Thread: 6WD vs 8WD
View Single Post
  #32   Spotlight this post!  
Unread 06-01-2011, 22:17
KrazyCarl92's Avatar
KrazyCarl92 KrazyCarl92 is offline
Registered User
AKA: Carl Springli
FRC #0020 (The Rocketeers)(EWCP)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2010
Location: Clifton Park, NY
Posts: 522
KrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond reputeKrazyCarl92 has a reputation beyond repute
Re: 6WD vs 8WD

Quote:
Originally Posted by IKE View Post
So, I was very inspired by some of the physics guys up above, and have a challenge:
Assume 16m dash (approx. 54 feet- robot length), and COF of 1.0. Also assume a 4 cim power-train at 300 Watts/CIM.
What weight is your bot so that you are just barely traction limited the moment you strike the other wall? Is this less than 4 cims & a battery?
First of all THANK YOU for putting it in meters to spare me the conversions necessary to use watts and meters. However, there would be a missing variable in the necessary calculations if I am not mistaken, because we would need to know a time that it would take to travel said 16m. But I can solve for this with time as a variable anyway.

PT = 4PCIM
P = 1200 watts (~80 - 95 % efficient depending on number of gears, transmission, and other variables)

Ff = mgµ = m*9.8*1 = 9.8m

Work = Force * Distance = 9.8m * 16 = 156.8*m

time = Work / Power = 156.8*m / (between 960 and 1140) watts = between .138*m and .163*m seconds

so to solve for mass (in kg) it would work out to between 6.135 * t to 7.246 * t depending on the efficiency.

Of course, this all assumes that the robot would be constantly accelerating at the maximum possible value (no slipping/static friction) and that the robot would be able to keep getting faster and faster, but I'm pretty sure it would be impossible to gear 4 cims without a transmission such that they provided exactly maximum static frictional force and still could reach rotational speeds that would allow it to continue accelerating...would probably need really really small wheels, but not too sure about that one.
__________________
[2017-present] FRC 0020 - The Rocketeers
[2016] FRC 5811 - BONDS Robotics
[2010-2015] FRC 0020 - The Rocketeers