pic: 1251 Prototype v 1.2

[tkwetzel]

Well...I finally made it back to Chief Delphi after being away for so long.

The sprocket size should not matter at all to answer their question. They asked how fast the wheels were spinning, not the motors. With an angle and distance you need the size of the wheels and possibly height of the arc of travel to find the rpm of the wheels to launch one of the foam balls that far.

Without calculations I will guess that the wheels are spinning at 1,900 rpm.

[Andrew Blair]

The size of the wheel has nothing to do with the RPM of them (Unless you say that their mass slows down the system). If we know the output speed of the Kit gearbox, and we know the ratio to the the wheels, we can, with some error, find the RPM of the wheels. Now, if we were looking for the linear speed from a reference point on the wheel, then wheel size would matter.

[Tom Bottiglieri]

Originally Posted by Andrew Blair

The size of the wheel has nothing to do with the RPM of them (Unless you say that their mass slows down the system). If we know the output speed of the Kit gearbox, and we know the ratio to the the wheels, we can, with some error, find the RPM of the wheels. Now, if we were looking for the linear speed from a reference point on the wheel, then wheel size would matter.

Who says the trannies are running at full power?

[Andrew Blair]

Originally Posted by Tom Bottiglieri

Who says the trannies are running at full power?

Thats one of the easiest assumptions. They're running the motors straight off of the battery, so the speed of the output is defined only by the battery voltage. Its rather easy to say that they were running a fairly charged battery; most people don't run a battery to nothing and then use it to power a launcher. An easier assumption than the estimation of the size of those two sprockets.

[i_am_Doug]

EDIT: im now guessing your team number ;p 1251.

[cire]

Looks like 1269 RPM to me

gear ratio * free speed of kit transmisson
3:1 * 423 rpm = 1269 rpm

edit - I estimated that the larger sprocket was 36T and the smaller one was 12T by looking at the picture.

[Rick TYler]

I know I'm coming late to the party, but 1,250 rpm, plus or minus two weeks.

(Bonus if you recognized the obscure movie reference.)

[Stephen P]

Originally Posted by tkwetzel

Well...I finally made it back to Chief Delphi after being away for so long.

The sprocket size should not matter at all to answer their question. They asked how fast the wheels were spinning, not the motors. With an angle and distance you need the size of the wheels and possibly height of the arc of travel to find the rpm of the wheels to launch one of the foam balls that far.

Without calculations I will guess that the wheels are spinning at 1,900 rpm.

You couldnt find out the rotational speed from just projectile distance, becausethis would require the assumption that 100% of the wheels energy is translated into the ball (a horrible assumption).

[tkwetzel]

Originally Posted by Stephen P

You couldnt find out the rotational speed from just projectile distance, becausethis would require the assumption that 100% of the wheels energy is translated into the ball (a horrible assumption).

That is not true. You could assume whatever efficiency of energy translation you want, but whatever number you use would be an estimate without knowing other information. You also have to estimate a few otehr numbers. But tehy gave you the angle and distance traveled.

[Andrew Blair]

Originally Posted by tkwetzel

That is not true. You could assume whatever efficiency of energy translation you want, but whatever number you use would be an estimate without knowing other information. You also have to estimate a few otehr numbers. But tehy gave you the angle and distance traveled.

You could, but the easiest assumption to use is the motor/tranny speed to the wheels. Problem with using the ball's throw is that you must estimate he distance, then the power transmission efficiency, then backsolve for RPM. Lots of error, though either way. it's hard to guess.