Go Back   VEX Forum > Official VEX Technical Support > UNOFFICIAL Answers - Ask the Community!

UNOFFICIAL Answers - Ask the Community! Community Members can provide UNOFFICIAL answers to the questions from the "locked" forum above.

Reply
 
Thread Tools
  #21  
Old 05-01-2012, 08:30 PM
StephenDsDude StephenDsDude is offline
Senior Member
VEX # 675B
 
Join Date: Jan 2012
Location: Buford, GA
Posts: 138
Images: 17
Re: fun with planetary gears...

As long as you have both wheels on each side going in the same direction with the same speed, it works like it normally would, no changes.

Strafing, however, would not be permissible with all 4 modes: you would have to use strictly torque/speed on the strafing motion.
__________________
  • Team Leader of Team 675B
  • Excellence Award at GSMST Qualifier (1-28-2012)
  • Tournament Champions and Excellence Award at Ola Mustangs Qualifier (1-19-2013)
  • Tournament Champions at Carrollton Qualifier (2-9-2013)
Reply With Quote
  #22  
Old 05-01-2012, 08:36 PM
mr. giggums mr. giggums is offline
Member
VEX # 355C
 
Join Date: Apr 2011
Location: Batavia, Illinois
Posts: 50
Re: fun with planetary gears...

Quote:
Originally Posted by StephenDsDude View Post
As long as you have both wheels on each side going in the same direction with the same speed, it works like it normally would, no changes.

Strafing, however, would not be permissible with all 4 modes: you would have to use strictly torque/speed on the strafing motion.
I don't see how it would work with either mode. If you have the ring gear adding speed to both of them when going forward it will work but if you reverse one wheel the ring gear will now subtract speed (thereby adding torque) from the one that is reversed. The same will happen if you are in the other mode to begin with.
Reply With Quote
  #23  
Old 05-01-2012, 08:42 PM
dontworryaboutit's Avatar
dontworryaboutit dontworryaboutit is offline
Senior Member
VEX # 254D
 
Join Date: Mar 2010
Posts: 639
Images: 1
Re: fun with planetary gears...

Quote:
Originally Posted by mr. giggums View Post
I don't see how it would work with either mode. If you have the ring gear adding speed to both of them when going forward it will work but if you reverse one wheel the ring gear will now subtract speed (thereby adding torque) from the one that is reversed. The same will happen if you are in the other mode to begin with.
I see this same problem as well.

In order to strafe, the front and rear motors must be going in opposite directions, which means that in whatever direction the third motor is going, it will make one side wheel go high-torque and the other go high-speed.

If you didn't use the third motor for strafing, then it would work, but then you only have 4 motors to strafe with.
__________________
254D = 254Doesn't work at competition
254D = redefining "18 inches" since 2009
First make it work, then make it work well.

Last edited by dontworryaboutit; 05-01-2012 at 09:32 PM.
Reply With Quote
  #24  
Old 05-01-2012, 08:42 PM
StephenDsDude StephenDsDude is offline
Senior Member
VEX # 675B
 
Join Date: Jan 2012
Location: Buford, GA
Posts: 138
Images: 17
Re: fun with planetary gears...

Quote:
Originally Posted by mr. giggums View Post
I don't see how it would work with either mode. If you have the ring gear adding speed to both of them when going forward it will work but if you reverse one wheel the ring gear will now subtract speed (thereby adding torque) from the one that is reversed. The same will happen if you are in the other mode to begin with.
When the side is uniform, all 3 motors (both rings and the common carrier) turn.
When the side is not uniform (i.e strafing, both wheels opposite directions), the motor controlling the carrier gears simply would not turn.
__________________
  • Team Leader of Team 675B
  • Excellence Award at GSMST Qualifier (1-28-2012)
  • Tournament Champions and Excellence Award at Ola Mustangs Qualifier (1-19-2013)
  • Tournament Champions at Carrollton Qualifier (2-9-2013)
Reply With Quote
  #25  
Old 05-01-2012, 09:19 PM
StephenDsDude StephenDsDude is offline
Senior Member
VEX # 675B
 
Join Date: Jan 2012
Location: Buford, GA
Posts: 138
Images: 17
Re: fun with planetary gears...



This is a mock-up of my proposed gearing.

Replace Traction Wheels with mecanums (my diagram's axles are too short and the view was obstructed).

Middle motor turns only if both wheels are turning in the same direction at the same speed. It would not turn if strafing (opposite directions).
__________________
  • Team Leader of Team 675B
  • Excellence Award at GSMST Qualifier (1-28-2012)
  • Tournament Champions and Excellence Award at Ola Mustangs Qualifier (1-19-2013)
  • Tournament Champions at Carrollton Qualifier (2-9-2013)
Reply With Quote
  #26  
Old 05-01-2012, 09:33 PM
dontworryaboutit's Avatar
dontworryaboutit dontworryaboutit is offline
Senior Member
VEX # 254D
 
Join Date: Mar 2010
Posts: 639
Images: 1
Re: fun with planetary gears...

I would have made the wheels further apart by having the center motor use the chain and the ones at the front and back directly driving the planet carriers.
But awesome CAD


You still have the same backdriving issue as I explained in the 4194B thread, so you'll need to put a lock in somewhere.
__________________
254D = 254Doesn't work at competition
254D = redefining "18 inches" since 2009
First make it work, then make it work well.
Reply With Quote
  #27  
Old 05-01-2012, 09:36 PM
StephenDsDude StephenDsDude is offline
Senior Member
VEX # 675B
 
Join Date: Jan 2012
Location: Buford, GA
Posts: 138
Images: 17
Re: fun with planetary gears...

Quote:
Originally Posted by dontworryaboutit View Post
I would have made the wheels further apart by having the center motor use the chain and the ones at the front and back directly driving the planet carriers.
But awesome CAD


You still have the same backdriving issue as I explained in the 4194B thread, so you'll need to put a lock in somewhere.
Eh, it's a mock-up. I would definately relocate those driven sprockets, and would probably use some chain on the carrier gear system; I was just making a demonstration.
Thanks

Yeah, I'm thinking about the backdriving issue as well. I'm pushing to get some pneumatics from the club to at least experiment with for the summer (we have to maintain 5 'equal teams' and we only have 1 or 2 sets).
__________________
  • Team Leader of Team 675B
  • Excellence Award at GSMST Qualifier (1-28-2012)
  • Tournament Champions and Excellence Award at Ola Mustangs Qualifier (1-19-2013)
  • Tournament Champions at Carrollton Qualifier (2-9-2013)
Reply With Quote
  #28  
Old 05-01-2012, 09:42 PM
dontworryaboutit's Avatar
dontworryaboutit dontworryaboutit is offline
Senior Member
VEX # 254D
 
Join Date: Mar 2010
Posts: 639
Images: 1
Re: fun with planetary gears...

Also I think you would want to gear down the center motor (for torque) as it's exerting force on both the front and the back (so needs twice the torque to maintain the force balance on the planets), but it might work either way.
__________________
254D = 254Doesn't work at competition
254D = redefining "18 inches" since 2009
First make it work, then make it work well.
Reply With Quote
  #29  
Old 05-01-2012, 10:05 PM
anthonyl14107096's Avatar
anthonyl14107096 anthonyl14107096 is offline
Junior Member
VEX # 4194B
 
Join Date: Apr 2012
Location: Taipei, Taiwan
Posts: 16
Re: fun with planetary gears...

Quote:
Originally Posted by murdomeek View Post
yes 4 motor HS drive, you can just chain the extra wheel if you want

as you have said, you will need 8 motors to power each wheel separately (to utilize the mecanum)

no, i do not think that a 8 motor drive is a good trade off just to have side to side movement

if you want mecanums, its better to do a "normal" (non planetary) drive train
Only six motors would be required for a mecanum wheel drive, follow the CAD model however drive the planet carriers of each planetary, then chain the entire thing to a single motor in high torque configuration with more emphasis on torque since it will have to fight two motors. This will actually allow for speed mode in torque mode, whilst allowing for strafing since the two planetaries would be able to operate independently when the third motor holds the chain still. I'm actually constructing a prototype as of this second. Hopefully I can get it working by the end of this week.
__________________
2013 Pan Pacific Design Award
2012 Pan Pacific Build Award
Planetary Gear System with Differential
Transmission
http://www.vexforum.com/showthread.php?t=69268
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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

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


All times are GMT -6. The time now is 02:07 PM.


VEX and VEX Robotics are trademarks or service marks of Innovation First International, Inc.
Copyright © 2002-2013. All Rights Reserved. VEX Robotics, Inc. is a subsidiary of Innovation First International, Inc.
All other product names/marks of others are the property of their respective owners.