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 Chief Delphi pic: Swerve Module, 2910 Off Season
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#31
05-09-2018, 06:31 PM
 Joe Johnson Engineer at Medrobotics AKA: Dr. Joe FRC #0088 (TJ2) Team Role: Engineer Join Date: May 2001 Rookie Year: 1996 Location: Raynham, MA Posts: 2,873
Re: pic: Swerve Module, 2910 Off Season

Is that a 4" bearing or 100mm?
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Joseph M. Johnson, Ph.D., P.E.
Mentor
Team #88, TJ2
#32
05-09-2018, 11:10 PM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by Joe Johnson Is that a 4" bearing or 100mm?
The bearing we ran is equivalent to a silverthin SA035XPO. 4" OD
#33
05-10-2018, 12:43 AM
 deltafief Registered User AKA: David Liu FRC #1540 (Flaming Chickens) Team Role: Mechanical Join Date: Jan 2017 Rookie Year: 2016 Location: Portland, Oregon Posts: 16
Re: pic: Swerve Module, 2910 Off Season

Just a general swerve question, how do you calculate the spacing and placement of the bevel gears?
#34
05-10-2018, 02:11 AM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by deltafief Just a general swerve question, how do you calculate the spacing and placement of the bevel gears?
Usually where you buy the bevel gears from will have info on the theoretical spacing. A lot of the times it is a distance measured from the back mounting face of one gear to the axis of rotation of the other gear. From there you can add a few thousandths of extra clearance to error on the side of not jamming or plan on doing some test fitting and tweaking to get the mesh just right with minimum backlash and no jamming.
#35
05-11-2018, 10:12 AM
 Spock81 Registered User AKA: James FRC #3663 (CPR) Join Date: Mar 2018 Rookie Year: 2018 Location: Washington Posts: 12
Re: pic: Swerve Module, 2910 Off Season

One general question not specifically swerve related but still relevant. Did you (or anyone else) notice the VersaWheels wear down especially fast during the season? We used them last year on a drop 6 and they had to replace them at least every competition. This year we switched to am Plaction wheels with their blue nitrile tread which seemed much better.
#36
05-11-2018, 11:07 AM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by Spock81 One general question not specifically swerve related but still relevant. Did you (or anyone else) notice the VersaWheels wear down especially fast during the season? We used them last year on a drop 6 and they had to replace them at least every competition. This year we switched to am Plaction wheels with their blue nitrile tread which seemed much better.
Yes, we noticed the wear on the VersaWheels also. We changed our wheels every competition as well. After one competition the wheels were almost worn enough to no longer be able to see the tread pattern. They still work fine though and I think we could have gotten 2 competitions out of each set of wheels if we measured them and used the compensation in our code for auto driving distances.
#37
05-11-2018, 09:22 PM
 Cash4587 Registered User AKA: Cooper Cash FRC #4587 (Jersey Voltage) Team Role: Mentor Join Date: Mar 2013 Rookie Year: 2013 Location: Houston, TX Posts: 527
Re: pic: Swerve Module, 2910 Off Season

Hey what ended up being the gear ratio for your robot this year or Theoretical/Adjusted speed, gear ratio and motor selection would be more helpful. Also how much did your robot weigh?
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Team 4587: Jersey Voltage - Lead Technical Mentor, Drive Coach
#38
05-12-2018, 05:55 PM
 Nick_Coussens #teamswerve #team775 AKA: FUN-InFiMidation Host FRC #0033 (Killer Bees) Team Role: Mentor Join Date: Jun 2010 Rookie Year: 2007 Location: Ferndale, MI Posts: 591
Re: pic: Swerve Module, 2910 Off Season

I'm curious to know what motor and overall ratio you ended up running for the steering of each module.

Great design, great robot, and great season! #teamswerve
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FUN: InFiMidation, Show Host (2018-Present)
FRC/VEX 33: Killer Bees, Design/Strategy Mentor (2018-Present)

FRC/VEX 2451: PWNAGE, Lead Strategy/Scouting Mentor (2013-2017)
FRC/VEX 2451: PWNAGE, Team President/Driver/Student (2009-2012)
#39
05-14-2018, 01:56 PM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by Cash4587 Hey what ended up being the gear ratio for your robot this year or Theoretical/Adjusted speed, gear ratio and motor selection would be more helpful. Also how much did your robot weigh?
Certainly, We ran CIMs with a 5.78:1 gear ratio for a theoretical free speed of 16.3 fps. Our robot weighed 119 pounds without battery and bumpers. We used a 25 amp SRX current limit to prevent against brown outs and the main breaker popping.

Last edited by PatrickW : 05-14-2018 at 05:52 PM.
#40
05-14-2018, 05:55 PM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by Nick_Coussens I'm curious to know what motor and overall ratio you ended up running for the steering of each module. Great design, great robot, and great season! #teamswerve
Thanks Nick! For the steering we used a bag motor on a 21:1 VP with an addition 3:1 belt reduction for a total of 63:1 from the motor to the rotation of the module. #teamswerve
#41
05-14-2018, 09:35 PM
 asid61 Design Simple AKA: Anand Rajamani FRC #1072 (Harker Robotics) Team Role: Mentor Join Date: Jan 2014 Rookie Year: 2013 Location: Cupertino, CA Posts: 2,983
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by PatrickW Certainly, We ran CIMs with a 5.78:1 gear ratio for a theoretical free speed of 16.3 fps. Our robot weighed 119 pounds without battery and bumpers. We used a 25 amp SRX current limit to prevent against brown outs and the main breaker popping.
25 amps per CIM? That seems very low.
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Team 1072 2017-present
Team 299 2017
Team 115 2013-2016 (student)

2018 Davis Finalists (w/ 6474 and 3880), 2018 Roebling Winners (w/ 3476, 1323, and 1778)

#42
05-15-2018, 04:45 PM
 PatrickW Registered User FRC #2910 (Jack in the Bot) Team Role: Mentor Join Date: Jun 2017 Rookie Year: 2009 Location: Mill Creek WA Posts: 57
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by asid61 25 amps per CIM? That seems very low.
It seems low to me too. After popping a main breaker at 30 amps at our first district event we turned the current limit down to 25amps and didn't have a single issue since. We aren't 100% sure that the drive train was the main reason the breaker popped, but our driver said he was still completely happy with the acceleration and how the the robot felt to drive at 25 amps, so we kept it there. I think I remember reading that 2767 ran a SXR limit of 40amps last year. What have other teams found works well?
#43
05-15-2018, 08:43 PM
 Mark Wasserman Registered User FRC #2767 (Stryke Force) Team Role: Mentor Join Date: May 2017 Rookie Year: 2010 Location: kalamazoo Posts: 156
Re: pic: Swerve Module, 2910 Off Season

Quote:
 Originally Posted by PatrickW It seems low to me too. After popping a main breaker at 30 amps at our first district event we turned the current limit down to 25amps and didn't have a single issue since. We aren't 100% sure that the drive train was the main reason the breaker popped, but our driver said he was still completely happy with the acceleration and how the the robot felt to drive at 25 amps, so we kept it there. I think I remember reading that 2767 ran a SXR limit of 40amps last year. What have other teams found works well?
St. Joe 2017, 80 Amp current limit = bushel basket of bad 775s.

East Kentwood 2017 until the end of season, 50 Amp current limit = 5 seconds of pushing then blown main breaker and possibly a bad 775.

2018, 40 Amp current limit AND geared slower (14fps vs. 17.5fps) = no drivetrain issues ever.

We even got into some pushing matches without releasing the magic smoke. All drive motors are on 40 Amp circuits.
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Not fast swerve, good swerve driven quickly.
Slow is Smooth, Smooth is Fast
#44
05-16-2018, 09:39 PM
 asid61 Design Simple AKA: Anand Rajamani FRC #1072 (Harker Robotics) Team Role: Mentor Join Date: Jan 2014 Rookie Year: 2013 Location: Cupertino, CA Posts: 2,983
Re: pic: Swerve Module, 2910 Off Season

I wonder what's different about swerve drives compared to regular non-limited 4-CIM drives that makes them pop breakers, especially main breakers. Really interesting that 2 teams had issues.
__________________
Team 1072 2017-present
Team 299 2017
Team 115 2013-2016 (student)

2018 Davis Finalists (w/ 6474 and 3880), 2018 Roebling Winners (w/ 3476, 1323, and 1778)

#45
05-17-2018, 11:56 AM
 Seth Mallory Registered User FRC #0192 (GRT) Team Role: Mentor Join Date: Mar 2007 Rookie Year: 2003 Location: Palo Alto, CA Posts: 278
Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by Joe Johnson View Post
Is that a 4" bearing or 100mm?
Quote:
 Originally Posted by PatrickW The bearing we ran is equivalent to a silverthin SA035XPO. 4" OD
This year we made the lower bearings on our lathe. We used 1/4" thick aluminium for the races, 1/4 bearings, and felt for seals. We then did the assembly and disassembly in lasagna pans. Think of all the loose bearings rolling on the floor.
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