Scioly.org

We used a water bottle and a CD and got 19th (our blade assembly was a quarter of an inch too big D:, but it got a least a full volt)

Was that at your state competition?

19th was at states, yea

I just got the new rules! The major change is the addition of load resistors! So this time, we'll actually have to generate power, not just voltage!

ichaelm wrote:The major change is the addition of load resistors!

This may/may not have an effect on the turbine design.

Edited: Sep 22, 2010
.....Note: Changed multimeter in picture to computer (Current rules call for using a computer probe instead of a voltmeter/multimeter to take measurements.)

Fleet,

The rules state that supervisors should use computer probes, but in your illustration you show a multimeter. Am I right in thinking that it wouldn't make any difference which you use?

It does. The rules also state that the average voltage over the testing period should be used for calculations. That's easy to do with a computer. But if you're using a multimeter, that's a pretty impossible task, so they let you use the maximum instead. But at any serious competition, they should have computer probes.

Also, just as an example of the design changes we'll have to make to adapt to driving a load: Last year they had a minimum diameter for the blades, since a smaller turbine would spin much faster and generate more voltage. This year, there is only a maximum diameter, because you need to take advantage of as much area as possible to generate as much power as possible. We will need to generate a certain amount of torque in order to get the blades to spin. The actual amount of torque will vary depending on the value of the load resistance and the specifications of the CD motor used. Once that torque is achieved, the blades will start to spin, and the faster they can spin while driving the load, the better. But it will be a whole lot different than spinning with no load. At least, assuming the load is high enough that it makes a significant difference. I should do some testing soon.

Aha. Thank you, ichaelm, I had not noticed the scoring change.

I forgot about the "computer probe" requirement in the current rules. In any event a computer probe can be viewed as just one form of multimeter. The point was to illustrate how the load resistor should be connected in the circuit.

fleet130 wrote:I forgot about he "computer probe" requirement in the current rules. In any event a computer probe can be viewed as just one form of multimeter. The point was to illustrate how the load resistor should be connected in the circuit.

Yes, and I appreciate the illustration. I was just hoping that I could get away with using a multimeter for the testing setup, since I've never used the probes. Ah well.