Go to Post It doesn't matter what material you pick, it matters how you execute your design. - JamesCH95 [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
  #16   Spotlight this post!  
Unread 15-01-2017, 12:45
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
So looking up an encoder will control the speed of the wheels and motor which will help increase accuracy
Tell us what language you plan to use to code your robot and you may get more detailed advice and help.


Reply With Quote
  #17   Spotlight this post!  
Unread 15-01-2017, 13:00
billbo911's Avatar
billbo911 billbo911 is offline
I prefer you give a perfect effort.
AKA: That's "Mr. Bill"
FRC #2073 (EagleForce)
Team Role: Mentor
 
Join Date: Mar 2005
Rookie Year: 2005
Location: Elk Grove, Ca.
Posts: 2,383
billbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond reputebillbo911 has a reputation beyond repute
Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
Our team is new to shooting high goal this year so we just wanted to know what to use for motors and wheels for an working shooter.

So far we have been using a 775 pro motor with a 5:1 gear ratio.
We used the kit of parts andymark wheels for the fly wheels
The first thing I would suggest is to take advantage of the Virtual KOP. In it you received a code for an encoder from Armabot that will attach directly to a 775 Pro. Use that with a Talon SRX, and you can have very stable, reliable control of your RPM in one afternoon.
__________________
CalGames 2009 Autonomous Champion Award winner
Sacramento 2010 Creativity in Design winner, Sacramento 2010 Quarter finalist
2011 Sacramento Finalist, 2011 Madtown Engineering Inspiration Award.
2012 Sacramento Semi-Finals, 2012 Sacramento Innovation in Control Award, 2012 SVR Judges Award.
2012 CalGames Autonomous Challenge Award winner ($$$).
2014 2X Rockwell Automation: Innovation in Control Award (CVR and SAC). Curie Division Gracious Professionalism Award.
2014 Capital City Classic Winner AND Runner Up. Madtown Throwdown: Runner up.
2015 Innovation in Control Award, Sacramento.
2016 Chezy Champs Finalist, 2016 MTTD Finalist
Reply With Quote
  #18   Spotlight this post!  
Unread 15-01-2017, 13:25
YashBrowns's Avatar
YashBrowns YashBrowns is offline
Registered User
FRC #4763
 
Join Date: Jan 2017
Location: California
Posts: 11
YashBrowns is an unknown quantity at this point
Re: Shooting Motors and wheels

Ye, last year we fried a couple of 775 pros last year and broke a fan blade on one of them, but other than that I love 775's
Reply With Quote
  #19   Spotlight this post!  
Unread 15-01-2017, 14:15
YashBrowns's Avatar
YashBrowns YashBrowns is offline
Registered User
FRC #4763
 
Join Date: Jan 2017
Location: California
Posts: 11
YashBrowns is an unknown quantity at this point
Re: Shooting Motors and wheels

Quote:
Originally Posted by Ether View Post
Tell us what language you plan to use to code your robot and you may get more detailed advice and help.


We r using c++ most likely
Reply With Quote
  #20   Spotlight this post!  
Unread 15-01-2017, 17:25
DBMJ99 DBMJ99 is offline
Registered User
FRC #5404
 
Join Date: Nov 2014
Location: United States
Posts: 3
DBMJ99 is an unknown quantity at this point
Re: Shooting Motors and wheels

For quick prototyping we wire up a motor controller in between the battery and the motor (and an in-line automotive fuse) and then use the thrifty throttle from Andymark to control the motor controller. This allows students to vary the speed of the motor to try various experiments. At $29 it's a lot cheaper than tying up a robo-rio for this and it's a lot quicker to set up.
Reply With Quote
  #21   Spotlight this post!  
Unread 16-01-2017, 00:38
Munchskull's Avatar
Munchskull Munchskull is offline
CAD Designer/ Electrical Consaltant
AKA: Anthony Cardinali
FRC #0997 (Spartan Robotics)
Team Role: CAD
 
Join Date: Jan 2013
Rookie Year: 2013
Location: Corvallis, OR
Posts: 532
Munchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to behold
Re: Shooting Motors and wheels

Want to drop a tip for everyone. If you choose to run Colson Performa wheels from vex for your shooter attempt to keep them under 6000 rpm. We proto typed with some and regret it. The rubber melted and got al sorts of hard and nasty. The 60A Andymark compliant wheels are way more consistent and hold up at higher speeds. They are also rated for over 9000 RPMs.
__________________
“In theory, theory and practice are the same. In practice, they are not.” ― Anonymous
Anthony Cardinali
4th year of FRC
Class of 2017




Last edited by Munchskull : 16-01-2017 at 00:50.
Reply With Quote
  #22   Spotlight this post!  
Unread 16-01-2017, 01:43
Ekcrbe's Avatar
Ekcrbe Ekcrbe is offline
When can I watch Einstein again?
AKA: Erik Boyle
FRC #4640 (Metallic Panthers)
Team Role: College Student
 
Join Date: Jan 2012
Rookie Year: 2012
Location: New York, NY
Posts: 333
Ekcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond repute
Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
Our team is new to shooting high goal this year so we just wanted to know what to use for motors and wheels for an working shooter.

So far we have been using a 775 pro motor with a 5:1 gear ratio.
We used the kit of parts andymark wheels for the fly wheels
There have been a lot of good suggestions so far, especially on the control side of things. But as a note on the actual shooter design, it's hard to say whether 5:1 is a good speed for your wheels without knowing what size wheels you're using. There are probably four main variables in designing a shooter in FRC*: wheel surface speed, contact distance, compression profile, and wheel/hood material (durometer, coefficient of friction). Of course, wheel surface speed and contact distance are both functions of wheel diameter. So if you use larger wheels, you can have a higher reduction from the motor, but for small wheels, you'll want them spinning faster.

In an ideal world, you would have plenty of traction and distance to get the balls up to speed and have no slip between the balls and your wheel(s)/hood. Then the exit velocity of the balls could be calculated quite simply by equating the surface speed of the wheel(s) and balls.**

This, put simply, is not going to happen in real life. The balls will slip on the wheels, but how much they do so depends on how well the wheels can grip the balls. The more distance you can keep the balls in contact with the wheels (this means larger diameter wheels or a larger angle in contact), the closer you can get to this ideal. Softer wheels are also sometimes advantageous for this, at the expense of faster wear.

Additionally, how much you compress the ball/wheels how that compression is distributed over the path of the ball has a major, if somewhat complicated, impact on your shots. In general, more compression can allow for more energy transfer, but only up to a certain point. After that point, you're just excessively deforming the balls and bogging down the shooter.

And finally, a general rule of thumb that I've come to follow is that softer balls should take harder wheels and vice versa. This year, the prototypes I've seen online and with my old team are suggesting that hard wheels will probably be fine—These balls can compress a bit. But all these are just guidelines, and your mileage may vary with any of them.

*Actually, I'll add a fifth, but it's not as much about geometry and it's important this year, so I'll keep it separate: motor power. Shooters this year should have a pretty high throughput, so be prepared to use your newfound closed-loop control knowledge that you got from the fine folks here to keep your shooter at its proper speed as you're shooting. With that in mind, consider whether one motor will have enough power to keep the wheels spinning at their proper speed as balls go through. If not, you can add another motor to increase your available power and help your speed rebound between shots.

**If you use a single-wheel shooter with a hood, the exit speed of the ball would be half the surface speed of the wheel, and for a double-wheel shooter like a pitching machine, the ball speed would equal the average of the two wheel surface speeds.
__________________
Four years of FRC 68 Truck Town Thunder
2012 Championship Newton Division Finalists—Thanks 330 and 639 for the Full Court Press!
2013 Kettering University District Chairman's Award Winners!
2014 Great Lakes Bay Region District Winners—Thanks 288, 4819, and 5166! | 2014 Waterford District Chairman's Award Winners! | 2014 Michigan FRC State Championship Chairman's Award Winners—Congratulations 33 and 503!
2015 Center Line District Chairman's Award Winners! | 2015 Lansing District Winners—Thanks 314 and 1684! | 2015 FIRST in Michigan District Championship Chairman's Award Winners—Congratulations 503 and 2137!


Reply With Quote
  #23   Spotlight this post!  
Unread 16-01-2017, 02:10
YashBrowns's Avatar
YashBrowns YashBrowns is offline
Registered User
FRC #4763
 
Join Date: Jan 2017
Location: California
Posts: 11
YashBrowns is an unknown quantity at this point
Smile Re: Shooting Motors and wheels

We r using a 4 by 2 wheel and have about .04 inches of compression
Reply With Quote
  #24   Spotlight this post!  
Unread 16-01-2017, 02:13
YashBrowns's Avatar
YashBrowns YashBrowns is offline
Registered User
FRC #4763
 
Join Date: Jan 2017
Location: California
Posts: 11
YashBrowns is an unknown quantity at this point
Smile Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
We r using a 4 by 2 wheel and have about .04 inches of compression
We also changed the wheel from the kit of parts andymark ones to colson performa wheels which are shooting the balls much better

Thanks with all the help, I will post a video soon of our shooter in action
Reply With Quote
  #25   Spotlight this post!  
Unread 16-01-2017, 02:42
Munchskull's Avatar
Munchskull Munchskull is offline
CAD Designer/ Electrical Consaltant
AKA: Anthony Cardinali
FRC #0997 (Spartan Robotics)
Team Role: CAD
 
Join Date: Jan 2013
Rookie Year: 2013
Location: Corvallis, OR
Posts: 532
Munchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to beholdMunchskull is a splendid one to behold
Re: Shooting Motors and wheels

Quote:
Originally Posted by Ekcrbe View Post

*Actually, I'll add a fifth, but it's not as much about geometry and it's important this year, so I'll keep it separate: motor power. Shooters this year should have a pretty high throughput, so be prepared to use your newfound closed-loop control knowledge that you got from the fine folks here to keep your shooter at its proper speed as you're shooting. With that in mind, consider whether one motor will have enough power to keep the wheels spinning at their proper speed as balls go through. If not, you can add another motor to increase your available power and help your speed rebound between shots.
I would like to add to this great explanation.

Every time you shoot a ball you impart a portion of the shooters energy into your shoot robbing the shooter of the speed. At the same time motors are trying to "charge" the shooter back up with energy.

Unfortunately the motor(s) have a limit to how much energy they are able to put into the mechanism. This is correlated to the moment of inertia of the sum of you spinning parts and the free speed of the motors.

This equation is (1/2)Iw^2 or half the moment of inertia times angular velocity squared.

Your motors angular velocity is limited by its free speed RPM so the only way to add more energy is to increase the moment of inertia. For the sake of simplicity if we assume a solid relatively uniform mass in the form of a drum shooter then moment of inertia would be:

I=(1/2)m*r^2

For all wheel shapes this equation remains almost the same with the coefficient in front of the mass being the only change.

Using this knowledge increasing the mass and moving the mass farther out increases our energy storage meaning the that the energy imparted onto the ball has less effects on the overall speed allowing more consistent shots.

This concept is called flywheels and is a form of mechanical battery.

Sent from a sleep deprived highschooler at 11:42pm on there phone. Please go easy on me for typos and the sort.
__________________
“In theory, theory and practice are the same. In practice, they are not.” ― Anonymous
Anthony Cardinali
4th year of FRC
Class of 2017



Reply With Quote
  #26   Spotlight this post!  
Unread 16-01-2017, 07:08
D_Price's Avatar
D_Price D_Price is offline
Engineer/Mentor
AKA: Derek
FRC #1708 (Amp'd Robotics (formally Natural Selection))
Team Role: Mentor
 
Join Date: Jan 2007
Rookie Year: 2004
Location: McKeesport, Pa
Posts: 443
D_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant futureD_Price has a brilliant future
Re: Shooting Motors and wheels

+1

Quote:
Originally Posted by Ekcrbe View Post
There have been a lot of good suggestions so far, especially on the control side of things. But as a note on the actual shooter design, it's hard to say whether 5:1 is a good speed for your wheels without knowing what size wheels you're using. There are probably four main variables in designing a shooter in FRC*: wheel surface speed, contact distance, compression profile, and wheel/hood material (durometer, coefficient of friction). Of course, wheel surface speed and contact distance are both functions of wheel diameter. So if you use larger wheels, you can have a higher reduction from the motor, but for small wheels, you'll want them spinning faster.

In an ideal world, you would have plenty of traction and distance to get the balls up to speed and have no slip between the balls and your wheel(s)/hood. Then the exit velocity of the balls could be calculated quite simply by equating the surface speed of the wheel(s) and balls.**

This, put simply, is not going to happen in real life. The balls will slip on the wheels, but how much they do so depends on how well the wheels can grip the balls. The more distance you can keep the balls in contact with the wheels (this means larger diameter wheels or a larger angle in contact), the closer you can get to this ideal. Softer wheels are also sometimes advantageous for this, at the expense of faster wear.

Additionally, how much you compress the ball/wheels how that compression is distributed over the path of the ball has a major, if somewhat complicated, impact on your shots. In general, more compression can allow for more energy transfer, but only up to a certain point. After that point, you're just excessively deforming the balls and bogging down the shooter.

And finally, a general rule of thumb that I've come to follow is that softer balls should take harder wheels and vice versa. This year, the prototypes I've seen online and with my old team are suggesting that hard wheels will probably be fine—These balls can compress a bit. But all these are just guidelines, and your mileage may vary with any of them.

*Actually, I'll add a fifth, but it's not as much about geometry and it's important this year, so I'll keep it separate: motor power. Shooters this year should have a pretty high throughput, so be prepared to use your newfound closed-loop control knowledge that you got from the fine folks here to keep your shooter at its proper speed as you're shooting. With that in mind, consider whether one motor will have enough power to keep the wheels spinning at their proper speed as balls go through. If not, you can add another motor to increase your available power and help your speed rebound between shots.

**If you use a single-wheel shooter with a hood, the exit speed of the ball would be half the surface speed of the wheel, and for a double-wheel shooter like a pitching machine, the ball speed would equal the average of the two wheel surface speeds.
__________________
Team member 2004-2008
Team mentor 2008-20XX

http://team1708.steelcityrobotics.or...tics/Home.html
"Education is a powerful tool. Always use it to better someone else's life"
Reply With Quote
  #27   Spotlight this post!  
Unread 16-01-2017, 09:21
dkavanagh dkavanagh is offline
Registered User
FRC #0578 (Red Raider Robotics)
Team Role: Mentor
 
Join Date: Jan 2015
Rookie Year: 2015
Location: Rochester, NY
Posts: 23
dkavanagh is an unknown quantity at this point
Re: Shooting Motors and wheels

We've prototyped with a direct-drive CIM motor. Comes up to speed very quickly. 1st ball robs some speed, several more after that are consistent. Today we hope to add an encoder.
Reply With Quote
  #28   Spotlight this post!  
Unread 16-01-2017, 15:07
Ekcrbe's Avatar
Ekcrbe Ekcrbe is offline
When can I watch Einstein again?
AKA: Erik Boyle
FRC #4640 (Metallic Panthers)
Team Role: College Student
 
Join Date: Jan 2012
Rookie Year: 2012
Location: New York, NY
Posts: 333
Ekcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond reputeEkcrbe has a reputation beyond repute
Re: Shooting Motors and wheels

Quote:
Originally Posted by Munchskull View Post
I would like to add to this great explanation.
[snip]
...
[/snip]
Sent from a sleep deprived highschooler at 11:42pm on there phone. Please go easy on me for typos and the sort.
Thanks for providing the math. I probably would have done it, but I'm here on the east coast and it was even later for me, so I just wanted to get it done and get to bed.
__________________
Four years of FRC 68 Truck Town Thunder
2012 Championship Newton Division Finalists—Thanks 330 and 639 for the Full Court Press!
2013 Kettering University District Chairman's Award Winners!
2014 Great Lakes Bay Region District Winners—Thanks 288, 4819, and 5166! | 2014 Waterford District Chairman's Award Winners! | 2014 Michigan FRC State Championship Chairman's Award Winners—Congratulations 33 and 503!
2015 Center Line District Chairman's Award Winners! | 2015 Lansing District Winners—Thanks 314 and 1684! | 2015 FIRST in Michigan District Championship Chairman's Award Winners—Congratulations 503 and 2137!


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 12:41.

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