Would it be ill-advised to use Rev 2x1 max tube light for the outer square frame of a swerve robot? 29x29" frame. The light max tube has a wall thickness of ~1mm. Or is it advisable to use the thicker max tube?
1 mm is approximately 1/2 of 1/16, and that’s the thinnest I would go. So yeah, I’d consider 1mm too thin.
I think it depends on how you build your bumpers and what other structure you have in the area. If you build strong bumpers with little to no bumper gaps, you will be safe from impacts. (by strong bumpers, I mean that you should be able to jump up and down on your frames without any damage and little flex. I use 15+ ply birch or okume plywood and reinforced box jointed corners) With a nearly full size (and presumably nearly full weight) robot, I would be perfectly happy using thin wall, but only if you more structure. For example, the main tubes of our drivebase are flush with the bottom of our bumpers. On top of those tubes, we have one or more tubes running across the middle of the bot for supporting the battery and larger mechanisms. At the top of the frame we have another set of tubes at the frame perimeter flush with the top of bumpers. Using this type of more complex frame we have run robots with thin wall or polycarbonate tubes.
Please use thicker than 1mm tube.
A few reasons why:
- you want low COG anyways in this game
- high speed collisions may be dampened by the bumpers, but not entirely and that will go to the tube in some capacity. Over the course of a season this will cause some fatigue.
- ultimately your chassis is structural, and you always want to teach your team to consider a safety factor just like they would designing something for an engineering project (over design for damage)
- no one wants to replace their chassis frame mid season if it does get damaged or pinched (but you’d possibly have to since it could move your swerves out of alignment with a big enough hit)
Because you’ve mentioned swerve modules, there’s no way to avoid the tubes being used for a structural purpose and depending on which modules you have, there might not be a ton of connection points between the modules and the tube. This is why despite that Patricks comments are reasonable I would hesitate to say go all in on the 1mm tube.
As mentioned above, 1/16th or 0.1 tube are both great alternatives.
If you are planning on going over the cable guard I would use a thicker wall. Last year we used 1/16 wall and had to reinforce the swerve modules due to bending.
Like said before, unless you foresee a weight problem, use thicker. This year we are using 1/8 wall in our chassis for the first time in 15 years!
IIRC the thin wall max tube is comparable to 1/16" tube in terms of strength. However, you may see the tubes sustain damage over the course of the season, which is a pain to repain. I would suggest 1/8" wall tube as a baseline for the weight down low and greatly increased strength.
what caused that? Looks like that hole was used as a bearing seat maybe, which isn’t relevant to my use case with the SDS modules.
It’s relevant to any drive base taking a hard hit, which is what tore the shaft out of the tube.
The failure occurred during the semi-finals of our first event of 2016. The same robot made it through 4 more events with the only change being swapping out the 0.062" wall thickness longitudinal frame rails for 0.125" wall thickness tube of the same alloy.
It’s your robot. Do you feel lucky?