Go to Post "The secret to success is to acknowledge that you have limits, but to never acknowledge that you have reached those limits." - lady_raidan [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

 
Reply
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 16-02-2012, 09:02
Andrew Lawrence
 
Posts: n/a
Poor man's omnis (idea)

We have been having trouble turning, so a student of our suggested until we get normal omnis for our robot, we use PMOs "poor man's omnis", basically the plaction wheel without any tread. We have a 4WD wide configuration, and would have the PMOs in the front right and back left wheels of our robot with the front left and back right treaded.

What are your thoughts on this? Is it safe to do (will it break the plactions)? Do we loose anything significant by doing this instead of omnis?

Thanks, and enjoy your last 5 days!
Reply With Quote
  #2   Spotlight this post!  
Unread 16-02-2012, 09:07
JamesCH95's Avatar
JamesCH95 JamesCH95 is online now
Hardcore Dork
AKA: JCH
FRC #0095 (The Grasshoppers)
Team Role: Engineer
 
Join Date: Dec 2004
Rookie Year: 2001
Location: Enfield, NH
Posts: 1,866
JamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond reputeJamesCH95 has a reputation beyond repute
Re: Poor man's omnis (idea)

A simple idea is to wrap the wheel in zip-ties parallel to the axis of rotation. The zip-ties allow the wheel to slide side-to-side while maintaining some forward/backward traction. It's an old-school trick.
__________________
Theory is a nice place, I'd like to go there one day, I hear everything works there.

Maturity is knowing you were an idiot, common sense is trying to not be an idiot, wisdom is knowing that you will still be an idiot.
Reply With Quote
  #3   Spotlight this post!  
Unread 16-02-2012, 09:09
Andrew Lawrence
 
Posts: n/a
Re: Poor man's omnis (idea)

Quote:
Originally Posted by JamesCH95 View Post
A simple idea is to wrap the wheel in zip-ties parallel to the axis of rotation. The zip-ties allow the wheel to slide side-to-side while maintaining some forward/backward traction. It's an old-school trick.
Really? That's so cool! Thanks!
Reply With Quote
  #4   Spotlight this post!  
Unread 16-02-2012, 09:59
DampRobot's Avatar
DampRobot DampRobot is offline
Physics Major
AKA: Roger Romani
FRC #0100 (The Wildhats) and FRC#971 (Spartan Robotics)
Team Role: College Student
 
Join Date: Jan 2012
Rookie Year: 2010
Location: Stanford University
Posts: 1,277
DampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond reputeDampRobot has a reputation beyond repute
Re: Poor man's omnis (idea)

The main reason omnis make it easier to turn is that they have a lower coefficient of friction across the wheel than along the wheel. This means that anything that makes slipping side to side easier than forward and back could be considered a "poor man's omni."
Reply With Quote
  #5   Spotlight this post!  
Unread 16-02-2012, 10:07
Taylor's Avatar
Taylor Taylor is online now
Professor of Thinkology, ThD
AKA: @taylorstem
FRC #3487 (Red Pride Robotics)
Team Role: Teacher
 
Join Date: Jan 2006
Rookie Year: 2006
Location: Indianapolis, IN, USA 46227
Posts: 4,601
Taylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond reputeTaylor has a reputation beyond repute
Re: Poor man's omnis (idea)

We had originally planned to use the slick wheels from 2010. We found that they worked very well on carpet, but on the plastic bridge, the robot became uncontrollable. Slick wheels != PMOs.
I'd presume the same for Lunacy wheels.
__________________
Hi!
Reply With Quote
  #6   Spotlight this post!  
Unread 16-02-2012, 10:29
jwfoss jwfoss is online now
Chasing Elegant Simplicity
AKA: Justin Foss
FRC #0558 (Elm City Robo Squad)
Team Role: Mentor
 
Join Date: Aug 2006
Rookie Year: 2003
Location: New Haven, CT
Posts: 592
jwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond reputejwfoss has a reputation beyond repute
Re: Poor man's omnis (idea)

Quote:
Originally Posted by SuperNerd256 View Post
What are your thoughts on this? Is it safe to do (will it break the plactions)? Do we loose anything significant by doing this instead of omnis?
I wouldn't suggest running plactions on the ground without tread, there is a large chance that you will break off the edges that would clamp the tread. Another option would be to rivet the tread on upside down with treaded side on the wheel and the smoothish side outwards. I have seem teams do this in a pinch to reduce scrub when turning.
__________________
2003-2006 | FRC 0176 | Aces High - Student
2007-2010 | FRC 0229 | Division by Zero - Mentor in Training
2011-2013 | FRC 2168 | Aluminum Falcons - Mechanical Mentor
2013-20xx | FRC 0558 | Elm City Robo Squad - Mechanical Mentor
Reply With Quote
  #7   Spotlight this post!  
Unread 16-02-2012, 13:06
Phyrxes's Avatar
Phyrxes Phyrxes is offline
Has done the math, have you?
AKA: Dave Button
no team (No Team, Changed Schools)
Team Role: Teacher
 
Join Date: Dec 2007
Rookie Year: 2007
Location: Gainesville VA
Posts: 489
Phyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant futurePhyrxes has a brilliant future
Re: Poor man's omnis (idea)

For purposes of driving on carpet you can also cut a strip of "slick" plastic of your choice and rivet it on top of the tread on the plactions, or in place of the tread if the strip is thick enough.

Though I totally suggest NOT doing this if you want to be able to drive on the bridge.
__________________
Dave Button
Physics and Mathematics Teacher
Wakefield School
The Plains, VA

“Simplify and add lightness.”
― Colin Chapman, Team Lotus
Reply With Quote
Reply


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 11:42.

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