Go to Post Man I hate it when people muddy up our rampant speculation with facts and logic, jeez :D - rsisk [more]
Home
Go Back   Chief Delphi > FIRST > General Forum
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
 
 
Thread Tools Rating: Thread Rating: 4 votes, 5.00 average. Display Modes
Prev Previous Post   Next Post Next
  #13   Spotlight this post!  
Unread 17-03-2011, 10:10
JesseK's Avatar
JesseK JesseK is offline
Expert Flybot Crasher
FRC #1885 (ILITE)
Team Role: Mentor
 
Join Date: Mar 2007
Rookie Year: 2005
Location: Reston, VA
Posts: 3,735
JesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond repute
Re: Team Update #18

Quote:
Originally Posted by Ether View Post
Could you be a bit more specific? What "implied assumption" are you referring to?

The only assumptions used in the calculation were to ignore friction (which was explicit, not implied) and to ignore additional stored kinetic energy (rotational). These tend to cancel each other out. Over very short distances (such as 1/4"), the stored rotational KE easily overcomes friction, so it's actually a conservative assumption. You can demonstrate this for yourself, if you like: with the wheels raised, power your minibot with 12V and then remove the power. Observe how much the wheels turn after the power is removed.
Alright, I did say implied and you were explicit about the friction. Yet it was still ignored in the conclusion without any explanation in the original posts. Ok, so there's the explanation, which I still don't think allows for a valid conclusion based upon the calculation. Your latest statement makes the implied assumption that the unloaded motors act identical to the real system during impact. Impact forces induce shock into the gearing which momentarily increases the friction in the gearing/bushings with a positive correlation to the amount of force applied to the plate. Impact forces induce friction in the bolts on the triggering mechanism, which may be bind on the plate if the impact causes a torque moement. Thus it may take 474 newtons at a specific instance in time to slow a minibot down without taking friction into account -- yet until we characterize the friction in the system we're making a dangerous* conclusion that "more than enough force is applied to moving the plate".

*dangerous because the process of coming to the conclusions would then be acceptable to use elsewhere.

I can't characterize the friction with numbers or equations, which I will concede. Interestingly, that's the very specific reason we [industry] do shock testing for our real world complex systems. The equations simply don't match the results of the real implementation.
__________________

Drive Coach, 1885 (2007-present)
2017 Scoring Model
CAD Library | GitHub

Last edited by JesseK : 17-03-2011 at 11:01. Reason: clarity
Reply With Quote
 


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 12:16.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi