25-03-2008 07:59

Peter Matteson

Re: pic: 1625's swerve module (better pic)

You're the only other team I've seen do welded tube construction wheels. I thought we were alone with that because everyong else seems to hog them out of a billet.

25-03-2008 18:04

wowmuffin

Re: pic: 1625's swerve module (better pic)

Wow... those are beautiful. Are those wheels driven throught a screw gear or am I not understanding how the motor drives those wheels?

25-03-2008 18:26

A_Reed

Re: pic: 1625's swerve module (better pic)

It is done by changing the axis of rotation with a set of miter gears.

Nice setup, saw you guys on the MWR webcast, good looking robot.

25-03-2008 18:32

thefro526

Re: pic: 1625's swerve module (better pic)

I like how you used snap-rings instead of collars. That has to save a lot weight.

26-03-2008 00:20

Aren_Hill

Re: pic: 1625's swerve module (better pic)

these are faster to make and are also most likely lighter and stronger in the places the force is applied.
its really easy to just waterjet the sideplates and weld them on, these wheels are 1.75" wide


I LOVE SNAP RINGS!!! lol also the custom 7068 hex axles....not overkill at all...

26-03-2008 00:27

SgtMillhouse648

Re: pic: 1625's swerve module (better pic)

Yes, I loved your guy's setup when you brought over the spare module to compare to ours at MWR. It is a real slick setup, not to far from ours. Great job on the wheels, and I absolutely love the sprockets you guys use to steer. That is an amazing setup on that. Hawging out the middle of hte sprocket also has to save a ton of weight, and I liked the slotted holes in the sprocket (if I remember right) to fine tune each wheel's tracking before you went out onto the floor.
Malhon

26-03-2008 02:24

Chris Herold

Re: pic: 1625's swerve module (better pic)

Hey, I like it. They look great! Swerve drives are for me as a rookie pretty impressive just because of their advantages. I'll probably test my cad abilities during the off-season by designing one myself... I'll see but it's a nice piece of metal!

Chris

26-03-2008 07:22

Peter Matteson

Re: pic: 1625's swerve module (better pic)

Same reason we do wheels out tube and plate welded together.

26-03-2008 10:01

AdamHeard

Re: pic: 1625's swerve module (better pic)

How easy is it to hold the plates and tube concentric while rounding?

If it is just standard Al tube, how thick are the walls and how true to round is the outer surface?

26-03-2008 10:07

Peter Matteson

Re: pic: 1625's swerve module (better pic)

We cut a relief pocket in the plate so that it over hangs the tube and tube literally snaps into the plate. This gives us wheels as close to concentric as possible to make. I'll dig up some pictures and grab a few of the evolution of the design when I'm at the shop today so you can see what I mean.
Pete

Edit:
http://www.chiefdelphi.com/media/photos/31104?
http://www.chiefdelphi.com/media/photos/31105?
http://www.chiefdelphi.com/media/photos/31102?
http://www.chiefdelphi.com/media/photos/31103

Pictures now up.
End Edit

26-03-2008 12:09

Aren_Hill

Re: pic: 1625's swerve module (better pic)

We just used 4" o.d. 1/8th wall tube, and waterjetted the sideplates, due to the nature of a waterjet it puts a slight taper on things so when i had it make a
3.75 o.d. disc it pressed right into the side of the tube and held itself there solidly while it was welded.

they're as concentric as you'll ever need for wheels.

26-03-2008 12:54

sdcantrell56

Re: pic: 1625's swerve module (better pic)

How are you keying the wheel to the axle. I'm planning on using that type of wheel next year and just looking to compare ideas

26-03-2008 14:12

A_Reed

Re: pic: 1625's swerve module (better pic)

how is the lower plate supported? I know it used as a bearing surface, but it is sandwiched between plates or riding on small ball casters. I have always wondered how this work with swerve modules, I understand the rest of it but the lower support plate is the only gap in my limited knowledge of drive systems(I don't go into the kinematics...yet).

26-03-2008 14:30

hillale

Re: pic: 1625's swerve module (better pic)

The lower plate isn't necessarily a support plate, just a bearing surface like you said. Due to the nature of friction, it does a little support, but mainly it just rubs against flat plastic patches (lubed up to reduce friction) on the frame to aid in steering the modules. The face of the contact between the plastic and the plate is purely vertical. No horizontal contact is made between the plate and the frame. It is welded, in the corners, to the square tube that makes up the vertical body of the module.

31-03-2008 01:04

Aren_Hill

Re: pic: 1625's swerve module (better pic)

the bottom disc is simply supported by 4 tangential pieces of UMHW (ultra high molecular weight) plastic, that we keep white lithium grease on all the time to keep it slick. Rollers are more efficient but take longer to install and are heavier

31-03-2008 03:21

Un Luchador

Re: pic: 1625's swerve module (better pic)

With such an effective drivetrain, it's no wonder you guys went undefeated at Colorado. I love the way you guys keep the robot chassis facing forward through the match, but still have the swerve function to put you back into position. That's very innovative.
Keep up the hard work and military-like competing guys.

31-03-2008 06:29

Jimmy Cao

Re: pic: 1625's swerve module (better pic)

That module looks very simular to our initial idea, except we were putting the motor/transy inside the module itself.

It's very nice looking =D

31-03-2008 09:59

hillale

Re: pic: 1625's swerve module (better pic)

That's what we did last year, we had a cim mounted vertically through a dewalt on each of the modules. This coaxial design made maintenance much easier (though it has gone through 3 regionals and hasn't broken once). Here is a pic of our underbelly, http://www.chiefdelphi.com/media/photos/28596. I guess we don't have a closeup of the module from last year.

15-04-2008 13:31

Aren_Hill

Re: pic: 1625's swerve module (better pic)

This guy weighs in at 2lbs 14oz and i coulda taken a couple more ounces out of the steel sprockets. Lighter than last years

15-04-2008 16:42

lukevanoort

Re: pic: 1625's swerve module (better pic)

Have you thought about going to aluminum drive sprockets to save a touch more weight?

Is there a girl module?

15-04-2008 17:37

Re: pic: 1625's swerve module (better pic)

Hm, you should switch to Kevlar belting and aluminum pulleys. Then this setup would be truly frighteningly light. Out of curiosity, how many teeth does your steering sprocket have? I'm currently designing a bottom support crab, so I can finally post one that doesn't get hit with the "you're not supporting it right" complaint.

15-04-2008 17:38

Aren_Hill

Re: pic: 1625's swerve module (better pic)

Yes i have but during the season i was too busy to find a supplier or someone to have them made.

22-07-2008 16:58

Elgin Clock

Re: pic: 1625's swerve module (better pic)

Aren, do you have a white paper on this, or at least a picture of the other side of this assembly showing the bevel gears?

I got to see this up close at IRI, & was very impressed.
Not only did it perform great on the field, but it was relatively lightweight for what it consists of.

I'm trying to convince my teammates to experiment with as many drive trains as possible over the summer with our upcoming test chassis, & want to show them this one as a great example of swerve assembly.

22-07-2008 17:11

Aren_Hill

Re: pic: 1625's swerve module (better pic)

I myself do not own a camera, and if i did wouldn't have time to take pictures.
The module structure (alum parts) is almost all waterjetted parts, then welded onto a 3x3x1/8th wall tube that had bearings holes CNC'd into it.

it will have some revisions for next year if we continue to do swerve, such as better bearing support at the top. (right now 1/2" bearings are taking the thrust load....). I'm considering copying 148's wheels so we dont have to worry about retreading and steering the wheels would be easier

22-07-2008 19:14

roboticWanderor

Re: pic: 1625's swerve module (better pic)

418 has been doing them for years, exept we use 1"x1/4" stock to make spokes instead of using plate. then we speed hole them to make them even lighter.
here is a cad of them i don't have a good picture.