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Re: MagLev C

Posted: March 19th, 2014, 2:54 pm
by TheGatesofLogic
yup, yup, just noticed that, another question I have however is regarding supervisors choosing the start and stop lines, the problem being that many tracks attract the vehicle near the ends of the track which throw of consistent calculations, something I can see as being a major issue in more sensitive cases

Re: MagLev C

Posted: March 19th, 2014, 3:11 pm
by joeyjoejoe
We had this exact issue arise at our regional competition. Our track is 4 ft long with a 22cm car which leaves very little room for start line adjustment. We marked the start and finish line on our track but the supervisor could've changed it - just as long as it was less than 6 cm or so.
To compound the problem, our stopping mechanism consists of foam placed on top of opposite polarity magnets sitting just outside the end of the rails (a recommendation from this very forum in fact) so if you push the start location more than about 3cm back, the attraction to our stopping mechanism skews the data terribly. We thought of just building an 8ft track but, sadly, we didn't have enough magnets (or money or time....) so we just hope the supervisors will be understanding.

Re: MagLev C

Posted: March 19th, 2014, 3:42 pm
by chalker7
Submit an official clarification, no one can issue a binding statement through these forums.

Re: MagLev C

Posted: March 20th, 2014, 7:29 pm
by chalker
We've posted an slightly updated FAQ response that I'm sure will be of interest to many of you at http://www.soinc.org/node/292

"May a run still be considered successful if the vehicle momentarily stops at some point on the track after the start line and before the 95 centimeter line, and then begins moving again so that it passes the 95 cm line?
Yes. Although note that if the vehicle stops by design for more than 3 seconds (i.e. in order to stall for time), that is not allowed as it is a potential safety hazard and is not within the spirit of the rules.”

I received a lot of feedback, some public and some private, regarding this issue, and after consulting further with Physics committee members and the National Event Supervisor we thought this change strikes the appropriate balance between safety and various creative solutions.

Hopefully this will serve in the future as a good example of the fact we do take into account relevant feedback and are truly looking out for what's best overall for Science Olympiad (and we readily admit we don't always get things perfectly right the first, second, third, etc time;).

Re: MagLev C

Posted: March 21st, 2014, 8:06 am
by Stingray355
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.

Re: MagLev C

Posted: March 21st, 2014, 12:29 pm
by FawnOnyx
Stingray355 wrote: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.

Re: MagLev C

Posted: March 21st, 2014, 4:46 pm
by 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.

Re: MagLev C

Posted: March 30th, 2014, 3:18 pm
by 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.

Re: MagLev C

Posted: April 1st, 2014, 8:18 pm
by 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 :?:

Re: MagLev C

Posted: April 2nd, 2014, 6:22 am
by 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.