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Unread 02-04-2007, 08:14
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,770
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Re: AM shifter problems

Quote:
Originally Posted by JohnMorenski View Post
low gear works great, but in high gear. we cannot turn in high gear, the battery voltage on the O/I drops and the motors seem to stall,
This is a classic symptom of too much friction in turns. As other have pointed out, your drivetrain and final gear ratio couple to produce near stall current on the drive motors. The small Chalupas stall at 129 amps while the larger ones stall at 96 amps. Add that up and you are likely drawing something in the neighborhood of 300+ amps even if your wheels are turning. With a fully charged battery with an internal resistance of .011 ohms, you are already dropping 3.3 volts at the battery, plus whatever series resistance you have in the wires. Remember that the RC will go to backup mode when the input voltage falls below 8 volts and all outputs are disabled. As you draw current from the battery, that voltage drop takes you seriously close to the magic 4 volt drop and RC shutdown.
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.

Last edited by Al Skierkiewicz : 02-04-2007 at 08:17.