MagLev C

[FawnOnyx]

Bravo! I am disappointed that there isn't enough time for us to build our design but I am happy to know that some of the teams that rolled the dice will now be able to show off their devices.

A general comment that is in reference to the no IC policy. I think that at some point this will need to be reviewed for all of the events that use motors. Brushed motors are continuing to be harder to find as brushless motors now dominate the market. A few years ago brushless motors were very expensive but now prices have dropped dramatically. For teams that have a box full of brushed motors or a local source this will have little impact but for new teams that don't have a good source it might hinder their design options. At some point it might make sense to look at moving to current available technology.

With the lower prices for brushless, better selection and availablity and the likelihood that those that go on to careers in engineeering/technology will probably find an environment where brushless technology is the standard this might be a logical evolution.

I don't see this as an immediate issue and maybe a slow transition with brushless allowed in some Trial Events would be an option.

I think this was more of a problem with safety? Brushless motors could potentially be much more powerful and dangerous.

[Stingray355]

Maybe, maybe not, they come in various sizes and ratings and there are readily available charts and other rating systems that can be referenced to select a brushless that is similar or the same as a given 180,300,400 class motor. They are often much more efficient but I don't believe that their design is somehow more dangerous. The folks that define the events and rules test and are also very familiar with the technology I am confident they could spec out a safe event with brushless technology.

I found many, many brushless ducted fans for every brushed system I found when we were shopping for one for this season.

I think safety is a critical consideration and should never be compromised. I also see much more powerful and dangerous tools being used in the construction of these devices every season. As out of control as some of the devices were last year getting your finger nicked by a plastic propeller is not good, make a mistake with the 12" compound miter saw we use to cut most of our wood components for different builds and the consequences are much more serious. It uses a brushed motor.

[blakinator8]

I was thinking about the '5 failed runs and 2 successful runs' part of the rules. What, exactly, constitutes a 'failed run?' Can I deliberately turn off my device mid-run if I know that it's not going to meet its target time?
Standard caveat about not being the place for rules clarifications. I think it is reasonable to do this during your 8 minutes, and have it count as a failed run. I've been to tournaments where the supervisor would not let us have practice runs on our track , so I would just stop the device before it reached the second photogate.

[Aerospacevulcan]

the potentiometer I am using smells burned when I put it on a setting that makes the brushed edf turn slowly. Is this normal or can damage be done if it is left on for too long? Also has anyone been able to get accurate values from methods that do not use electronics to control the speed such as the friction one proposed

[Stingray355]

When we were building for SumoBots we found out about "Magic Smoke" Magic Smoke is the smoke rising from your device when the soul leaves the body of your robot. In competition we witnessed several teams make magic smoke, fortunately we did not .

I have heard of several teams making smoke this year in MagLev, particularly ones using 1/4 watt resisters. Without knowing the specifics of your battery/EDF/potentiometer I could only guess. You should look at the specs and do some basic calculations. If you are smelling something there is a reason for that.

For comparison we are using a variable resister rated for 100 watts with an EDF and a 6 cell NIMH, it gets warm after numerous back to back calibration runs.

[mp727]

My maglev car is not working. It looks like it is getting stuck to the track and I tried fixing it by putting tape on the side rails of the track, but it seems like it isn't working. I don't know what else i can do. Also my car doesn't weigh a lot either, so i dont really know what the problem is. I have a state competition in 4 days and I need to do something about it. Can someone please help me!

[FawnOnyx]

My maglev car is not working. It looks like it is getting stuck to the track and I tried fixing it by putting tape on the side rails of the track, but it seems like it isn't working. I don't know what else i can do. Also my car doesn't weigh a lot either, so i dont really know what the problem is. I have a state competition in 4 days and I need to do something about it. Can someone please help me!

Some things you can check for:
Are your car magnets spaced wide enough so they're centered directly over the track magnets?
Is the car just barely narrower than the track width?
Is the center of gravity low?
Sometimes higher side walls on the car may help.

I was in a really similar position last year before our state so don't panic, be patient, try those things and hopefully it'll work out! (It did for me)

[Stingray355]

Join the club only about half of the vehicles at our State competition were able to make a complete pass. Ours weighs very close to 2 kilos and I don't know if your lighter weight device is as sensitive to these same factors as ours but I can tell you where we found improvements. A key challenge this year is eliminating all sources of friction/drag (unless your design uses that to slow it down to run the designated time) The only parts of our device that actually makes contact with the track are two very small flanged roller bearings and the contact area is very small and has little friction. Note both are on the same side of the vehicle and the other side simply floats and never contacts the track, if it did there are two more flanged roller bearings that would be the contact points.
For us the need to have the track level was key to being able to run the longer times and also to run with any consistency. Our vehicle sees low or high points as a "hill or valley" and will react accordingly. We found that a good carpenters level is not precise enough and used it just to get it close. A more accurate indicator was the vehicle, we put it on the track without power of course and gently bumped it in both directions at all points on the track. Any deviations from level will show up in the behavior of the vehicle. This only takes a few moments and will allow the vehicle to run to its calibration.

Do this along with the suggestions made by FawnOnyx and I agree you will get it sorted out and be ready for the big competition. Good luck.

[jharmn]

On rule 2J, about the vehicle needing to operate in either direction: is this in reference to using the event-provided track, or is this relevant with bringing your own track as well (we have our own track)? With weight balance and prop torque change, this is a tricky issue that I don't want us to waste time tuning if it's not a real concern. Are we going to have to run the vehicle in both directions in order to get valid runs? This isn't entirely clear from the rules. We didn't do this event for regionals, and I haven't seen it conducted before, and wasn't sure about how this aspect works.

[Schrodingerscat]

On rule 2J, about the vehicle needing to operate in either direction: is this in reference to using the event-provided track, or is this relevant with bringing your own track as well (we have our own track)? With weight balance and prop torque change, this is a tricky issue that I don't want us to waste time tuning if it's not a real concern. Are we going to have to run the vehicle in both directions in order to get valid runs? This isn't entirely clear from the rules. We didn't do this event for regionals, and I haven't seen it conducted before, and wasn't sure about how this aspect works.

(Standard disclaimer: This is not the place for rule clarifications, any opinions expressed have no official standing)

My understanding is that at least the primary intent of 3.J is for photogate systems that cannot easily be reversed. Thus the event supervisor can require students to always enter and leave the photogate in one direction; however, it also says that you can rotate the track so your vehicle always moves one direction down the track.