Plastic VersaFrame Rigidity

How does the 2x1x.1 polycarbonate tubing Vex sells compare to 1/16th wall 6061-T6 aluminum 2x1? Is it stiff enough to use for frames and structural components?

Depends on what you’re using it for and how you’re using it. We bought some of this to play around with at the beginning of the season. Initially we were going to use it as cross-bracing for our robot frame, but as we finalized our shooter design it became impractical and we ended up using 1/8" thick aluminum tube instead (needed more rigidity on the wide face of it, and we had the weight to play with).

Honestly though, if you’re applying force on the narrow face or down the length of the tubing it’s probably fine for most structural applications. I don’t think I would build my drive base out of it (too much flex, and the potential for holes to wear out), but for manipulators, upper structure, and to some extent, frame support, it’s great.

The nice thing about using polycarbonate instead of aluminum is that it flexes but generally doesn’t permanently deform like aluminum (especially thin aluminum) does, so for anything that sticks outside of the robot or can otherwise take impacts it’s generally more durable.

If nothing else the stuff is fairly cheap, so it might be worth buying one to experiment with like we did. :wink:

We ended up using it because we made a fatal mistake in weight calculation. We used it to construct the less load bearing parts on our shooter (front and top bars), our Cheval/Portcullis arm manipulator, and the bar holding the winch for our climbing mechanism. All worked perfectly fine except the over the bumper arms*. When the inspectors at North Star noted that one of our hooks ever so slightly exceeded frame perimeter, we dremled a notch in the plastic bars so it’d hug the versaplanetary it previously just rested on.

Next match:
it immediately snapped in half upon its first use.

As we were already using a backup pair, I had to construct another one (thanks 2175 for letting me use your band saw so often)

If we had more time to reinforce structural integrity we definitely could have made it work, but a general rule of thumb that I would have moving forward is that it’s great for static parts that are well protected from high impact blows and don’t bear a lot of weight, but the moment you attach a piston to it or put it on a shaft for some motor actuation, there should be a little red flag going up. Shock impact is not its friend. Nor mine, for that matter.

*The design and start of fabrication for the arms was literally a few hours of me and another guy on my team thinking of the simplest and most weight effective way without having to change anything else about our bot’s design and previous over the bumper mounting system. Similar performance for a tenth of the weight.

Edit: Chris did bring up that it doesn’t deform like aluminum does, which would make it good for manipulation, but keepin mind and learn from our mistake that you don’t deform it enough beforehand.

Edit #2: be extra careful when drilling holes in it. Using a large bit (bearing holes, et al) can end badly if you go at all too fast. Chop chop there goes a nice hole. And without supporting the inside of the channel you may end up bending the channel as you press down on it. Avoid that by sticking fitted wood blocks in the channel. Deburring holes also comes with caution. Deburring the plastic channel unwaringly can result in unevenly removing plastic, resulting in a bumpy hole rather than a happy one. Go slowly and press very lightly on the channel.
Long story short just be extra cautious when working with it.