I am not sure about the software issue. I have heard of problems in the G environment where the only solution was to rebuild the program on a fresh file, but I have forgotten the particulars of the issue. I have never found the robots able to reliably and repeatably travel a straight line for more than a foot or two. I encourage the students to think about driving to a wall or rely on sensors when they get close to their target... tho my success with helpful questions depends on the makeup of the team. :-) That said, I noted that the softer wheels have a lot more variance and we have maybe eight tractor treads no two of which are quite the same size. The only way to be sure is to experiment with combinations of hardware, tho that discipline too depends on the maturity of the team. -----Original Message----- From: Tom Bove [mailto:[log in to unmask]] Sent: Saturday, October 23, 2010 12:11 PM To: 'Randy Greene'; [log in to unmask] Subject: RE: Variance in Bricks? Our team is using a 2 yr old mindstorm's brick and an education version brick purchased this year. Both have firmware 1.31 downloaded and both are running on AA batteries (refreshed at the same time.) We notice a difference in how programs are being executed- I don't think the problem in this case is related to motor differences. For example, one brick will execute a 90 deg turn and run a loop driving forward until the ultrasonic makes it stop. The other brick seems to be jumping the loop - by this I mean it seems that while executing the turn, the ultrasonic sensor is activated and triggering a stop before the robot has driven forward. Are there any other software differences I might have overlooked? Both were running the same program written in the education disc downloaded program. The other variance we've seen is within loops- One robot will stay straight with a continuous loop, whereas the other has significant drift. I am willing to attribute that to motor differences, but would love to hear any other thoughts. Thanks Tom Team 2280 - The Blockheads -- To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". -- VADCFLL administrative announcements are sent via VADCFLL-ADMIN-L. Visit https://listserv.jmu.edu/archives/vadcfll-admin-l.html to subscribe. -- To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list". -- VADCFLL administrative announcements are sent via VADCFLL-ADMIN-L. Visit https://listserv.jmu.edu/archives/vadcfll-admin-l.html to subscribe.