paper: 1625 Swerve Through the Ages

[MattC9]

Originally Posted by Dillon Carey

Yes, the middle wheel was dropped on the 6 wheel. It was adjustable via placing different sized spacers between the thrust bearing on top of the module and the frame. I believe we ended up with somewhere around 1/8 of an inch drop.

Ok so how did this effect you chain run? Did you have to adjust the sprocket every time you put another spacer in? And since you only had 4wheels on the ground at a time were the front 2 wheels and the back 2 wheels in sync? and how did that work?

(sorry for all the questions, this is really interesting)

[Garrett.d.w]

Dillion,
your modules are amazing (a lot smaller than what my team used this year). We used a "hybrid" swerve system. We had four modules, the front and rear wheels were turned as sets using window motors. The front modules were populated with omni wheels, and the rear ones had traction wheels. This was to allow us to drive it like a tank robot, as we had very little time actually practicing with the robot in swerve mode. This resulted in a robot that was easy to drive, but yet had some curious turning/ strafing abilities.

I would like to ask you how you guys set up your controls (aka, which buttons did what). We had difficulties coming up with controls that were intuitive enough to be driven without thinking about what buttons to push (this is for "true swerve", without the omni wheels). If we can fix this problem in the offseason, I hope to convince the team that it is worth pursuing swerve drive this year (game allowing of course).

Thanks.

[Dillon Carey]

Originally Posted by MattC9

Ok so how did this effect you chain run? Did you have to adjust the sprocket every time you put another spacer in? And since you only had 4wheels on the ground at a time were the front 2 wheels and the back 2 wheels in sync? and how did that work?

(sorry for all the questions, this is really interesting)

First of all, don't worry about asking questions.

When we added spacers to adjust the module height, we also flipped spacers around to adjust the sprocket height. Even if it was slightly out of alignment it wasn't a big deal, because of how long of a chain run it was.

All of the wheels were always pointing the same direction. There was one loop of chain that went around the entire robot.

Originally Posted by Garrett.d.w

I would like to ask you how you guys set up your controls (aka, which buttons did what).

We had 2 joysticks, which functioned just like a normal 2 joystick skid steer system. when you pulled the right trigger, it switched to single joystick swerve control. We added one other mode before champs, we called it 469 mode. we designed it specifically in case we had to play defense on 469. when you hit the top button on the right joystick, the modules turned 90 degrees and locked there. Then when you moved the joystick left or right, it strafed left and right. I ended up using only our "469 mode" and normal 6 wheel drive all the way through champs and IRI, barely touching the true swerve mode.

(This is where the idea for the 2011 lobster drive started)

[MattC9]

2011 lobster? I would like to hear this

[rutzman]

Originally Posted by MattC9

2011 lobster? I would like to hear this

This is lobster drive.

[Ether]

Originally Posted by Dillon Carey

All of the wheels were always pointing the same direction.

It is common to refer to this as "crab drive", to differentiate it from swerves with other steering designs... some of which have also been dubbed with various names (but few as widely accepted and understood).

[Dillon Carey]

Originally Posted by Ether

It is common to refer to this as "crab drive", to differentiate it from swerves with other steering designs... some of which have also been dubbed with various names (but few as widely accepted and understood).

I know that the different names refer to different styles, I just have never known whivh name refers to which orientation. On 1625 we usually just call them all swerves, then add some detail about the steering setup. Slightly less effective communication, but overall easier to understand in my opinion.

[Joe G.]

Can someone tell us more about these 45 degree modules? I'm confused how they would be oriented relative to the ground and robot, and how they would be arraigned into a full swerve drive. What advantages might these give over traditional 90 degree modules?

Thanks!

[Aren_Hill]

We've actually hunted down some 20deg or something bevel gears since then, but the goal of that module was to decrease the number of parts by removing the horizontal axle. It would still be oriented with the support bearing straight up top, but with the wheel running on an angle in relation to the floor.

Not on the top of the list if we do another swerve, but a fun idea to toy with nonetheless

[Sharp Cheddar]

I'd like to pitch making a swerve drive to my team because all we ever did was the traditional 4 wheel/4 motor drive (and mecanum this year). We really like the mecanum but we lost all of our districts in Michigan this year (especially Niles) due to us getting pushed around. On to my main question, I heard that crab/swerve drives can weigh a lot, how much does your swerve weigh?

[AustinSchuh]

Originally Posted by Sharp Cheddar

I'd like to pitch making a swerve drive to my team...

Not to sound like a broken record, but if you want to make a swerve drive during the season, you should make one in the off-season first. Every team that I know of who has done swerve has either done one in the offseason first, and been very glad that they tried a swerve then first, or wished they had made one in the offseason before they made one during the season. Swerves are hard to build and program.

[Sharp Cheddar]

Originally Posted by AustinSchuh

Not to sound like a broken record, but if you want to make a swerve drive during the season, you should make one in the off-season first. Every team that I know of who has done swerve has either done one in the offseason first, and been very glad that they tried a swerve then first, or wished they had made one in the offseason before they made one during the season. Swerves are hard to build and program.

My team starts up pre-season when school starts and that's when i plan on pitching to my team for us to make a swerve drive. We may not use it in 2012 but it'd be good to be getting it started. I've done plenty of research on swerve drives already to know that they need to be started off-season or pre-season because they're complicated. But my team is 74, and we're an old team that should use our resources creating such drive trains. Of course we will come up with problems just like any team creating a swerve drive for the first time. But to reply to your comment, i made no intentions to go to my team right at kickoff saying, "Hey, let's make a 100% successful swerve drive this season." I understand that it takes a lot to make one of these and i thank you for your heads up on the difficulties as i will probably have to make a presentation on this for all of the team and mentors. And if i have to I'll speak with team 141 Wo-Bot because they are right in our city and they have a pretty good crab drive.

[Hawiian Cadder]

Originally Posted by AustinSchuh

Not to sound like a broken record, but if you want to make a swerve drive during the season, you should make one in the off-season first. Every team that I know of who has done swerve has either done one in the offseason first, and been very glad that they tried a swerve then first, or wished they had made one in the offseason before they made one during the season. Swerves are hard to build and program.

My team didn't, in 2004 or 2003 they(we) attempted a coaxial swerve without any prototyping, it went about as badly as was possible.

*it was the first time they had done a custom gearbox setup, the got the tollarances wrong which caused the gears to heat up and burn whatever grease was on them.

*the 80-20 frame kept warping, and throwing chain

*programmers got less than a week with any drive-train (no prototype)

Prototype it in the off season, and maybe even take it to an event.

[Dillon Carey]

Originally Posted by Sharp Cheddar

how much does your swerve weigh?

I don't have a for sure weight, but I'd estimate the 2010 swerve was 40-45 lbs