2 wheels vs 1 wheel in a linear shooter
 

What are the advantages to having two wheels in a linear shooter? Disadvantages?

Re: 2 wheels vs 1 wheel in a linear shooter
 

your frisbee has better momentum with two wheels. Unless your motor is good enough that it can take care of that. Also to make sure that after you shoot it reaches top speed faster with two since when using only one youre asking your motor to do more work. Hope this helps!

the down side is that youre using an extra motor and adding some more weight.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Does it have better momentum because of the increased contact? And wouldn't the frisbee have the same speed of the last motor?

Re: 2 wheels vs 1 wheel in a linear shooter
 

Our understanding is the additional contact time results in higher speed.

With one wheel, the frisbee just touches the wheel for a fraction of a second. Two wheels allow for a preliminary speed-up followed by a final acceleration and fly-out of the shooter.

A circular pathway shooter allows vast amounts of contact but has its own flaws. It seems like the linear shooter compensates for this lack of contact by having two wheels.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Additional contact helps as does avoiding slippage but I think it is more about the relative rotation. The max velocity you can impart with one wheel is half the tangential velocity (because the frisbee is also rotating in proportion to the wheel's rotation and in the opposite direction). With two wheels you can approach the tangential velocity.

You want the firsbee to spin for stability so if using 2 wheels I think one might try running the two wheels at slightly different speeds.


HTH

Re: 2 wheels vs 1 wheel in a linear shooter
 

I believe the 2 wheels we are talking about here are on the same side of the frisbee (i.e. both wheels are opposite the guide rail).

With 2 wheels, the maximum frisbee speed is still half the wheel tangential velocity.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Just out of curiosity, has anyone tried using two wheels with one on each side of the shooter? My team prototyped the common build with 2 wheels on the same side, but I'm curious how the other 2 wheel build would work

Re: 2 wheels vs 1 wheel in a linear shooter
 

What's wrong with a circular path?

Re: 2 wheels vs 1 wheel in a linear shooter
 

Search is your friend. Discussed at length in that thread.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Frisbees, in general, work by spinning, so having wheels on only one side is just a more elegant and efficient way of imparting spin.

Here's another reason why two wheels is theoretically better than one: Let's say you spin your one wheeled shooter up to a set speed. When the Frisbee contacts it, momentum will be lost, so the Frisbee will leave at less than half the original set speed. The motor can compensate by accelerating the wheel back to its original speed, but more likely than not, the Frisbee will already be gone by then. Two wheels allows you to "sacrifice" the first wheel's momentum so that you don't have as much of a momentum loss at the final wheel.

This is also why a curved track or a belt on a linear track is nice for hurling discs because there is a long period of contact during which the flywheel/Frisbee system recovers any lost momentum.

Of course, I may be unintentionally exaggerating - I have no idea whether the loss of momentum is actually consequential, since I haven't done any of the math.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Others answered, but here is the physics 1 equation:
The impulse momentum theorem

F Δt = m Δv

How much force AND how long you apply it determine your change in momentum. More contact = more time

Re: 2 wheels vs 1 wheel in a linear shooter
 

Has anyone out there tried three wheels in a linear shooter?

Re: 2 wheels vs 1 wheel in a linear shooter
 

Our team is also interested in people's thoughts and/or experiences with a 3 wheel linear shooter. If we go with a linear shooter we're thinking of allowing to add a third wheel if it should be necessary.

There are other ways of adding speed to a two wheel shooter, such as a pneumatic or spring trigger mechanism. Until we finish testing, we're keeping all options open for now.

Graham.

Re: 2 wheels vs 1 wheel in a linear shooter
 

I'm skeptical that a third wheel is necessary.

My engineering intuition tells me that the first wheel should be governed at a speed approx 75% of the second wheel. You should then be able to get plenty of exit velocity without slipping.

Has anyone out there tried a speed difference of this magnitude?

Re: 2 wheels vs 1 wheel in a linear shooter
 

We're hoping two are sufficient. Our tests indicate that it can probably be done with two.

I also question why a speed differential is needed. Why not just impart as much energy as you can with each wheel? We're not looking to maximize efficiency here, just fire discs as fast as possible. What is wrong if the first wheel got the disc to near full speed, then the second wheel doesn't have to do much more.

Graham.

Re: 2 wheels vs 1 wheel in a linear shooter
 

By that logic why would you need a second wheel if you're attempting to impart as much energy as possible with the first wheel? As stated, the idea behind the two wheel shooter is because of the contact time between discs and wheels. If you use the first wheel to accelerate the disc and the second to propel the disc, you get comparable results to a circular shooter.

Re: 2 wheels vs 1 wheel in a linear shooter
 

I didn't say it was "needed". I was speculating that you can squeeze more performance from a given shooter by doing so.

If that's your goal, then the first wheel should be driven slower than the second.

There's a wheel speed above which the exit velocity of the frisbee from that wheel actually starts decreasing, presumably due to excessive slipping. The first wheel reaches this point before the second one does because the frisbee speed coming into the first wheel is so much slower than for the second wheel.

Re: 2 wheels vs 1 wheel in a linear shooter
 

I think if you can control the speed of the 1st wheel from like 40% to 75% of the second wheel, you can also effectively control the distance. Am I correct?

Re: 2 wheels vs 1 wheel in a linear shooter
 

The second wheel probably has more effect on the exit speed.

Re: 2 wheels vs 1 wheel in a linear shooter
 

May I suggest the following equality:

sum("wheels") from 1 to infinity = "belt"

I know it's not really the same, but still.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Our tests would indicate that one wheel is not enough. Some things to consider are how much compression is needed to impart enough speed to the disc, and how that compression effects the disc and it's trajectory.

I'm questioning why it's necessary to second guess how much each wheel will add, and why it would be necessary to have different wheel speeds for the first and second wheel. What's wrong with running both wheels at full speed. Maybe under ideal conditions, perfectly round and clean and dry disc, full speed is achieved with the first wheel, but maybe under less than ideal conditions the second wheel is needed. Under some circumstances the second wheel is just insurance.

Graham.

Re: 2 wheels vs 1 wheel in a linear shooter
 

You said in your earlier post that your goal was to "fire discs as fast as possible".

I interpreted this to mean "with the fastest exit velocity achievable with a given 2-wheel linear shooter" .

If that is the correct interpretation of your post, then you would want to get the maximum speed increase (change in speed) as the frisbee passes through each wheel.

Based on tests run by Team 2073, this would indicate that the second wheel should be run at a faster speed than the first, to achieve your goal.

Re: 2 wheels vs 1 wheel in a linear shooter
 

2 wheel linear shooter make your frisbees to go further

Re: 2 wheels vs 1 wheel in a linear shooter
 

I also followed your math here:

I understand that the rotation of the frisbee as it contacts the wheel causes less than its full velocity to be transferred in an ideal situation, however why is it that the maximum exit velocity of the frisbee will theoretically be one half that of the tangential velocity of the wheel?

Re: 2 wheels vs 1 wheel in a linear shooter
 

Ether,

Yes, I said "firing discs as fast as possible", but there are some upper limits here.

There is evidence indicating that too much compression leads to distorting the disc, with adverse effects on the accuracy of shot, and people are also reporting a plateauing of the achievable disc exit speed where an increase in wheel speed does not result in a proportional increase in exit speed.

So, my thinking is that yes, doing the firing in two (or maybe three) milder steps is the way to go, but I take your point that if the first wheel got the speed then why add a second wheel. My reasoning is that the second wheel simply makes sure the speed is correct, adding something extra in the case of a dirty or warped disc, but not adding any more speed in other more ideal circumstances. I'm concerned more about consistency.

Graham.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Think of a car traveling down the highway at 60 mph.

The geometrical center of each tire is traveling at 60 mph.

At any instant in time, the bottom of each tire is traveling at 0 mph, and the top of each tire is traveling at 120 mph.

It's the same with the frisbee.

Re: 2 wheels vs 1 wheel in a linear shooter
 

We are using two wheels in our shooter one to give the disk a spin and the other to propel the disk forward.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Just for the record, that was someone else's point, not mine.

Re: 2 wheels vs 1 wheel in a linear shooter
 

How does the first wheel spin the frisbee without propelling it forward?

And how does the second wheel propel the frisbee forward without adding additional spin?

Could you post a picture?

Re: 2 wheels vs 1 wheel in a linear shooter
 

Makes sense - thanks for the explanation.

Re: 2 wheels vs 1 wheel in a linear shooter
 

To allow for more contact time with the frisbee so the acceleration can be distributed over 2 wheels instead of just 1, to minimize slipping and improve final exit speed and consistency.

Lots of discussion going on about this in this thread, and other threads.

Re: 2 wheels vs 1 wheel in a linear shooter
 

https://www.youtube.com/watch?v=ARUhI8Qob5w

This is our prototype 1 wheel shooter. We made a 2-wheel shooter but the video we have of it is poor in quality. We will post a new video of the 2-wheel in the very near future.

Here is the video anyways: http://www.youtube.com/watch?v=EYpbyVbMbD8

Re: 2 wheels vs 1 wheel in a linear shooter
 

If you wanted a long time for contact in a linear shooter couldn't you use a belt instead of a wheel?

Re: 2 wheels vs 1 wheel in a linear shooter
 

This was mentioned in post #10, and also here.

Re: 2 wheels vs 1 wheel in a linear shooter
 

Theoretically yes, but practically no. A few people have tried it and had serious issues with it.