How to build good bumpers
 

I figured in light of Frank recently confirming the return of bumpers, I would see what other teams have done in the past that has worked, and maybe what has not worked regarding good bumpers. For 2014, 1073 used hinges , some c-channel, and a few pins that we could swap out fairly quickly. The only problem was that the hinges weren't all that great, and IIRC, they were constantly loose.

Re: How to build good bumpers
 

I know that either 1114 or 254 (I cant remember) uses a special low friction material to slide by opponents during pin-holds.

Re: How to build good bumpers
 

I believe 254 uses sailcloth or something similar.


The biggest thing with bumpers is to get the fabric nice and tight. What some teams will do is to staple (or otherwise secure) one side of the fabric, then have several people stretch it over the noodles and hold it while someone staples the other side down.

Re: How to build good bumpers
 

Tape your noodles in place before you wrap the bumper. This helps a lot in the assembly process and especially helps prevent sagging noodles.

Staple one side, then stretch the fabric as tight as you can before stapling the other side. Any amount of sag in the bumper is bad.

Remember that your bumpers can (by 2014 and previous rules) weigh up to 20 pounds, and there's no reason you can't make your structure that you use to mount the bumpers as beefy as you would like.

Re: How to build good bumpers
 

For reference, our standard set of plywood bumpers mounted with wood tee nuts weigh somewhere around 12 lbs, so there is a lot of room to grow.

Re: How to build good bumpers
 

The Lunatecs have recently made reversible bumpers out of thick fabric and velcro. Basically the red and blue fabric is sewn together on one side and then again in the middle. The free ends are then stapled to the backboard. Volia, you add velcro and you have a single set of bumpers that can be used for both (or all 3:eek:) alliances.

Re: How to build good bumpers
 

Another trick used to get the bumpers tight is to compress them before stapling. Some teams report using a custom device they made, but we just used our three large (10"?) c-clamps and a table top, and do one edge at a time.

Securing bumpers them with angle brackets works well, as long as you have an inch or more of bumper above the top of your frame perimeter. Mount two bolts to each side of the chassis facing up (should be easy with the KoP chassis; just use the holes already there), drop the bumpers over the robot into place, and secure with a second nut on each bolt. (Wing nuts or power nut driver recommended). Rivet nuts mounted in the frame and (captive?) bolts passing through the bumper's brackets could probably also be used for this, but we haven't tried it.

Re: How to build good bumpers
 

This^

It's more work during the build, but it is so worth it at competitions.

You will need a heavy duty sewing machine to work with the sailcloth.

Re: How to build good bumpers
 

Totally agree with reversible bumpers. Why have a quick change bumper when you can just flip the color around even faster.

https://www.youtube.com/watch?v=XYTiRxLw7oA

Re: How to build good bumpers
 

By the 2014 rules (and specifically the Q&A), pre-compressing your bumper noodles as you assemble them isn't legal. I'll find the actual rule after work, but I remember this being shown / proposed in a CD thread in 2014 and a Q&A ruling came in declaring it illegal. Sorry for the vagueness.

Re: How to build good bumpers
 

Team 74 did the same thing in 2014. It was pretty convienient at competitions.

Re: How to build good bumpers
 

In my mind the reversible bumpers and bumper covers teams have produced in the past never looks as "polished" as separate well made bumper sets. The key to good looking bumpers? Pick quality materials (plywood, noodles, and fabric) and take your time.

Re: How to build good bumpers
 

Yes. Plywood. Get the good, sanded both sides stuff, not the sheathing grade that is rough. It's only a few dollars more.

In 2014, someone decided hardwood planks (oak or maple, I think) would be suitable. They ended up splitting along the grain in several places.

Re: How to build good bumpers
 

From 2014:
Please note that while previous answers like this may provide guidance on the general thinking towards a rule area, unless/until it's asked for this season, there is no official ruling that applies for this year. Which means you may or may not be flagged for it by an inspector if it's not crystal clear in the rules/q&a for this year.

Re: How to build good bumpers
 

Sure, separate sets may look a little better than reversible bumpers (and everything looks better than bumper covers!), but honestly, the convenience factor more than makes up for any slight visual difference between them, assuming they are both well made.

A few years back we had a huge issue with our state championship and teams bumpers. With only 30 teams at the event, you were queueing after only being in your pit for about 10 minutes. Teams with separate bumper sets had a lot of trouble making that turn around time... And let's face it, you want to spend that time on robot improvements, not changing your bumpers!. Good reversible bumpers look good and can be changed by one person in under a minute while standing in the queueing line. You just can't beat that!

Re: How to build good bumpers
 

Why used sanded material when the other material works just as well and you'll be covering it up? That's like using high polished material when you plan on painting it anyway. Price difference is small ($19.18 vs $26.58) but I just don't see the point, does smooth plywood hold staples better than rough plywood?

And I think the rules have specified plywood for as long as I've been making bumpers, so hardwood shouldn't even be considered anyway. Plywood will take an impact better due to the crossing grain structure over hardwood, the results of hardwood would be exactly what you stated.

Re: How to build good bumpers
 

Solid wood became legal in 2013 or 2014. A typical 1x6 is perfectly legal and effective bumper material and teams don't even have to cut it to width. (bumper heights are +-0.5“). We used 1x6s in 2014 and didn't have any splitting problems. We played at 2 regionals, champs, and 5 off season events, plus demonstrations and we haven't broke any wood and our 2014 drive train had a lot of power behind it. We also used the full 20lbs for our bumpers each set weighed over 19.5lbs, with a sheet metal frame covering the top edge and 1/8" aluminum L on bottom edge.

Re: How to build good bumpers
 

Just like you would design a component of your robot, design your bumpers to be quick change.

This is a requirement on 2826 for bumpers. 1 or 2 people need to be able to replace the bumpers in 1 min.

This requirement can be met several ways and reversible is one of them but I have yet to find a set of reversible bumpers that I would be willing to put on 2826's robot.

Re: How to build good bumpers
 

There will be more than twice the usual number of teams at events this year who will need help with bumpers: rookies last year didn't need bumpers, after all.

Hmm, 6" bumper height is much desired in some cases, IMO. I'll have to look into this.

Re: How to build good bumpers
 

They will be 5.5" since a 1x6 is actually (3/4" x 5 1/2")

From the 2014 manual
Also when talking about compressing the noodles.

Re: How to build good bumpers
 

I agree, we used reversible bumpers in 2014, and they were an absolute blessing. We rarely even needed to take our bumpers off, so being able to switch colors in 30 seconds in queue gave us one less thing to worry about. Definitely would recommend.

Re: How to build good bumpers
 

I was not referring to compressing the noodles so much that they would be undersized when the clamps were released, just enough to simplify installation by not having to pull the cloth tight while stapling (1/8" to 1/4"). After the clamps are removed, there is no way to tell that they had been compressed.

I agree; we did reversible bumpers one year (2013?), and we never did get rid of the last bits of Velcro showing and several matches (especially when we were strongly defended) a corner or two pulled loose. The tensioning trick can also be used for reversible bumpers; just be sure not to staple the loose end down!

Re: How to build good bumpers
 

I definitely agree that making nice-looking bumpers reversible is harder... although perhaps even then they wouldn't be quite up to 2826 standards.

There are some teams that put the time in to make them look pretty good though... I was very happy with how our reversible 2014 bumpers turned out, although they do require a separate right and left bumper to enable the reversing (the 'reversing fold' on each side is vertical, not the more common horizontal).

Re: How to build good bumpers
 

For 2012-2014, 225 used a homemade bumper cover attached by velcro. It wasn't always the prettiest (especially in 2014 when holes got poked through the cordura almost every competition), but it made for quick color changes and wasn't too intensive to make. I'd advocate making a cover for many lower-resource teams and only dealing with one set of bumpers, that way not a lot of time needs to go into designing and building the mounting system (and you can just use steel angle or something else heavy you can easily acquire from the hardware store).

If we were making bumpers today--I would build 2 sets, primarily to make sure we could set them as low to the ground as possible. I'd also use ballistic nylon or sailcloth for the sides instead of cordura, maybe the front and back as well.

Re: How to build good bumpers
 

There is nothing more frustrating that having to futz with bumpers at a competition.

Thoughts.

1. Baltic birch plywood. Not cheap 5 ply wood from the home center.
2. Corners cut at 45 degree angles transmit impact loads better than 90 degrees, all things equal.
3. Use sheet metal corner brackets on the outside of corners. Simpson A23 or equivalent work well.
4. Use a large diameter bit (e.g., 1") to cut recess holes for hardware that extends beyond the plane of the chassis, so that you don't have to have perfect alignment of the hardware/holes. Don't put so many holes that it impairs the integrity of the plywood -- that's what the inspector will be looking for.
5. Use a pneumatic stapler.
6. Pay attention to minimum clearance between ground and bottom of bumper. In 2014 this was 2". You will want to allow a bit of sag in the fabric so don't put the backing plywood right at 2".
7. Many fabric stores carry a polyester gabardine that is suitable for bumper use. Make sure that the fabric you select doesn't have any stretch to it.
8. Pay attention to color. There are often swatches of red and blue fabric in the kit of parts. It's not an aesthetic decision -- you want your bumpers to look like everyone else's. Don't send Grandma* to the fabric store to "get some red fabric."

RockyWoods has the 1000D Cordura in a coated version for $12 a yard. "Red" and "Royal Blue" are the colors.

* or Grandpa

Re: How to build good bumpers
 

If well made bumper covers can look nice.

https://frc2175.smugmug.com/2013/201...SC04358-X3.jpg
https://frc2175.smugmug.com/2013/201...SC04340-X3.jpg

Though if proper thought is put into changing and making bumpers (and robot geometry easily allows) I would almost always choose two separate sets of bumpers.

Re: How to build good bumpers
 

Here's where I take a moment to brag. 1712 has used bumper covers every season where red/blue bumpers were mandatory. In general, I'd agree that our covers (blue) looked less professional than the actual (red) bumpers.

However, in 2013, we took a slightly different approach and ended up with, as described by another team, the "best bumpers in MAR." Instead of 1 cover that stretches around all 4 bumper segments, we made our bumpers symmetrical (2 red and 2 blue), and had a reversible cover. The result looked terrific, and largely held up to a very rough game.

Re: How to build good bumpers
 

My team has always had issues with our material. I saw the post earlier about buying material from rockywoods, and I was wondering what other places people buy their material from?
Thanks!

Re: How to build good bumpers
 

Aesthetics is not the issue. The plywood that is sanded on both sides is generally made from a larger number of thinner and better quality wood than the lower grade, un-sanded, rougher plywood. The cheaper, rougher plywood tends to have more voids in it. Often, these voids, especially those on inner layers, are discovered to be in critical locations after the pieces are cut.

My personal (empirical) experience is that the better grades of plywood do hold fasteners (staples, nails, screws) better. I also find it nicer to work with since it splinters much less when cut. For the ultimate, use Baltic birch like MrRoboSteve.

Re: How to build good bumpers
 

We have used MDF instead of plywood successfully in 2014 just to get a bit more weight down low. You just have to be aware that small screws can strip out the hole if not careful.

Re: How to build good bumpers
 

This is the requirement 1648 uses in our bumper designs as well. Our bumpers since 2012 have all looked nice and take very little time and effort to mount properly. We make wrap-around bumpers and mounted such that one would only undo a few wing nuts, and then lift the bumper up by hand. Couple of examples: 2014, 2013

We typically use a plywood backing and tape the noodles to the board. We connect the boards for each side and use small cut up noodles to fill the gap, and then we put the cloth around the entire bumper, stapling and cutting to minimize sag.

Re: How to build good bumpers
 

I've bought 1000D Cordura off eBay before. Was able to get it for about $8 per yard (60" wide). The blue came in fine but the red smelled really bad for some reason. Once we let it air out it was all okay.

Re: How to build good bumpers
 

In that case it isn't a few bucks more. Cheap S2S plywood is still just standard 5 ply only smooth. From what it sounds like you are describing, it would be almost double the cost.

In my opinion, bumpers are a waste of Baltic birch plywood. Utilitarian items don't need furniture grade material when sheathing does just fine.

Re: How to build good bumpers
 

You can create a great bumper with a sheet of CDX plywood, no question.

Quality AC sanded pine plywood from a reputable mill is a good alternative. The price difference between that and a sheet of C3 birch plywood like this one has been small enough that I usually take the birch plywood, which is nicer to work with. For example, the Menards web site is showing 3/4" thin veneer birch plywood at a lower price than a 3/4" AC sanded pine sheet -- both about $40. That's enough plywood for two sets of bumpers, with plenty to spare. Of course, we'd have to see whether that pricing held up when you got to the store, but you get the idea.

I've also had issues with mediocre glue in lower grades of plywood from the home center. Finally, the thinner veneer holds staples better.

Re: How to build good bumpers
 

We have had trouble getting numbers to stick to Cordura.
Does your team use paint or stick-on numbers?

If you use stick-on numbers, are they sticky or iron on?

Also, where do you buy your numbers?

Dave
Team 2976

Re: How to build good bumpers
 

Find a local graphics business that can cut vinyl and heat press for you or even look into embroidery (think custom t-shirt shop). Vinyl will be cheap, and that is how we do ours. My classroom has all the equipment so we usually only spend about $4 and an hour of labor. Our material runs about $1.25 per foot and is 15 inches wide.

I would expect that you get get the service donated and pay material cost and be around the same. I would guess less than $30 to pay for a cut and press of eight sets of numbers.

Re: How to build good bumpers
 

OK, I guess it is time to weigh in here...
In 2014 I decided to test the rules since so many teams had problems making good bumpers. I gave the rules, the cloth, plywood cut to size and a stapler to a couple of freshmen and two moms who wanted to help. I gave them no further instruction except to make them look like bumpers from previous years. They did a marvelous job. They stapled to one edge as proposed above, inserted the noodles (without fasteners or tape), stretch the fabric and then had the students lean on the back as the fabric was stapled. That little bit of squeeze does not change the dimension but does get the fabric tight.
As to why compression was not allowed, we know from experience that the full dimension of the noodle gives the best reaction to a robot to robot hit. Remember that round, hex and star shapes have been allowed in the past. It is the dimension that is important. The rules were modified to allow dimension lumber ("solid, robust wood") to make it easier for teams that have issues obtaining plywood. We just know that plywood backed up by robot frame with 2.5" pool noodles give the best protection. Having been around at a time when robot hits could put a team out of competition due to frame failure, bumpers help keep teams playing as long as they are able.

Re: How to build good bumpers
 

Yes, Baltic birch is a waste for bumpers. I have not seen or used plywood that is sanded on both sides that does not have the same number of plys as the rough stuff. My preference is to use the plywood that is sanded on both sides AND had more layers than the un-sanded plywood. It looks like one of us is comparing apples to oranges and the other is comparing pears to oranges.

Re: How to build good bumpers
 

We have used iron-on bumper numbers in 2013 and 2014. The first few were pretty tricky to apply but after we got familiar with the pressure and time needed from the iron, they turned out great. In 2013 we got the numbers from the company that included a sample in the KOP, and in 2014 we got them from Andymark. I will try to find links when I get home.

Re: How to build good bumpers
 

For our cloth we usually go with:

http://www.robopromo.net/product_p/rp_fb.htm

They sell reversible bumpers and we have never had any issues with them. The reversible bit makes it a LOT easier and quicker at competition.

Re: How to build good bumpers
 

We paint on our numbers using a stencil we make each year. That way our numbers are always in our font. We may be going with the vinyl and press route this year however assuming we can get bumpers built in time to do it.

Re: How to build good bumpers
 

Integral to the good bumpers is a good mounting system. Bumpers must be secure, and simple to mount/remove.

We have always struggled with this, what are others doing?

Re: How to build good bumpers
 

These things:

http://www.mcmaster.com/#standard-qu...e-pins/=zg9mm4

They are SOOO worth the investment. I really hope any new bumper rules allow us to continue using them.

Re: How to build good bumpers
 

Let's talk about on-field performance for a second. I'm getting a vibe that some people in this thread dabble (or more) in carpentry.

From match to match at competition, will the more expensive lumber be more likely, less likely, or about as likely to:

1. Prevent internal robot damage as the cheaper stuff?
2. Cause fewer structural integrity maintenance issues as the cheaper stuff?
3. Cause fewer cosmetic maintenance issues as the cheaper stuff?
4. Require different tools to deal with a different type of wood than the cheaper stuff?
5. Be as readily available to teams who realize at competition they want to replace it or build bumper for others with it, like the cheaper stuff is?

Same questions, but comparing heavier to lighter lumbers?

Re: How to build good bumpers
 

Plywood probably does the best job of spreading impact loads, because it's less likely to break than dimension lumber. Strandboard and MDF (particle board) will be the worst due to fastener issues.

I would put quality plywood in the first rank, dimension lumber in the second, and strandboard and MDF in a distant third. Plywood is best because it has grain in two directions. Dimension lumber is good, but hard impacts to the ends can cause dimension lumber to split along the grain, and the impact of that can vary from a minor problem to wrecking your bumper attachment mechanism.

Strandboard and MDF will have trouble with impacts on the edges, and have poor fastener holding, particularly through collisions. Strandboard is a sliver factory.

Fastening fabric via staples to the edge of strandboard could be an issue. Otherwise should not be a difference.

No meaningful difference in woodworking methods.

11 ply 3/4" birch plywood with a poplar core is probably the least commonly available. That said, you can get it at Menards so it's not like it's tough to get. 3/4" plywood, strandboard, MDF, and dimension lumber are all available at any home center.

if I was planning ahead, I'd rip 5" x 96" lengths of plywood in our shop, as it's much easier on the big table saw than at a competition. That size is more convenient to load into a trailer with our pit than a 4' x 8' sheet of plywood, as we need the walls free to tie down our load.

Re: How to build good bumpers
 

How do you use these to attach bumpers? Do you orient them vertically (which is basically like what I suggested but with a pin rather than a bolt), horizontally parallel to the bumper, or horizontally through/into the wood of the bumper? Do you use the receptacles, retaining caps, or just holes in your chassis to catch the sear balls?

Unfortunately, those would constitute manufactured parts, at least the past few years. It would be lovely to be able to bring a nice supply of these and (similarly manufactured) 15.5" wide strips of red and blue cloth to provide for teams whose bumpers are not up to spec (or nonexistent). Cutting a 1x6" down to 5" in a pit sounds a lot more feasible than cutting a 5" strip from a sheet of plywood.

Re: How to build good bumpers
 

I'd be interested to know how you'd fit a 96" bumper on your robot while still following all the bumper mounting and support rules. (Other than in 2015, that is.)

I would rather suspect it'd be counted as "trim for transport", which does not automatically render it a manufactured part.

Re: How to build good bumpers
 

Perhaps in an "excess of caution", 3946 has considered any cuts that we'd made other than directly across a piece of stock, whether wood, aluminum, wire, or tubing (and that, if it was to a specific length) in a part prior to the competition event to to constitute a manufactured part. Where is this "trim for transport" rule? I've searched the 2015 rules, and this phrase does not appear. All occurrences of "transport" refer to "TRANSPORT CONFIGURATION" or transportation of the robot to the venue. The only occurrence of "trim" concerns the input leads of motors, servos, and solenoids. I don't plan to search for "for".

The way we understand the rule, we'd have to pre-cut to (perhaps) 5 7/8" before competition, then cut down to 5" and to length during competition in order for a bumper segment not to count as a "manufactured part". Doable, but less than ideal.

Re: How to build good bumpers
 

It's an interpretation of a rule--but it's obsolete*. (My bad on that one.)

On the other hand... it needs some revisiting (Frank et. all, if you're reading this...). I believe that your cutting to 5 7/8" would also cause that plywood to be counted as a Fabricated Item, and that would naturally cause some problems. This would also apply to stock aluminum, PVC, and pretty much anything else that is in a different dimension than it came from the supplier. (So... anybody want to see how unsafe transporting large plywood scraps into the venue is? No? Anybody want to enforce that rule? Yeah. Right.)


*There used to be a third category of material in addition to COTS and Fabricated. "Raw" material referred to material as it came from the supplier, with just enough cuts to get it into a more transportable form--e.g. cutting an aluminum tube to two 10' pieces instead of one 20' one--which many places will do anyway--or ripping plywood in half.

Re: How to build good bumpers
 

We've used them in the past by attaching via angle on the backs of the bumpers and then slotting that into spacers on the chassis. If I can find time tomorrow then I'll try to take a picture and upload it.

Re: How to build good bumpers
 

I would definitly say that's "excess of caution". Also to clear things up you are allowed to reuse bumpers and build them any time you want or at least you could in 2014.

Re: How to build good bumpers
 

Piggybacking on this (assuming it stays the same for this upcoming season!), it's important to note that the rules in 2014 made it pretty clear that bumpers were not part of the robot, but rather were required to be attached to every robot. This means that pre-cutting parts to make bumpers for other teams at an event would NOT count towards your withholding (assuming we have withholding again), as those parts are not intended for repair or upgrade of a robot.

2015 R17:
So please, being as much precut bumper wood, cloth, and noodles as you want!

Re: How to build good bumpers
 

Yeah, since it's not part of the robot it escapes the fabricated part rules.

You would not need to walk far into the pit at a competition to find items that are normally sold "by the foot" (e.g., extrusion, wire) being treated as COTS items for purpose of the withholding calculation. Updating rules to reflect this commonly accepted practice would be an improvement, IMO.

Re: How to build good bumpers
 

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)

Re: How to build good bumpers
 

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.

Re: How to build good bumpers
 

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.

Re: How to build good bumpers
 

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.

Re: How to build good bumpers
 

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.

Re: How to build good bumpers
 

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.

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

Re: How to build good bumpers
 

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

Re: How to build good bumpers
 

If you're looking for simple start-to-finish instructions on how to construct bumpers, check out our "Bumper School" video series. Here's the link:

http://www.robopromo.com/category_s/1825.htm

I also saw some talk about different kinds of bumper materials to use. We have a video for that too. Link below:

https://www.youtube.com/watch?v=ZEGSTCd6G3w

Re: How to build good bumpers
 

I'm with MrBasse. We still have some linear segments of our Aerial Assault bumpers, and they are still so tight that you can't pull the pool noodles out of the end without a real concern that the noodle will tear rather than slide. We had several matches where we were double-teamed as we did full-court runs because our alliance partners could not pick up or even reliably herd a ball down field. We had nothing but the fabric (stapled to the wood) holding the noodles in place. We have signs of fabric wear, but no loosening that would allow the noodles to visibly sag when viewed from the side.

Re: How to build good bumpers
 

I have a secret for newbies and veterans alike.
When you are attaching the fabric, staple one side first starting the middle and working out to the ends. When you pull tight to attach the second side, have a student or two, press down on the back of the bumper to compress the noodle a little (1/4" or less). Even if you don't get the fabric tight, when you release the bumper, the noodles will naturally push back on the fabric and tighten everything up.

Please read the robot rules carefully, the bumper rules do change from season to season dependent on game.

Re: How to build good bumpers
 

R21 c introduces an element teams may overlook in building their bumpers.

"C. use a stacked pair of approximately 2 ½ in. round, petal, or hex “pool noodles” (solid or hollow) as the BUMPER cushion material (see Figure 4-7). All pool noodles used on a ROBOT must be the same diameter, cross-section, and density (e.g. all round hollow or all hex solid). Cushion material may extend up to 2 ½ in. beyond the end of the plywood (see Figure 4-8). To assist in applying the fabric covering, soft fasteners may be used to attach the pool noodles to the wood backing, so long as the cross section in Figure 4-7 is not significantly altered (e.g. tape compressing the pool noodles) All pool noodles used on a ROBOT must be the same in order to maintain the desired interaction between ROBOTs in the cases of BUMPER-to-BUMPER contact. BUMPERS containing pool noodles of vastly different construction may cause a “ramp” effect when interacting with other BUMPERS." (emphasis mine)

The requirement that bumpers contain pool noodles of uniform physical shape and characteristics is a departure from prior years. As the KOP contained solid round noodles, teams using them will need to acquire more solid round noodles to comply with R21 c. Use of a mixture of solid and hollow noodles would appear to contravene this rule.

Re: How to build good bumpers
 

This allows veteran teams to use the solid noodles that they have on hand from the 2015 game doesn't it?

Re: How to build good bumpers
 

Sure does. Just thinking this is easy to overlook and, at this time of year, is likely to require an online purchase for many teams.

Re: How to build good bumpers
 

I noticed this as new, too. Inspection could get interesting, as good bumpers have the pool noodles completely hidden between cloth and wood by a combination of stitches and staples. My guess is that the inspectors will check every few inches of each noodle with a "thumb test" similar to "kicking the tires" as a rough, informal way to check tire pressure on car/truck tires. Just in case, bring your stapler and sewing machine to competition!