Cheap C-channels for prototyping

Hi, I’m wondering if there’s a way to get a cheap c-channels for prototyping purposes? For example maybe cardboard or plastic ones etc that are very cheap so we don’t feel guilty cutting and trashing them.

The reason is even though we tried to measure carefully (NOTE: we still can’t do CAD yet, sadly…), we still sometimes need to cut the channels just for the sake of testing our ideas/prototypes, and unfortunately it so far leads to trashed parts when the prototype doesn’t work…

Thanks

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Things we’ve done prototyping with in the past:

  • Cutting appropriately-sized sections of cardboard from a box & using brads to hold them together while still allowing movement
  • Vex steel pieces (because we ended up with a lot in our first year before starting to only purchase aluminum and we rarely use much of the steel in the competition robot)
  • Vex IQ pieces (because we started in IQ and had them available)

Maybe you could purchase inexpensive lumber and cut it into more rigid pieces?

Hopefully you’re already doing this, but make sure you cut as little as you can get away with when you put your prototypes together! For instance, leave a long shaft long and just let it stick off to the side or leave the tower or arms sticking out of 18" in a prototype, since you know you can cut those later. Also, piece together multiple smaller excess pieces to create the appropriate size for your prototype if possible (even if you’ll want a nicer piece once you know it works).

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We tried cardboard but it’s rather hard to make them into C channels

As for using lumber: do you mean just use as solid blocks? (ie. not shaped like C channels). I’m not sure if that will work in most of the cases… But I guess we can try for some parts.

Thanks

I strongly suggest you use some type of CAD software to do prototyping. Once you get the hang of it, it’s usually much quicker than building an actual robot and it really lets you play around with things that you might want to do in the future but don’t exactly have the parts yet (like modeling transmissions or something). I personally use Inventor.

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how does one learn to use inventor @rakibsta got it and have bean playing around with it for a few months but i can whip up an iq prototype five times over before i figure out how to make l chanel exzist in inventor is it just trial and error in your case did u have a mentor or did u watch a utuber do it first?

Watch videos on YouTube. I’m pretty sure there is a series on there specifically for vex parts that goes through cutting metal and creating imates.

PS it’s on Autodesk inventor

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i know im not that dum thank u @64540A

Bad Idea Alert: just 3-D print C-channels! The files already exist, so you’d just need to import and print!

/s

That is an awful idea because filament to make these C-channels would most likely (I haven’t run The numbers) be more expensive than just buying more C channels. Plus there’s the time factor of printing.

So that this post isn’t altogether useless (apart from the mild comic relief), I’ll actually say something useful.

In my experience, I usually have enough parts that I can find or marry together enough parts to accomplish what I need to. But, as exact resource management seems to be in play here, CAD is a very powerful tool to use. It allows you to avoid wasting shop time prototyping and rather spend the time efficiently building.

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As the others have mentioned, CAD software is a powerful tool. It may seem daunting at first, but you get the hang of it over time.

It’s also generally a good idea to base your design around standardized parts, e.g. C-channels with holes in multiples of 5 and/or to compromise for prototypes (eg making an oversized robot).

If you REALLY, REALLY wanted, and have access to to a drill press, you can buy aluminum C-channel stock for about 15$ per 8ft from McMaster (shipping costs are going to be a nightmare though) and you’ll probablly still end up buying VEX C-channels because competition-legal.

You’re correct in that it’s a bad idea, but for the wrong reason. I worked out a 2x35 hole C-channel to cost about $0.53 in PLA and $0.44 in ABS.
(Volume of a 2x35 hole c-channel is 21.22cm³, density of PLA is ~1.25g/cm³, density of ABS is ~1.04g/cm³, and 1kg of filament is about $20)

The real reason it’s a bad idea is due to the resulting part having layers perpendicular to the face of the C-channel, which can easily shear apart. I printed some as a joke and they broke withing a week of being thrown around. I suppose you could reinforce the model with ribs, but it’d still be susceptible to shearing. And there’s also the need for a 3D printer to 3D print stuff.

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