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.