[OCCRA]: OCCRA 2010 VEX Workshop OSTC-NE 06Oct10

[apalrd]

1. I wasn't at the workshop this year. I went last year, and assumed I was good.

2. I read the PDF's you posted. You did some math on speed and torque. JVN has a really really nice design spreadsheet for rotary mechanisms (See JVN's Design Calculator http://www.chiefdelphi.com/media/papers/2059). I first calculated the aprox. needed gear ratios by hand, and punched them into the calculator. I assumed the weight of the mechanism was neutral because of counterforce (notice I didn't say counterweight?) and the motor would only have to drive the ball. I over-estimated the arm length since I hadn't actually built it yet, and it said with a BIG motor (which does around 17 n-m of torque, BTW, the JVN calc needs numbers in n-m's). It said it would work quite well, and gave me the loaded output speed and motor current draw. I built it. It works well. The numbers say I can go a little bit faster, but then it would be uncontrollably fast (And I am trying to do the feedback with only P if possible, but I might need D).

Just a friendly reminder to OCCRA teams: Do the math! Just because a mechanism is large does not mean it will move slowly! With bungee you can do it easily!