you know, ours stopped working correctly tonight also.  Meeting is over and it won't be run again until Saturday's tournament at MW.
----- Original Message -----
From: [log in to unmask] href="mailto:[log in to unmask]">Eric Palmer
To: [log in to unmask] href="mailto:[log in to unmask]">[log in to unmask]
Sent: Thursday, November 04, 2010 7:39 PM
Subject: Re: [VADCFLL-L] NXT merry go round effect

3rd year as coach and nothing worked tonight. So be it. We are running through it again and again. Team is excited however. 

Sent from my iPhone

On Nov 4, 2010, at 6:45 PM, Brandy bergenstock <[log in to unmask]> wrote:

Well, if others getting better results perhaps it is only us. I'll answer your questions in case you have any more thoughts-

Each decision that the kids make in their robot design matters.  Using the "knob wheel" as a drive gear would be a bad idea for precision, while most of the "normal" gears work quite well.
We're using the gears that the machine came with (the whilte and orange ones) and didn't create any gear boxes ourselves.  (that made it into the final robotic design)

  What kind of tires are they using?  Are they rigid or bendable?
We're using the 8.2 cm tires, the big ones, because the inch to .1 rotation is 1 inch and a breeze to figure out when quickly updating the robot.  Because we're using rotations and not distance or time, that should increase our precision. Should.
 Are they using crawler tracks? Nope.
  What kind of gear ratios are they using?  1"=.1 roation
 Are they using programming techniques that depend on consistent battery voltage?
 Not to my knowledge. We're programming it to go straight certain distances then turn, then go back or forward, and turn again.  Not complicated stuff.

 Is their chassis rigid or highly flexible?
Chassis is rigid.  We have noticed that becasue of the length and position of the back wheels, sometimes they can squeeze together slightly and I try to remind the kids to open them up before sending it out. But altogether, it should resemble a hard chassis.
  Is the weight of the robot over the drive wheels or offset?
They fixed this by adding a counter weight  during the 5th week and taking off a side mounted gear.  It was a hard decision and limited what missions the kids could do, but ultimately it did lead to slightly higher, but not perfected consistency.
 Is the weight unevenly distributed?  All the rules of physics apply and everything affects the outcome.
I can only say it's better and it was, so perhaps it's still the main issue. I had asked a while ago if anyone knew of any programs or books that would help with robotic design to counter some of these problems, and ultimately I purchased a book to help me understand the basic designs better and their pros and cons, but if you're not having the same problems, then it MUST be our design. :(  Hope we'll figure it out after the competition.  We're looking forward to seeing what all the other robots look like :)

  Or that the spinning back wheel of the classic "tribot" design can alter the the direction of the robot as it swings around when you start to back up.
This design was abandoned in the 3rd week for a much more stable design that wasn't as twitchy.
 Then have them ask the robot designers of that team "How did you get your robot to be so consistent?  What did you learn about inconsistency?  Did you use any special parts that helped (e.g. different wheels)?"  The answers will mean so much more to the kids coming from other kids rather than from a book or coach, and they might get more excited about competing next year with their new-found knowledge.
I will ask them to write down their observations.  ( I know at least two or three of them will find this the best part of the competition.)
I always tell my kids that their goal is to have each mission work 9 out of 10 times.  Their tendency is to try an idea once and if it doesn't work to fiddle with it.  How do they know if that wasn't the 1-in-10 failure and that the next 9 times it would have worked great, unless they tried it multiple times?  So even learning good engineering "process" is something that produces consistency in the outcome.
They have been keeping a log to track data and the rule I asked them to follow was no adaptations to the program until they had seen it run 3X in a row.  Then fix it if it's still wrong. 
I hope your team can turn your frustration into a quest for more knowledge and understanding.  After all, that's what makes a great engineer!
Yes.  We are upbeat about all they have accomplished- the programming, research, teamwork.  I am as sunny as a summer day when it comes to what they have accomplished and at the meetings, but afterward, I'm disappointed I couldn't lead them to better answers.  Not give them answers, that's worthless, but even send them in the right direction to look around.  The pitfalls I knew about, I had lesson plans that taught about it and had them experimenting to figure out the concept.  It was great, but I clearly am lacking on the design side :(  It will be fascinating to me to see one that works better than ours. 

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