Shooter Track Material - grippy or slick?

[Patrick Levy]

Hi,

My team is going with a 1/4 turn shooter with an 8" wheel mounted directly to a CIM motor in the middle. We are currently trying to tweak it to get better distance. There is a debate going on whether we want the track that the frisbee rolls on to be grippy or slippery.

One side says that the wheel RPM is so much larger than the final velocity of the frisbee that it should be slick to allow for greater spinning of the frisbee. This will also cause less of a reduction in the RPM of the wheel as it accelerates the frisbee.

The other side says that to get the largest velocity the frisbee should grip the track without slipping so that the frisbee exits as the same velocity as the wheel is rotating.

What do you think?

Pat Levy
Team 3202
St. Paul, MN

[EricLeifermann]

Originally Posted by Patrick Levy

Hi,

My team is going with a 1/4 turn shooter with an 8" wheel mounted directly to a CIM motor in the middle. We are currently trying to tweak it to get better distance. There is a debate going on whether we want the track that the frisbee rolls on to be grippy or slippery.

One side says that the wheel RPM is so much larger than the final velocity of the frisbee that it should be slick to allow for greater spinning of the frisbee. This will also cause less of a reduction in the RPM of the wheel as it accelerates the frisbee.

The other side says that to get the largest velocity the frisbee should grip the track without slipping so that the frisbee exits as the same velocity as the wheel is rotating.

What do you think?

Pat Levy
Team 3202
St. Paul, MN

Prototype both and see what works better.

[rlowe61]

I've reviewed multiple videos of shooters, not all FIRST related. Also this year we've prototyped with different surfaces, wood, aluminum, foam, etc. Seems there are a lot of fine variables, between surfaces, both of wheels and walls, but also the amount of pressure placed on the disk. It's an 11" disk, but 11" of space doesn't give you the optimal velocity. Proto-type different things and find what works best for you, and remember 1/16 of an inch between the wheel and the wall can make a huge difference.
WHEELS: Solid, rubber, wrapped in foam, treaded....don't be afraid of trying different surfaces, it's almost fun to see the differences.



Good Luck

[Ether]

Originally Posted by Patrick Levy

One side says that the wheel RPM is so much larger than the final velocity of the frisbee that it should be slick to allow for greater spinning of the frisbee.

You've got that backwards. You want the rail to be grippy if you want greater spinning.

The other side says that to get the largest velocity the frisbee should grip the track without slipping so that the frisbee exits as the same velocity as the wheel is rotating.

That's backwards too. If the frisbee grips the track without slipping, your exit speed will be limited to half the tangential speed of the wheel, but you'll get the greatest spin.

[TheCrayButton]

We are using tred on the side of ours. You can see it in the video. We have found that grippy material works better.

VIDEO: http://www.youtube.com/watch?v=BzIke...er_profilepage

I hope that helps

[Mr V]

Originally Posted by Ether

You've got that backwards. You want the rail to be grippy if you want greater spinning.




That's backwards too. If the frisbee grips the track without slipping, your exit speed will be limited to half the tangential speed of the wheel, but you'll get the greatest spin.

No if the rail is slick the Frisbee will spin more and it's exit speed is lower. The slick rail allows the Frisbee to spin without moving down the track while the grippy rail causes it to advance at 1/2 the tangential speed of the shooter wheel (assuming no slip between the Frisbee and wheel). This is based not only on my gut feeling but our prototyping.

[Ether]

Originally Posted by Mr V

The slick rail allows the Frisbee to spin without moving down the track

Hmm. Got an video? I'd like to see that.

[IndySam]

No I'm with Ether, if the frisbee is against a slick surface it will slide along that surface and not get as much spin. If the surface is sticky it is forced to spin because it can't slide.

In all our testing the sticky surface always spins more and gets more distance than a slick surface.

[billbo911]

Originally Posted by Mr V

No if the rail is slick the Frisbee will spin more and it's exit speed is lower. The slick rail allows the Frisbee to spin without moving down the track while the grippy rail causes it to advance at 1/2 the tangential speed of the shooter wheel (assuming no slip between the Frisbee and wheel). This is based not only on my gut feeling but our prototyping.

This is going to require some hard data before I take it as fact.
Video, Chronograph, anything with solid numbers.

I'm only challenging this statement because it is opposite of what our analysis showed.

Originally Posted by IndySam

No I'm with Ether, if the frisbee is against a slick surface it will slide along that surface and not get as much spin. If the surface is sticky it is forced to spin because it can't slide.

In all our testing the sticky surface always spins more and gets more distance than a slick surface.

Exactly!

The spin causes the Frisbee to fly more stably and for a greater distance because of that stability. "Muzzle velocity" is not the only factor involved with Frisbee flight. Try hitting it with a tennis racket. You'll see very quickly the impact spin has on the flight of the disk.

[ctccromer]

I went to Ruckus (the skateboard shop) and bought us a thing of Grip Tape roughly... 1ft by 3 ft? for $7. It worked great for us

[slijin]

Originally Posted by Mr V

No if the rail is slick the Frisbee will spin more and it's exit speed is lower. The slick rail allows the Frisbee to spin without moving down the track while the grippy rail causes it to advance at 1/2 the tangential speed of the shooter wheel (assuming no slip between the Frisbee and wheel). This is based not only on my gut feeling but our prototyping.

Did your prototyping consider compression? When we say "grippy," we're really just referring to the friction between the disc and the rail.

[Tom Line]

Originally Posted by ctccromer

I went to Ruckus (the skateboard shop) and bought us a thing of Grip Tape roughly... 1ft by 3 ft? for $7. It worked great for us

We considered that, but are extremely concerned about what it will do to the longevity of the frisbees. 'Grinding' the end of them on the tape like that probably isn't a good idea. We're considering some thin die-rubber or something similar.

[jvriezen]

On our linear belt driven shooter, we found slick went further. I believe it is because we got higher velocity and less (but sufficient) spin as the disc slipped against the slick surface. We hope to gear up the belt speed and may need to try again. But then again, we used one other trick that is likely relevant, but that's a trade secret -- haven't seen it in any other shooter videos or descriptions.

[FrankJ]

So coat your rail & bottom plate with your physics professor's frictionless goo. Will the Frisbee just sit there & spin?

[AdamHeard]

Originally Posted by FrankJ

So coat your rail & bottom plate with your physics professor's frictionless goo. Will the Frisbee just sit there & spin?

No. As you stop playing with frisbees and instantly make billions selling the frictionless glue.