Physics Lab B/C

[WhiteIndian]

On our tests it had many of the constants we needed, including specific heats. So you should be fine. Maybe review them just in case.

Okay! Thanks alot everyone!

[Littleboy]

Where can I find a picture of one of Greg Doe's propellors? from last year or this year.

[Greg Doe]

Littleboy,
Unless someone out there got a picture without my knowledge, there arn't any pictures anywhere.
I never took any, and to my knowledge my students never took any. Because we were so far ahead of the competition last year, I asked my students to keep our design under wraps. This year will
be different, as one of my teams had to be satisfied with a second place at regionals. We have
since discovered a modest performance increase, but don't know if it would have been enough
to make a difference. Our state event will be Saturday, so I guess we will find out then.
This is an excellent event for testing and experimentation. The materials are cheap, the test
equipment is easy to assemble, and the time to build a turbine is short. Between myself, and
my three teams we have built dozens of turbines. Someone or another brainstorms an idea and
we all try it. A lot are failures, but when we have a success we share it.

Like so many of the Science Olympiad events, the competition gets tougher and tougher each year as more and more people figure it out. I'll try to get the results to post here, but I can't promise.
Last year after the event was over, the voltage scores were posted on the door of the classroom.
If they do it that way this year I'll record them. If not it will be up to the memories of my students.

Don't fret too much though. There's a lot of design secrets that even a picture wouldn't reveal.
If you haven't run out of time, keep experimenting, that's how we got to where we are, and I
full well expect that there are others out there who are getting similar, or better performance.
Good luck, and don't give up.
Greg Doe
Smyrna, TN

[StampingKid]

There are plenty of pictures and actual models of blades from which to design a turbine out there even better --look at the Wright Stuff props, look at a ceiling fan, look at your box fan used for testing and reverse engineer. You will see that almost every one is set at an angle. You will also see that some have camber but others do not. Google things like difference between wind turbine and ceiling fan and you get this site
http://www.scientificamerican.com/artic ... fan-blades Looking at who asked it, where they are from and when more than likely it was somebody working on PSL in 2009 as Stroudsbourg, Pennsylvania or at least East Stroudsbourg shows up frequently on these forums. This is definitely a lab event as only with testing and retesting can you improve a blade. I have found that looking at the blade when testing it is important as you might be able to visually see if it is strong enough and balanced. Check the wright stuff forum out for how to balance a propeller.

[StampingKid]

How you put your blade on the testing mount is real important, too. If I test the blade once and get a high score, I retest to see if I can repeat the score. If there is a big difference it usually can be traced to checking the mount to make sure that the blade is square with the mount and not wedged. Sometimes one of the three spring bearings on the cd mount wedge against the cd inner rim or part of the blade near that rim edge and it might be there on an angle. This is usually something you can see visually when the blade is running and sometimes results in your blade being blown off the mount.

And at competition give the blade a spin on the mount before testing. Last year at regionals, the team before had jammed the mount backwards into the hardware on the stand and it would not spin until the event supervisor readjusted it.

And after any readjustment, spin it again. There is only one shot to turn that fan on.

And before you give a still blade a flick to start know which way it spins. (you can mark it on the blade with an arrow). A flick in the wrong direction will start it but it more than likely will not run for long. And again, there is only one shot.

[fleet130]

I have tried a 1-bladed design, and it's doing worse than my 2-bladed one.

It took a while to find this but, as they say, "better late than never".

Nuts and Volts magazine has been running a series of articles on "Experiments with Alternative Energy". There is a photograph of a life-size commercial, one-bladed, wind turbine in the bottom right-hand corner on page 52 of the March 2010 issue.

[Littleboy]

How well do 2 bladed ones do?

[illusionist]

How well do 2 bladed ones do?

based on my testing, they tend to be more efficient than the 3-bladed designs...

[Avis_de-Incendia]

How well do 2 bladed ones do?

based on my testing, they tend to be more efficient than the 3-bladed designs...

I can confirm this.

[fleet130]

And one blade designs seem to be slightly more efficient then 2-bladed ones. However, they introduce different problems that may over-ride the increase in efficiency.