New AndyMark Products (Swerve & Steer module?)

[ehochstein]

I've noticed AndyMark coming out with some new products for the year, they actually just tweeted out a "Swerve & Steer" module.

Here is their new product page.

What do you guys think about the new products for the year? I really like the look of the swerve module, can't wait to see it in use on some robots.

[coolhandluke811]

So I since they announced I guess I can talk about it a little

I was able to hold one of these recently during a visit to AndyMark recently. I've never worked directly with swerve drive but I've held team's samples and such.

Keeping it short, this is the cleanest, lightest swerve module I've ever held and was kind of blown away by it. It has some nifty built in wiring options for potentiometers that I admired as well.

[DiehardCybercard]

Thanks for posting that Evan, we're excited to see these in action this year. For those interested the product page now has pictures. http://www.andymark.com/product-p/am-3009.htm

[magnets]

These are a bit of a game changer....
$1300 buys you 4 swerve modules WITH motors!

Depending on the game, we may just have to buy some of these.

[notmattlythgoe]

Originally Posted by magnets

These are a bit of a game changer....
$1300 buys you 4 swerve modules WITH motors!

Depending on the game, we may just have to buy some of these.

Am I seeing right that it also includes an encoder(not the absolute)?

[ehochstein]

Originally Posted by notmattlythgoe

Am I seeing right that it also includes an encoder(not the absolute)?

Originally Posted by AndyMark

The PG71 has an encoder on the back side of the 775 motor, which can help keep track of the steering location.

I believe so!

[AdamHeard]

Originally Posted by Wiifi

I believe so!

A sensor on the back of the 775 with that much reduction after is going to be pretty sloppy imo.

The long cantilever on the bevel pinion worries me too.

[notmattlythgoe]

Originally Posted by AdamHeard

A sensor on the back of the 775 with that much reduction after is going to be pretty sloppy imo.

The long cantilever on the bevel pinion worries me too.

Aren't you getting more precise control by reducing after the encoder instead of before?

[Andrew Schreiber]

Originally Posted by notmattlythgoe

Aren't you getting more precise control by reducing after the encoder instead of before?

Play in gears adds up.

[Jared]

These modules look really awesome. One question: what bearings are you guys using for the rotation, and what holds the robot's weight. I can't quite tell from the picture what's going on.

Originally Posted by notmattlythgoe

Aren't you getting more precise control by reducing after the encoder instead of before?

You care about the module's angular displacement, not the motor shaft's. There's some backlash in the planetary gearbox and the second gear reduction, so you may be able to rotate the motor a little bit without having the swerve module rotate. In the end, I'd imagine that this doesn't cause too much error.

[notmattlythgoe]

Originally Posted by Jared

These modules look really awesome. One question: what bearings are you guys using for the rotation, and what holds the robot's weight. I can't quite tell from the picture what's going on.



You care about the module's angular displacement, not the motor shaft's. There's some backlash in the planetary gearbox and the second gear reduction, so you may be able to rotate the motor a little bit without having the swerve module rotate. In the end, I'd imagine that this doesn't cause too much error.

Thanks, the more you know.

[Danny Blau]

Hi CD
There is an encoder on the back of the 775 motor and there is also a mount for an absolute encoder on the main mount plate.

The robot's weight is carried by a bronze thrust washer, the lateral loads are carried by a large OD roller bearing.

Thanks
Danny

[Adrian Clark]

Originally Posted by AdamHeard

The long cantilever on the bevel pinion worries me too.

I noticed that too. I did some quick calculations on the bending of the shaft under stall conditions and got .000187 max deflection. But keep in mind that's at the end of the shaft, not the mating surface of the bevel gear. So it seems the long cantilever shouldn't be a problem at all.

For those interested, the values I used to calculate the deflection are as follows:
.75 length of unsupported shaft
26.5 angle of pinon pitch cone
20 degree pressure angle
3/8" 4140 hex shaft
47 lbs radial pinon load under stall
145 in-lbs at pinon under stall
25 and 50 mm pitch diameters (from AM site)

-Adrian

[mman1506]

Wow, I'm confident we could build this faster than our versa-chassis. I really love how it comes fully assembled, the drive train is something I want to touch as little as possible. Being able to purchase a replacement module and just swap it in is awesome.

[asid61]

8.2lbs is a little much, but still realy good with everything on it.
Are the gears steel or aluminum? Are there alternate gear ratios available?
I'm wondering if there's a way to remove the first stge of gear reductions without compromising anything. This could easily be made half a poun dlighter if that were the case.

EDIT: I can't see in the cad how the smaller bevel gear is constrained axially. Is there a shaft collar I'm missing?
DOUBLEEDIT: Same goes for the large bevel gear. It appears to only be constrained by a single e-clip and the wheel. And the wheel is not constrained.