Re: Why not to shift?
 

This past year actually our turbo mode came in handy. Our robot traversed the barrier with ease and could defend our lane before another drive team could see what was up.

Re: Why not to shift?
 

It also did substancial damage.

Re: Why not to shift?
 

Care to elaborate?

Re: Why not to shift?
 

At the rah cha cha ruckus this year, we found that turbo-ing over the barrier really damaged our robot. We did it once, and the radio fell off, and the entire underside of our robot was dented up and scratched, not to mention that our bridge actuator was all bent up. This was also contributed to by the pneumatic wheels having a lot of bounce in them, in addition our drivers extremely defensive driving style during those matches.

Re: Why not to shift?
 

So, what you are saying is, turbo mode isn't bad for a robot, it's just what was done while in turbo mode that was damaging to the robot.::ouch::
OK, good to know. ;)

Re: Why not to shift?
 

Going over the bump in high gear is fun too! For a moment it felt like Dukes of Hazard which was cool before the image of your robot mangled and broken in a heap fills your head! :p

We've done that move three times this season with only a few surface scratches!

Re: Why not to shift?
 

Only three times?

http://www.flickr.com/photos/daniele...57629155165512
http://www.flickr.com/photos/daniele...57629491142326


If you run a turbo mode, you are limiting your normal non-turbo driving in one of two ways:
-If you just divide/multiply the output by a constant, you're limiting the motor to substantially less mechanical power than it is capable of, and your acceleration will be worse in slow mode, due to reduced voltage, in addition to the high gearing.
-If you actually speed-control to a lower output speed, you will still maintain the acceleration of the actual gear but your drivers will still be limited. This is OK in some cases, depending on what you are trying to do, but you are still limited to the acceleration of the actual gear.

So, a turbo button is just limiting the drivers. It won't allow you to gear any faster, because your acceleration will suffer in non-turbo mode. My recommendation is to either gear a single-speed down to the speed you actually want to drive at, or run a real shifter.

Re: Why not to shift?
 

Yes only three thankfully! They were all accidental but when we did we went near vertical. We have footage of the first one which was the worst considering we went airborne!

Re: Why not to shift?
 

For a team with 6 drive motors (for example, let's say a 775 and two CIMs), how fast would the robot be traction limited at? I would assume if a 2 CIM drive is traction limited at 6fps, then with a 775, the traction limited single speed gearing allow for a top speed around 8fps. Could you, theoretically, just throw power onto the drive until you were traction limited at, say 13fps?

On a related thread, how many motors can you give a drivetrain while still drawing less current than the main breaker will pop at? An unsophisticated analysis says that even 4 CIMs drawing 40 amps (ie, accelerating from a stop) will pop the 120 amp main breaker. Is the limit on the number of motors which can reasonably be put in the drive dictated by the main breaker?

Re: Why not to shift?
 

Actually, those circuit breakers won't ever trip at the rated current. Take a look at the attached datasheet to get a feel for the trip times. According to the data sheet, at 200% rated current, they should take at least 10 seconds to trip. It looks like about 20 seconds at 150%. That's assuming no heavy bumps, of course.

So based off that, on a 4CIM drivetrain, you'd likely fault out jaguars or trip your 40A breakers before you tripped the main 120A breaker.

Re: Why not to shift?
 

I have to say pushing other teams is over rated. If your going to get a shifter to have more pushing power don't waste your time. Best thing to do is keep things simple. Get your robot to do one thing perfect trying to be jack of all will make you a master of none.

Re: Why not to shift?
 

I agree that you should master one thing, though I don't think many teams use shifters just for their pushing power. If you have a second speed, it allows you to gear your for a higher speed. This means that you are more effective at solving the game task. In addition however, it also allows you to be able to win many of the pushing matches you will face in eliminations. In my opinion, the shifter allows you to be a more effective scorer.

Re: Why not to shift?
 

Going across the feild at 22 fps and 10 fps will not save enough time for the average team. Slower is faster in the world of FIRST. The biggest problem teams have (i would say 90%) is they think their better then they are.

Look at the last few games where both alliances put up 0 points. Most of them were to worried about shooting fast or shifting to be faster when they can't even score 1 ball/tube. 2010 is a perfect example, you could have pushed 3 balls in and hung and won over 70% of your games.

Re: Why not to shift?
 

Agreed. Single speeds can play defense just as well as shifter.

Re: Why not to shift?
 

I definitely agree that shifters are overated. They only help teams that are already preforming well(teams that spend time at the end of the build season tuning and practicing with their robot). However, I think that there is little reason to not use shifters this year. Companies like Vex and WCP have made them super easy(and cheap) to integrate into whatever drive you choose to run.