Wind Power B/C

[arod129]

Sample voltages people are getting?? Mine reaches 2V at 5 ohm resistance... is that good or bad?

[chalker]

Sample voltages people are getting?? Mine reaches 2V at 5 ohm resistance... is that good or bad?

It's really hard to compare voltages. Every setup is going to be different in terms of motor, fan, etc. That's why raw voltage is part of the team score, but rather we normalize the voltages vs. all the other teams competing at a given tournament.

[WILL]

The dormant awesome90220 has returned from hibernation.

Are there any wind power tests out there? Not like the test exchange physics lab tests, but ones from this year. I've hit a study wall

I've also been hoping to find some of these. I have little knowledge of what the tests might actually look like, other than what the rules provide.

I'm fairly certain that the tests at different invitationals/regionals will vary by a lot, but there were some multiple choice questions on what happens in certain conditions(EG making the blade longer or changing pitch of blades), some true/false questions regarding power generation(EG true or false hydroelectric power is affected by climate), and "short answer" questions like name a way of storing wind energy for future use. Questions along those lines.

[dragon-fruit35]

I had a quick question on what is considerd part of the blade assembly? The blade, or the jointing piece in the middle? THANKS!!

What do you mean by the jointing piece? The CD?

[soyuppy]

Several factor that will affect your blade score, and they all are determined at the actual event/trial competition.
1. Motor and box fan are different in each event
2. Resistance Load
3. Your placement among other competitors

Ideally you want to score high enough from everyone else so that it doesn't matter what written test score you get, you still come out a head. Look at the score sheet from soinc it will show you the combine score on what if scenarios.

Having said all this, of course, my top observed score at invitational events are 300-400 mV. I don't know what value would consider competitive or 1st place score, but 400 mV blow all other competitors to dust.

Now if you are getting 2V, chance are your motor is a different class. not the CD motor. Be prepare for reality check in the competitive event when the actual CD motor will be used. Voltage are normally in the mV.

[JimY]

I ran Wind Power C at an invitational last weekend. The test did not comply with the 5 questions from each of the 5 categories spec in the rules, and I didn't have enough time or the inclination to make it comply. It did have 25 questions, however. So, teams should be prepared for tests that don't comply with the national rules until they actually get to Nats. Regional and state tests might comply and they might not. My opinion is that since this is a high school level physics event, it should involve less trivia and more calculations. Anyway, teams came in with binders ranging from zero to about 4 inches (there was only one that thick and the next largest was MUCH smaller). Before making the test, I read my team's binder and decided to include nothing that was in it. Boo hoo for them. The team with the huge binder got the second highest test score, and they spent much of the test time looking up information in it, so kudos to them for being well prepared.

For device testing, since there were up to 37 teams competing in the event, we went with 2 testing setups, one at each fan speed. I came up with 2 nearly identical setups (same model CD motors, same resistance resistors, same style fans) such that with a standard blade device, I get nearly identical voltages on both low and high with either motor paired with either fan. So, when one team's device fit on one of the hubs but not the other, we ended up doing both tests with the same fan/motor pair, despite the national rules. If anyone else is planning on using two setups for blade testing, you might want to check this on yours in case something similar happens.

Some general observations and thoughts on device testing:
- it did not look like many teams had spent much time working on blade designs, as few spun really well at both speeds. Some teams were probably sand-bagging too.
- the number of individual blades on any device ranged from 2 to around 10-12
- in general, the 3D printed ones were inferior to others, but it looks like different angle blades cloud be fitted into many of them to potentially improve the speeds/voltages/power
- many teams placed their blades right at the center of the fan, so obviously had not tested for optimal position at each fan speed, or were just sand-bagging.

Another thing I decided to do was completely separate the written test and device testing. I gave 25 minutes for the test, then we did as many device tests as we could in the remainder of the time block. If a team could not come back to test their device later in the day, they were put at the front of the line. Of the 3 time blocks the event ran, only 1 of them had untested or partially tested devices by 5 minutes before the next block started, as many of the teams in that block took much of their 3 minutes at the low speed test station (my station). We also had 13 teams in that block, but only 33 total of the potential 37 overall. So if anyone decides to run the event segregated like this and has a similar number of teams to get through in a time block, you might want to reconsider. I just wanted all teams to have the same amount of time to do the test, in case they took longer at the device stations.

As for the testing setup, I used 2 ring stands with a cross bar for each fan. The motor was connected to a ring stand clamp on the cross bar. We allowed the students to adjust their blades in the x, y, and z directions. They could also adjust the angle in two different directions. We did not let them touch the fan or the motor when making their adjustments. As far as impound, with the number of teams we were expecting, rather than having a line form while doing measurements, we just checked in the devices and saved the measuring for after the written test. That was a mistake, as one team's device as impounded did not meet the 3 cm radius clearance spec on the back of the device, and we didn't know it, so we didn't give them the chance to modify it as specified in the rules. So, ideally, we would have checked in and done measuring at the same time before releasing each team. Then we probably would have spotted that particular device and given them a chance to alter it.

Anyway, I hope our experiences come in handy for all levels (student, coach, and event supervisors). It was considerable work, but it was fun too.

[samlan16]

I ran Wind Power C at an invitational last weekend...

Anyway, I hope our experiences come in handy for all levels (student, coach, and event supervisors). It was considerable work, but it was fun too.

Thanks for the report- not too many proctors think to do anything like this!

[ElementalClockwork]

Hi Guys,

Wow it's been a long time since I've been on here

Anyways, it's my first time doing this event (and my first time going solo ) so I have a few questions, wondering if anyone could answer them?

1) Is the event's raw score going to be measured in voltage? And if so, does anyone know what a really good voltage should be? I kind of want a general idea of what voltage my wind design should reach, and so I can factor it into the formula given that we have a specified resistance.

2) Can we 3D print our blades?

3) I'm a little unsure about the setup for the design, about attaching our blades to the CD. Can we have sticks attached to the CD with our blades on them? And does anyone know how to put a resistor onto the motor for testing?

Thanks guys!

[samlan16]

...so I have a few questions, wondering if anyone could answer them?

Sure!

1) Is the event's raw score going to be measured in voltage? And if so, does anyone know what a really good voltage should be? I kind of want a general idea of what voltage my wind design should reach, and so I can factor it into the formula given that we have a specified resistance.

The scoring is done by power such that

and the reason for this is to account for the varying resistance of test rigs at different tournaments. I have heard of some teams getting 2-4 mV but do not know their specific resistances to calculate the power.

2) Can we 3D print our blades?

You can as long as you are not using a metal filament, but this option may not give you the most lightweight blade possible. Thus, you will likely run into trouble with drag forces.

3) I'm a little unsure about the setup for the design, about attaching our blades to the CD. Can we have sticks attached to the CD with our blades on them?

You absolutely can, but you can also glue you blades directly to the CD. Keep in mind that you may not glue anything to the clear center part of the CD.

And does anyone know how to put a resistor onto the motor for testing?

As far as I'm aware, the resistor is in series with the motor. Correct me if I'm wrong.

Thanks guys!

You're welcome!

[soyuppy]

is sanding the CD to create rough surface for the glue to hold on stronger consider a modification of CD?
I would think this would be OK because this is in the category of affixing the blade.