The chassis allows for altering of its frame perimeter from 24x24 to 30x30 and will automatically regenerate all of the structural elements.
We have mounting positions for either a PDP or PDH.
Options also include using a higher capacity Odyssey PC925 Deep Cycle battery or a FRC legal battery. We use the Odyssey to provide added weight and also increase testing time between battery swaps.
Battery designs all include our hot swap design which we ran all of 2023.
We focused on making the chassis compatible with MK4i from SDS but make some effort in making sure other types of SWERVE pods would also fit.
We have already built a 24x24 frame and a 30x30 frame and performed load testing to see the failure points. We have also run some FEA as well.
This document describes some of the efforts but is still a bit unfinished:
We are toying around with the idea of selling the manufactured frame as we understand that not all teams will have access to a laser cutter. Also, it would be fairly expensive to send one chassisā worth of parts to an online laser cutting service. The concept is that we would take pre-orders up to around mid November and stage material. Then when the game is released, we would give everyone that pre-ordered 3 days, i.e. Tuesday January 9th, to lock in a size. We would then generate all of the DXFās, send everything thru our sponsor that runs an industrial laser cutter. We would pack and ship the unassembled frame components, minus the rectangular tubing that can be sourced locally. The hope is to get chassis into teams hands by the end of week 2.
Totally not sure what the details are yet. Iām not sure how crazy of an idea that is and if any teams out there might even be interested. (If you are interested, please PM me.)
As always comments, questions, criticisms are all welcome.
Whatās the purpose of the odometry pods? It feels like extra parts for what you can already get with a gyro and the internal encoders on your Falcons/NEOs
Having so many sheet metal parts feels like youāre over complicating what could be 6 2x1 aluminum tubes, some gussets, and a wooden belly pan. I feel like you want as simple as possible of a chassis if you are saying itās a āKOP Swerve FRC Chassis.ā
We come from a FTC background where ODO pods are very common. Itās an option weāre exploring in FRC. We havenāt found any definitive study that shows ODO pods are completely unnecessary.
We also design with the manufacturing tools we have. And with a laser cutter, high part count becomes less detrimental.
Considering how many teams have run very good autos without odometry pods, and the accuracy that these teams can get, Iād assume that they arenāt necessary.
How was the odometry pod accuracy going over the cable bump and over the charge station last year?
We assumed that is what everyone else is assuming and as such there might be a hole left un-investigated and worth investigating. We like doing things no one else is doing. Sometimes it leads to deadends, sometimes there is something there. Never know til we give it a try.
Super cool concept! Others have had some good adviceā¦ I have a few things Iāll poke at since I think there might be some easy ways to improve.
Be careful assuming that itās safe to load up the swerve modules like this. These are isolated, in part, to decouple gearbox deformation from frame deformation*. Battery suspension could be enough to cause misalignment in the gears that could lead to early failure. Coupling in dynamic loads could cause more issues.
You can take advantage of the manufacturing methods youāre using and add material where youāre seeing āredā in your FEA results. Using larger fillet radii and shaping the struts to be wider in regions of higher bending will make better use of your material and make a crack less likely.
Iāll also caution about relying on FEA to validate that your structure is strong enough. The physical deflection testing is an awesome start to verifying that your model is representative of reality (so long as the deflection/stiffness data matches), but itās easy to apply contacts and boundary conditions that are not representative of reality. This is before even talking about mesh convergence, or the fact that weāre seeing 3-7x the yield strength of aluminum in the results shown
Re: the odo pods, Iād be interested to see some A/B testing. We saw nearly cm accuracy on multi-gamepiece autos when we didnāt get wheel-liftingā¦ I always assumed weād need vision localization to do anything better than that, but maybe yāall are onto something!
In any case, this is a cool project and a very good opportunity to learn a bit about structural design + design-for-manufacturing.
*disclaimer, I havenāt been on a team running SDS modules and am myself making some assumptions about design intent.
Look at 6328. They had apriltag vision processing set up very well, and had extremely accurate autos (did not see them mess up once). They had the hoghest avg auto epa of any team in their division, and over half the match they moved autonomously. Whenever they had rainbow lights flashing, they were autonomously moving.
Not to say odo pods are the wrong way, try it out because it would be interesting to see how well it worked.
We made room in this chassis design for odo pods as well as TOF sensors and Vision cameras. All of these weāre experimenting with during the pre-season and certainly do not need to include them in a competition chassis if we find that they are unnecessary.
I would love to have feedback on the usefulness, usability and the efficacy of the reconfigurable chassis itself and the ONshape CAD. We just started using ONshape this summer and if there is a better way to organize all of the files, would love to understand that.
This is great! thank you for sharing it with the overall FIRST community!
Im no CAD expert and i love the configurability of parts depending on what teams would want.
Elmer - a few notes on the OnShape side of things. Note that I am no expert, I just have some preferences. Whenever you make a tube, using Juliaās tube featurescript makes that way easier. I donāt know if you have checked out onshape4frc.com/ yet, but I highly recommend downloading those featurescripts. Featurescripts are the second biggest advantage to OnShape imo behind the cloud capability. For frames and anything with tubes, I like to do individual rectangles, extrude individual FS, tube converter FS, then group constraint in an assembly.
I would also have put the variables in a variable studio. The downside of these is it increases overall load time, but you have one centralized place for all your variables and you know how they all relate to each other without having to dig through them.
I also would not have all these parts in one document. I like to make each document one student sized chunk of work. Generally we keep sub assemblies in individual documents, so we would have had the frame as one and the electronics as another. How you did it is fine, I am just sharing a little more personal preference here.
Overall, looks pretty nifty. I donāt like the cross beams next to the swerve modules as was pointed out earlier, but other than that itās a pretty sweet design. On the odo pods, people are allowed to find different solutions to problems that have already been solved once. That type of creativity should not be shot down as foolish. What works best for 6328 might not work best for 9312, and thatās OK!
Very cool design! How are the odometry wheels sprung into the ground? Iād be curious to see how they would hold up on the charge station and cable protector.
āOdometry podsā arenāt a new concept to FRC ā 1986 was playing on Einstein with them in 2017, before most FTC teams knew what a Gluten Free was. Theyāre usually under a different name on CD, usually involving the words āpassiveā and āomnisā
In fact, back when 254 was figuring out colsons vs. carpet grain, they themselves were using them but ditched after switching to nitrile.
