MagLev C

[Flavorflav]

Thank you. As it happens, I actually knew what Gangnam Style was - irony, you see. My generation loves it.

[bearasauras]

OK Bear, it was used in this passage:

As an aside, here's a fun quick experiment you can do. Take 2 flat fridge magnets and put them face to face (magnetic side touching magnetic side). Slowly slide them back and forth past each other, then rotate one of the magnets slightly in relation to the other. Rinse and repeat this process until at some point you'll feel the magnets 'clicking' in small steps when you try to slide them past each other. You've now aligned the Halbach arrays with each other and what you are feeling is the attraction when the North and South poles align, versus the repulsion when the like poles align. If you use a ruler you can count the number of steps over a 1cm and figure out the actual width of the magnetic domains.

So if part of it is BS, I guess that it makes the whole paragraph BS times 3 for all of the national folks that are getting a good laugh at my being naive.
Gee, dumb me--I thought that this was a science site rather than Saturday Nite Live.

Wait no, I was being serious. I didn't get the rinse reference either.

[Flavorflav]

Looking through the rules, I see no restrictions on the type or placement of magnets on the track. Given general rule 2, this should mean that we can use any kind of magnets (including rare earth) in any configuration we desire. Does anyone disagree with that interpretation?

[Balsa Man]

Chalker, would you care to give your unofficial opinion about the ducted propeller-motor combinations? If a student uses their own motor and a separate ducted fan, is the motor allowed to go up to 65 cm, or does that larger size apply only to commercial ducted fans with integral motors?

I think a better question would be;

Is the duct on a ducted fan considered part of the propeller or part of the vehicle?

If it is part of the propeller, it would be allowed to extend outside of the track rails (the only exception to the width rules) and the 6cm limit would be significant in limiting the size of the motor/prop combination.

If it is part of the vehicle it cannot and would be limited to the width of the track (65.09mm on a 2 9/16" track or 76.2mm on a 3" track) since no part of the vehicle is allowed outside of the sides of the track.

Unofficially, the duct is part of the vehicle. It is not allowed outside the track rails (hence the 6cm width of it, which was originally put in to account for the standard width track, then we forgot to update to account for the wider/narrower range allowed for team provided tracks).

Regardless, the reason behind the rules is that we want to limit the overall size of the motors to help try to avoid too powerful motors that could cause injuries. Since there are commercially packaged ducted fan/motors available, we realized it might be hard to directly measure the diameter of the motor, so we put in the 6cm limitation to ensure teams didn't have to disassemble their devices to be checked (the assumption being that the duct blocks the motor from being easily measured). Thus the language specifies ducted motor/propeller. If the propeller is the only part ducted, then you can easily measure the motor and the normal limit applies.

So, it sounds like - and just trying to confirm; there was no consideration of.....equivalancy of thrust from a 20cm dia conventional prop (w/ a conforming motor), and commercially available 6cm diameter ducted fan w/ a 9v, brushed motor?

[illusionist]

Looking through the rules, I see no restrictions on the type or placement of magnets on the track. Given general rule 2, this should mean that we can use any kind of magnets (including rare earth) in any configuration we desire. Does anyone disagree with that interpretation?

Actually, rule 3.k says - "Any magnets, except rare earth magnets, may be used on the vehicle"

So that clearly states that rare earth magnets can't be used on the vehicle, but I'm not sure about the track. As of now, it seems to me you can. Although it'd be best to submit an official rule clarification later.

[chalker]

So that clearly states that rare earth magnets can't be used on the vehicle, but I'm not sure about the track. As of now, it seems to me you can. Although it'd be best to submit an official rule clarification later.

The primary reason for the prohibition of rare earth magnets on the vehicle is because if you accidentally put one down on a 'standard' track, you can very easily demagnetized some of the track magnets, resulting in a 'dead spot' that effectively ruins the track (particularly if the track uses magnetic tape).

When you bring your own track, you take that risk upon yourself. Thus (unofficially of course), you can use rare earth magnets on your own track. However I'm not sure what advantage it would give you besides additional cost.

[chalker]

So, it sounds like - and just trying to confirm; there was no consideration of.....equivalancy of thrust from a 20cm dia conventional prop (w/ a conforming motor), and commercially available 6cm diameter ducted fan w/ a 9v, brushed motor?

Generally, yes we didn't consider that. There were far too many other issues to work out with the rules.

[Balsa Man]

So, it sounds like - and just trying to confirm; there was no consideration of.....equivalancy of thrust from a 20cm dia conventional prop (w/ a conforming motor), and commercially available 6cm diameter ducted fan w/ a 9v, brushed motor?

Generally, yes we didn't consider that. There were far too many other issues to work out with the rules.

Thanks, Chalker. Understand; I'm sure there were...

[bearasauras]

So that clearly states that rare earth magnets can't be used on the vehicle, but I'm not sure about the track. As of now, it seems to me you can. Although it'd be best to submit an official rule clarification later.

The primary reason for the prohibition of rare earth magnets on the vehicle is because if you accidentally put one down on a 'standard' track, you can very easily demagnetized some of the track magnets, resulting in a 'dead spot' that effectively ruins the track (particularly if the track uses magnetic tape).

When you bring your own track, you take that risk upon yourself. Thus (unofficially of course), you can use rare earth magnets on your own track. However I'm not sure what advantage it would give you besides additional cost.

I don't know much about this event or magnetism but would stronger magnets allow you to better control the position of the vehicle so that it's less likely to bump into the sidewall as it's going down the track, thus minimizing the lost of energy?

[chalker]

I don't know much about this event or magnetism but would stronger magnets allow you to better control the position of the vehicle so that it's less likely to bump into the sidewall as it's going down the track, thus minimizing the lost of energy?

On the 'standard' track, the magnets are only on the floor, not on the sidewalls. You only use them to levitate the vehicle. Stronger magnets just mean a larger gap, not necessarily increased stability and definitely not any type of lateral (side to side) stability.