2 wheels vs 1 wheel in a linear shooter

[CalTran]

Originally Posted by Oldbikerider

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.

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.

[Ether]

Originally Posted by Oldbikerider

I also question why a speed differential is needed.

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

Why not just impart as much energy as you can with each wheel?

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.

[falconmaster]

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?

[Ether]

Originally Posted by falconmaster

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?

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

[Ninja_Bait]

May I suggest the following equality:

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

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

[Oldbikerider]

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.

[Ether]

Originally Posted by Oldbikerider

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.

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.

[Dinoyan]

2 wheel linear shooter make your frisbees to go further

[Andrew Zeller]

Originally Posted by Ether

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

I also followed your math here:

It translates into approx 21 mph, assuming no slipping.

3600 rpm / 60 min/sec = 60 rev/sec

60 rev/sec * pi*4/12 ft/rev = 62.8 ft/sec

62.8 ft/sec / 2 = 31.4 ft/sec

31.4 ft/sec * 3600 sec/hour / 5280 ft/mile = 21.4 mph

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?

[Oldbikerider]

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.

[Ether]

Originally Posted by boarder3512

why is it that the maximum exit velocity of the frisbee will theoretically be one half that of the tangential velocity of the wheel?

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.

[Unbound]

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

[Ether]

Originally Posted by Oldbikerider

I take your point that if the first wheel got the speed then why add a second wheel.

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

[Ether]

Originally Posted by Unbound

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

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?

[Andrew Zeller]

Originally Posted by Ether

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.

Makes sense - thanks for the explanation.