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.
But the portion of the rail which wraps around the vehicle does not have a magnetic field, so you can't use magnetic repulsion to keep your vehicle off of the side rails.
chalker wrote:
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).
If wheels were allowed on the sides but not the bottom, the vehicle would still have to levitate.
chalker7 wrote:
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.
Not having one to play with, I wonder if that is a workable idea. Will it be very hard to separate the vehicle from the track if you do that? We don't want magnets getting ripped off during this 'check' process.
Student Alumni
National Event Supervisor
National Physical Sciences Rules Committee Chair
chalker wrote:
Not having one to play with, I wonder if that is a workable idea. Will it be very hard to separate the vehicle from the track if you do that? We don't want magnets getting ripped off during this 'check' process.
I'm not entirely sure, but I imagine that could be a relatively easy thing to accomodate during construction with proper attachment procedures.
National event supervisor - Wright Stuff, Helicopters
Hawaii State Director
This is very simple to do. I often see teams accidentially set up their car the wrong direction on the track to start and they just lift it back up and switch it...pretty simple. I've never seen a car that has a problem with this, but that doesn't mean it does not exist. Certainly a valid consideration for the rules next year.
Andy Hamm
Boyceville Science Olympiad
Boyceville, WI
Yes, removing a reversed car from the track shouldn't be a problem, espwcially if teams are cautioned to slide their cars off the end of the track instead of lifting them off; this is how I personally glue the magnets to the frame of the car, by having the magnets in reverse position then glueing the body down backwards, and it has always worked fine.
Doesn't Earnshaw's theorem imply that, especially at rest, the car must touch the sides? From experience, in order to move at all the car must fit the track perfectly along the entire run. Therefore I take issue with rule 3.l on the grounds that tracks not only vary from one track to another, but they vary in width along the length of a single track. This rule, as I understand it, bans the use of self-adjusting mechanisms, such as wheels on springs, as previously mentioned, which appears to be the only viable solution to this problem. Teams in the past were plenty smart enough to put into place the type of adjustable sleds mentioned, including shims, thick tape, and interchangeable sleds, yet the event was still plagued with stationary cars.
Furthermore, why is there an issue with wheels on the sides? As long as they are not powered, they contribute neither to the propulsion of the car nor its levitation beyond the sides of the car making contact. Unpowered wheels could be used on self-adjusting mechanisms, as previously mentioned in this thread, and/or simply to reduce friction, and the use of low friction materials is certainly not banned.
blue cobra wrote:Teams in the past were plenty smart enough to put into place the type of adjustable sleds mentioned, including shims, thick tape, and interchangeable sleds, yet the event was still plagued with stationary cars.
Based upon what we saw last year at Nationals, this is not true. SOME teams are smart enough to do this... a significant number weren't.
We've been having some good conversations amongst the physics committee members about how to deal with this. Our current thinking is to use the following wording in place of the current 3.j wording:
The vehicle must be 100% levitated as it moves down the track (inadvertent contact with the track is permitted). Students will demonstrate that their vehicle is levitated before their run starts by pushing the vehicle down to the bottom of the track and then letting go. A levitated vehicle will pop back up to its original position by itself.
Student Alumni
National Event Supervisor
National Physical Sciences Rules Committee Chair
That seems like a perfect definition for levitated, and I would love to see that in next year's rules! However, I believe the word "inadvertent" should be removed, as contact with the track seems necessary for stability.
My team's time was 1.3/1.4 which was 2nd place