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Unread 31-01-2003, 12:37
kmcclary's Avatar
kmcclary kmcclary is offline
Founder 830/1015;Mentor 66/470/1502
FRC #0470 (Alpha Omega Robotics)
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Time for Plan B...

Quote:
Originally posted by Jeff Waegelin
If you don't already have a gearbox designed, a one-speed drive, wheel shifter, or maybe a drill shifter (see the white papers) might be a better solution. Multiple speeds are nice, but don't spend too much time on it. We did that last year, and ended up assembling our robot in the last 3 days because we spent too much time on our transmission. Don't let your desire for a three-speed bot hinder your performance in other areas.
My old team also got caught in EXACTLY that transmission boondoggle last year. We had some GREAT college mentors (find some if you're near a college town), but we didn't watch one pair of them close enough and they took some students down a garden path of a too complex multigear drivetrain another team designed because it "was cool".

The problem was, they couldn't make it, and would NOT LET IT GO when the deadline passed. By the time we finally realized they were STILL on it (after repeated requests to drop it) we were finishing week FIVE with NO drivetrain in sight!
We YANKED them from it and SLAPPED together a SIMPLE drive (two drill motors in their cases bolted to a board, and a 3:1 gear set) in less than TWO DAYS. BTW, it worked FINE. In fact, we ended up locking it into "high" with the ring trick because RELIABILITY was more important than speed switching! (Those cheesy gearboxes tended to slip.) Turned out, after ALL of that hassle, ONE speed worked GREAT!

But as a result of that construction delay, we were almost DEAD. We had NO time to debug our payload, NO practice time, and basically shipped a non-functional robot to our first regional. We spent all of Thursday and half of Friday just getting it all RUNNING (we were a ten point "brick" for our first two matches <sigh>).

Once running, the lack of driver practice time started showing...

We didn't REALLY get the robot running as we wished until our SECOND regional, because of all of the OTHER things we had to debug AFTER having a running drivetrain. Needless to say, our stomach acid levels were pretty high from the stress, and no one could even WATCH other matches because we were stuck in the pits working. NOT much fun...

All of that could have been avoided if we'd simply made a simple mule in the first place.

Lessons learned:
- There MUST be DEADLINES for ALL phases of this project, and the number one construction deadline (after freezing the design) is to get that mule RUNNING.
- You MUST have a Plan B in place for each phase, AND the rime reserved to execute it.
- Once you've passed the deadline for Plan A, DROP IT, no matter HOW tempting it is to "just put a LITTLE bit more work" into it. You must know when to quit, and having hard deadlines enforces that.
- Complex drivetrains are SECONDARY to the schedule. Priority #1: Make it MOVE. THEN tweak it to make it move BETTER if you have the time.
- PRACTICE TIME MUST NOT BE SACRIFICED.

Don't forget, this year you also have the AUTONOMOUS period to debug! Depending on your strategy, you may need part or all of the PAYLOAD package running to even START debugging that phase, so you SHOULD be close to finishing your PAYLOAD construction by now.


IMHO, You're well beyond the "time to switch to Plan B" with your drivetrain. FIRST even stated that "you should have a drivetrain running by week two", and we're now finishing week FOUR.

My recommendation: Use WHATEVER is running now. If not running slap together the FIRST recommended drive and a pair of casters. Whatever you do, make it a hard goal that "before this weekend is out, we WILL have a running mule". Even ONE speed will get you beyond this point. Do NOT spend more time on the drivetrain. Instead, get to PAYLOAD and AUTONOMOUS MODE debugging asap.

Bottom line: IMO, my old team last year literally wasted the first regional's $5000, and didn't have much fun simply because we didn't stick to the build schedule and allowed tinkering to go on WAY too long. That's NOT happening this year with my new team.

THIS YEAR: We had a running drivetrain maneuvering on a "switch box" by the end of week TWO. NOW we're upgrading it with a better drive while the payload and electronics teams finish their work. However it WAS running then, AND we're set up to reinstate the original drive in less than a day as Plan B if pressed.

Trust me... If you're dead for the autonomous period, or spending all your time at your first regional in the pit fighting to simply get your payload to perform because you spent too much time on the drivetrain (or worse, you're still trying to get it to MOVE at the regional) you've just lost a LOT of the fun of the competition. Your performance will suffer without enough debug and practice time.

Good luck!

- Keith
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