Making Bumper Weight?

[Ian Curtis]

Last year, our robot was completely surrounded by standard bumpers. We built them to specification, with holes drilled in the 3/4" plywood to make weight. As of this Q&A (http://forums.usfirst.org/showthread.php?t=8343&highlight=holes+standard+bumper) that is no longer legal. Our bumpers are just as specified <R08> and cover the perimeter of the the robot base completely, with the addition of some embroidery fabric. They weigh a little bit more than 16 pounds. Has anyone else run into this problem?

[Manoel]

You guys gotta be using some dense plywood, we usually build our robots to the maximum dimensions and our bumpers never exceed 10-11 pounds!

[thefro526]

+1 on the dense plywood ours only weight like 10 or 11 lbs

[Fab.Master]

could also be the number or type of fasteners used

[EricH]

330's bumpers last year made weight, and they would be fully legal this year (other than having been on a previous robot and being fabricated items).

[jgannon]

Another vote here for 10 or 11 pounds... that's how I remember them weighing in last year, and we had a full set of bumpers for 28x38. Are you sure that's plywood you're using, and not 3/4" aluminum? ;)

[lukevanoort]

Another vote here for 10 or 11 pounds... that's how I remember them weighing in last year, and we had a full set of bumpers for 28x38. Are you sure that's plywood you're using, and not 3/4" aluminum? ;)
Or, say, rock maple or walnut plywood (I have never seen either of those in plywood form though... its kind of unfortunate, those would be some darn strong materials). Actually, it wouldn't surprise me if the plywood used was made of birch... while not as heavy as maple, it is a bit heavier than pine, for example (and I think it is used in boats, so it shouldn't be that hard to come by).

[GaryVoshol]

What kind of hardware are you using? I ran into weight problems one year when I used 1 x 1/8 angle to protect the edges. Now we are using 3/4 x 1/16 angle on the 5" ends, 1/2" on top and bottom edges.

If that doesn't help, the only thing I can suggest is to make one or more of the bumpers smaller. You'd have to eliminate about 8-10 linear inches, still covers far more than 2/3, and if done judicially would most likely give you the protection you desire. Good luck.

[MrForbes]

I guess we'll find out today...we are planning on using heavy hardware so it's easy to get the bumpers on and off quickly (bolt and nut, but they are big!), although only two bolts per bumper.

Also we are not planning on using the aluminum angle, because it's so much work to make all those parts and screw them on. Lots of staples will have to do....again...

Thanks for the reminder to check weight before we actually put them together!

[lancerbotics]

If we have read the rules correctly, as long as you are using the standard bumpers as they are diagrammed in the rules, they do not count against your weight or dimensions. Is this correct or are we totally off base?

[EricH]

If we have read the rules correctly, as long as you are using the standard bumpers as they are diagrammed in the rules, they do not count against your weight or dimensions. Is this correct or are we totally off base?
Correct...HOWEVER, they have their own weight restriction (15 lbs) and size (in the Bumper Zone, they can't extend more than a few inches from the robot).

[aapl.jlo]

I'd side with these guys, those are some heavy bumpers. Still, I would think that the more weight you could get at the bottom the better since we're going to be using robots that reach up high for the overdrive balls. Still I haven't read enough to know how heavy you can make them.

[Ian Curtis]

What kind of hardware are you using? I ran into weight problems one year when I used 1 x 1/8 angle to protect the edges. Now we are using 3/4 x 1/16 angle on the 5" ends, 1/2" on top and bottom edges.

If that doesn't help, the only thing I can suggest is to make one or more of the bumpers smaller. You'd have to eliminate about 8-10 linear inches, still covers far more than 2/3, and if done judicially would most likely give you the protection you desire. Good luck.

We're already using exclusively 1/16" angle. I'm not sure how they're attached, but in the past it's been with some decently sized bolts. We'll probably look into different plywood.

[Mr.G]

We are also overweight on our bumpers without even using the angle aluminum. I can't believe how much time we have wasted on these things, they came out nice, but are useless right now until we can get some weight out of them. I hope FIRST doesn't keep this mandatory bump rule for next year.

[Mike Schreiber]

I agree,I know they want to cut back on defense, but mandatory bumpers stunt creativity, and force a rectangular robot. They also make any design involving changing orientations really difficult. Personally I dislike bumpers, but rules are rules, and we'll just have to cope.

[Vikesrock]

I agree,I know they want to cut back on defense, but mandatory bumpers stunt creativity, and force a rectangular robot. They also make any design involving changing orientations really difficult. Personally I dislike bumpers, but rules are rules, and we'll just have to cope.

*looks at pictures of my team's robot*

Nope, definitely not rectangular. The only thing bumpers force in terms of shape is straight segments at least 6in. long for at least 2/3 of a projected external perimeter.

I will agree with you that changing orientations is far more difficult with bumpers.

[Rikit]

Weight issues here (Team 1912) too. I don't get it, we built them to the requirements and used standard 3/4" BC grade ply, standard pool noodles, fabric, very light weight alum angles, small screws, 4-sided (27x37) and came in at 17 lbs. A bunch of 1" lightening holes in the wood, trimming off excess fabric etc. and we are just now getting close to the 15 lb requirement.

Any help would be greatly appreciated!

RikiT-

[EricH]

Weight issues here (Team 1912) too. I don't get it, we built them to the requirements and used standard 3/4" BC grade ply, standard pool noodles, fabric, very light weight alum angles, small screws, 4-sided (27x37) and came in at 17 lbs. A bunch of 1" lightening holes in the wood, trimming off excess fabric etc. and we are just now getting close to the 15 lb requirement.

Any help would be greatly appreciated!

RikiT-You are also now in possession of a pair of non-standard bumpers, according to Q&A. They are not allowing any holes in the backing (other than for mounting hardware). Multiple people have asked.

Maybe just ditching the aluminum angles would work.

[MrForbes]

We used 3/4 plywood, medium weight cloth, pool noodles, and stapled on the cloth instead of using angle, 26 x 36 plus noodles in the corners, and they weigh about 12 pounds including a pound of hardware.

[Engineer]

That Q&A question was mine. We had to re-make the boards due to the answer. The wood shop teacher used a plywood that is birch with a maple surface (it think). It was much lighter than the standard stuff you get at the hardware store. I would say that our bumpers probably weigh in at 7-8Lbs. and our frame is 24.5 x 34.5 inches. Sorry I didn't see this earlier or I could ask what exactly it is and where you could get it, but by that time, it will be time to ship.

[Rikit]

Thanks all, we'll remake them with a lower density wood. I'd seen that Q&A response, just forgot to note it and mention that we're now taking a step back...

RikiT-

[Al Skierkiewicz]

I am betting that teams that are overweight are using steel angle instead of aluminum for backing the bumper or have attached mounting brackets to the bumper instead of the robot frame. Mounting brackets are weighed with the robot, not the bumper.

[GaryVoshol]

We've only got minimum length (2/3's) bumpers, and they weigh about 7-8 pounds. So a full set would be about 12 pounds. We're using 1/2" angle aluminum 1/16" thickness top and bottom. 3/4x1" 1/16 thick angle on the 5" vertical pieces, to make sure there is a good surface to take hits. I've seen inadequately protected boards from bumpers that were taken apart after the season, and they ain't pretty.

[Ian Curtis]

I am betting that teams that are overweight are using steel angle instead of aluminum for backing the bumper or have attached mounting brackets to the bumper instead of the robot frame. Mounting brackets are weighed with the robot, not the bumper.

We reweighed them with an industrial scale, accurate to .1 lbs, and got 14.6 lbs, so we're pretty sure we're safe. However, we used 1/2"x1/2"x1/16" aluminum angle, and mounted our brackets to the robot.

[jimbot]

Why don't you just take the front bumper off? All its going to do is hinder your arm movement. And besides, nobodys going to ram you in the front, unless they're going in full reverse. (Isn't that illeagal?) This method would reduce your bumper weight by a full 25%. Any reasons not to?

[jgannon]

Why don't you just take the front bumper off? All its going to do is hinder your arm movement. And besides, nobodys going to ram you in the front, unless they're going in full reverse.
Or, y'know, unless you'd actually want to run into somebody else.

[Ian Curtis]

Why don't you just take the front bumper off? All its going to do is hinder your arm movement. And besides, nobodys going to ram you in the front, unless they're going in full reverse. (Isn't that illeagal?) This method would reduce your bumper weight by a full 25%. Any reasons not to?

Yup. In 2006 we left our front unbumpered so we could pick up balls from the floor. We bent in at least 3 separate guards (each one beefier than its predecessor). Additionally, if our bumper gets in the way of the arm we have really big problems, big as in our arm is no longer attached to the robot. :ahh:

So bumpers are super super good.

[AdmiralAllen]

lol.........this is an interesting conversation......

we were never struck with even thinking about issues like this......
we covered our bot with the bare minimum....


we just built a frame strong enough that it dosen't matter if it had bumpers or NOT!

[DarkFlame145]

we just used some plywood and the pool noodles. Our heaviest bumper is like a little more then 3lbs