pic: Small CIM in wheel swerve

[Bryce2471]

loading photo ...

[asid61]

4.6lbs per module? I think you've finally made a swerve that can be lighter than a WCD.
Much applause.
Is the two-plate design lighter than just flipping the motor over and using a planetary gearbox?

EDIT: Is that a custom gear on the bottom?

DOUBLEEDIT: Oh wait, MiniCIM. Dang, that was almost the dream.

[cad321]

Are you certain your materials are set correctly? A mini CIM weighs 2.16lbs according to VEX. If they are set correctly and that is in fact how light the module is, than I must say, very impressive.

[Bryce2471]

Originally Posted by asid61

4.6lbs per module? I think you've finally made a swerve that can be lighter than a WCD.
Much applause.

Thank you. This was mostly a design experiment for me, but I suppose it could be useful in a game like this year where a lot of weight is needed for the manipulators, and maneuverability is important, but pushing power is not.

Is the two-plate design lighter than just flipping the motor over and using a planetary gearbox?

i'm not sure about lighter, but I thought it would be a shame to put such a tall gearbox on such a short swerve module.

EDIT: Is that a custom gear on the bottom?

Yes. Several of the gears are custom so it would require access to a good laser, water jet, or wire EDM.

DOUBLEEDIT: Oh wait, MiniCIM. Dang, that was almost the dream.

Yep...
Maybe one day.

Originally Posted by cad321

Are you certain your materials are set correctly? A mini CIM weighs 2.16lbs according to VEX. If they are set correctly and that is in fact how light the module is, than I must say, very impressive.

Thank you, the mini CIM is accounted for, at 2.16 lbs. I'm pretty sure that the materials are correct, but like I said, there are some details that aren't in the CAD.

[Clayton Summerall]

What motors turning the left right motion? Pg or 750 maybe?

[Bryce2471]

Originally Posted by mcnabb2936

What motors turning the left right motion? Pg or 750 maybe?

In the CAD, it is an AM-912, but in reality, I would probably use a banebots RS 550.

[GeeTwo]

Originally Posted by Bryce2471

i'm not sure about lighter, but I thought it would be a shame to put such a tall gearbox on such a short swerve module.

If you used a worm gear for steering, it seems to me that you could orient both motors horizontally and get the module height down to the wheel diameter. You'd also save some weight on a second gear stage at a bit of loss of steering efficiency. You'd need slip rings for the drive motor since you couldn't run the wire out through the rotation hub, which might eat up the weight savings.

Also, what is the light colored gear to the lower right of the main rendering? I don't see what else it engages, and I also don't see it in the reflection.

[aphelps231]

Great work, would you be willing to share STEP files so we could take a look?

[Ryan_Todd]

Originally Posted by GeeTwo

Also, what is the light colored gear to the lower right of the main rendering? I don't see what else it engages, and I also don't see it in the reflection.

From the looks of the reflection, I would say that it's paired with another pinion underneath the bottom support plate via a live axle, which in turn is what engages the great big ring gear that goes around the perimeter of the module.

That makes for a 3-stage reduction in total, so I am inclined to agree that a worm gear would be a viable option here.

[GeeTwo]

Originally Posted by Skywalkar

From the looks of the reflection, I would say that it's paired with another pinion underneath the bottom support plate via a live axle, which in turn is what engages the great big ring gear that goes around the perimeter of the module.

That makes for a 3-stage reduction in total, so I am inclined to agree that a worm gear would be a viable option here.

Thanks, Skywalkar - I see it now. The reflection plane must be tilted down as it approaches the viewpoint (or the vertical on the module is tilted away at the top). I thought it strange that the dark gray gear did not engage with anything except to pass through to the yellow gear below the lower plate.

[InFlight]

Bryce,
Really nice concept once again.

Are you using a Silver Thin Bearing to support the the pivot assembly?

The planetary drive inside the wheel is a great idea, are there two stages there for ~9x reduction?

[evanperryg]

Originally Posted by InFlight

Bryce,
Really nice concept once again.

Are you using a Silver Thin Bearing to support the the pivot assembly?

The planetary drive inside the wheel is a great idea, are there two stages there for ~9x reduction?

This is what I'm most curious about, what kind of speeds are to going to get out of these? I'm sure there's an encoder mount somewhere, but where is it? Very, very impressive design.

[InFlight]

With a large steering gear like that you can't use an absoule encoder.

Team 141 at championships had a similar large steering gear setup. They used an incremental encoder to count steering input revs, but also had a pivot extension that triggered a proximity switch to calibrate the nominal forward position. Really elegant and beautifully machined swerve drive. They used a Kaydon brand bearing, very similar to the Silverthin ones. I had the pleasure of talking with the 141 students and mentor for quite a while, really an exceptional team.

[Scott Kozutsky]

Originally Posted by InFlight

With a large steering gear like that you can't use an absoule encoder.

It appears there's an absolute encoder on the top of the entire module, likely connected by bent polycarb like 2451 and 3928 before them.

[sanddrag]

On 696, we had a large 84T 20DP steering gear, and a 1:3.5 ratio between that and our MA3 absolute encoder. That is, the steering encoder would pass through 3.5 rotations for every one rotation of the swerve module. We had to physically set the wheels pointing straight at the start of each match (which is probably good practice anyhow), and there was a good bit of math and code involved, but we were able to very reliably track the position of our wheels at all times, resulting in fine control and operation.

Was it easy or friendly to do it this way? No. Is it possible? Yes. Would we run anything other than a 1:1 ratio to an absolute encoder again? Maybe not. It's kind of a pain. We likely will look into using a zeroing sensor and incremental encoder next time if we cannot maintain a 1:1 ratio with an absolute encoder.