Quick Swerve Frame Idea

I’ve been inspired by the recent release of WCP’s new Swerve X to think about new Swerve Module and frame designs. I’ve come up with some interesting options for modules which I’ll post soon.

In the meantime, I wanted to highlight this idea for a new way to build 2x1 frames for swerve. By inserting (~10" long) diagonal members at each dorner, you can mount any COTS module such that it reaches the edge of the frame perimeter. This has several advantages:

  • 2" more wheelbase
  • stronger frame corners
  • the ability to remove modules easily sideways,
  • maintaining the lower CG of a tube-below-plate arrangement
  • module interchangeability
  • legal bumper mounting (as long as the modules touch the corner of the bumper
  • more distance between modules to mount superstructure

The downsides are:

  • it uses up roughly 10" more length of 2x1 tubing compared to a square frame (but that’s only about 0.5 pounds total.)
  • Since it uses ~9" worth of corner for the structure (compared to 6" of bumper minimum) you can’t have a maximum width bumper cutout this way. (A cutout could still be done though with a fancier structure.)

Here’s how a 27x27" frame would look with the WCP, SDS and TTB modules:


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As a former road racer, more track and wheelbase are always a plus and a lower CG just adds even more goodness.

Some interesting thinking here - thanks for sharing it.

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I like the idea of taking a new approach, but I’d be a bit concerned about leaving my swerve modules right behind my bumpers with no further protection.

How does this work with bumper rules?

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As long as the module contacts the bumper within 1/2" of the corner, the design would pass the bumper rules.

As for whether the modules are strong enough to take whatever bumper loads without the additional frame in front - that’s a matter for testing :slight_smile:

Why aren’t you using the Swerve X Corner module? They’re designed for the exact purpose of pushing module as far into the corner as possible.

Wouldn’t a belly pan make the angle braces somewhat redundant?

Maybe I’m missing something here but it doesn’t seem all that efficient of a design…

@orangemoore This idea is compatible with the Swerve X corner module, but it doesn’t require it.
It will work with SDS, TTB and other future / custom modules. Moreover, I think it makes for a stronger corner joint than what WCP has shown so far for mounting their Swerve X corner above the tubes.

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Thanks to @AllenGregoryIV for this idea: If you are able to make custom triangular gussets as shown in purple, it’s even easier to mount COTS modules to this frame (although slightly different gussets might be required for each vendor)

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At the cost of 1/8" on each side you could use some flat stock for a bit more protection.

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Flat stock pales in comparison to the MOI of rectangular tubing. It’s the depth of the tubing that would help most, not the thickness of the material.

That being said, something to guard the corners is better than nothing.

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Many teams have used the corner to mount skids to deal with field elements. This would complicate or prevent skids. Our team ran without skids and survived. In the future, I think we would consider skids.

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I wonder if we could make curved bumpers to follow the curvature of the module plate…

Purple. Nice touch!

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I really like this frame. Inspired by it, I made a different swerve frame concept with the same goals. It retains the advantages of a larger wheelbase, and easier installation/removal of the modules. This frame uses the same amount of tubing as a square frame, and (with some gusset modification) allows for max width bumper cutouts. The biggest advantage in my opinion is the extra space you have to put additional tubes across the frame for mounting other structures. It is heavier than a standard square frame, and the original modified frame. The large gusset and tube plugs add more weight than a standard L-gusset, amounting to a total of 1.312lbs heavier than standard, so .812lbs heavier than the original modified frame. Using a thinner/smaller gusset could shave some of this weight. Reducing the total width, making the diagonal sections .25in wide instead of .375in wide, and changing the material thickness to .09in instead of .125in saves a total of .2lbs. But this saving is small, and I was worried about reducing the strength of the corner too much so I prefer the beefy gusset.


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CAD link: Onshape

This biggest downside I see to frame styles like this is how much harder a full width over the bumper intake becomes. Most teams who ran swerve modules and an intake like that (in 2020/21) had the intake plates between the edge of the frame and the motors of the module when the intake was actuated. These designs eliminate that space in favor of increased wheelbase. The game, which determines the risk of tipping (robot design plays a role too, but elevators games generally mean more tipping) and the ideal intake style, really determine whether these modified frames are better than a standard frame. In a game like 2019 or 2018 I think these modified frames would improve stability, but for 2020 I would stick with a standard frame to make the intake easier.

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very cool concept! and If your intake can pivot from a higher spot on your robot you can still do full width relatively easy, some good examples are the rear intake we recently added and 33 from 2019 (I’m sure there are countless others also)

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I would be a little worried about that frame, especially if you have a cutout on one side. While the gusset plates between the main frame members and the short extrusions that go around the module will help with frame strength, the only thing supporting the joint between the two short extrusions is the module plate and since the module plate is on the top of the frame whereas the gussets are on the bottom, you are relying on the strength of the box section of the extrusion to carry some potentially large impact loads - especially if you had a frame cutout on one side.

Ever since we experienced how badly unsupported portions of the frame can be bent in 2017 (I’m looking at you, SPORK :grin:), we have run a second frame bar parallel to the side bars such that the swerve module would fit between the outer frame bar and the parallel frame bar and the two modules on each side of the robot are boxed in. That idea would certainly work here if you extended the 5.75" length of extrusion all the way to the opposite side. I would certainly recommend something like that if you are going to have a cut-out in the frame. We have used thick wall 1"x1" for our frame rather than 1"x2" extrusions, for our frames, That second, parallel frame bar could easily be a 1"x1" so the weight penalty is not that bad. I would install that 1"x1" extrusion on the bottom of the frame so that it integrates into the gusset plates and could also be attached to a belly pan to help with the shear loads. You can put a short piece of 1x1 on top of it under the module plate.

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With the SDS swerve modulues, the radius of what would now be the “frame perimeter” is 2.5". Unless we came up with some way to curve the bumper corner, the gap would be well more than 1/2" long at the end/corner of the bumper. Some kind of “filler” frame perimeter structure would be needed to make standard rectangular bumpers on this legal. Or maybe, I’m just being dense today and missing something??

This would/could be different with alternate swerve modules…

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something as simple as a modified corner gusset riveted to the SDS mounting plate would resolve the issue.

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Enter at your own risk…

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Plywood, schmywood.

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I don’t quite see why it is any different than a “standard” swerve frame. When I say standard this is what I mean, and I am under the impression this is the standard setup for a swerve frame when the main plate is above the frame.

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The only difference between this and my modified frame is the orientation of the corner. Could you clarify what makes the inverted corner weaker than the normal corner?

I completely agree with the comments about bumper cutout, but this applies equally to any frame design. Extra rails that run across the robot are necessary to make the frame strong enough. Extending the 5.75in piece like you mentioned is a great way to get max bumper cutout. Realistically there would be extra rails going across the frame with or without a bumper cut for the purpose of mounting other structure, like I mentioned in the first post.

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Marky Mark’s 3/4” Plywood and Emporium needs some business.

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