Most Expensive Part to Never Make a Robot

In the same vein as my other thread “Favorite Robot Concept that Never Made the Cut” I am curious what yall have blown your oh so precious robot budget on.

Embarrassingly for me it was a set of 40" drawer slides for an elevator in 2018 for my first elevator design. We got them in and went huh these are too heavy… Makes you wonder why i didn’t read the documentation. Regardless a great $200 plus $150 in shipping well spent.

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We cut out all the parts for a transverse climber but it was too heavy and we got a motor controlled mid rung Infinite Recharge type climber but it was also pretty heavy and didn’t fit well on our robot so we ended up making an everybot climber at competition.

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This part did end up making it on the robot, but it was way more expensive and difficult than it needed to be

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2590 tried using carbon-fiber tubes to support both their alliance partners during the endgame climb in 2018. The rigidity we found would have required four tubes to be under each robot, so eight total. Seemed to be getting out of hand. Decided to try out a folded sheet metal trapezoidal tube instead which ended up working. I don’t remember the exact price, but I think with the carbon fiber schedule we wanted and the stock lengths we needed to buy, each tube was around $100 dollars. That $~200 of tube we got for testing, which would have meant ~$800 for the final thing, didn’t make the cut.

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We bought a lot of redlines to create an 8 redline drivetrain in 2019…

Cries in Brushless

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Back a few seasons, when 3D printing wasn’t as prevalent as today…

SLS nylon mecanum wheels. 6" IIRC. Set of 4.
A season or two before that, 2" SLS metal mecanum wheels, for testing.

I’m not sure we ever sat down and did the cost accounting for the material…

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I think in 2016 1923 wanted to attempt to reach the climbing bar using something called Rolatube.

Essentially a 2in diameter composite tube that rolls up onto a spool. We actually used it one year in FTC for a climber (way over-built), but it ended up exceeding the single COTS part cost limit for FRC.

Obviously there are much more weight and cost effective solutions, but we thought it was cool and easy to implement at the time.

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HA! I was right about those. We were thinking they might have been cast for a bit. They were in my miscellaneous future robot parts bookscase. I’ll put in a pic if I find them.

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My dad has one of the 6" units, with the experimental roller designs, in the garage.

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Genuinely forgot redline even existed lmao

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@troy_dietz I was at my folks’ place today, and took these.

On a cost basis, one reason we never did check it was because we weren’t sure how to pro-rate, if at all. The deal was that you’d prorate based on what you could get as far as material (shop that did the printing was a sponsor). But, for an SLS machine where material is sold by weight, do you use a) the weight of the part, or b) the weight of the material required to make the part (which is about the size of the print volume of the machine)?

I’ll give you a clue: One of those numbers might actually have been low enough that we could make this work…

For anybody wondering: the little posts are for a sprocket. The textures on the rollers? Let’s just say we were getting “creative” with how to handle some things.

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I have to put this here, don’t I?

The cost of the aluminum alone would do the trick, not to mention the number of CIMs

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Oh man billet chassis always a good joke didnt think anyone ever modeled one up!

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I’m sure there were other times, but the one I remember best was all the polycarbonate tube and sheet and adhesives to build a ramp for a Power Up buddy climb. Quite a few hundreds of dollars, much of which wasn’t going to be usable for anything else later.

FWIW, the best adhesive for sheet polycarbonate from the home center doesn’t stick to polycarb versaframe - and makes it brittle, to boot. Fortunately, we figured out we didn’t have the weight budget before we started on round 3 of adhesives testing.

We have a custom chassis we design and cut out on our CNC router. The whole thing was cut out from 1 4’x4’ sheet of .08" aluminum.

Cut it all out and assembled it

That’s when I realize I didn’t do a drop center, I did a lifted center on accident

Scrapped an entire 4x4 sheet of aluminum

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Run it upside down?

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or if the design doesn’t allow for that Omni wheels on the corners and a slightly oversized center wheel

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SLS is a tricky one. I have used it a ton on robots since 2018. I have always costed it from the part weight. But its hard to use the straight part weight since no one runs them with 100% virgin powder (research purposes vary). Most of the time, people use 60-80% recycled powder in builds. Here is a little guy we will be testing more this off-season. Lots of area on the hub to do some generative design for light weighting.


-Ronnie

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In 2018 the team talked about being one of those cool ramp bots. We may have ordered 4 pneumatic cylinders for this - 2" bore with something like a 20" stroke. Close to $700 in cylinders that didn’t make it on the robot. Someday we’re going to need those for something. Someday.

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I feel stupid even remembering this, but not only did it not make the final robot, we were never supposed to have it manufactured. This was an old iteration of a part on our climber, and while the final version could’ve been made on a regular 3 axis, the CAD for this somehow got in the files we sent to out-sourcing, and it made the entire batch of parts go to a 5 axis.

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