusation.

The other teams i was reffering too are mostely from Israel, where this rule is not beeing checked at all and when i think about it, its probably for a good reason:
Because there are a lot of things that we have to order from the states and are not available here. Usually it takes there things about a week and a half to arrive and the cost us about three times of the original price because of the delivery and custom payments. As you can see i was reffering to the order of parts, thats at least what i've meant.

So im sorry for my previos posts and if i've affended anyone...

Re: Best Drivetrain
 

I would like to make one note: While you can't actually build anything for the competition robot before Kickoff, you can order parts and test designs pre-season. Then it's a lot easier to do them in the season, because you already have some idea of what's going on.

Re: Best Drivetrain
 

Another good source of parts are previous years robots. 949 in it's seven year history has only kept three and a half robots complete, the rest have been taken a part and reused in other years robots. You can't use the machined aluminum but the bearings, wheels, and sprockets are all in good condition. You do have to remember the cost of the parts from year to year to report it on the parts list.

-Jim

Re: Best Drivetrain
 

Yep, that is legal, provided that they're not assembled into the mechanism that they were in on the old robot. Also provided that they aren't custom when removed.

Re: Best Drivetrain
 

I wish weve had three and a half robots to keep alive. every year we are forced by budget issues to take out all of the parts you mentioned from the previous robot..

Re: Best Drivetrain
 

I really hope someone from GDC is reading this. IMHO, we are overdue for a new robot footprint. I'd like to see it get smaller, maybe 35" x 25" or something similar.

A smaller footprint would encourage lighter robots. It might also encourage finesse (read: manueverability and control), rather than raw traction, as a distinguishing feature of FIRST's most capable machines.

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I agree the best drivetrain is the one that gets your robot in position for a scoring attempt, or to stop an opponent's scoring attempt, or to support your ally's scoring attempt, and right quick. Which type that is will always depend on game design.

931's last five drivetrains were:

2004 -- custom 4WD with four independent motors, two 9" pneumatics, two 9" custom dual omniwheels. Not finished early enough to perfect control, but reasonably effective.

2005 -- 6WD with #35 chain and 4" Colson wheels, powered by two kit transmissions (thanks, Paul -- those were incredibly tough and easy to use). We unfortunately put a great drivetrain on a questionable chassis, made from 8020 with poorly reinforced corner joints.

2006 -- custom holonomic. We built our own ominwheels and gearboxes, and a custom chassis made from aluminum channel with gusset plates and lots of 1/4-20 clinch nuts. A work of art that won a design award at IRI, but not particularly effective for keeping our ball shooter on target.

2007 -- 6WD with kit gearboxes on a kitbot chassis, #35 chain to the kitwheels on the center and #25 chain to the AM aluminum omniwheels on the corners. Very reliable and manueverable, resulting in a good offensive robot when the defense was light. We were easy to turn when defended heavily.

2008 -- custom live axle 8WD with #35 chain to the four center wheels, and #25 chain to the 1/8" raised corner wheels. AM Supershifters with one CIM per side. Very controllable, resulting a consistent 4 line hybrid mode and good speed during teleo.

Our custom drivetrains in '04, '06, and '08 were all fun to build and we learned a lot. But my overall takeaway is this: if it looks feasible to use a 6WD kitbot chassis next year, I'll be pushing the team to do that.

931 won regional Chairman's Awards in both of the years that we used 6WD with kit gearboxes. :) Coincidence? Or does spending less time fiddling with custom drivetrains allow us more time for other aspects of our program?

Re: Best Drivetrain
 

I thought the weight/height rules last year were a good start. How about leaving the footprint the same and reducing maximum weight by 25%? That would generate some creative engineering, and force some serious priority-setting.

FRC robots have been pretty much the same since I've been with the program. I think it's time to start making some steam rise up from overactive brains.

Re: Best Drivetrain
 

I think that the width requirement was intentional - just barely small enough to get through doors with the bumpers on. The GDC is trying to give us problems to solve wherever we go with the robot. One of the disadvantages I see to going to a smaller footprint is the impressiveness factor. One of the most common comments that I get is "I didn't realize the robots you kids make were so big." Bigger is not always better, but it is often good for showing off, one of the best ways to promote FIRST.

Re: Best Drivetrain
 

I understand that you are mostly correct. Back in the day, the teams with 36" by 36" robots had a hard time fitting through standard doors, as I understand it. So they changed it. They changed it again, before bumpers didn't count against weight or size.

Re: Best Drivetrain
 

If you build a preseason prototype drive and decide it fits the game, it can become your practice bot. When the season starts, give it to your auton programmers and let them tune their code while the mechanical teams are building the competition robot. If you build similar drive trains every year keep your old robot together because it can also be used for this.

Re: Best Drivetrain
 

heh, one thing we do pride ourselves in is that our robot is practically completely designed and built by students on our team. and i assure you, if we can lay out a great chassis with a t-square, anyone else can, at least with little bit of care and thought, anyone can learn to draw a line strait or drill a hole right, thats what mentors and teachers are there for. what i am saying is that #25 chain is as simple and easy to use and work with as 35. also, sprocket spacing is a lot easier (each link is 1/4 inch long, making spacing a snap)!

Re: Best Drivetrain
 

#35 chain has much more room for spacing and alignment error as it larger and stronger.

For a team already struggling with a drive, get it done with #35, and then maybe work on #25 in later iterations.

#25 isn't a magical thing to be afraid of, but definitely requires decent tolerances.

Re: Best Drivetrain
 

I believe one of the factors of not changing the footprint in recent years is due to cost. If the footprint were to change, lets say to double the size, that would mean a larger kit frame, longer chain, etc. which may cost FIRST or some other vendor more to create. It may also not be feasible for the playing field size to have 6 robots on at the same time.
I truly believe one of the big issues with the 2008 game is that the field was too small to have 6 robots fighting traffic trying to achieve the game challenge.
Also, if the footprint changed by just a few inches, why even do it?

Re: Best Drivetrain
 

For the same reason that they changed it in 2005. Prevent teams from pre-building drives.

Re: Best Drivetrain
 

I think you can essentially create the "same/similar" type drivetrain even if the dimensions change by a few inches.