m R g S r

What material will have a high coefficient of friction with smooth plywood?

This is for a project in school involving mechanical tug of war.


Anyway...Any advice on this would be helpful. Anyone have any ideas on what we could use?


Tug of War

Eight teams, each consisting of at most three students, will be formed to participate in a Tug of War competition. In this project each team must design a device capable of competing in a tug of war with other teams’ devices. The competition surface consists of a 3/8” thick 4’8’ sheet of Birch plywood with a smooth surface, laid on the floor (see Figure 1). As shown in the figure 1, devices designed by two teams (teams A and B) are connected to each others by a 10” long spring. Each device is placed 5” from the centerline.


Rules of Competition:

1. Device size and weight:

The device size should not exceed 6”8”10” and it weight should be less than or equal to10 pounds.

2. Connection hook:

The device must be equipped with a standard hook that will be provided by the instructor. This hook connects the device to the spring shown in Figure 1. The hook should be placed on each device 3” above the competition surface. If the hook separates from the device the team will be declared the loser in that competition.

3. Power source:

Each device can only use potential energy as the source of power (for example energy stored in a spring).

4. Crossing the centerline:

Any device that crosses the centerline will be declared loser in that competition.

5. Time Limit:

The competition between two teams lasts for one minute. Each team after connecting their devices to the connecting spring will be given a start sign by a referee. All competitors must then remove their hands from their devices (failure to do so will disqualify the team). The device that ends up furthest from the centerline after one minute will be declared the winner.

6. Groups and competition procedures:

A week before the final competition, using a random drawing, two groups, each consisting of four teams will be formed. In the first round of competitions, all teams in each group compete against each other. Two teams with the largest score from each group would go to the second round.

In the second round (semifinal), the first team of group A competes with the second team of group B, and the first team of group B competes with the second team of group A. The winners of the semifinal compete for the first and second places, and the losers of semifinal compete for the third and fourth places. Figure 2 shows details of competition at various stages.

99_GS-T

Rubber?

Haha, sorry if this is off topic, but I'm just interpreting the rules...

Make the hook hinge and if possible rise up when it's pulled on. Also, make the vehicle react to this with raising the rear end and making the car FWD. This could get the weight to transfer to the drive wheels and potential pull weight off the competitors drive system.

Or design it so that it could be swapped depending on the drive configuration of the other car. If their drive system was on the front, have it drop the hook so it would unweight the drive wheels of the other car. Set it up to make your car RWD in that case.

Bjorn

anti-slip tape used in bathtubs

99_GS-T

Double sided tape...

.RTErnie

something to think about...the horizontal location of your attachment(loop for the spring) The height is restricted to 3" which is where the ATTACHMENT MUST BE!!! But by making the spring go over a 10" barrier first and then down to the 3" attachment you can still maintain the 3" height, but get the advantage of having a 10" tall point from which the forces act. (cheating but by following the rules) LMK if you dont understand and I will make a picture for you. basically if you look at the FBD when your attachment points both at 3" but your spring must first go over a 10" wall...you change the total force of their pull. The tension in the spring will pull (thinking that your object is on the right of the spring) Horizontally in the negative direction and vertically in the negative direction... the resultant force will be something along the lines of a force that is like (if they were spaced 21" apart) 3:1 cosine of .333 is 20 degrees from the horizon. so if they pull with a force of 100N then you will effectively have a force at the point where the spring is stretched over teh body of your "object" that has a vertical magnitude of 33N. So you use their force against them creating a 33N force DIRECTLY down at that point. I would suggest putting that point the furthest away from the competitor as to not create a moment about your closest edge and flipping your object. And putting your coupler on the other side(facing away) from the competitor.

m R g S r

Professor stated it would be best to have a fixed platform and not something on wheels. so fwd and rwd is out.

He also said that surface area is not a factor in this, so it does not matter what size the base is.

Also, he reccommended looking into materials which have a coefficent of friction greater than 1. What is out there?


Thanks

m R g S r

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn &raquo;</TD></TR><TR><TD CLASS="quote">anti-slip tape used in bathtubs</TD></TR></TABLE>

we asked him about sandpaper, and he said it wouldn't work so well.

the playing surface is smooth wood.

m R g S r

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTErnie &raquo;</TD></TR><TR><TD CLASS="quote">something to think about...the horizontal location of your attachment(loop for the spring) The height is restricted to 3" which is where the ATTACHMENT MUST BE!!! But by making the spring go over a 10" barrier first and then down to the 3" attachment you can still maintain the 3" height, but get the advantage of having a 10" tall point from which the forces act. (cheating but by following the rules) </TD></TR></TABLE>

Alright

But we were thinking of having the hook pull back on the spring. I think the spring attaching the two "vehicles" would get hung up on the barrier.

Sounds like a good idea though. Can you make a quick sketch for me?

We were also thinking of using 1" by 1" angle iron for the base and some strap metal for the structural parts. (barrier, track for the hook to slide on etc...)

Actually, my professor reccommended using the tracks that a keyboard shelf slides on. (from a computer desk)


BTW, thanks for the help, and this isn't cheating FYI, he told us to ask around on message boards and such

.RTErnie

Go buy some VHT and get some real soft rubber and get it siped. then make a way for the vht to soak into the sip cracks. That **** will be rediculous. here is the idea I had. The thick line is the spring. It will bind at that point, making it essentially pull FROM that point, but its attached at the point 3" off the ground.

Formula Racing

reheat some gluesticks and spread it about 1" thick across the bottom.. Keep height down and weight low in the front by the hook.

mrbsponge

non skid coating they use on navy vessel floors, sure stopped me when i fell on the ****! i didnt slide a bit. and they sell it at hardware stores now, just brush it on

m R g S r

I don't think we can use any kind of adhesive.....

We are not allowed to ruin the playing grounds (wood surface)

and glue/residue left on the surface would be considered ruining it i guess.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTErnie &raquo;</TD></TR><TR><TD CLASS="quote"> here is the idea I had. The thick line is the spring. It will bind at that point, making it essentially pull FROM that point, but its attached at the point 3" off the ground.

</TD></TR></TABLE>

Yea, but it is just a fixed mount then? It's a tug of war, I don't think it we can just have the spring attach and have a 10lb block sitting there....I mean we could, but I don't think we will be graded well with that......

turbotommy

are you allowed to have something that pivots? sort of like an arm...

...and can the hook move?

m R g S r

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turbotommy &raquo;</TD></TR><TR><TD CLASS="quote">are you allowed to have something that pivots? sort of like an arm...

...and can the hook move?</TD></TR></TABLE>

yes, hook can move and can pivot.

I heard the winning team last year used mouse traps as their power source. just a thought......

HiProfile

I would agree with the rubber idea. Assuming you can melt rubber (real or synthetic) onto the surface into holes/trenches, that should work. At the very worst, I would think it would only produce ***** of rubber, which wouldn't ruin the board, nor be considered residue. Rubber leaves marks only when you have a few hundred PSI on the rubber, this could be .2psi at the most (static), and I wouldn't think it would even quadruple with the spring they're using. I'd also suggest 'storing' it in a heated blanket, since it's temp shouldn't be considered a energy source.

If you can't think of anything and throw it together morngin of the comp, fasten some anti-slip foam used for carpets to a cinder block.

PolyPill

Maybe this is a dumb idea and might not work in your size restrictions, but what if you make it into a sort a lever. Put most of your weight up in the air and when the battle begins you drop it using gravity to your advantage. That would give an initial jolt to the opponent, then maybe also use some mouse traps as you stated to finish the job. It takes the most energy to get the opponent moving, after they've begun to move it should be easier to pull them.

I'm just trying to think a little bit different.

Half assed image

m R g S r

I don't quite get the picture.......

How would the hook move?

And the movement of the hook looks like it would do nothing, because the two "vechiles" are attached by a spring......

GCOAP

you could build a trebuchi(sp) just launch the other teams devices dont know if that would be allowed but it would cause them to cross the center line.

Eddiebx

crazy glue the base to the wood,

or just put on those tack strips used when carpeting the floor, its got these little sharp nails that stick out and dig in. before launching your vehicle press that **** into the wood hard and your set

PolyPill

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by m R g S r &raquo;</TD></TR><TR><TD CLASS="quote">I don't quite get the picture.......

How would the hook move?

And the movement of the hook looks like it would do nothing, because the two "vechiles" are attached by a spring......</TD></TR></TABLE>

umm, half assed picture, the pole is removed, the weight drops thus moving the hookup and up and to the left in an arc like a lever....It probably wont work exactly like the picture, like someone stated make it more like a trebuchet, which uses springs and a big *** weight with gravity to throw things....the picture was more of a way to demonstrate using gravity to your advantage, like in a tebuchet.

http://www.geocities.com/Silic....html

I think the winner will be who ever can generate the most energy, not who has the best sticky surface, if you generate enough energy in the opposite direction, the friction wont be much of an issue.

monicle

I say cut up a large inner tube, double or tripple up the layers so the hook doesnt rip out, put a large rivot or something in as a connection point for the hook, then slap the rubber down on the plywood and use bricks for weight to keep the rubber to the wood. spread them out so theres a larger contact surface on the wood.

PolyPill

The size limitation seems to be a big factor here, if the floor is that smooth and flat, why not use some big suction cups? Those suckers are super hard to move, although I'm not sure if they will slide.

m R g S r

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PolyPill &raquo;</TD></TR><TR><TD CLASS="quote">The size limitation seems to be a big factor here, if the floor is that smooth and flat, why not use some big suction cups? Those suckers are super hard to move, although I'm not sure if they will slide.</TD></TR></TABLE>

holy ****, i forgot about suction cups. no one brought that up. yess...that wont ruin the playing grounds at all. im gonna ask the teacher secretly if we can use em.

Finest

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by m R g S r &raquo;</TD></TR><TR><TD CLASS="quote">

holy ****, i forgot about suction cups. no one brought that up. yess...that wont ruin the playing grounds at all. im gonna ask the teacher secretly if we can use em. </TD></TR></TABLE>

If you use suction cups, then you won't be able to move either. And isn't the point of this exercise to pull your opponent across the median? You'll still need to incorporate something to pull them across.

monicle

if its not a laminated wood surface or laqured or something I highly doubt that the suction cups will hold suction at all. plywood though smooth in a general sense isnt smooth enough to allow a suction cup to seal to. I could be wrong though cause i dont know exactly the condition of the plywood. If its straight off the pile at home depot then its not going to work.