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I like the safety switch, but it may be harder to implement than you think. A normally closed switch will bounce off the stop block and cause the vehicle to oscillate at the end, to put one on ours I had to put a latching relay on it and use a switch to trigger and another micro switch in the front the stop.

We're running a simple click-on, click-off button switch near the front - lexan bars across the track past the finish line. Press button to start, when it hits the lexan at the end, switched off. Lexan provides a little give (but plenty strength) for the finish impact. Little retainers over the top edge of the rail that keep the back end from sumersaulting when stopped.

I had a bit more of an accident, several gause pads and a couple stitches were needed. But now I know better and it wont be an issue again.
I use a dpdt switch on my front, easy flip on an off. I have a pillow-y-thing at the end of the track it runs into and stops it so i can switch it off.

wlsguy wrote:

Lake101258 wrote:Has anyone tested to see whether the rectangular ceramic magnets or the strip magnets from Kelvin are better?

The ceramic magnets have more lift but also have more weight. I don't know the weight / lift ratio of each but would suspect the ceramic magnet is more powerful.

But in respect to the track which would be more efficient to use. I feel like the strips would give a more reliable constant field but not as strong. I am thinking about doubling up the strips (one on top of the other)

Not sure I know what you mean by "efficient" but my experience has been that the strip magnets are much weaker than the other magnets (are they indeed ceramic??).


As far as accidents go, only the coach (me) has been stupid enough to grab a car in motion and he paid for it with the loss of a few tablespoons of blood. After that, we were all much more careful.
We had a switch setup at the front much like Balsaman mentions but it finally broke so we now use a sled design. The sled has opposite polarity magnetic strips on it to stop the car and the entire assembly has medium-friction washers on the bottom so that it can slide in a path (created about its left and right edge with wood screws) for about 6 inches. This is a much more controlled deceleration than a pillow and has less of a chance of contacting our props.

I think requiring the car be designed to power itself off at the end of the run would be a good idea.
The exact method could be left up to the students but it should not be counted as part of the length of the vehicle.
It would also need to fit below the 20cm limit so as not to interfer with the photogates.

One idea would be to use a pull on, push off switch similar to this one.
http://www.repairconnector.com/products ... T-12V.html

On scoring: it says that the max score is 110, but I could see how someone could get over that, am I missing something?

If your the best VS so that the RS is 50, and you get a perfect score on the test (50), and the time you travel is <1 second and you guess exactly right, then the TSX10 would be > 10 points if the times is less than 1 second. So its possible to get a 110+? right?

Nope, (1-(|RT-PT|/RT))X10 will, if you guess exactly right be the same as : (1-(0/RT))X10=(1-0)X10 =10 regardless of whether you are under 1 second.

joeyjoejoe wrote:Nope, (1-(|RT-PT|/RT))X10 will, if you guess exactly right the the same as : (1-(0/RT))X10=(1-0)X10 =10 regardless of whether you are under 1 second.

Oh... Darn parenthesis...

Regarding stopping the vehicles at the end of the run, a simple solution the national supervisor came up with is to just put a metal plate on the table at the end of the track. The vehicles fall off the track and their magnets immediately lock them onto the plate so they won't move any further.