BOM lists [these](Ultra-Thin Ball Bearing, Steel Ring, Open, for 2-1/2" Shaft Diameter, 1/4" Wide McMaster-Carr) McMaster bearing part numbers, but they seem rather pricey. Did you use them just because of their cad existence, but actually buy cheaper ones?
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Correct, just the McMaster model. We sourced those bearings from ThriftyBot, they’re also available from WCP (WCP-1503), both for much more reasonable prices.
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- Why are there two different enums for the wanted and current superstates?
The idea is that you can process a wanted state and compare it to the current state of the system and thus make a decision to transfer to some intermediate state if necessary. Not sure if we really used this functionality though.
- Why do you guys take in the RobotContainer when constructing the Superstructure class?
Looks like we used it last year to access our operator dashboard.
- What are the naming conventions for each action (e.g. some functions are the same as the enum name, others say handle[enum name], others say are[condition], etc.)
We did not really maintain a strict naming convention. Methods starting with ‘are’ return booleans for action checks. Methods that are the same as the enum name or handle are typically the methods that actually do the actions necessary for that state.
- What is the path from button to action (from what I can tell it’s button > superstructure check > actual state > action)
Yup
- What benefits you guys found doing state machine rather than normal cb
Readability - in 2023 we had these mega sequences of commands that were bound to each button and it was doable but inefficient to follow what was going on and debug. We like the way this compartmentalizes things better. We could have achieved the same robot functionality with cb.
Hopefully we will be releasing the 2025 code soon - stay tuned for that
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hello! these parts imported without a number in the cad. I was wondering what these were/where I could procure/make them.
Thank you!
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Looking forward to it!
In the meantime, we are planning to put our completed subsystems on the base this weekend and wire it all up. We’ve been running the base getting new programmers up to speed, with the support of 2 new remote mentors from PNW.
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dang that color scheme looks fantastic on those parts! excited to see this bot compete behind the 359 bumpers
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The part number for those screws is REV-21-2805. From REV robotics.
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We just about finished everything (sponsor panels and bumpers last).
Thanks for all of the quick responses we had about this robot. There are many intricacies to making this robot, and the previous experiences definitely helped make this happen.
Now on to testing things out, programming with new student leads (with 2 remote mentors and a former student at WPI), and practice for the next 3 months before 3 events in 4 weeks. We did not have a Java mentor since switching to it in 2022. Chezy Champs would have been great to attend with 2910, but last year we weren’t ready and feel that we needed more time with a lot of new students. Our new operator just finished 7th grade.
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Amazing work on the 2025 robot and thanks for sharing the CAD and tech binder in such detail.
We’re currently running a cable carrier (drag chain) setup for our extension mechanism similar to yours but face serious durability issue, almost everytime we run the extension, our drag chain got snapped and cause massive repair to reattach or restring the wires.
We suspect this may be related to the wire gauge or flexibility. Would you be willing to share what gauge wires (and wire types, if possible) you run inside your drag chain for the wrist and intake?
Any tips would be hugely appreciated!
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We used 14 gauge space saver wires from McMaster for the power wires inside the cable chain.
It’s very important that the wires in the cable chain are the correct length such that they are not preloading the chain in tension. We have also talked about (but have never actually implemented) putting a string inside the cable chain that is anchored at both ends to ensure the chain links don’t see tension.
What cable chain are you using? All cable chain is definitely not created equally.
We used igus 045-20-018. We were moderately happy it with it. We’re considering giving E2C-10-20-018 a try. Seems like it is more heavy duty despite being almost as compact.
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Was this made in onshape or solidworks?
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Hi Patrick, thank you so much for sharing these details.
We’re from China, hence we metric-ized the entire robot. The cable chain is some 10-20 sized, radius 18 product. We also thought about using a string to share the load inside the chain, but found it somewhat difficult to implement cleanly.
Right now, our main issue is that the extension drive cable and the cable chain tend to fail together after just a few motion cycles. Based on our observations, it seems like the cable chain itself shouldn’t fail unless the string does first — which makes me wonder: is it possible that the real root cause is how the string is tensioned.
Would love to hear your thoughts on that.
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We use Autodesk Inventor for CAD. Once we exploded the view we used Adobe to convert it to an eps file, to print it large on our Mimaki printer.
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If the cascade string breaks than the cable chain will likely break immediately. We found that the extension string we were using increased in length considerably (probably about 3/4") until it was fully broken in. Some of this if from the knots getting tighter. When bringing up the arm we found it was important to tension the cascade stings often initially. If the cascade stings go slack they can get off of the pulleys and abrade on the bearings block edges. We used sand paper strips to floss the holes that the string goes through in the 3X3 tube and stage-0 front bearing blocks. In operation the sting does not move through those holes, but when tensioning it is pulled across them. Having those edges rounded helps a lot with the tensioning.
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Thanks! We will have a try. It is a pain to repair this arm ngl.
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Yeah agreed, the arm definitely has some failure modes that take a while to repair. This is why we always had a complete spare ready to use at competition. The entire arm is designed to be swapped very quicky. We are able to swap the arm in under 10 minutes comfortably.
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Patrick, same here!
At Champs this year, our belt snapped in match 10. Luckily we won, and had to go back on the field in match 12 against the #1 seed. We were able to swap it all out just in time.
Easier to swap first then repair.
As for pre stretching the rope, not sure how you folks do yours. We stretch ours using two adjacent mills vices. Afterwards, it still stretches when we first break it in and run it, so we do one more adjustment, then all good.
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