pic: Robot is coming together....

looks similar to ours, out of curiosity why the circle pockets? we always use triangles but never really thought about why.

I would assume it’s for ease of manufacturing. Taking an aluminum tube to a mill and cutting out a row of circles is a fairly simple procedure.

With limited CNC time our team uses circles. In addition with properly spaced out circles we could also put in several mount holes without disturbing the circular pattern.

I have never really been a fan of a lot of the triangles because most teams end up doing triangles that contain a lot of zero force members. Done right the truss looks great and performs well though.

if your intent is to lighten… then it makes no difference… if your intent is to make a structure with the minimum weight and a definable way of transfering energy (either from gravity or collision or something else…) then triangles are the way to go.

Both look good… but circles waste material when it comes to the transfer of energy (think straight lines…) Our design this year utilizes triangles to distribute the energy of a high speed collision through the entire robot… always putting our rivets in shear and not in tension along with putting our sheet aluminum in compression only.


We used circular holes to lighten the beam for the ease of manufacturing. Our team does not have a mill, all milling (which is generally very little) is done by our sponsors. Those beams were made by our team members who manually did it on a drill press.

For sure. Generally when we lighten our robot, we arbitrarily take out material in areas of low stress, but when we want to eliminate serious amounts of material and retain a LOT of strength, we have some of our more mathematically-inclined students and our resident structural engineer go to work. For example, our lifter from last year had to be strong enough to support 450 pounds of load (which it never used, sadly), yet still needed to be strong, so we did all of the stress analysis and turned the main support member into a truss, which I guess is two adjacent triangles.

As an old-time robot inspector, I think you need to check the bumper rules. It doesn’t look to me as if your numbers meet the 3/4 in. stroke requiremtent. Hate to be the bearer of bad news, but though you might want to know before you hit your first regional!