Go to Post Welcome to FIRST, side effects may include...... - spears312 [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 Rate Thread Display Modes
  #46   Spotlight this post!  
Unread 20-05-2011, 16:57
kramarczyk's Avatar
kramarczyk kramarczyk is offline
is getting his kicks.
AKA: Mark Kramarczyk
FRC #3096 (Highlanders)
Team Role: Mentor
 
Join Date: Mar 2006
Rookie Year: 2006
Location: Sterling Heights, MI
Posts: 602
kramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond reputekramarczyk has a reputation beyond repute
Re: 6WD vs 8WD

Quote:
Originally Posted by Hawiian Cadder View Post
... the goal of having the outer wheels raised is to make them act more like omni wheels. for the purpose of the argument imagine all we care about is drive systems with omni wheels on the corners.
You may want to look further into this assumption.

As you raise the wheel (or increase the center wheel drop) you decrease the load on those wheels. Yes, it decreases the sideways slipping force on the wheel, but it also decreases the tractive force in the same proportion. The first point is that it never really behaves like a omni wheel, just as a wheel with less traction.

The second point is that the load drops off across the distance of your wheel dropped (teams range from 1/16-1/4") which makes it hard to tune. I worked with an adjustable drop 6WD for a few years and we discovered that 2-3mm drop was what worked for us as optimum. Outside that sweet spot we began to get significantly different driving performance. We also discovered that a 1/2 day of matches was enough wear on gum rubber treads to get us outside this range. We eventually decided that it was not worth the effort and decided to let the wheel off the ground and allow the robot to rock between the two 4 wheel systems. It was much simpler in the long run and allowed us to apply our resources elsewhere. I know the 2011 kitbot configuration has enough lift to accomplish this.

You may want to spot check with teams to see if all of their wheels are actually on the ground or just really close. How might having one set of corners off the ground affect the logic you used above?
__________________
Mark

Brick walls are for other people. - Randy Pausch
  #47   Spotlight this post!  
Unread 26-05-2011, 12:36
Wayne TenBrink's Avatar
Wayne TenBrink Wayne TenBrink is offline
<< (2008 Game Piece)
FRC #1918 (NC Gears)
Team Role: Engineer
 
Join Date: Apr 2007
Rookie Year: 2006
Location: Fremont, MI, USA
Posts: 527
Wayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond reputeWayne TenBrink has a reputation beyond repute
Re: 6WD vs 8WD

For Logomotion, we had an 8WD chassis with 6" wheels. The four at the corners were "kit" wheels. The four in the center were closely spaced pneumatics with adjustable drop. (I noticed in St. Louis that 330 used the same arrangement). We adjusted the tire pressure and center wheel drop so that the corners were about 1/16" off the floor on a hard surface, and had light contact on the carpet.

We were quite happy with the arrangement. It turned very well, since the pneumatic tires had better traction and higher loading than the corner wheels. It didn't rock or bounce during accelearation or turning since the corner tires were hard. During acceleration or in a pushing situation, all four pneumatics and one set of corner tires were in contact with the carpet. It was very difficult for others to push or turn us.

It was a good balance between the agility of a 6WD with center drop or omnis, and the pushing power of an 8WD with pneumatic tires.
__________________
NC Gears (Newaygo County Geeks Engineering Awesome Robotic Solutions)

FRC 1918 (Competing at St. Joseph and West MI in 2017)
FTC 6043 & 7911
  #48   Spotlight this post!  
Unread 27-05-2011, 11:38
Triple B Triple B is offline
all hail Passmore
AKA: Mike D is FTG too
None #0233 (The Pink Team)
 
Join Date: Apr 2003
Rookie Year: 1999
Location: Canaveral Groves, FL
Posts: 133
Triple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant future
Re: 6WD vs 8WD

eight
__________________
See Ya
  #49   Spotlight this post!  
Unread 27-05-2011, 11:44
Chris is me's Avatar
Chris is me Chris is me is online now
no bag, vex only, final destination
AKA: Pinecone
FRC #0228 (GUS Robotics); FRC #2170 (Titanium Tomahawks)
Team Role: Mentor
 
Join Date: Dec 2008
Rookie Year: 2006
Location: Glastonbury, CT
Posts: 7,718
Chris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond repute
Send a message via AIM to Chris is me
Re: 6WD vs 8WD

Quote:
Originally Posted by Triple B View Post
eight
Why 8?
__________________
Mentor / Drive Coach: 228 (2016-?)
...2016 Waterbury SFs (with 3314, 3719), RIDE #2 Seed / Winners (with 1058, 6153), Carver QFs (with 503, 359, 4607)
Mentor / Consultant Person: 2170 (2017-?)
---
College Mentor: 2791 (2010-2015)
...2015 TVR Motorola Quality, FLR GM Industrial Design
...2014 FLR Motorola Quality / SFs (with 341, 4930)
...2013 BAE Motorola Quality, WPI Regional #1 Seed / Delphi Excellence in Engineering / Finalists (with 20, 3182)
...2012 BAE Imagery / Finalists (with 1519, 885), CT Xerox Creativity / SFs (with 2168, 118)
Student: 1714 (2009) - 2009 Minnesota 10,000 Lakes Regional Winners (with 2826, 2470)
2791 Build Season Photo Gallery - Look here for mechanism photos My Robotics Blog (Updated April 11 2014)
  #50   Spotlight this post!  
Unread 27-05-2011, 13:44
Triple B Triple B is offline
all hail Passmore
AKA: Mike D is FTG too
None #0233 (The Pink Team)
 
Join Date: Apr 2003
Rookie Year: 1999
Location: Canaveral Groves, FL
Posts: 133
Triple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant future
Re: 6WD vs 8WD

From my experience, the 8 gives you more stability at higher speeds and better predictability of how the robot will handle. We also decreased the diameter of the outside wheels instead of offseting the axle height.
mike d
__________________
See Ya
  #51   Spotlight this post!  
Unread 27-05-2011, 14:57
IKE's Avatar
IKE IKE is offline
Not so Custom User Title
AKA: Isaac Rife
no team (N/A)
Team Role: Mechanical
 
Join Date: Jan 2008
Rookie Year: 2003
Location: Michigan
Posts: 2,149
IKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond reputeIKE has a reputation beyond repute
Re: 6WD vs 8WD

Quote:
Originally Posted by Triple B View Post
From my experience, the 8 gives you more stability at higher speeds and better predictability of how the robot will handle. We also decreased the diameter of the outside wheels instead of offseting the axle height.
mike d
Did you change the ratios to match teh diameter changes, or just allow for the inherent scrub to occur?
  #52   Spotlight this post!  
Unread 27-05-2011, 15:22
Triple B Triple B is offline
all hail Passmore
AKA: Mike D is FTG too
None #0233 (The Pink Team)
 
Join Date: Apr 2003
Rookie Year: 1999
Location: Canaveral Groves, FL
Posts: 133
Triple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant futureTriple B has a brilliant future
Re: 6WD vs 8WD

no change of ratio, just let it ride.
__________________
See Ya
  #53   Spotlight this post!  
Unread 27-05-2011, 16:09
Alan Anderson's Avatar
Alan Anderson Alan Anderson is offline
Software Architect
FRC #0045 (TechnoKats)
Team Role: Mentor
 
Join Date: Feb 2004
Rookie Year: 2004
Location: Kokomo, Indiana
Posts: 9,113
Alan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond repute
Re: 6WD vs 8WD

Quote:
Originally Posted by IKE View Post
Did you change the ratios to match teh diameter changes, or just allow for the inherent scrub to occur?
Our 2007 "Rack 'n' Roll" robot was a six-wheel drive with no center drop. It had extra-thick tread on the center wheels and it drove like a dream. We never figured out whether the very slight discrepancy in wheel circumference made any difference one way or the other. There was some conjecture that a teeny bit of scrub on the corner wheels might actually result in better turning.
  #54   Spotlight this post!  
Unread 30-05-2011, 11:47
Blake L's Avatar
Blake L Blake L is offline
Registered User
FRC #2016 (Might Monkey Wrenches)
Team Role: Programmer
 
Join Date: May 2011
Rookie Year: 2010
Location: Ewing, NJ
Posts: 8
Blake L is an unknown quantity at this point
Re: 6WD vs 8WD

Personally, I like 8WD, although my opinion might be a bit biased because I haven't driven a 6WD robot anywhere near as much as I've driven an 8 wheeled one.

This year my team used eight 4" diameter wheels geared 7:1 and I loved it.
Here is a video of us playing with the chassis a week into build season:
http://www.youtube.com/watch?v=inI40uMKuEE

If I remember correctly, the center two wheels are dropped 1/16". We later added another two motors to the drive train which gave us a nice balance of speed and power.
  #55   Spotlight this post!  
Unread 03-05-2012, 16:00
Dr. Shocker's Avatar
Dr. Shocker Dr. Shocker is offline
Alumn
FRC #1126 (SparX)
Team Role: Mechanical
 
Join Date: Dec 2010
Rookie Year: 2011
Location: Webster
Posts: 31
Dr. Shocker is on a distinguished road
Re: 6WD vs 8WD

Quote:
Originally Posted by Grim Tuesday View Post
Can someone tell me what a "West coast drive" is?
From what I understand, West Coast Drive is essentially a 6/8 wheel drive platform with cantilevered wheel axles, but I've seen a few mentions that it might have to do with how you actually power the wheels.
  #56   Spotlight this post!  
Unread 03-05-2012, 17:17
R.C.'s Avatar
R.C. R.C. is offline
2017... Oooh Kill em, Swerve!
AKA: Owner, WestCoast Products
FRC #1323 (MadTown Robotics)
Team Role: Engineer
 
Join Date: Feb 2008
Rookie Year: 2006
Location: Madera, CA
Posts: 2,184
R.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond reputeR.C. has a reputation beyond repute
Re: 6WD vs 8WD

Quote:
Originally Posted by Dr. Shocker View Post
From what I understand, West Coast Drive is essentially a 6/8 wheel drive platform with cantilevered wheel axles, but I've seen a few mentions that it might have to do with how you actually power the wheels.
If you go to CD Media and search FRC254 or FRC968. They have many awesome pics of their chassis that is dubbed "WestCoast Drive".

Key Features are:

-Cantilever Wheels
-Direct Drive
-Inline system
-CAMS
-Sliding Bearing Blocks
-Small Wheels (We goofed, big wheels are ugly )

There are a few other tidbits, but that should sum it up.

-RC
__________________
R.C.
Owner, WestCoast Products || Twitter
MadTown Robotics Team 1323
  #57   Spotlight this post!  
Unread 03-05-2012, 17:38
MichaelBick MichaelBick is offline
Registered User
FRC #1836 (MilkenKnights)
Team Role: Alumni
 
Join Date: Oct 2011
Rookie Year: 2010
Location: Los Angeles
Posts: 734
MichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant futureMichaelBick has a brilliant future
Re: 6WD vs 8WD

Quote:
Originally Posted by R.C. View Post
If you go to CD Media and search FRC254 or FRC968. They have many awesome pics of their chassis that is dubbed "WestCoast Drive".

Key Features are:

-Cantilever Wheels
-Direct Drive
-Inline system
-CAMS
-Sliding Bearing Blocks
-Small Wheels (We goofed, big wheels are ugly )

There are a few other tidbits, but that should sum it up.

-RC
Yeah, small wheels are amazing: they can potentially reduce a sizeable amount of weight. I would have perfered to use small wheels on our robot this year, with 8wd instead of 6, but it all worked out in the end. I was wondering though, I don't remember 254 or 968 ever using cams. Do you have a picture? Also, to add on to your list, just some things that are also really nice:

-2 speed
-Custom gearboxes
-Custom wheels
__________________
Team 1836 - The Milken Knights
2013 LA Regional Champions with 1717 and 973
2012 LA Regional Finalists with 294 and 973
To follow Team 1836 on Facebook, go to http://www.facebook.com/MilkenKnights
To go to our website, go to http://milkenknights.com/index.html
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
What does it take 6WD/8WD to be successful? TEE Technical Discussion 26 06-05-2010 08:30
pic: Rastogi 8wd Iteration 1.2 Akash Rastogi Extra Discussion 56 05-05-2010 15:16
pic: Sheetmetal 8wd Akash Rastogi Extra Discussion 16 02-05-2010 15:38
pic: Concept 8wd Drivetrain sdcantrell56 Technical Discussion 77 25-11-2008 23:05
8WD drivetrain? David Sherman Technical Discussion 16 09-04-2006 17:32


All times are GMT -5. The time now is 16:54.

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