Bumper Material

[78Grimey78]

Hello CD, My team has come to the recognition that we want to start using the "Slicker" bumper material. The material when contacted with other bumpers will cause less friction, which is what our team wants. I know that team 971 The Spartans use it and I'm sure many other teams use it also. If you could just reply with the name of the material or the website that you get it from. Thanks!

[TheKeeg]

I know team 67 used a pleather (foe leather) material on their bumpers. Adam Freeman shared a link on another thread

http://www.joann.com/pleather/xprd757783.html

Thread: http://www.chiefdelphi.com/forums/sh...d.php?t=127938

They looked amazing.

[Cynette]

We've flipped the Cordura fabric and used what would be considered the back of the fabric as the front whenever we've wanted a slipperier surface.

[kevincrispie]

971 used a material called Ballistic Nylon this year, and it helped us enormously in getting out of friction pins. Our entire drivebase design, from the shape to the bumper material helped us evade defense and was a big reason why we were so successful.

Ballistic Nylon has a coefficient of friction of 0.3 on the normal Cordura, compared to a coefficient of friction of 0.5 of Cordura on Cordura. It terns out this difference is enough to get out of most pins. Our testing showed that we could drive out of pins even without an octagonal shape.

Many other teams have used low friction bumpers this season and in the past. 1678 and 1717 both used the Ballistic Nylon fabric this year. Other teams (and they will have to correct me if I get these fabrics wrong) include 1114 and 148 using sailcloth and 2056 using some kind of vinal. For championship, 254 decided to change from Cordura to sailcloth, and it really upped there performance. They were much harder to defend at championship than at SVR or on the practice field. Sailcloth has a coefficient of friction of 0.25 on Cordura, but tends to be more expensive that Ballistic Nylon. It is also less durable than Ballistic Nylon.

We also experimented with using Sailkote on our bumpers (Sailkote is a sail lubricant for those who don't know). This seems to only help significantly with the actual sail fabric, and take the coefficient of friction on Cordura down to 0.2 from 0.25. However, we'd likely need to get some sort of Q+A ruling to do that to be safe, as it becomes a user applied material to the fabric. We tried spraying it on Ballistic Nylon and it did not work well enough to justify the effort involved and the extra cost.

Some low friction materials are not as sturdy as Cordura, which is why we did not use them. We did stress testing on the Ballistic Nylon and found that it was about as strong as Cordura. Ballistic Nylon does wear, but not to the extent that it would not be considered a "smooth, rugged material" as specified in the manual. Materials like silk are slippery, but just fall apart during the rigors of FRC gameplay.

Also, a note on the pleather material that HOT uses: they would be better served to talk about this than me, but I was talking to Mike Schreiber at championships, and he mentioned that pleather is very slippery on Cordura, but gets stuck to field elements. The positive of these other materials is that generally doesn't happen.

There's been a lot of advancement in bumper materials over the last couple years, and it definitely makes a difference in on field performance.

Hope this helps.

[Adam Freeman]

Originally Posted by kevincrispie

Also, a note on the pleather material that HOT uses: they would be better served to talk about this than me, but I was talking to Mike Schreiber at championships, and he mentioned that pleather is very slippery on Cordura, but gets stuck to field elements. The positive of these other materials is that generally doesn't happen.

The Pleather was very slippery on the Cordura, but the combination of it's stickyness on the walls and the degraded appearance (stretching) after aggressive play, we will not be using it moving forward into 2015.

I am most hopeful to find the sail cloth material that 254 used, since it had a great appearance all through Champs, and was extremely slippery.

As Kevin mentioned, their Ballistics Nylon material also seemed like a great material that was very durable, good looking, and slippery.

I will say that I think the bumper material is really the icing on the cake to a properly designed drivetrain and driver training. Effective drive design for # of wheels, wheel type, track width, wheelbase, etc... are probably far more important than finding the very best bumper cover material. Even with the slippery material that we had this year, we had a drivetrain that was extremely succeptible to t-bones, side pins, being pushed off course, etc... We will be working this summer and next year to design a better drivetrain that can either get out of and/or make it harder for us to get stuck in these situations. I don't think we know exactly how to do this, but we have some ideas.

[Lil' Lavery]

How did the teams with alternate bumper material feel about their ability to defend (namely "friction pin") other teams?

[Adam Freeman]

Originally Posted by Lil' Lavery

How did the teams with alternate bumper material feel about their ability to defend (namely "friction pin") other teams?

Just as it was harder to lock us up, it was definitely harder to friction pin teams. We "tried" to play more of a positional defense on in-bounders and scorers to not let them get to their desired spot...but once they got around, we had a hard time holding.

It didn't effect us too much, since we were usually playing defense while waiting for the ball to advance or get scored, so we were only doing it to try and add time to cycles...not completely shut teams down.

My opinion (as a mostly offensive team) is the slippery bumper could help give that little edge to save a split second to get into position to score quickly. I subjectively feel they are more of a benefit to an offensive team, than a detriment to a defensive team.

If I wanted to build a defensive machine, I would stick with the Cordura. Cordura on Cordura seems to be like velco "hook and loop" on the field.

Just my $0.02

[XaulZan11]

Our bumper making team will not be happy when I suggest we make four sets of bumpers next year...

[kevincrispie]

Originally Posted by Lil' Lavery

How did the teams with alternate bumper material feel about their ability to defend (namely "friction pin") other teams?

Direct friction pinning is generally harder to do with lower friction bumpers, but we were still able to play effective, and in some cases more effective defense than we did last year. This was mainly due to the octagonal shape, as we we able to more easily get the front of our robot onto another robot and into a pinning position. We could also pivot and use the side of the drivetrain to block a robot from escaping.

One thing to consider for a defense robot is the opposing alliance's ability to play counter defense on it. It will actually be harder to play counter defense on a robot that has lower friction bumpers, so it isn't necessarily a bad idea to go all in on low friction bumpers. If you want to make a T-bone machine, go for the Cordura. However, there are things you can do with robot design that will make a lower friction bumper defensive robot just as or more effective than one with higher friction bumpers.

Though, to expand off of Adam's comments, a better bumper material won't be the difference between fielding a bad drivetrain and a good drivetrain. A lot of the teams doing it are chasing that last 1-5%. Making sure you prioritize drivetrain design is a better goal for most teams to focus on. That being said, it's probably easier to change you bumper material than it is to design a new drivetrain. It's just important to keep in mind there are many factors that go into building top notch drivetrains.

[Woolly]

Originally Posted by XaulZan11

Our bumper making team will not be happy when I suggest we make four sets of bumpers next year...

Well, if you're going to make 4 sets, why not make a 5th set that's just for display?

[Mike Marandola]

What about cordura on the front and back, and sailcloth or ballistic nylon on the sides? Best of both worlds.

[kevincrispie]

Originally Posted by Mike Marandola

What about cordura on the front and back, and sailcloth or ballistic nylon on the sides? Best of both worlds.

This is certainly possible, and something we considered (albeit very briefly) for this season. One issue is that the colors all the fabrics come in are quite different, so while you might get the desired functionality, the aesthetics of you bumper would arguably not be as good. We considered having higher friction material in the front of our robot to aid in ball pickup, but we tested our prototypes with lower friction material and it wasn't a problem.

Additionally, lower friction bumpers doesn't just help you get out of friction pins as the colloquial definition of a "friction pin" would dictate. Having a lower friction bumper material simply helps you avoid getting caught or slowed down on other robots and field elements, and this can be a benefit to not just avoiding pinning, but also to ensure better mobility around the field. As such, having lower friction bumpers on all sides of your robot.

To explain our reasoning, we realized that having ballistic nylon could limit our ability to pin other robots, but we felt that our defensive abilities were not limited to just pinning people. Our driver(s) and our drivetrains are far more versatile than that, and we have other defensive play in our playbook. Therefore, and costs were outweighed by the large benefits. This year, we still think we were able to play effective defense, and we didn't feel we were hurt by having lower friction bumpers.

[Michael Hill]

Why not use the recommended bumper material like everyone else? I'm surprised FIRST hasn't put the hammer down on the exact material that must be used (rather than recommended).

[AdamHeard]

Originally Posted by Michael Hill

Why not use the recommended bumper material like everyone else? I'm surprised FIRST hasn't put the hammer down on the exact material that must be used (rather than recommended).

They are following the rules EXACTLY. They are using rugged, smooth cloth.

Nothing wrong here at all.

[Abhishek R]

Originally Posted by Michael Hill

Why not use the recommended bumper material like everyone else? I'm surprised FIRST hasn't put the hammer down on the exact material that must be used (rather than recommended).

What's wrong with engineering better bumpers? If they feel their robot performs better with a different fabric, I don't see any major concerns because they still serve the same function: protecting the robot and other robots.