HDPE or ICE FLOOR
 

I've been around for a while and I know quite a bit of FIRST history. I was wondering if this years game had a ice or HDPE floor. What wheels would you use: tread, wheel diameter and why? Also, would teams move away from omni's because too much traction wouldn't be that BIG of deal like the past couple years. Imput would be great.

Preseason Preparation, the game hints always make me curious. :yikes::confused::ahh:

Re: HDPE or ICE FLOOR
 

Surface area really is useless on HDPE, so your wheel width doesn't matter.

I want to say red linatex was the tread type that worked best on the HDPE in 2003.

Re: HDPE or ICE FLOOR
 

Anybody ever tried Mecanums on HDPE? :yikes:

Re: HDPE or ICE FLOOR
 

Link for it, i found some random sites?

Re: HDPE or ICE FLOOR
 

I don't think so. Mecanums became popular after 2004, when HDPE last made its appearance in a game.

Then again, it's possible...

Re: HDPE or ICE FLOOR
 

FN Sheppard
Brecoflex

Re: HDPE or ICE FLOOR
 

Ice skates, you'll be able to outrun all the other teams.

Re: HDPE or ICE FLOOR
 

I would use some sort of gummy or rubber (like soft rubber) wheels.

(hey you never know with those type of wheels you might be able to do burnouts on HDPE)

Re: HDPE or ICE FLOOR
 

Saw blades.


Isn't that what Bond's car used in Die another Day to get traction on the ice? Q knows how its done.

Re: HDPE or ICE FLOOR
 

Whats HDPE?

Re: HDPE or ICE FLOOR
 

Okay... I really like the saw blade idea, and will always cast my ballot in Q's camp. But I doubt they'd make it through tech.

So although my fellow Canadians may strip me of my citizenship for letting out this little piece of information, nothing grips ice quite like broomball shoes. Bet you didn't even know broomball was a sport. (Well, aside from those of you in the other snowy bits of the world.) Mind you, from my experience a key aspect of broomball involves beverages that would be out of place at an FRC competition.... so my impression of the outstanding grip of broomball shoes may be... um... imprecise... at best.

On the other hand, Moon Boots (http://www.moon-boots.com/) also had very good grip on the ice. I had a pair back in the 80's that not only kept my toes warm in -40 but almost never slipped. Of course, I doubt the ones they make now would be nearly as good. I'm getting old enough to start to be grumpy that way. :P

Now someone just needs to wrap them around a set of AM or IFI traction wheels and the ice races are on!

Jason

P.S. HDPE = High Density PolyEthylene. Not so different from what 4L milk jugs (I guess gallon jugs for most of the CD community) are made from. A relatively low-fiction polymer (plastic) with almost a waxy finish, usually (but certainly not always) white in colour. It has a longer molecular chain than the Low Density Polyethylene in the milk jugs, and a higher tensile strength, but has a similar feel to it.

Re: HDPE or ICE FLOOR
 

HDPE stands for High-Density Polyethylene. It is a hard plastic used for all sorts of things.

As mentioned in this thread FIRST has previously used ramps made of HDPE as obstacles. The diffuser panel for the 2007 light box was a sheet of HDPE if your team still has that sitting around the shop.

Re: HDPE or ICE FLOOR
 

I would probably say ice is not a possibility, for two reasons.
First, maintenance between matches would be annoying. Zambonis?
Second, not all venues are capable of doing that. Also because of this, most off-season events wouldn't happen.

Re: HDPE or ICE FLOOR
 

Broomball... Like Curling?

Also, take some thick sheet metal, curv it around kitbot wheels, and sharpen them so that they are like ice blade "blades". Maybe even for braking you can make them slide sideways and kick up all that ice...:D

....except they would prolly go with HDPE:ahh:

Re: HDPE or ICE FLOOR
 

conveyor belts for traction,

luckily we are only miles from g&t conveyor systems (they make airline baggage handeling things)

Re: HDPE or ICE FLOOR
 

We certainly know the idea has been floating around in the GDC's heads for a few years:


http://www.chiefdelphi.com/media/photos/22422
:p

Re: HDPE or ICE FLOOR
 

Oh man, talk about putting images in my head!!

Most of all, I keep seeing Dave's "Boot-Drive" robot that keeps showing up in his game animations. Every year a drive train like that hit's our design considerations process. Every year we laugh, then move on to more serious concepts. Maybe this year we will consider it a bit more seriously. Hey, take a look at the new Vex leg wheels. It makes you really think:rolleyes:

Re: HDPE or ICE FLOOR
 

Except played with a ball instead of a stone?

Re: HDPE or ICE FLOOR
 

Ahhhh....that explains the first part of Game Hint #2!

Re: HDPE or ICE FLOOR
 

More like hockey played with brooms and a nice big ball (say, a little smaller than a playground ball). Oh, and you don't wear ice skates. The groups I've played with used street shoes. Evidently, that isn't the only way to do it.

Re: HDPE or ICE FLOOR
 

Like I said earlier, surface area doesn't matter.

HDPE and ice are as close as possible to an "ideal" surface from a physics standpoint. The reason surface area might matter on carpet is because the tread can interlock with the carpet.

On ice or HDPE the surface is totally slick, so there is no possible way for the tread to interlock with the HDPE, and thus surface area does not matter, only coefficient of friction and normal force.

Re: HDPE or ICE FLOOR
 

HDPE is what milk jugs are made of. We have made several robots out of HDPE. Very easy to work with and we keep lots of it on hand. Very strong and durable.

Re: HDPE or ICE FLOOR
 

For the stack attack game, we found that McMaster-Carr Grip all neoprene rubber had very good traction on HDPE. Our problem was that it gripped to well on carpet (4" wide wheel). If we had less width and more power than the drill motors it would have worked well.

Re: HDPE or ICE FLOOR
 

the conveyor belts they make are for moving bags around an airport, they are a like tiny little plastic plates with rubber tread on them, were you thinking like timing belt kinda thing?

Re: HDPE or ICE FLOOR
 

Traction is directly related to frictional force. Force = mu * N, where mu is the coefficient of friction and N is the normal force (force directed directly away from a surface that something with friction is on). Notice the lack of area in that equation? Yep, there's a reason for that. Namely, surface area doesn't matter.

There's been discussion of this issue already, some years ago. Look it up.

And, the only way to increase mu is to increase the coefficient of friction. You can a) change materials or b) dig one material into the other. If you try doing b) to an HDPE section of the field, I'll call a rules violation, assuming there is a "no damaging the field" rule again.

Re: HDPE or ICE FLOOR
 

i know, i think ive read that......

i was thinking treads becuase i felt they would give the most stable platform on a slick surface

really its either that or wheels, and i dont think they would make the entire floor HDPE.........

Re: HDPE or ICE FLOOR
 

Ah, stability? Again, not determined by surface area. It's determined by some other things, like CG and wheelbase.

Let's say you have a rectangular robot at max dimensions, with the wheels (or treads) a little bit inside the max. It looks like this:
_________________
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That's the wheelbase as seen from the top. As long as you keep your CG above that area, you won't tip. As soon as the CG goes outside that area, you've got a split second to get it back before the big crash. If you have treads, you'll still have the same area.

Re: HDPE or ICE FLOOR
 

ah, wheelbase(couldent think of the word for it) thats what i meant......

i never implied that they were going to be wider than a wheel..............

there like this
http://www.chiefdelphi.com/media/photos/28106

except flat

Re: HDPE or ICE FLOOR
 

Erich - Don't forget to remind your audience that inertia exists, and that it makes a moving robot do things that a stationary robot would not (like tip over even if the CoG is within its wheelbase)...

Re: HDPE or ICE FLOOR
 

Oh, Newton's first law?:p

That is true, especially if there's a sudden stop or change of angle involved. See, in physics (and in Statics), you can usually get a really, really good approximation of forces and how they'll react with each other by finding the CG and having all the forces act from that, unless you're dead sure that the force acts elsewhere (like friction, which gets as close as it can to the floor, or an impact from another robot, which should be within the bumper zone).

If you've got a robot traveling at constant speed, the only forces acting on it are weight, the normal force (cancels out the weight), friction (applied to the wheels) and whatever force you need to maintain equilibrium (applied to the wheels). Now, a sudden stop! The force needed to maintain equilibrium has been effectively distributed through the robot, and there is a sudden forward force at the CG (for simplicity--there's a rule saying I can move it there, I just forget which one) and a reverse force on the lower section of the frame. This creates a moment, causing the robot to rotate forwards. If a corrective force is not applied, the robot continues to rotate and goes splat. This effect is not helped if the CG is high, as there is now a much bigger "lever" for the forward force to act on, and it takes much more force to stop due to the way moment is calculated.

Re: HDPE or ICE FLOOR
 

This isn't _entirely_ true. In an ideal physics world, yes, but there are cases where surface area is proportional (or inversely proportional) to grip.

-Racing cars have very large, wide tires (even though this increases unsprung weight) because it means that if the tire hits an imperfection in the track, it doesn't lose grip. Since the track is always imperfect, this has the effect of effectively very slightly raising the car's coefficient of friction (although the ideal rubber-on-ashphalt coefficient remains the same)
-Skates have very little surface area because it takes a lot of pressure at the skate-ice interface to create the microscopic layer of ice that the skate glides on.

Likewise, I'm not sure the rubber-on-carpet case is a cut-and-dry Ff = uFn case. It might be like Velcro: if you have two big sheets together, it is much harder to pull one off sideways than if you have two small sheets together. Despite the normal force being the same, it takes much more force to move the two sheets relative to each other when there is more surface area in contact.

There have probably been some teams that have done tests, it would be interesting to see the results.

Re: HDPE or ICE FLOOR
 

If they do a mostly-HDPE field, I think we'll see alot more tank tread attempts for drive trains this year. The successful ones will have the right tread pattern.

However, I suspect that if we see any HDPE, it will only be on part of the field, or a small field element. That stuff isn't exactly the cheapest material around...

Re: HDPE or ICE FLOOR
 

Sort of true. However, your Velcro analogy isn't exactly a wise one. Velcro is designed to lock together. It's designed not to move in any direction. The more locks you have on a door, the harder it is to open, right? The same for Velcro. Rubber on carpet isn't designed that way, and neither is rubber on HDPE. And, with velcro, if it's on some smooth surface, it won't stick. There's a piece of HDPE in every field box because of this fact.

Skates are designed to create semi-frictionless motion (or to use friction to create that!). They need to melt the ice and have it immediately re-freeze. Ever wonder why ice is considered frictionless?

As for the racing car analogy, that's more the right track, but you're still off. I'll link to a thread shortly that will help. (There's also a quote from the spotlights--"A drag racer can have all the output torque in the world, but it does no good on ice."--Paul Copioli) I also remember reading that the wide tires are actually to dissipate heat.

http://www.chiefdelphi.com/forums/sh...surfa ce+area
This thread is the most recent in a series asking if you get more traction (aka friction) for a wider wheel. If you want to argue that with Copioli and Baker, go right ahead. Oh, and Baker and the TechnoKats did tests on tank treads vs. wheels. See linked thread.

Re: HDPE or ICE FLOOR
 

Note that my response was entirely in response to what I quoted, and was admittedly off-topic in an HPDE thread. You said "surface area doesn't matter" in a paragraph that didn't make any mention of HPDE, giving the impression you were referring to all traction-related cases. Hence my giving of examples where surface area DOES matter.

I was just pointing out examples where the frictional forces between two surfaces was decided by phenomena beyond Ff = u*Fn.

And they found that even on a slippery surface like HPDE, surface area makes a (very slight) difference. On a surface like a carpet where interlocking between wheel rubber and the surface will be more likely, I'll bet that relationship is greater. However, since this thread is about HPDE, I'll stop posting and we can keep discussing via PM if you want.

The message I'm trying to drive home is: Designing by idealized physics equations is not always the best approach. There are cases where it isn't. Use them as very strong suggestions, but do some empirical tests to see if other factors come into play as well.

Re: HDPE or ICE FLOOR
 

It's not, according to Baker and 45. It's about the same. And the gains there are lost elsewhere (same source).

You're right, designing to ideal situations is not the best way to go. It can provide a pretty good approximation, however. If it didn't, we wouldn't use ideal cases at all, now would we? It'll give you an idea of what will happen, so you can definitely reject ideas. If you have a bunch of ideas that should work, you can mock them up and see if there's something you missed in the "ideal case" that should have been there.

Re: HDPE or ICE FLOOR
 

Darn reality... always getting in the way of those beautiful equations! Actually I would suggest that the real test as to how well one understands an equation is by how well one understands the limitations on the equation.

Were it not for the limitation on damaging the playing field, a very small, but hard, contact area would provide dramatically greater friction than a very large soft one. I believe someone previously mentioned using saw blades as tires. Of course it might be even better than that to use Gecko Toe Pads as a traction material.

Suction cups would also stick nicely to a smooth surface.

Personally, I think it might also be interesting to see a section of the playing field filled with pea gravel to a depth of a few inches.

Jason

Re: HDPE or ICE FLOOR
 

i just dont want to slip while im carrying the robot:D

Re: HDPE or ICE FLOOR
 

From experience, if it's HDPE, you probably won't slip unless you try to.

Re: HDPE or ICE FLOOR
 

gooey, pneumatic tires that are just about flat. Or maybe tank treads.

Re: HDPE or ICE FLOOR
 

ill probobly find a way:yikes:

we are very clumsy:ahh:

Re: HDPE or ICE FLOOR
 

I can only think of one recent year, 2003, where HDPE was a surface you HAD to interact with to be competitive, and even then, the most dominant team just used roughtop tread. 111 didn't win because they could push, they won becuase they employed a superior strategy for controlling the top; ramps and a crab drive.

Since most FIRST fields are mostly carpet, and if HDPE is used as a floor it will probably be minimal, I would suggest you really think twice before designing a base for HDPE. As, I imagine the base optimized for HDPE would not be optimized for carpet, and would require a good deal of new design and research. I believe this time, and possible weight/complexity, would be better spent on other aspects of your robot design.

Bah, what I'm really trying to say is, don't just look at a problem at face value and say, I'm going to solve you for what you appear to be at face value. In 2004, teams thought they had to climb onto the HDPE platforms to hang from the bar, some made radically complex drivetrains to achieve this. When I saw 60/67/254 hang from the ground (and 60/254 at AMAZING speed as they used their drive motors to power their winch) and completely ignore the platform, I was inspired. Not only did they not have to design any radical crazy drivetrain to climb onto the platform, allowing them to stick with a simple 6 wheel, they were able hang faster than anyone.

I highly doubt that, "Lets push", "No, lets push HARDER!", will ever be a good strategy in FIRST. You can't mention 71 in 2002 as a counterexample, as their extreme pushing ability was just one piece of the puzzle that made their robot dominant that year.

Re: HDPE or ICE FLOOR
 

Adam,
I wholeheartedly agree with you except for one other variable. What if the game doesn't allow you to interact with anything but HDPE (or some other kind of slick surface) ?? The teams that have adapted to a different kind of surface and gone ahead to make a robot that thrives on a slick surface will most certainly have an advantage..

Natural selection right? Survival of the fittest...the teams that will thrive are the teams that will be able to adjust quickly to a change of environment..

Just my 2 cents.

-brando

Re: HDPE or ICE FLOOR
 

This is actually a serious question:

What do you guys think of teams drifting around on the field during a match?

Controlled drifts, of course.

Re: HDPE or ICE FLOOR
 

I'm thinking that if it's drifting on carpet, the carpet will bunch up even more on the ends of the field than it already does, but I would like to see that (drifting) happen on a game one of these years for low (height-wise) robots only - for tipping safety concerns of course.

Re: HDPE or ICE FLOOR
 

It's not impossible, but it's rather unlikely we'll get a field like that.

Re: HDPE or ICE FLOOR
 

it would be fun (to do and watch)

i saw teams do it this year.....

Re: HDPE or ICE FLOOR
 

Need for Speed: Underground - FIRST Style. Teams are awarded points depending on the length of their drifts. :)

I predict an increase in the demand for mecanum wheels.

Re: HDPE or ICE FLOOR
 

I agree that the possibility of that happening is very slim, but I envisioned the topic at hand being able to handle a terrain not seen in FIRST games before.

Re: HDPE or ICE FLOOR
 

I've been away from the game for 10 years and am returning as a rookie mentor. Is there anywhere that documents the various successful (and spectacularly unsuccessful) teams from year to year? Their strategies, tactics, designs, and capabilities? I'd love to read up and have some of my kids learn more about the different year's challenges and contendors. Thanks,

-mca

Re: HDPE or ICE FLOOR
 

Other than Chief Delphi, I would HIGHLY recommend The Blue Alliance (TBA) as a source on this. For anything 2006 or newer, they probably have match video to watch.

Next up: the two Behind the Design books (FIRST Robots: Behind the Design and Behind the Design: Rack n' Roll ) cover 30 designs each from 2006 and 2007 respectively. These were developed by FIRST and published by Rockport Publishing. As a team, you want at least one of the two, and probably both. We're talking the next best thing to sticking your head in a top-quality robot.

There are some legends out there that you may have missed: Beatty 2002, for example. Look around Chief Delphi for that robot. This is widely held to be one of the best FRC robots ever.

For the rules, FIRST has some old manuals up on their website. You might look through those, as there have been a lot of changes from your time. Alliance size is the biggest.

If you'd like to PM or email me, go ahead and I'll see if I can help you out.

Re: HDPE or ICE FLOOR
 

Just a thought

For a completely ice or HDPE floor or track, I wouldn't go with a drivetrain at all, I would do this.

Only problem is that since they don't interact with the floor, they have bad climbing and poor traction.

any rubber-on-floor method for ice/HDPE would have its drawbacks, as there is still a loss of traction involved when the rubber doesn't grip the floor. Not to mention the fact that since the floor is low-friction, it would be hard to stop or turn the bot once it started going. One of these would be complex to build, but any team that attempted it would be granted the engineering award x10, but that's just MHO.

Re: HDPE or ICE FLOOR
 

The only downside to this design is trying to obtain enough lift and propulsion with the voltage put out by the batteries, but i agree if a team could pull it off it would be pretty cool...

Re: HDPE or ICE FLOOR
 

The hovercraft idea would be an amazing feat, but what is the durability of the skirt? I think we all know how much our robots get beat up in matches.

Re: HDPE or ICE FLOOR
 

How would you attach the (probably) required regulation bumpers on the hovercraft?

Re: HDPE or ICE FLOOR
 

Lift and propulsion is easy. Less than 1 PSID is needed between the underside of the robot and the topside. Propulsion is even easier once lift is attained as traction goes way down.

There are many excellent fabrics that (such as multi layered Kevlar) that would be very suitable and wear resistant. You'd need to design the cloth pattern for the skirt properly and you might want to weigh down the bottom to prevent the cloth from not unfurling properly.

Attaching the bumpers is easy, the question would be if the bumpers must stay in the "bumper zone" during play. If so then they would have to either articulate or would have to be positioned so that your cushion height does not move them out of the "bumper zone". Gotta love engineering challanges :D

Re: HDPE or ICE FLOOR
 

Didn't the rule regarding bumpers specify that only standard ones could be exempted from the dimensions? Not to say that rule will show up again, but the skirt could probably be considered a "nonstandard bumper" and there wouldn't be a problem with the size, since it would be bundled up either on the sides or on the bottom of the robot.

Re: HDPE or ICE FLOOR
 

Lat year 'standard' bumpers were required.

This year ... well, we'll find out in 6 days :D

Re: HDPE or ICE FLOOR
 

This thread is kinda funny now after kickoff :D

Re: HDPE or ICE FLOOR
 

Yes, it is. ;)

I know what wheels I'd use... they came in the kit, but I bet we'll be the only robot with them. I don't think people realize just how innovative they are, and they may overlook them when designing their robots ;)

Re: HDPE or ICE FLOOR
 

Hdpe , they gave you wheels to start with :ahh:

Re: HDPE or ICE FLOOR
 

I'm stuck on wondering if this is sarcasm or if your team found some excellent loophole in the rules and have somehow kept it secret.