Bumper Attachment Design

[gwin99]

Has anyone used these? I figure it might make the whole process easier, and they aren't all that much more expensive than buying the fabric for two sets of bumpers: http://www.robopromo.net/product_p/rp_fb.htm
Also, if we do end up going the reversible-route, what kind of attachments should we go with? Does anyone have some close up renders / CAD / pictures of a solid design they'd reccomend? If we went the reversible route I obviously wouldn't be using my current design with pins and such...

[MrBasse]

Here is a simple CAD view of our bumper mounts. It is just 1/8" steel that is screwed to the bumpers with 5/8" wood screws. The holes are 1/4" and the ends have a hole in the middle that is drilled and tapped to 1/4-20. On the sides the holes are drilled through the frame and bolted using a 1/2" 1/4-20 bolt and lock nut.

We used velcro our first year of reversible bumpers, and it drove me nuts. Between the velcro not holding together or pulling through the stitching that held it to the fabric, I swore never again. Elastic is so fast and so easy, I can't see any better way of doing it anymore. I have heard the robopromo fabric pieces are nice, and they do save a few headaches too.

[gwin99]

And are those rail things done on a cnc? If not, how'd you machine them?

[MrBasse]

Originally Posted by gwin99

And are those rail things done on a cnc? If not, how'd you machine them?

No CNC, I wish we had access. We had to go old school. We made them with a ruler, a piece of 3/4x1/8 steel strap, a marker, a drill, a grinder, and a MIG welder. It was tough to make them identical, but we got it close.

[Al Skierkiewicz]

I need to remind everyone here that while it is good to talk about designs, rules do change from year to year. I caution you to wait until the game is revealed before locking into a design.
That being said, I tell teams that you should never depend on the attachment hardware to be the mechanical basis for your bumper design. Many teams that use the attachments you show in the drawings above, have considered the forces involved in robot to robot interaction and designed the mounting such that bumper forces transfer to the frame through contact with the frame not through the hardware. In your first render for instance, if the brackets were such that the frame held the brackets in place and the hardware just kept it from falling off, that is a good design. In the third render, it appears that just gravity and the hardware keeps everything in place. If the other robot bumper system is lower than yours, the resulting force will force the bumper up and off the frame, leaving you with a bumper dragging behind you or left on the field.
As far as reversible bumpers go, I think they are a good idea when designed properly. I have said many time before, if you go to great lengths to make a beautiful robot, why would you put bumper covers that sag, drag on the floor, open and show the opposite color, etc. I am a proponent for bumper covers that do not have parts that sag outside of the bumper zone.