TTB Swerve Discussion

As far as I can tell there’s nothing stopping you from replacing the NEO with a Falcon or any other CIM class motor, though it doesn’t seem like there’s enough space to replace the VP with one

1640 Has run a swerve module based on a SDS design with 3d printed wheel supports and main steering pulley. The wheel module has not failed through testing last fall, 1 competition and driving last spring and summer. They are printed from 24$ a roll PETG. Expensive and harder to print nylon CF is not needed. The main concern with the TTB module is the barriers this year. They went with a 3" wheel. We use a 4" wheel. There is a big difference in the contact point on the barrier from 3 to 4. Before committing to a printed wheel module this year we tested the printed parts by running a fully weighted robot over the barrier repeatedly at 12 - 14 FPS. This is violent with a 4" wheel. A 3" wheel concerns me. Your entire robot needs to be tough to take this abuse. TTB do the destructive testing and show everyone. Our programmer put the robot on the center barrier cross and did a full speed spin for about 1 minute before the robot wiring failed - not the printed parts. The other concern and needs testing is robot to robot impacts. In our district comp in finales, we saw very aggressive defense played on us and our robot took repetitive high speed impacts. The swerve module took it. We did have to use nylon CF for the driven pulley of the CVT. It has held up. So don’t dismiss printed high stress - impact 3d printed parts. Designed properly they can have a place on the robot. However, test, test, test. If the 3" wheels do not cut it on the barrier, then I would not pick this swerve. It would be best if a team does not have to fear the barriers. Our module used 2 Neo’s. After, we came out of lock down the module was redesigned for a neo550. 6 - 48 and 11 to 60 reduction on steering. The neo 550’s are fine.

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Seems weird to me that there’s so much critique about this product wrt the specific 2020 field. I’d imagine COTS products are generally designed for a median game, which doesn’t usually involve such drastic shock loads directly to the module. Nor do I see TTB ever saying that running full speed into the rendezvous was a design consideration for this, as I think most would agree it’s an atypical requirement compared to drivetrains for most other games.

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There have been similar field features in 2019 (ball corrals) and 2016 (secret passage). And obviously there’s also more blatant terrain features in some games as well (2019 platforms, 2018 parking platform, 2016 defenses, 2012 bridges, etc). Even most “flat” fields have some sort of structure or wire shielding or elevated marking that isn’t coplanar with the floor. This is something I’ve learned the hard way back in 2005, where even just the simple triangles placed on the field to mark loading areas shifted the balance of our omnidirectional drive enough to cause traction issues with the wheels that had less normal force on them. I’d argue that truly flat fields are the exception to the rule, and being able to drive over bumps in the field would be a median challenge for drivetrain consideration.

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Just because this thread was created to compare COTS swerve options:
(Do not take my affiliation with any party as any sort of motivation, I am doing my best to be impartial)

Well said Mike, but of course there is more.

Teens screw up things and break them. Mentors screws up things and break them. NASA has screwed up things and broken them and is probally making loads of mistakes today, that is part of the process. S**t happens. The “cost” to run anything is far more than greenbacks.

  • How much does it cost if when you screw up any of these (modules)?
  • What is likely to break? Do yo need to buy from the supplier or can you make it in house?
  • Are things likely to break in the context of FRC standard game design?
  • What about a crazy FRC (drivetrain) design requirements? Is that crazy requirement supported in the context of the COTS item? Could you modify it if not?

All these COTS options provide is a different end to a mean. Some are cheaper for some teams to maintain than others based off of financial, time, expertise, and other considerations. Not every team has the specific mix of resources to maintain certain systems. If I was to start a team today, from a shop standpoint I am providing (in order): basic hand tools (powered and not), a solid workbench/vise, drill press, belt/disk sander, the best 3D printer I can afford for the team, small lathe (primary for trimming shafts), [a long list of other things], (near the end of the list) full CNC milling capabilities.

Competition is good for the consumer here (While those in the market to sell these modules may have a different viewpoint as it may contribute to their daughter’s college fund).

Furthermore, it is nice to see a novel design enter the space again. Don’t get me wrong, copying a design for personal use and learning its ins and outs is an excellent exercise. But there have been a lot of “Team X presents such-and-such-swerve” and it is all the same design under the hood, (it may be that is what the team needs based off their mix of resources). But there is more than one way to skin a cat. Some design is ubiquitous FOR VERY GOOD REASON. But engineering challenges do not work well when EVERYTHING is ubiquitous, it’s not really an engineering challenge then is it? Verity is the spice of life. And yes I am aware that another COTS solution here doesn’t necessarily help the verity argument from all points of reference, but if there is a community out there using COTS components as inspiration or as a benchmark for their own designs a greater pool of COTS solutions gets people thinking.

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I think our experience could be relevant to this discussion.

Here is the module we used this year:
https://www.chiefdelphi.com/t/team-2471-2020-hermes-swerve-module/367416

It uses a 3d printed 3" wheel and 3d printed forks. We were fairly happy with the module over all, we did have some reliability issues though.

We had a couple of forks lose their tip below the wheel shaft bolt hole. This was only on practice bot forks that were accidentally printed with default infill. (Edit: This also didn’t seem to keep the module from working. We would usually notice when we flipped the bot to work on the electronics)

We also had one instance of bevel gears skipping and wearing down, but I believe the module was assembled with the wrong spacer.

The biggest issue we had with the design was that the bolts would loosen in their heat set inserts.

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Huh. looks like the baby between the thrifty swerve module and the SDS module (don’t ask me how that timeline works, it’s probably best not to think about swerve modules having babies)

EDIT: …and don’t tell @Ryan_Dognaux and @PatrickW about the Mean Machine module lovechild, something tells me they would not approve of their modules “seeing eachother” XD

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This is a fair point. I’ve adjusted the price on both the main module and 3D print at home module kits. #ForTheBrand

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I guess sometimes the bot needs to become thriftier.

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I guess Finn isn’t going to college :frowning:

What’s bad for Finn is good for the teams!

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He had to sell his house but he is still dropping prices, what a king.

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Whoops…

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JK it’s all good, I edited the html

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SimpleVillainousAmericanavocet-size_restricted

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I think the point being made here is that for $20 more* (before the price drop) you could have a full metal module that’s been tested in comp. Is $80 across the robot worth the peace of mind? absofreakingloutley (edit: worth it to me. Your opinion may vary, but keep in mind that’s ~1/3 the cost of a single match)

With the price drop that’s now ~$300 saved, which is likely more of a push for low resource teams (they shouldn’t be doing swerve anyway if that’s a significant portion of their budget but I digress).

*ignoring whatever VP stuff you already may have, but I have issues with that argument as now you have 4 less VPs to use on the robot… The very position a team looking to save money would likely to be in.

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Let’s not forget about WCP - WCP SS Swerve with an all-in cost of $547 (775pro, victorspx+CANcoder, Neo+SparkMax). Not to mention its #einsteintested! Probably a more apples to apples comparison than the AM swerve and steer and still a price crusher.

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otherwise known as over-engineering based on conjecture

Let’s say I’m going to buy a plane.
Plane A has a known safety factor of 1.3 thanks to continual development and testing.
Plane B has an unknown safety factor, likely in the range of 1.1 to 1.4, and is ~7% less expensive than Plane A. Perfectly adequate for the task for all we know.
I plan to use this plane for several flights over a long period of time and don’t want to preform as regular inspections and maintenance.

Which you choose is up to you, but that’s not “over-engineering based on conjecture”, that’s engineering: the choice itself.

Peace of mind in FRC and the real world gets other people off your back and lightens your conscience if something fails, but if your team values its limited monetary resources more than that the choice is obvious.

To be clear, I’m not knocking TTB swerve, it just seems that people are quick to misinterpret intentions and values of other people and teams.

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@Ryan_Dognaux, @Mark_Wasserman - do you think it would be possible to modify the TTB module to use a dead axle? You’d have to modify the wheels to hold the bearings, bevel gear, and a spacer, but it seems to me like there would be room. I’m thinking a dead axle would be even stronger than a live axle (since it ties the two sides of the fork together), but feel free to convince me otherwise.

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