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  #31   Spotlight this post!  
Unread 05-09-2018, 06:31 PM
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Re: pic: Swerve Module, 2910 Off Season

Is that a 4" bearing or 100mm?
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Unread 05-09-2018, 11:10 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by Joe Johnson View Post
Is that a 4" bearing or 100mm?
The bearing we ran is equivalent to a silverthin SA035XPO. 4" OD
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Unread 05-10-2018, 12:43 AM
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Re: pic: Swerve Module, 2910 Off Season

Just a general swerve question, how do you calculate the spacing and placement of the bevel gears?
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Unread 05-10-2018, 02:11 AM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by deltafief View Post
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.
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Unread 05-11-2018, 10:12 AM
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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.
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Unread 05-11-2018, 11:07 AM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by Spock81 View Post
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.
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Unread 05-11-2018, 09:22 PM
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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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Unread 05-12-2018, 05:55 PM
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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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Unread 05-14-2018, 01:56 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by Cash4587 View Post
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.
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Unread 05-14-2018, 05:55 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by Nick_Coussens View Post
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
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Unread 05-14-2018, 09:35 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by PatrickW View Post
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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Unread 05-15-2018, 04:45 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by asid61 View Post
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?
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Unread 05-15-2018, 08:43 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by PatrickW View Post
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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Unread 05-16-2018, 09:39 PM
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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.
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Unread 05-17-2018, 11:56 AM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by Joe Johnson View Post
Is that a 4" bearing or 100mm?
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Originally Posted by PatrickW View Post
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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