How do you support your Vex arm towers?

Hey guys! I’m working on a Vex robot design and as I was mounting the supports for the arm I’m using, it occured to me that there are probably several non-obvious ways to support the vertical metal pieces you need to support a Vex arm on a chassis. So I have a few questions that would be best answered with picture examples. How do you guys mount your arm supports to a Vex chassis? I’ve done it two ways before: Standoffs (like the Protobot arm, good for short arms only), or by bolting C-Channel to each chassis rail, possibly putting on two more with standoffs, effectively making two towers. I was going to use the latter method, but since I’m trying to make my robot as light as possible so it can gear the drive more aggressively for speed, I don’t think it’s the ideal solution. So how do you guys mount arm supports to your chassis anyway? Pictures would be awesome!


Triangles are your friend. For our Clean Sweep robots, we one piece of chassis right angle down to our frame attached my a 2 hole piece of bar stock bent at a right angle. We made another triangle off of that onto the back of the robot using slotted angle, perpendicular to the first triangle, again attached to the frame by a 2 hole right angle piece. I don’t think we have any pictures, but as I find them, I’ll post them. In terms of structure, this is about as stable as it can get with minimal parts.

I’ve always just got away with the ‘chassis’ pieces forming an H kinda shape - two pieces per side (4 total), as I normally need to put something in between them, and something running perpendicular to the chassis pieces, have one in front of me right now, very little flex in it. Will try and take a photo if I can find my camera.

agree with the triangles
even the skinny 1 x 25 are A LOT better than nothing
when we first built our catapult, it had no support, it pretty much destroyed itself when we tried to reload it, but after we added the 1 x 25’s, they made a HUGE difference
another one is have more vertical bars that is on the outside of the one you have, and have another bar bolting them all together
it works too but it packs alot of access weight
if you dont get what im saying, i could sketch up a few paint pics for you

I’m also curious as to how you mount your arm tower pieces, etc.

oh, just normally with nuts and bolts :wink:
sometimes the triangle with the 1x25 piece isnt exactly the hypotneuse
so its not exactly 90 degrees
but that doesnt affect it THAT much…

Basically, where do you attach the vertical pieces, as well as the angled ones for support?

I usually attach vertical pieces directly to the chassis similar to this design that 677 used. By mounting the main towers like this the angled supports can easily be mounted down to the chassis as well. it requires them to be bent the thickness of one piece of vex metal or the use of some washers to space the support off the chassis but it is a really nice option.

I am a huge fan of using 1-25 for supports, they don’t even have to be that long although it won’t hurt too much weight-wise to make them a bit longer. I used some short bars to support the main arm on my tennis ball tosser. [


On a related note, it looks like in one of those pictures the shaft holding the arm in place is cantilevered. Is this okay? I’ve always supported the shaft on both sides if possible, or ran a continuous shaft between two supports and two arm pieces - can you get away with just one like that?

It depends on weight and how far from supports it is. Obviously having a shaft double supported is better but that is also weight added to your bot so see what you can get away with.


If you can’t afford the space/weight to fully support the shaft on both sides, one can put a bearing block on standoffs and run the shaft through it.