Physics Lab B/C

[vofbassist]

Bring your windmill pre-assembled. So that would be with your blades attatche to your CD.

[an_olympian]

Thank you!
Actually I have another question about size limits: do the blades have to be *between* 25 and 28 cm diameter (i.e. 25 is minimum and 28 is maximum) or is the maximum somewhere arbitrarily between 25 and 28 cm (i.e. anywhere lower than that arbitrary value is fine)? And are there limits on the depth of the blades or how far they can "stick out" from the CD (I know this isn't an "official" rules forum or anything, but does anyone know)?

Thanks so much!!

[Sir_L_Jenkins]

So, here's one of my questions about CD aspect of the blade assembly. Do we have to use a standard compact disc (the kind you put in your computer, stereo, etc), or can we use things like micro-CDs (think things similar to nintendo gamecube discs) which are vastly smaller, yet have the same size hole to mount the CD. If we could use the smaller one, it would reduce drag/increase air flow quite a bit as there wouldn't be a bulky CD behind it. Also, as we're allowed to modify the CD as long as we leave the hole, could we simply just cut out the entire CD except for a small ring the hole to use that as a mount?

[andrewwski]

3b says you're allowed to modify the CD as long as you don't modify the center whole...I'd assume that means you can modify the size. Which you would definitely want to do then - it's going to allow you to greatly reduce the mass (and thus rotational inertia), drag, and increase the blade length.

[Paradox21]

The whole reason for using a CD for a base is to standardize the hole. I think the competition rigs are made of disected walkmans. The outcropping that you stick a CD into on a portable CD player is attached to a motor which, when spun will produce current that is measured with a multimeter or something similar. So you should not use any CD that has a non-standard sized hole. But you can, and probably should, cut down the CD. All you need from it is the hole.

[vofbassist]

Thank you!
Actually I have another question about size limits: do the blades have to be *between* 25 and 28 cm diameter (i.e. 25 is minimum and 28 is maximum) or is the maximum somewhere arbitrarily between 25 and 28 cm (i.e. anywhere lower than that arbitrary value is fine)? And are there limits on the depth of the blades or how far they can "stick out" from the CD (I know this isn't an "official" rules forum or anything, but does anyone know)?

Thanks so much!!

25 is the minimum and 28 is the max. And if you can't find a rule that limits the depths of the blades, I would think they can stick out as far as you want them to.

[georgexu316]

Hmmm I'm a little confused-- could someone help? Is the CD provided at the competition and we have to attach our blades to it, or do we bring the blades already attached to a CD? o_o

well the rules say "modification of the CD (except the center) is allowed", so I assume that implies that you have to bring your own CD, modified or not.

[georgexu316]

The rules say that the "blade assembly" have to be within a certain spec. Does that apply to the blades only? or to everything I bring?
I'm thinking of building an interesting rubberband mechanism to go with it, but I to have legs to support my part of my windmill, and it would probably be taller than what the requirement says the "blade assembly" must be.

[jazzy009]

The rules say that the "blade assembly" have to be within a certain spec. Does that apply to the blades only? or to everything I bring?
I'm thinking of building an interesting rubberband mechanism to go with it, but I to have legs to support my part of my windmill, and i would probably be taller than what the requirement says the "blade assembly" must be.

CD can be modified, you are required to bring a CD (blades should already be mounted on it, no building at the competition)

Rubberbands...? Okay...specs are 25cm-28cm diameter (diameter of blades on the CD).

Why do you have legs? The CD will be mounted on an old CD player motor which in most cases will be clamped to a ring stand-like thing. Maybe I'm reading your post wrong...

[Flavorflav]

Thank you!
Actually I have another question about size limits: do the blades have to be *between* 25 and 28 cm diameter (i.e. 25 is minimum and 28 is maximum) or is the maximum somewhere arbitrarily between 25 and 28 cm (i.e. anywhere lower than that arbitrary value is fine)? And are there limits on the depth of the blades or how far they can "stick out" from the CD (I know this isn't an "official" rules forum or anything, but does anyone know)?

Thanks so much!!

25 is the minimum and 28 is the max. And if you can't find a rule that limits the depths of the blades, I would think they can stick out as far as you want them to.

They can stick out as far in front as you want. They cannot project past the CD at all, however. This is to ensure that they cannot hit the testing apparatus.