I cannot figure out whether the Atwoods are equal speed or not equal speed in forward and reverse. I looked for numbers, I asked around, and I tried to test it, but I’m still confused. Could somebody give me a yay or nay on whether they are equal in speed in both directions. This is vital to my bot design, and I really need to know. Thanks, everyone.
I recall a thread earlier where it was stated the Atwood brushes are symetrical so that would mean same forward and back. edit christina posted the post I was refering to, so now you have a vague awnser based on an educated guess… sorry 
However if I were you I wouldnt take my word for it and wait for someone like Joe or Nate to verify…
Actually, I asked this question a little while ago. Dr. Joe answered with this:
"As to asymmetry in the Chiaphua’s. I think that the brushes are symmetric, but I am not going to risk taking the motors apart to find out (by the way, if you do, don’t take the armature out of the magnets – again I have REAL DATA to show that you can lose as much as 10% of the output of the motor by simply taking the armature out of the housing and putting it back in again – it is a magnitism thing I have been told). "
Seems like that’s the best answer we’re gonna get. 
~Christina
Are the drills still asymmetrical? The data page FIRST put out looks different, but the drills are the same, right? Oh, this darn drivetrain redesign is driving me bonkers!
Today we directly connected a 8 wheelchair wheel on the motor and it was totally wicked!!! That sucker was turned into a fan. It could have chopped your head off.
I made a suggestion that we make a driveable cart that we could drive around in the pits with those motors. Imagine little me breaking peoples ankles off.
OUCH imagine getting hit at that speed. Has anyone acually figured out their MPH lol?? Imagine a head on collision with robots that had their drive powered by them!
Acually we should put a fan on the end and have it cool our drill motors down!!! they would never get hot. They would surely eatz up lots of current.
*Originally posted by Dan_550 *
**Are the drills still asymmetrical? The data page FIRST put out looks different, but the drills are the same, right? Oh, this darn drivetrain redesign is driving me bonkers! **
Based solely on acoustic judgement - I do think they’re still asymmetrical. There’s a distinctly different noise coming from them when they run in reverse.
*Originally posted by Dan_550 *
**Are the drills still asymmetrical? The data page FIRST put out looks different, but the drills are the same, right? Oh, this darn drivetrain redesign is driving me bonkers! **
The drills are probably still asymmetrical… Since it would make sense for a drill to be more powerful in “forward”, or drilling direction. But this isn’t too big a deal.
Just have more driver practice, and your drivers will be able to drive that robot straight. But if you really want to… Compensate the difference in the program, although you will be limiting voltage to the drills spinning in forward to match speed of the backward running motors…
Drivers’ practice is still the way to go… You never know if you will need those forward running drills pushing as hard as possible. 
Also, you can use the gyro (Yaw Rate sensors) to sense changes in drive train direction and program the robot to drive straight.
http://www.chiefdelphi.com/forums/showthread.php?s=&threadid=1600
http://www.chiefdelphi.com/forums/showthread.php?s=&threadid=1750
One of the Drill motors is designed to run more efficently in the reverse direction (Draws same amperage and will obtain same speed as other two in the fwd direction). This was mentioned at the Motor workshop and we confirmed it with testing.
There’s a backwards drill motor? Which one? Is it the one that came sans a trans? This is becoming more wierd by the minute…
In most drills the motors spin faster when they are in foward direction. They are just talking about how much slower they are in reverse and if they are slower in reverse.
Please correct me if i am wrong!!!
This forward/reverse thing comes up very often.
Let me just say that I am skeptical still.
In general, we have not bothered with such things. I have gotten 12V speed-torque curves (actual test data) from the manufacturer (not only do I call these guys constantly begging for them to donate motors to FIRST, but my day job more or less involves using motors and gears to make doors open, grind coffee beans, etc…) which tells me that at least at 12V, there shouldn’t be much of an effect (less than 10% difference from forward to reverse as I recall).
BUT…
Jim Zontag of the Killer Bees, Mike Gray of the HOT Team, Raul-the-Magnificent of Wildstang, and a host of other folks wise in the lore and magic of FIRST tell me that I am just plain wrong on this issue.
What is a rookie to do?
Well, I suppose that if you are using 4 Wheel Drive or Tank Drive, you shouldn’t worry much about it at all. In years when we have had 4 wheel drive, our robots go straight with only 1 side driving. In order to turn we had to drive one motor one way and the other motor the other way – really. In such cases, it seems hard to argue that a small effect like we are discussing will make any noticeable difference at all.
If you are using 2 wheel drive with castors or have somehow compensated for the scrubbing effects of multi-wheel drive (for instance by using 6 wheel drive with the center set of wheels 1/4 inch lower than the outer wheels), then your robot will not be so intent on going straight. In these cases, if it is easy for you to turn the motors around so they are going the same direction, I say do it. Why not? If it is not easy, finish your robot early and get enough driver time so that they can compensate.
I know I am muddying the waters a bit, but I think it is important for folks to realize that it is far from clear what to do in this case.
Experts disagree…
Joe J.
The Chiaphua motors are symmetric. The drill motors are, without question, asymmetric.
In a slow machine, the asymmetry probably makes little difference while the machine is in motion.
However, a fast machine will be difficult to control unless the drill motors are positioned as to keep them rotating in the same direction.
Whether the robot has a fast or slow ground speed, motor asymmetry will cause it to yaw during the launch. Over correction and speed reduction are common operator responses. Both result in decreased performance and sometimes genuine fear of using the full motor authority. Improper joystick trim can make the situation worse.
Spinning the drill motors in the same direction makes the driver confident that the machine will respond to his/her commands. High operator confidence generally results in good performance, but perhaps more important: consistant, repeatable performance.
The difference between forward and reverse speeds is about 12 percent as measured with a strobotach.
To illustrate the value of spinning the motors the same direction, make yourself a little “Segway” ™ thingy with the CG below the axle centerline.
Power it with drill motors fastened directly to the wheels. It will refuse to run in a straight line. Its a good autumn experiment, or maybe between competitions.
Mike Gray
If you’re using tank drive with a motor on each side it shouldn’t be a problem, the driver can compensate if needed for the miniscule difference.
If the atwood motors are not the same, they are not far off. Our robot is has slightly more tension on one drive belt and one side does run slightly faster. Nothing serious.
That difference in drill speed is quite miniscule, as I saw and felt just a little while ago. I had it in low, and it was less than 2’’ curve per yard of travel – too little for me to give a hoot about. Now, in high gear, I dunno, but the concrete test surface was severely traction limiting, so all I was able to do with it was make eight burnout marks… Oh, well, tomorrow is another day.