Go to Post What is this "off season" of which you speak? - Alan Anderson [more]
Home
Go Back   Chief Delphi > Technical > Technical Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rating: Thread Rating: 2 votes, 4.00 average. Display Modes
  #16   Spotlight this post!  
Unread 06-11-2003, 12:32
Madison's Avatar
Madison Madison is offline
Dancing through life...
FRC #0488 (Xbot)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1999
Location: Seattle, WA
Posts: 5,246
Madison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond reputeMadison has a reputation beyond repute
Quote:
Originally posted by Andrew
(Note: you can only effectively have six wheels on the floor if you use a suspension.)
Could you elaborate?
__________________
--Madison--

...down at the Ozdust!

Like a grand and miraculous spaceship, our planet has sailed through the universe of time. And for a brief moment, we have been among its many passengers.
  #17   Spotlight this post!  
Unread 06-11-2003, 12:47
WakeZero WakeZero is offline
FIRST-a-holic Strategist
#1011 (CRUSH)
 
Join Date: Feb 2002
Location: Tucson, AZ
Posts: 316
WakeZero will become famous soon enough
Send a message via AIM to WakeZero Send a message via Yahoo to WakeZero
I am a big fan of four wheel drive. Too many times have I seen teams use a two wheel drive with casters, and not be able to control it. Either they turn about too spontaneously, or they can't focus enough power in one direction to get up a ramp... ick

Four wheel drive really isn't as hard as it seems. The key is to make sure that your wheels aren't super, super sticky because you need them to slip enough to turn. With four wheels, you still get a zero turn radius... but you also get pushing power
__________________
2004 Arizona Regional -- Semifinalist
2003 NAT Galileo Division -- Highest Seeded Rookie (20th)
2003 NAT Galileo Division -- 100% Autonomous Completion (7 for 7)
2003 Arizona Regional -- Rookie All-Star Award
2003 Arizona Regional -- Quarterfinalist

Alumni on Team 64, The Gila Monsters
College Mentor/Founder of Team 1011, CRUSH
  #18   Spotlight this post!  
Unread 06-11-2003, 13:43
RogerR's Avatar
RogerR RogerR is offline
its spelled *ya'll*, not *y'all*
AKA: Roger Riquelme
FRC #3844 (Wildbots)
Team Role: Teacher
 
Join Date: Feb 2003
Rookie Year: 2001
Location: Somerset, KY
Posts: 913
RogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond reputeRogerR has a reputation beyond repute
Send a message via AIM to RogerR Send a message via MSN to RogerR
Quote:
Originally posted by Andrew
last year, team 16 had two driven front wheels and a steerable back wheel, same principle
actually, i believe that they used a 'tricycle' steering system, where they powered the steerable back wheel. this would allow them to have a turning radius of zero, but not have to worry about side slip like a 4- or 6-wheel drive robot would have to.

I may be wrong about this, as i'm going on what i've seen in the pictures.
__________________
"But to say that the race is a metaphor for life is to miss the point. The race is everything. It obliterates whatever isn't racing. Life is a metaphor for the race." -- Donald Antrim
  #19   Spotlight this post!  
Unread 06-11-2003, 15:19
Rpifirst Rpifirst is offline
Registered User
AKA: Nuz
#1493
Team Role: Mentor
 
Join Date: Aug 2003
Rookie Year: 2002
Location: troy
Posts: 43
Rpifirst is on a distinguished road
Send a message via AIM to Rpifirst
Also with 4 wheel drive you can acieve asymetric sp? drive whinch is a major major advantage.
__________________
Nuz
Lambda Chi Alpha
E.H.1103
  #20   Spotlight this post!  
Unread 06-11-2003, 15:58
UIDzero's Avatar
UIDzero UIDzero is offline
Registered User
no team
 
Join Date: Nov 2003
Rookie Year: 1996
Location: Austin, TX
Posts: 16
UIDzero is an unknown quantity at this point
Send a message via AIM to UIDzero
my fav design

for multiple arenas I always liked what I call the "rocking horse" design,lol though I am sure all you future MEs know the real name for it Basically at any given time you have 4 wheels touching with 2 in the front and 2 in the back, so it allows to body to "rock" while still maintaining "4 wheel stability". I attacked a really rough draft of the basic concept.
Attached Thumbnails
Click image for larger version

Name:	archwheel.jpg
Views:	120
Size:	9.8 KB
ID:	1577  
  #21   Spotlight this post!  
Unread 06-11-2003, 19:16
Andrew Andrew is offline
Registered User
#0356
 
Join Date: May 2002
Location: Little Rock, AR
Posts: 393
Andrew is a name known to allAndrew is a name known to allAndrew is a name known to allAndrew is a name known to allAndrew is a name known to allAndrew is a name known to all
Quote:
Originally posted by Andrew
(Note: you can only effectively have six wheels on the floor if you use a suspension.)



Could you elaborate?
Any support system that has more than three points of contact is indeterminate. Think of the crappy table at the restaurant where one leg is too short and the table rocks back and forth between two different determinate conditions.

If you have six wheels, for instance, the platform has to be exactly machined and the surface flat (or compliant) in order for all six wheels to be on the ground at once.

If the tires wear or the frame gets bent or the surface changes such that the there is about 1/16" to 1/8" difference between the highest tire and the lowest tire, the machine will settle on a support of three or four tires.

The way to avoid this is to put all six wheels on a suspension where the wheels have 1/4" or more travel. The spring in the suspension will allow the tires to accommodate to the variations in wheel diameter and surface.

Technically, the carpet is a "suspension" in that it has a surface springiness. Also, unless the robot frame is really, really stiff, there is some compliance in the frame. This is usually enough for the four wheeled robots to have all four tires on the ground.
  #22   Spotlight this post!  
Unread 06-11-2003, 19:56
Clark Gilbert's Avatar
Clark Gilbert Clark Gilbert is offline
Registered User
no team
Team Role: Alumni
 
Join Date: May 2001
Rookie Year: 2000
Location: Columbus, IN
Posts: 1,946
Clark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond reputeClark Gilbert has a reputation beyond repute
Re: my fav design

Quote:
Originally posted by UIDzero
for multiple arenas I always liked what I call the "rocking horse" design,lol though I am sure all you future MEs know the real name for it Basically at any given time you have 4 wheels touching with 2 in the front and 2 in the back, so it allows to body to "rock" while still maintaining "4 wheel stability". I attacked a really rough draft of the basic concept.
This is the way that the Technokat track drives have been for the past few years. It's always been a very slight curve, but when the robot is on flag ground you can barely tip it back and forth. It seemed to help out a ton in 2001 when we had the metal tracks, and we reduced the curve a little bit in 2002-2003 with the rubber belts. I wish i still had all my Technokat pictures, but my PC locked up right before I left for college and I didnt feel like fixing it.
__________________
Purdue Alumni
Cummins, Inc.
  #23   Spotlight this post!  
Unread 06-11-2003, 21:12
T967's Avatar
T967 T967 is offline
5 IA teams, WHOs w/me?
AKA: Seth F.
no team
Team Role: Student
 
Join Date: Nov 2002
Location: Marion, Iowa
Posts: 241
T967 is on a distinguished road
Send a message via AIM to T967
Two wheel has in many cases solved alot of younger teams problems they had with 4 wheel. Easier to move around simpler too build. However the 4 wheel and up class have won the comp. alot more as vet teams have perfected these designs. Probable the 2 most extreme wheel systems I've ever seen were at the Final round last year. Wild stang with their 360 degree swivel 4 wheel. and That 6 wheel monster that was getting air off the ramp, 26 I think. Usually 2 wheels have that agility that 4 wheelers don't come close to.
__________________
Old dude wondering if he can really get back into this crazy thing called FIRST.
  #24   Spotlight this post!  
Unread 07-11-2003, 00:50
Jnadke Jnadke is offline
Go Badgers!
#0093
Team Role: Alumni
 
Join Date: Jan 2002
Location: Appleton, WI
Posts: 775
Jnadke is on a distinguished road
Send a message via ICQ to Jnadke Send a message via AIM to Jnadke Send a message via Yahoo to Jnadke
A few ideas to point out...

-Last year 1064 had an articulated tread system where they had 4 mini-treads in place of 4 normal tank drive wheels. The cool thing is, these treads could rotate. On one position all 4 treads could be flat on the ground, giving supreme traction. At another extreme, the treads could rotate at an angle so that only the two closest ends were touching. This would cut down on the turning friction (although I think the real reason was for the ability to drive over other robots).
Pictures here

Fundamentally, the design makes a lot of sense. As your wheels are closer together (wheel base is greater than the distance between the wheels), you would experience a lower turning friction. Unfortunately they didn't perform well at the regionals they attended...


-Team 16 had a 3-wheeled design in a somewhat triangular shape. The two wheels in the front were powered by drill motors, and then they had one rear wheel that could pivot, but it was powered by two CIM motors. This type of radial system does have advantages, because you have the ability for radial movements (circles, etc), and tank style.
__________________
The best moments of our lives fall in two categories: those that did happen and those that did not.

Last edited by Jnadke : 07-11-2003 at 01:03.
Closed Thread


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
"Automatic Transmission" Madison Technical Discussion 70 24-11-2003 09:03
Direct drive or Chain? Suneet Technical Discussion 32 27-03-2003 23:00
Tank Stearing - 4 wheel drive Joe P Technical Discussion 12 04-03-2003 23:05
"Motors and Drive train edition" of Fresh From the Forum Ken Leung CD Forum Support 6 29-01-2002 12:32
wheel drive Greg Needel Technical Discussion 3 29-01-2002 12:12


All times are GMT -5. The time now is 21:28.

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