Go to Post A true team can only be formed by people who care about each other and that have a common goal... - keehun [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
  #61   Spotlight this post!  
Unread 04-02-2017, 03:39
Cothron Theiss's Avatar
Cothron Theiss Cothron Theiss is offline
Registered Muser
FRC #4462 (Full Metal Jackets)
Team Role: College Student
 
Join Date: Feb 2016
Rookie Year: 2013
Location: Kingston, Tennessee
Posts: 601
Cothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond reputeCothron Theiss has a reputation beyond repute
Re: Climb Stopping Mechanism

Hmm... I wonder if you could build a slip knot into the Retaining Feature of the rope. It holds under tension, but after a match, make sure the robot is supported and release an inch or two of slack. It'd be all in the rope, so even the teams that show up without the slightest consideration of this issue can implement a solution.
__________________
"It's taking longer than expected, which was to be expected."
Reply With Quote
  #62   Spotlight this post!  
Unread 04-02-2017, 08:48
James3245 James3245 is offline
Mentor
FRC #3245 (Ravens)
Team Role: Mentor
 
Join Date: Apr 2013
Rookie Year: 2010
Location: Sandy, Utah
Posts: 40
James3245 is on a distinguished road
Re: Climb Stopping Mechanism

a prudent approach:

Decouple the winch and the sensor trigger system. Winch system needs to be powerful, sensor trigger system does not.

1. Stop the climb well short of the sensor disk. Do this via encoder or careful operator control.
a ratcheting device, such as a wrench, ensures that when power is killed the climber drum doesn't unwind. Robot is now hanging a few inches below sensor.

2. Activate a low power device (pneumatic piston or a cam on a small motor with its own ratchet) that extends up and holds pressure on the sensor disk through the end of match. Or do it passively with a compression spring.

3. After match lift robot up. As long as the trigger device on robot is low power two people should be able to overcome it easily and thus easily take tension off the winch ratchet system.

This type of solution has likely been covered in another thread but it seems worthwhile to emphasize in this thread that triggering the sensor with your winch system, and the trouble that can ensue, is unnecessary.

The forces involved that can damage the field, your robot, and possibly you, are of such magnitude that added complexity in the form of the additional trigger subsystem would likely pass the cost/benefit test.
Reply With Quote
  #63   Spotlight this post!  
Unread 04-02-2017, 11:25
AveryLevin.'s Avatar
AveryLevin. AveryLevin. is offline
Registered User
FRC #4276
Team Role: Programmer
 
Join Date: Feb 2016
Rookie Year: 2014
Location: Huntington Beach
Posts: 8
AveryLevin. is on a distinguished road
Re: Climb Stopping Mechanism

Out team will be using a ratcheting winch that will shut off once our Vex bumper switch is pressed. The shut off is on a delay so our robot will be able to push the pad more than an inch before we stop climbing.
Reply With Quote
  #64   Spotlight this post!  
Unread 04-02-2017, 19:39
Daniel_LaFleur's Avatar
Daniel_LaFleur Daniel_LaFleur is offline
Mad Scientist
AKA: Me
FRC #2040 (DERT)
Team Role: Engineer
 
Join Date: Apr 2005
Rookie Year: 2003
Location: Peoria, IL
Posts: 1,984
Daniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond repute
Send a message via MSN to Daniel_LaFleur
Re: Climb Stopping Mechanism

Quote:
Originally Posted by Ken Streeter View Post
Just FYI, I agree with your point that teams need to have a solution to the problem.

However, in this circumstance, the force applied on the rope after hitting the stop at the top isn't "the full power of the winch + the weight of the robot pulling on the rope..."

Rather, it's the maximum of the two. (Which is likely to be the "at stall" torque from the winch.)
Hmmmm.... Not sure if I understand your why here.

As the robot climbs the rope the weight of the robot causes tension on the rope equal to the weight of the robot ... Agreed

But once the robot encounters the hard stop at the Davit, it will give an upward force on the davit equal to the torque of the winch. Since every action produces an equal and opposite reaction the Davit will push down on the robot equal to the torque of the winch. This will be added to the force of gravity on the robot, thus the rope will see full force of the winch + weight of the robot.

Please show me where I am wrong.
__________________
___________________
"We are not now that strength which in old days moved earth and heaven; that which we are, we are;
One equal temper of heroic hearts, Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield. "
- Tennyson, Ulysses
Reply With Quote
  #65   Spotlight this post!  
Unread 04-02-2017, 20:23
dirtbikerxz's Avatar
dirtbikerxz dirtbikerxz is offline
Captain | Driver | CAD | Junior
AKA: Rohit Gondi
FRC #3991 (KnightVision)
Team Role: Driver
 
Join Date: Nov 2014
Rookie Year: 2015
Location: Baton Rouge, LA
Posts: 494
dirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud of
Re: Climb Stopping Mechanism

We just tested a few ideas today, and settled on a process. So we put a standard socket wrench (locked in place) on the end of the climber hex shaft. Our climber is very close to the bottom of the bot. Two drive team members than lifted the bot enough so that tension of the rope was taken off the hex shaft, and since the climber is close to the bottom of the bot, the person on that side of the bot, was able to flick the lever easily with one hand, while holding that side of the bot with the other hand, and then both drive team members guided the bot slowly to the ground, and the rope just unspooled.
__________________

Team 3991: Driver since freshman (2015-), Captain since sophomore (2016-), CADer
"The human condition is not perfect. We are not perfect specimens, any of us. We're not robots." - Michael Ovitz
My posts may or may not reflect the views of my team, they are my opinions, and mine alone.
Reply With Quote
  #66   Spotlight this post!  
Unread 04-02-2017, 20:48
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: Climb Stopping Mechanism

I found this in Q&A and it may help a few teams. While it it legal for a PILOT to assist in removing the ROPE from the DAVIT, the laws of physics likely wouldn't allow it in the 'clamping to the field' scenarios above. https://frc-qa.firstinspires.org/qa/381

We're going to pneumatically actuate a vice grip into a brake off the gearbox of our winch. We'll probably add some cushioning to our contacts to make sure the touchpad stays engaged if we drop a few tenths of an inch. Anyone know alternative names for them?
__________________

Drive Coach, 1885 (2007-present)
2017 Scoring Model
CAD Library | GitHub
Reply With Quote
  #67   Spotlight this post!  
Unread 04-02-2017, 22:27
AdamHeard's Avatar
AdamHeard AdamHeard is offline
Lead Mentor
FRC #0973 (Greybots)
Team Role: Mentor
 
Join Date: Oct 2004
Rookie Year: 2004
Location: Atascadero
Posts: 5,529
AdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond reputeAdamHeard has a reputation beyond repute
Send a message via AIM to AdamHeard
Re: Climb Stopping Mechanism

Quote:
Originally Posted by dirtbikerxz View Post
We just tested a few ideas today, and settled on a process. So we put a standard socket wrench (locked in place) on the end of the climber hex shaft. Our climber is very close to the bottom of the bot. Two drive team members than lifted the bot enough so that tension of the rope was taken off the hex shaft, and since the climber is close to the bottom of the bot, the person on that side of the bot, was able to flick the lever easily with one hand, while holding that side of the bot with the other hand, and then both drive team members guided the bot slowly to the ground, and the rope just unspooled.
Did you do this after crashing into the top and holding full stall for 1 seconds?
Reply With Quote
  #68   Spotlight this post!  
Unread 04-02-2017, 22:39
dirtbikerxz's Avatar
dirtbikerxz dirtbikerxz is offline
Captain | Driver | CAD | Junior
AKA: Rohit Gondi
FRC #3991 (KnightVision)
Team Role: Driver
 
Join Date: Nov 2014
Rookie Year: 2015
Location: Baton Rouge, LA
Posts: 494
dirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud ofdirtbikerxz has much to be proud of
Re: Climb Stopping Mechanism

Quote:
Originally Posted by AdamHeard View Post
Did you do this after crashing into the top and holding full stall for 1 seconds?
Oh... nope. Ya now that you mention it, I can see how that may be a problem, lol. *sigh* back to the drawing board
__________________

Team 3991: Driver since freshman (2015-), Captain since sophomore (2016-), CADer
"The human condition is not perfect. We are not perfect specimens, any of us. We're not robots." - Michael Ovitz
My posts may or may not reflect the views of my team, they are my opinions, and mine alone.
Reply With Quote
  #69   Spotlight this post!  
Unread 04-02-2017, 23:07
tig567899's Avatar
tig567899 tig567899 is offline
Team 6070 Programming Captain
AKA: Tiger Kong
FRC #6070 (Gryphon Machine)
Team Role: Programmer
 
Join Date: Jan 2016
Rookie Year: 2016
Location: Mississauga
Posts: 41
tig567899 has a spectacular aura abouttig567899 has a spectacular aura abouttig567899 has a spectacular aura about
Re: Climb Stopping Mechanism

Quote:
Originally Posted by Daniel_LaFleur View Post

As the robot climbs the rope the weight of the robot causes tension on the rope equal to the weight of the robot ... Agreed

But once the robot encounters the hard stop at the Davit, it will give an upward force on the davit equal to the torque of the winch. Since every action produces an equal and opposite reaction the Davit will push down on the robot equal to the torque of the winch. This will be added to the force of gravity on the robot, thus the rope will see full force of the winch + weight of the robot.

Please show me where I am wrong.
The force on the davit is equal to the torque of the winch minus the weight of the robot - opposite forces cancel. The davit will push down on the robot equal to that force - thus: weight of robot (due to gravity) + winch force - weight of robot = winch force.
__________________
Reply With Quote
  #70   Spotlight this post!  
Unread 05-02-2017, 18:21
Basel A's Avatar
Basel A Basel A is offline
It's pronounced Basl with a soft s
AKA: @BaselThe2nd
FRC #3322 (Eagle Imperium)
Team Role: College Student
 
Join Date: Mar 2009
Rookie Year: 2009
Location: Ann Arbor, Michigan
Posts: 1,946
Basel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond reputeBasel A has a reputation beyond repute
Re: Climb Stopping Mechanism

Based on tests today of our first iteration climber, it seems reasonable to (a) get the climb scored but not stall into the touchpad, (b) relieve the load on a switchable ratcheting wrench by lifting the robot further into the touchpad thereby allowing you to switch the ratchet, (c) remove the rope from the field thereby releasing the robot, and (d) remove the rope from the robot in the pit. Our tests proved that this is difficult but feasible with a manual climb, but would be much more repeatable and faster with an automatic climb. The key is to not finish your climb with full power. I would warn folks that with the high reductions many climbing gearboxes have, it could be difficult to remove rope by backdriving the winches by hand.
__________________
Team 2337 | 2009-2012 | Student
Team 3322 | 2014-Present | College Student
“Be excellent in everything you do and the results will just happen.”
-Paul Copioli
Reply With Quote
  #71   Spotlight this post!  
Unread 05-02-2017, 18:30
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: Climb Stopping Mechanism

Quote:
Originally Posted by Oblarg View Post
We're using a flex-head ratcheting wrench, i.e. just an ordinary ratcheting wrench except there's a pivot between the head and the handle. In order to lower the robot, we simply undo the velcro strap holding the wrench handle in a constrained position (i.e. between two bolts) and pivot it out of the way. The wrench rotates with the winch as it unspools.
We tried this today. We climbed with 130lbs attached to our climber's production frame using production motors & gearing. Rope touch to Touchpad was about 4 seconds, so it wasn't a 'crash' into the top - but we did intentionally stall the motors at the top for a second or two. The ratchet wrench was held in place by one 1/4-20 bolt - the threaded end, no less. While under load we popped it loose with a large flathead screwdriver very easily. During further tests and refinement, we added a string to pop it out at the end of the tests. It also worked very well. We climbed about 30 times, and it worked every time. We'll put a 3/8" steel stud around that bolt in the future.
__________________

Drive Coach, 1885 (2007-present)
2017 Scoring Model
CAD Library | GitHub
Reply With Quote
  #72   Spotlight this post!  
Unread 05-02-2017, 18:54
Karibou Karibou is offline
Steel is love. Steel is life.
AKA: Kara Bakowski
FRC #0341 (Miss Daisy)
Team Role: Mentor
 
Join Date: Dec 2007
Rookie Year: 2008
Location: Conshohocken, PA
Posts: 1,855
Karibou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond reputeKaribou has a reputation beyond repute
Send a message via AIM to Karibou
Re: Climb Stopping Mechanism

Quote:
Originally Posted by JesseK View Post
We tried this today. We climbed with 130lbs attached to our climber's production frame using production motors & gearing. Rope touch to Touchpad was about 4 seconds, so it wasn't a 'crash' into the top - but we did intentionally stall the motors at the top for a second or two. The ratchet wrench was held in place by one 1/4-20 bolt - the threaded end, no less. While under load we popped it loose with a large flathead screwdriver very easily. During further tests and refinement, we added a string to pop it out at the end of the tests. It also worked very well. We climbed about 30 times, and it worked every time. We'll put a 3/8" steel stud around that bolt in the future.
We ran a test today using around 150lbs and a flex-head wrench held in place in some 1x1 c-channel about halfway down the wrench. Worked like a charm; wrench folded up with no problems!
__________________
Kara Bakowski
Michigan Technological University///Materials Science and Engineering '15///Go Huskies! #tenacity
kabakowski(at)gmail(dot)com
FRC 341 (2016-present): Mechanical/build mentor
Volunteer (2010-present): MAR Seneca '17, FTC Hat Tricks Qualifier '16, Brunswick Eruption '16, MAR Montgomery '16, MAR Westtown '16 Portcullis Victim, MAR Springside-Chestnut Hill '16, Ramp Riot '15 '16, FiM Escanaba District '14 '15, MidKnight Mayhem '13 '15 '16, FiM Detroit District '13, IRI '10 '12, FiM Waterford District '11 '12, MARC '12, CMP Galileo '11
FRC 1189 (2008-2011): Team Captain, Pit Crew, Website group leader, Team Education group leader, Proud Alum. We've got spirit, yes we do...


WMWBS '10 '11
Reply With Quote
  #73   Spotlight this post!  
Unread 05-02-2017, 21:07
electronicsdude's Avatar
electronicsdude electronicsdude is offline
Registered User
AKA: Spencer
FRC #4918 (The Roboctopi)
Team Role: Engineer
 
Join Date: Jan 2015
Rookie Year: 2014
Location: Port Townsend, WA
Posts: 18
electronicsdude will become famous soon enoughelectronicsdude will become famous soon enough
Re: Climb Stopping Mechanism

Quote:
Originally Posted by sauhaarda View Post
What strategies are you using to stop climbing the rope after the button is pressed at the proper pressure? Are you planning on a manual stop? A pressure plate stop? A stop based on stall torque? It seems to me that there is a very small window to stop the robot from applying to much pressure on the plate. How are you teams trying to address this issue?
1/2 inch ratcheting flatwrench for retaining. Use the onboard current sensing of the PDP to kill the motor when it reaches a load higher than just lifting, aka semi-stall instance.
Reply With Quote
  #74   Spotlight this post!  
Unread 05-02-2017, 22:52
Ken Streeter's Avatar
Ken Streeter Ken Streeter is offline
Let the MAYHEM begin!
FRC #1519 (Mechanical Mayhem)
Team Role: Engineer
 
Join Date: Feb 2005
Rookie Year: 2005
Location: Team: Milford, NH; Me: Bedford, NH
Posts: 475
Ken Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond reputeKen Streeter has a reputation beyond repute
Re: Climb Stopping Mechanism

Quote:
Originally Posted by Daniel_LaFleur View Post
Hmmmm.... Not sure if I understand your why here.

As the robot climbs the rope the weight of the robot causes tension on the rope equal to the weight of the robot ... Agreed

But once the robot encounters the hard stop at the Davit, it will give an upward force on the davit equal to the torque of the winch. Since every action produces an equal and opposite reaction the Davit will push down on the robot equal to the torque of the winch. This will be added to the force of gravity on the robot, thus the rope will see full force of the winch + weight of the robot.

Please show me where I am wrong.
Quote:
Originally Posted by tig567899 View Post
The force on the davit is equal to the torque of the winch minus the weight of the robot - opposite forces cancel. The davit will push down on the robot equal to that force - thus: weight of robot (due to gravity) + winch force - weight of robot = winch force.
tig567899's reply above states it pretty well.

However, as an illustration to help think through it, consider a robot that weighs 150 pounds ('bot + battery + bumpers), and a winch that can pull with 151 pounds of force.

If the 150-pound robot with a 151-pound-pulling winch were halfway up the rope, and a bystander put a hand out and pushed down with just one pound of force, the robot would stop ascending the rope, and be able to go no higher. It would only take 1 pound of downforce to do that.

The situation is no different with the davit -- only 1 pound of additional downforce is needed to stop the 151-pound-pulling winch from hoisting the 150-pound robot.
__________________
Ken Streeter - Team 1519 - Mechanical Mayhem (Milford Area Youth Homeschoolers Enriching Minds)
2015 NE District Winners with 195 & 2067, 125 & 1786, 230 & 4908, and 95 & 1307
2013 World Finalists & Archimedes Division Winners with 33 & 469
2013 & 2012 North Carolina Regional Winners with teams 435 & 4828 and 1311 & 2642
2011, 2010, 2006 Granite State Regional Winners with teams 175 & 176, 1073 & 1058, and 1276 & 133
Team 1519 Video Gallery - including Chairman's Video, and the infamous "Speed Racer!"
Reply With Quote
  #75   Spotlight this post!  
Unread 05-02-2017, 23:04
BethMo BethMo is offline
Registered User
FRC #0948 (NRG (Newport Robotics Group))
Team Role: Mentor
 
Join Date: Mar 2007
Rookie Year: 2003
Location: Bellevue, WA
Posts: 96
BethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud ofBethMo has much to be proud of
Re: Climb Stopping Mechanism

Quote:
Originally Posted by James3245 View Post
2. Activate a low power device (pneumatic piston or a cam on a small motor with its own ratchet) that extends up and holds pressure on the sensor disk through the end of match. Or do it passively with a compression spring.
Depending on the geometry, this is likely to run afoul of the perimeter rules. You'd need to be hanging at an angle such that this extension doesn't reach past the bumpers. (Or have a smaller-than-maximum-size robot.)
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 12:00.

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