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Unread 10-12-2003, 01:49
Unsung FIRST Hero
JVN JVN is offline
@JohnVNeun
AKA: John Vielkind-Neun
FRC #0148 (Robowranglers)
Team Role: Engineer
 
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Re: Shifting Gears

Quote:
Originally Posted by Matt Adams
Emphasis to PAIR and OR added by me.
I definite "competitive" as a max speed greater than 10 feet per second, and having a maximum applied force of 150 lbs.
Well... of course!

As Joe mentioned above... that's what Power is all about... and any single pair of our motors simply don't have enough to handle the speed, AND the torque you mention simultaneously.

All you rookies listening?
This is one of the most common "errors" people make:
"Our robot is fast as hell! And it can also push the world! We don't need a shifter, or other motors."

*bzzzzzzt* Try again.

Unless you shift, or have extra motors... my robot will always either be able to out push you, or out run you. NO ARGUMENTS WILL CHANGE THAT.

Physics, does not lie (only FIRST team representatives do).


I agree 100% with what Matt stated (and more importantly, so does Physics).
I also typically use a ~1.2 coeff of friction (130 lb robot * 1.2 coeff ~ 150 lbs pushing force) and 10-11 feet per second as my benchmark points for low and high gear. It is NOT physically possible to have both using the drills, chips, FP individually. (Unless.... you shift!)

*phew*
This is a sore subject for me. I'm sick of 80%+ of FIRSTers not understanding this MOST FUNDAMENTAL concept of drivetrain physics. Everyone should take the time to understand the principles behind the robots... (it makes scouting a heck of a lot easier when you can recalculate a robot's theoretical performance based on some quick questions, and a mental calculation).


Again... if anyone has questions on stuff like this, you are more than welcome to email or IM me. There are also plenty of whitepapers, and threads covering topics like this. Or... ask your friendly neighborhood FIRST mentor/engineer!

John
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In the interest of full disclosure: I work for VEX Robotics a subsidiary of Innovation First International (IFI) Crown Supplier & Proud Supporter of FIRST
 


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