Bumpers (and West Coast Drive)

[Grim Tuesday]

Our team is looking into building a practice chassis; west coast drive style, based off of the 'universal chassis' by team 221. However, thinking about it, how do teams connect bumpers, as usually required by the manual to this frame? In the past, our team has always essentially clamped them onto out outer frame. However, with a WCD, you simply don't have an outer frame. How do teams who use it get their bumpers on? Do you have a raised superstructure?

Lets make this a more general thread: I've seen lots of interesting ways for teams to get bumpers on and off, and our team has experimented with a couple methods of attachment (our latest was wing nuts). What do other teams use? What works well?

Thanks in advance.

[Chris is me]

This year's bumper rules were great in that the manual only required supporting members every few inches. This let us mount bumpers with relatively simple brackets made out of tube stock, as shown here.



These probably weighed more than they needed to, but since they were so close to the ground they are one of the last parts one would need to lighten anyway.

[FrankJ]

To make the chassis complaint with 2011 rules you would need to build a perimeter frame around the chassis. Design your attachment points into the perimeter.

Last year we fabricated a C-Channel that slipped over the KOP simple chassis C-channel. The C-channel was bolted to the bumpers, holes drilled in the bumper C-channel to match the vertical holes in the chassis C-channel vertical holes. The bumpers where attached using Knob detent pins. (similar to grainger # 3JDC3). Bumper change in less than a minute. AndyMark sells a similar system.

[JesseK]

In 2009, the common thing to do with WCD drive trains was to add the brackets pictured in Chris's photo and then run a 1/2" square aluminum tube above it.

In 2010, this wasn't an issue since the bumper zone was so far above the wheel base.

In 2011, some WCD's still used the outer 1/2" rail, some used what Chris's photo has.

In the 2009 & 2011 cases, the bumpers were actually mounted to the 2x1" vertical supports.

[thefro526]

Originally Posted by FrankJ

To make the chassis complaint with 2011 rules you would need to build a perimeter frame around the chassis. Design your attachment points into the perimeter.

According to the 2011 rules, a full perimeter is not required for bumper mounting. The method Chris posted above is perfectly legal.

[EricH]

Originally Posted by thefro526

According to the 2011 rules, a full perimeter is not required for bumper mounting. The method Chris posted above is perfectly legal.

To add to that, the definition of frame perimeter does not require that the outer perimeter be solid material. If I had blocks sticking out each corner on a diagonal, the outer edges of those blocks define the frame perimeter. (Now, to attach bumpers, I'd need further blocks in the middle. But that's not counted in the definition of frame perimeter.)

Note, all the rules stuff is subject to change for next year. Therefore, after Kickoff, any answer given in this thread should be reviewed for compliance with the 2012 rules.

Regarding attachment, I've heard of rivets (drill the rivet out to change bumpers), blind nuts embedded in the back of the backing, quick-disconnect pins of various stripes, and various bracket systems. I've never had a problem with the blind nuts, except that on occasion they can fall out (a dab of glue when installing can do wonders for that) and depending on your robot's design, the bolt heads can be "fun" to get a wrench onto.

[George C]

We've had good success the past few years by using a T nut on the inside of the bumper board. To prevent them from falling/being pushed out, we fasten a short piece of 1/8 x 3/4 flat aluminum over the T nut using #4 x 3/4 wood screws on the inside of the bumper board. The aluminum flat has a clearance hole through it. A threaded post screws into that. The post has a 3/32 hole in the other end for a hairpin cotter pin (aka R pin). The post fits through a hole in the frame or bracket installed for the job. A bit of Loctite stops the post from loosening off but allows for some adjustment in and out.

[ajlapp]

Last year's rules allowed for a quite a gap.....we added some standoffs to the outside of the chassis rail.

Worked great.

SuperLight Chassis with bumper mounts

[Marc S.]

Check out 973's 2011 cad(link in signature). We used very simple 1/8" plates that went directly from the 2x1 frame to the bumper. Although they weren't attached to the bumper they still supported it and was a lot cleaner than the 1/2x1/2 tube we used in 2009.

[AdamHeard]

Originally Posted by Marc S.

Check out 973's 2011 cad(link in signature). We used very simple 1/8" plates that went directly from the 2x1 frame to the bumper. Although they weren't attached to the bumper they still supported it and was a lot cleaner than the 1/2x1/2 tube we used in 2009.

More importantly, it was a lot lighter and a lot less work.

[sdcantrell56]

Originally Posted by AdamHeard

More importantly, it was a lot lighter and a lot less work.

I always wondered if you and RC were going to get called out on those mounts. Based off of never having issues with them I'll definitely be adapting something like that if it fits with our design. Nothing simpler.

[AdamHeard]

Originally Posted by sdcantrell56

I always wondered if you and RC were going to get called out on those mounts. Based off of never having issues with them I'll definitely be adapting something like that if it fits with our design. Nothing simpler.

Called out? It met every requirement of the rules.

Visually they looked weak, but that's only to someone who can't do simple engineering calculations. Even factoring in possible buckling they could take over a thousand pounds of force per mount, and there were several per side.