How to build good bumpers

[Drew250]

Hey My team found a great site for 1/4" diameter, 2.50" grip length quick release pins! One-handed release should make for a quick bumper removal. (http://www.vlier.com/product_index/s...alllock-b.html)

[rich2202]

One other tip on making a bumper:

If the minimum height is 4" off the ground, then make your bumper 5" to allow for sagging of the noodles.

[GeeTwo]

Originally Posted by rich2202

One other tip on making a bumper:

If the minimum height is 4" off the ground, then make your bumper 5" to allow for sagging of the noodles.

How do you get an inch of noodle sag? We have never had as much as 1/4" of noodle sag, even before doing clamps and just pulling the fabric tight by hand.

IIRC, the more recent games (excepting 2015) have required bumpers to fit in the "bumper zone" between 2" and 10" above the floor. The bumpers are nominally 5" tall, giving 3" of design leeway. In 2014, when we were picking a big ball up over the bumpers, we went low. In 2013, when we did not have a frisbee pickup, we went a bit higher to reduce the chance of our bumpers and drive getting caught on a frisbee. IIRC, in 2012 (before I was directly involved on the team) we put the bumpers near the middle of the bumper zone as we intended to play defense. Unless you need to have 4+" of ground clearance, I don't know why you'd go to the top of the limits.

[rich2202]

Originally Posted by GeeTwo

How do you get an inch of noodle sag? We have never had as much as 1/4" of noodle sag, even before doing clamps and just pulling the fabric tight by hand.

I've seen a lot of sagging bumpers. If your wood ends exactly at 4'" (assuming the limit is 4"), I can guarantee you that some part of the noodle/covering will materially sag below 4". Especially after it has encountered another robot (or the wall) a few times.

As I recall, the noodles themselves are not stapled, or otherwise attached to the wood, so all that is holding up the noodles is the cloth. That cloth will loosen up.

[MrBasse]

Originally Posted by rich2202

I've seen a lot of sagging bumpers. If your wood ends exactly at 4'" (assuming the limit is 4"), I can guarantee you that some part of the noodle/covering will materially sag below 4". Especially after it has encountered another robot (or the wall) a few times.

As I recall, the noodles themselves are not stapled, or otherwise attached to the wood, so all that is holding up the noodles is the cloth. That cloth will loosen up.

I wouldn't guarantee that. Ours never have since we started focusing actual energy on our bumper design.

And properly attached cloth won't loosen up very much. If it did we would all have pants that fall off and baggy seat fabric in our cars and on our couches. Make them extra tight at first and any slop that develops will bring the bumpers to the place where you want them to be by competition time.

[Basel A]

Originally Posted by rich2202

I've seen a lot of sagging bumpers. If your wood ends exactly at 4'" (assuming the limit is 4"), I can guarantee you that some part of the noodle/covering will materially sag below 4". Especially after it has encountered another robot (or the wall) a few times.

As I recall, the noodles themselves are not stapled, or otherwise attached to the wood, so all that is holding up the noodles is the cloth. That cloth will loosen up.

A game update was applied in 2014 to allow the noodles to be attached. I would hope that the updated rule is applied in future games that have bumpers.

Originally Posted by Team UPDATE - 2014-02-11

To assist in applying the fabric covering, fasteners may be used to attach the pool noodles to the wood backing, so long as the cross section in Figure 4-8 is not significantly altered (e.g. tape compressing the pool noodles).

As such, my team had duct tape holding the noodles in place against the plywood. This eliminated concerns about noodle sag.

[pmangels17]

With regards to the backing material, I do have some expertise I'd like to share. I spent four summers (plus two high school years) working at a lumberyard, and I build a lot of stuff with wood at home too. Firstly, almost any plywood is going to be way more robust than any dimensional lumber or planking, because there are no grains. If at all possible, buy plywood, you will not regret it. Secondly, though the difference between S2S (sanded on two sides) and sheathing isn't huge, and both will work for your purposes, S2S ply is so much nicer to work with, it doesn't chip the way CDX or sheathing might, and overall it can be heavier and stronger if you get the god stuff.

Also, if you go to your local lumberyard and ask if they'd like to sponsor the team and donate the material:
1. There's a good chance that they will be willing to help you out, because...
2. They probably have scrap cuts leftover from homeowners who came in but didn't want a 4x8 sheet
3. Nobody wants to buy these cutoffs, so they tend to stack up
4. It's probably good stuff, because people (read: contractors) who buy CDX are doing sheeting work and buy in bulk or cut it on site, and homeowners who buy good furniture-grade wood in sizes that fit in their sedans, and leave the cutoffs behind