ball speed

[Ken Loyd]

If you position your robot in the center square at the start of a match and shoot balls through the center goal, have you exceeded the 26 mph speed
limit?

Ken

[ForgottenSalad]

Just a note it's not 26mph, it's 12 meters/second (36 feet/second).

(Is that actually equal to 26mph? I didn't do the math on it.)

[Jack Jones]

Originally Posted by ForgottenSalad

Just a note it's not 26mph, it's 12 meters/second (36 feet/second).

(Is that actually equal to 26mph? I didn't do the math on it.)

It's 26.8 MPH = 39.3 FPS = 12 m/s

The answer to the original question is: Maybe?

A shot from there at max velocity - aimed dead center - should just skim the bottom of the hole. But that dosen't account for drag nor the spin on the ball. If the ball has top spin, then it won't hang as well and would probablly miss low. OTOH, a shot with enough backspin should be able to hit it.

[Donut]

Originally Posted by Ken Loyd

If you position your robot in the center square at the start of a match and shoot balls through the center goal, have you exceeded the 26 mph speed
limit?

Ken

Which square are we talking about? I've calculated that from the front square it is ~27 feet to the goal, middle is ~30 feet, and back is ~34 feet. With a 45 degree angle shooter firing balls at 12 m/s mounted at about 54 inches high, I believe you could get the balls into the goal from 41 feet ignoring air resistance and spin.

From the first 2 starting positions, I'd say yes, from the back one, maybe...

[Inverted]

I calculated the velocity of the ball when fired at full speed (powered directly from the battery) from our device, and it's about 10.5 m/s (25 mph, give or take). As long as you have one wheel shooting, you're legal with any speed. It should shoot from about 25-30 feet.

[Donut]

Originally Posted by Inverted

I calculated the velocity of the ball when fired at full speed (powered directly from the battery) from our device, and it's about 10.5 m/s (25 mph, give or take). As long as you have one wheel shooting, you're legal with any speed. It should shoot from about 25-30 feet.

If your calculations did not have air resistance, that might not be true, just a warning.

I don't think long range shots will be a problem. 30 feet is do-able, possibly 35...

One wheel shooting will not ensure you're in the legal limits. We shot a ball 47 feet with our one-wheeled shooter, and I know that's not legal.

[DonRotolo]

Originally Posted by Inverted

As long as you have one wheel shooting, you're legal with any speed. It should shoot from about 25-30 feet.

I dunno about that, we have a one wheel shooter that was measured at a LOT faster than legal.

Don

[petek]

Originally Posted by Jack Jones

It's 26.8 MPH = 39.3 FPS = 12 m/s

The answer to the original question is: Maybe?

A shot from there at max velocity - aimed dead center - should just skim the bottom of the hole. But that dosen't account for drag nor the spin on the ball. If the ball has top spin, then it won't hang as well and would probablly miss low. OTOH, a shot with enough backspin should be able to hit it.

I think you'll find that ball spin will be the major factor determining whether you make a shot at that distance. If I got my numbers right, a spin of 5 rev/sec would generate lift about equal to the mass of the ball. The vector of the lift is perpendicular to the axis of rotation and the the direction of flight. A back-spin generates positive lift, a front spin negative and side spin causes a curve ball. In any case, we've observed that with back-spin the ball trajectory is more linear than parabolic for 25 ft or so.

NASA has a nice page explaining the effect of lift on a rotating cylinder.

[Klutch1019]

For some reason i dont think my team will have a problem with the speed limit or anything on our robot...

[Ken Loyd]

Thank you one and all for your responses. I posted the question on FIRST Q & A. The response was that with an angle higher than 30 degrees the shot would be possible and legal. This is good because we are averaging 6 out of 8 in 10 seconds.

Ken