MagLev C [Trial]

chalker
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Re: MagLev C [Trial]

Post by chalker » December 9th, 2011, 8:52 am

Littleboy wrote:Maybe something about it having to be made adjustable to best fit the track. And have a different rule stating that wheels or something similar is not permitted.

Basically that's essentially what we did.
3.c says "...is recommended to be designed with removable width to accommodate track variations (e.g. shims, thick tape, etc). "
3.l says "The vehicle must be designed to not intentionally physically contact any part of the track. "

You can't limit 3.l. to just 'wheels', because people will engineer devices that have a similar result (i.e. thin rails, skids, etc)

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Re: MagLev C [Trial]

Post by chalker7 » December 9th, 2011, 9:38 am

chalker wrote:
Littleboy wrote:Maybe something about it having to be made adjustable to best fit the track. And have a different rule stating that wheels or something similar is not permitted.

Basically that's essentially what we did.
3.c says "...is recommended to be designed with removable width to accommodate track variations (e.g. shims, thick tape, etc). "
3.l says "The vehicle must be designed to not intentionally physically contact any part of the track. "

You can't limit 3.l. to just 'wheels', because people will engineer devices that have a similar result (i.e. thin rails, skids, etc)
But the issue is the "intentionally physically contact any part of the track" bit. By adjusting the width of the vehicle to make a tight fit, you are inherently "intentionally" touching the track. It's no different from having tight skids on the sides of the vehicle (in fact, what is the difference between a skid and a shim that would make it a tight fit?).
More importantly, what is the problem with having wheels and/or skids on the sides? I understand that we want to have the vehicles be "completing levitating" to model real maglev trains, but we've already gotten away from that model by making the vehicles wind-propelled and having sides on the track that are not lined with switching electromagnets (that the vehicle WILL touch).

Allowing wheels and skids might alleviate some of the issues and fears people have with this event. By having automatically adjusting wheels/skids on the sides (spring mounting them), teams will not have to worry so much about a supervisor's track being slightly different from their own and they will be able to overcome the slight gap between the two track sections that is frequently a problem.
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Re: MagLev C [Trial]

Post by Flavorflav » December 9th, 2011, 9:42 am

I thought the wording was pretty clear. I was less clear on the reasoning , though - why should wheels on the sides be illegal? It seems like a pretty neat solution to the problem, and I can't see how it is a violation of the spirit of the event. Sure, real maglevs don't have them - but they get to wrap around the rail, which is a solution that is not open to us.

ETA: I appear to be agreeing with chalker7, who was posting at the same time.

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Re: MagLev C [Trial]

Post by chalker » December 9th, 2011, 11:21 am

Flavorflav wrote:I thought the wording was pretty clear. I was less clear on the reasoning , though - why should wheels on the sides be illegal? It seems like a pretty neat solution to the problem, and I can't see how it is a violation of the spirit of the event. Sure, real maglevs don't have them - but they get to wrap around the rail, which is a solution that is not open to us.

ETA: I appear to be agreeing with chalker7, who was posting at the same time.

The fundamental reason we don't want wheels is because as soon as we allow them, there will be a slippery slope in the design process, resulting in lots of vehicles that essentially ONLY have wheels and no magnets / levitation (meaning it's no longer a maglev event).

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Re: MagLev C [Trial]

Post by fleet130 » December 11th, 2011, 10:11 am

A major advantage to mag-lev is the tremendous reduction of friction in the vehicle/track interface. The introduction of wheels in the design would tend to negate this advantage and thus decrease performance. On the other hand, I would be surprised if real-world mag-lev vehicles don't use some type of guide wheels/skids to prevent incidental contact with the track. Imagine a mag-lev train screaming along at 100+ MPH experiencing a loss of levitation. Wheels/skids are needed to prevent/minimize damage.

Since the vehicle is likely to contact the track at one or more points during a run, it could be beneficial to have some type of wheels/skids to reduce friction if/when contact occurs. If there are no magnets in the vehicle, it's fairly easy to come to the conclusion it doesn't comply! Whether "levitation" occurs could be more difficult to determine. Simply state that "Magnets must be used to levitate the vehicle. When sitting at rest on the track in the starting position, no point on the vehicle may contact the track."

Let the contestants discover what is beneficial and what is not. If they use something detrimental to performance, the lack of investigation/understanding will be reflected in the score.

Of course this is always subject to interpretation/misinterpretation. Your comments/suggestions are welcome!
Flavorflav wrote:they get to wrap around the rail, which is a solution that is not open to us.
No, but the rail "wraps" around the vehicle.
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Re: MagLev C [Trial]

Post by twototwenty » December 12th, 2011, 6:34 am

With a car with width adjustment device of shims, the friction created would be static friction, if I'm not mistaken, whereas with wheels, the friction would be kinetic and a lot smaller, thus better preserving the spirit of the competition.

Personally, i think a good solution to this problem would be just saying that the vehicle must be levitated by magnets and propelled by fans, because it is inevitable that it will touch the sides of the track. That is, afterall, the point of the track: to guide the vehicle.

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Re: MagLev C [Trial]

Post by chalker » December 12th, 2011, 10:50 am

twototwenty wrote:With a car with width adjustment device of shims, the friction created would be static friction, if I'm not mistaken, whereas with wheels, the friction would be kinetic and a lot smaller, thus better preserving the spirit of the competition.

Personally, i think a good solution to this problem would be just saying that the vehicle must be levitated by magnets and propelled by fans, because it is inevitable that it will touch the sides of the track. That is, afterall, the point of the track: to guide the vehicle.

I think you are missing the point of the 'adjustable width' rule. We've found in practice that there is variability in track widths. Far too many teams have shown up with cars that are 'just in spec' only to find them get stuck halfway down the track cause of the variability. We are trying to ensure that teams can compete by being able to make adjustments to their vehicles. If we don't put that in the rules, some event supervisor somewhere will disallow adjustments.

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Re: MagLev C [Trial]

Post by chalker » December 12th, 2011, 10:53 am

fleet130 wrote: Simply state that "Magnets must be used to levitate the vehicle. When sitting at rest on the track in the starting position, no point on the vehicle may contact the track."

That's a good starting point. But I'd be concerned over whether most vehicles 'sitting at rest' would be able to sit perfectly square such that the don't contact the side rails. I suspect (and would love for someone to do some tests) that slight imbalances in the magnetic fields cause the vehicles to twist to one side or the other, touching the side rail naturally. If that is the case, any suggestions on how to reword this?

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Re: MagLev C [Trial]

Post by chalker7 » December 12th, 2011, 8:26 pm

chalker wrote:
fleet130 wrote: Simply state that "Magnets must be used to levitate the vehicle. When sitting at rest on the track in the starting position, no point on the vehicle may contact the track."

That's a good starting point. But I'd be concerned over whether most vehicles 'sitting at rest' would be able to sit perfectly square such that the don't contact the side rails. I suspect (and would love for someone to do some tests) that slight imbalances in the magnetic fields cause the vehicles to twist to one side or the other, touching the side rail naturally. If that is the case, any suggestions on how to reword this?
How about saying if the vehicle is laying in the reverse direction, the sides of the vehicle cannot touch the sides of the track. Presumably reversing the magnetic field like that would pull the vehicle down onto the track and hold things tightly without worrying about any twisting from imbalances.

Either that or allow the vehicle to touch the sides.... By the way, I have yet to hear a good distinction between skids and shims. Clearly, skids are meant to contact the walls in a low friction manner whereas shims are meant to increase the width of the vehicle, but I would have an incredibly difficult time distinguishing between the two on a maglev vehicle.
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Re: MagLev C [Trial]

Post by twototwenty » December 13th, 2011, 6:25 am

chalker wrote:
twototwenty wrote:With a car with width adjustment device of shims, the friction created would be static friction, if I'm not mistaken, whereas with wheels, the friction would be kinetic and a lot smaller, thus better preserving the spirit of the competition.

Personally, i think a good solution to this problem would be just saying that the vehicle must be levitated by magnets and propelled by fans, because it is inevitable that it will touch the sides of the track. That is, afterall, the point of the track: to guide the vehicle.

I think you are missing the point of the 'adjustable width' rule. We've found in practice that there is variability in track widths. Far too many teams have shown up with cars that are 'just in spec' only to find them get stuck halfway down the track cause of the variability. We are trying to ensure that teams can compete by being able to make adjustments to their vehicles. If we don't put that in the rules, some event supervisor somewhere will disallow adjustments.
I thoroughly understand the point of the adjustable width rule. What I meant to say before was that if the part of the adjustable width device, which would inevitably touch the track, should be able to consist of wheels just as much as it should be able to be shims. Bothe would touch the track, but wheels would produce less friction and therefore better preserve the spirit of the competition: having a magnetically levitated car. My point was that saying "no wheels" shouldn't necessarily be included in future rules.

I personally like chalker7's idea, with the car in reverse direction not being able to touch the track, as no matter to vehicle, when it is being levitated, it will touch the track, no matter what.

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