Wind Power B/C

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daydreamer0023
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Re: How good would my speed scores be on average

Post by daydreamer0023 » February 9th, 2017, 4:14 pm

Alex-RCHS wrote:
highbuilder wrote:I made my first ever design using curved balsa wood and at the invitational, I got 181 low speed and 340 high speed. I wanted to know how good these scores would be on average.
Like DragonFruit said, it's really hard to compare. You could try asking the proctor what the highest score was at the tournament, although they don't always tell you.

The only thing you can compare it to is previous designs. As long as you keep getting better, you can't go wrong!

For comparison purposes, my team and I have been testing at 670 mV HS and 400 mV LS without any resistor wired in. At regionals we got 360 mV HS and 210 mV LS, with 6.7 ohms of resistance. We think the difference is due to the fan being different, not the resistance, but we aren't sure.
Correct me if I'm wrong, but each individual motor has its own built-in resistance that factors into the resistance added into the circuit, which is why the readings might have been different. The fan difference might factor in some, but I doubt that it would make as much of a difference as the reason I mentioned above.

Also, if you're looking for a better direct comparison due to all of the different things factoring into resistance, I would measure the rpm of the blade (I think that was what we did last year).

Hope this helps!
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Re: How good would my speed scores be on average

Post by Alex-RCHS » February 9th, 2017, 4:37 pm

daydreamer0023 wrote: Correct me if I'm wrong, but each individual motor has its own built-in resistance that factors into the resistance added into the circuit, which is why the readings might have been different. The fan difference might factor in some, but I doubt that it would make as much of a difference as the reason I mentioned above.

Also, if you're looking for a better direct comparison due to all of the different things factoring into resistance, I would measure the rpm of the blade (I think that was what we did last year).

Hope this helps!
By "individual motor" you mean the one where the turbine is attached, right? I'm sure that would have some effect, but I think the fan would make more of a difference. Power is proportional to V^3, so as little as a 26% increase in velocity could double the power (and thus the voltage).

Measuring rpm would be nice, but it wouldn't account for the difference in fans.

What did you use to measure rpm?
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Re: How good would my speed scores be on average

Post by daydreamer0023 » February 9th, 2017, 4:46 pm

Alex-RCHS wrote:
By "individual motor" you mean the one where the turbine is attached, right? I'm sure that would have some effect, but I think the fan would make more of a difference. Power is proportional to V^3, so as little as a 26% increase in velocity could double the power (and thus the voltage).

Measuring rpm would be nice, but it wouldn't account for the difference in fans.

What did you use to measure rpm?
Fair point - what type of fan were you testing on, out of curiosity (not that it really matters that much - we have a rather broke fan at school because our school really, really needs funding :/)?

We used a tachometer and a bit of the tape that came with it to measure rpm.
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Re: How good would my speed scores be on average

Post by Alex-RCHS » February 9th, 2017, 4:54 pm

daydreamer0023 wrote:
Alex-RCHS wrote:
By "individual motor" you mean the one where the turbine is attached, right? I'm sure that would have some effect, but I think the fan would make more of a difference. Power is proportional to V^3, so as little as a 26% increase in velocity could double the power (and thus the voltage).

Measuring rpm would be nice, but it wouldn't account for the difference in fans.

What did you use to measure rpm?
Fair point - what type of fan were you testing on, out of curiosity (not that it really matters that much - we have a rather broke fan at school because our school really, really needs funding :/)?

We used a tachometer and a bit of the tape that came with it to measure rpm.
It's a white box fan with 5 blades. I think it's this one: https://www.lowes.com/pd/Lasko-20-in-3- ... an/1114391
(lasko 20 inch box fan, 3 speed)
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Re: How good would my speed scores be on average

Post by CVMSAvalacheStudent » February 9th, 2017, 4:55 pm

daydreamer0023 wrote:
Alex-RCHS wrote:
By "individual motor" you mean the one where the turbine is attached, right? I'm sure that would have some effect, but I think the fan would make more of a difference. Power is proportional to V^3, so as little as a 26% increase in velocity could double the power (and thus the voltage).

Measuring rpm would be nice, but it wouldn't account for the difference in fans.

What did you use to measure rpm?
Fair point - what type of fan were you testing on, out of curiosity (not that it really matters that much - we have a rather broke fan at school because our school really, really needs funding :/)?

We used a tachometer and a bit of the tape that came with it to measure rpm.
When I did Wind Power two years ago(I don't quite remember the right year), the tachometer broke so we had to use tape.
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Re: Wind Power B/C

Post by maxxxxx » February 12th, 2017, 6:43 pm

I know that what's said on here isn't official, but there is no minimum distance between the blade assembly and the fan during testing right? And since I do want to make the answer official, would it be better to submit a FAQ, or a Rules Clarification?
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Re: Wind Power B/C

Post by kenniky » February 12th, 2017, 8:17 pm

maxxxxx wrote:I know that what's said on here isn't official, but there is no minimum distance between the blade assembly and the fan during testing right? And since I do want to make the answer official, would it be better to submit a FAQ, or a Rules Clarification?
Last year had a bit in the rules that stated minimum distance; since that isn't there anymore, I think it's safe to assume that there is no minimum distance
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Re: Wind Power B/C

Post by pyt1ger » February 13th, 2017, 12:16 am

maxxxxx wrote:I know that what's said on here isn't official, but there is no minimum distance between the blade assembly and the fan during testing right? And since I do want to make the answer official, would it be better to submit a FAQ, or a Rules Clarification?
I can't find anything in the rules about minimum distance from fan, but in the competitions I've attended (SoCal) they all have had a minimum distance of around 1-2 inches.

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Re: Wind Power B/C

Post by maxxxxx » February 13th, 2017, 4:21 am

kenniky wrote:
maxxxxx wrote:I know that what's said on here isn't official, but there is no minimum distance between the blade assembly and the fan during testing right? And since I do want to make the answer official, would it be better to submit a FAQ, or a Rules Clarification?
Last year had a bit in the rules that stated minimum distance; since that isn't there anymore, I think it's safe to assume that there is no minimum distance
That's what I thought, but on Saturday at a comp they used a minimum of 5cm rule and since that was the State ES I wanted to make sure. If I want an official answer should I submit this as a FAQ? I don't want to get to States and have the same problem.
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Re: Wind Power B/C

Post by RestingDoll » February 13th, 2017, 5:44 am

maxxxxx wrote:
kenniky wrote:
maxxxxx wrote:I know that what's said on here isn't official, but there is no minimum distance between the blade assembly and the fan during testing right? And since I do want to make the answer official, would it be better to submit a FAQ, or a Rules Clarification?
Last year had a bit in the rules that stated minimum distance; since that isn't there anymore, I think it's safe to assume that there is no minimum distance
That's what I thought, but on Saturday at a comp they used a minimum of 5cm rule and since that was the State ES I wanted to make sure. If I want an official answer should I submit this as a FAQ? I don't want to get to States and have the same problem.
I don't think 1 cm vs 5 cm would decrease wind speed by that much. In any case, everyone would be affected the same amount.

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