Hovercraft B/C

[petermai6655]

I'm not sure exactly what you're saying, but for calculating rotation speed for the voltage, you can do some tests. First hook up a voltmeter to the ends of the battery, and record that, then run the motor with a slow mo cam and put a stopwatch next to it to calculate rpm. Then do multiple tests, and see if there is a curve. Hopefully this helps

You could also wing it and hope for the best!

Best strategy in this whole thread.

I am wondering if you are referring to a high tech slow motion camera (thousands of frames per second) or if a budget camera set to a high framerate of like 120fpm would be fine? (Basically, I'm asking whether or not a 120fps camera will be fast enough to pick up the fan blade.)

[retired1]

Last year I bought a strobe tachometer at a very nice price. Do not remember where.

[cheese]

You could also wing it and hope for the best!

Best strategy in this whole thread.

I am wondering if you are referring to a high tech slow motion camera (thousands of frames per second) or if a budget camera set to a high framerate of like 120fpm would be fine? (Basically, I'm asking whether or not a 120fps camera will be fast enough to pick up the fan blade.)

Sorry for the bad info. I tried it myself at 240fps, but I couldn't get anything for my 12000 rpm fan. It just was the first thing that came to mind. If you know ballpark rpm, you can do the math for how many fps's you need. If you have a high-tech camera (I would assume not) try it. But otherwise I would try a tachometer like this: https://www.amazon.com/Digital-Photo-La ... tachometer.

[petermai6655]

Are tachometers allowed during the event? I know that "Tools and supplies do not need to be impounded" but that doesn't specify what tools are allowed. My event coordinator allowed the use of voltmeters (but they needed to be impounded apparently).

[LittyWap]

My consistency is about +-0.05 seconds

Really??? That's crazy

That is just... Amazing! Congrats! If you're using a potentiometer based system, how do you account for different track surfaces? Also, if you are trying to vary the velocity of the hovercraft, how do you take into account the acceleration before the velocity levels out? That's the thing that is causing my inconsistency.

I am not using a potentiometer system, for ours was really unwieldy and inconsistent. I use cover sheets, and as for the track surfaces, I just get a lot of data. Like. A LOT OF DATA. I guess it payed off, because we recently got a build score of 49.1, a mass of 1996g and a time score 0.3s off target.

[LittyWap]

Are tachometers allowed during the event? I know that "Tools and supplies do not need to be impounded" but that doesn't specify what tools are allowed. My event coordinator allowed the use of voltmeters (but they needed to be impounded apparently).

Yea same here. I used a voltmeter but it had to be impounded. I'm guessing they don't want you to cram some programs in there? Idk

[cheese]

Really??? That's crazy

That is just... Amazing! Congrats! If you're using a potentiometer based system, how do you account for different track surfaces? Also, if you are trying to vary the velocity of the hovercraft, how do you take into account the acceleration before the velocity levels out? That's the thing that is causing my inconsistency.

I am not using a potentiometer system, for ours was really unwieldy and inconsistent. I use cover sheets, and as for the track surfaces, I just get a lot of data. Like. A LOT OF DATA. I guess it payed off, because we recently got a build score of 49.1, a mass of 1996g and a time score 0.3s off target.

So how did you compensate for battery voltage curves?

[cheese]

It says "The vehicle must be less than 20.0 cm tall when the propellers in motion when non-levitated." So if my hovercraft is 19 cm tall when non-levitated, but then goes to 25 cm when levitated, it's okay?

[ericlepanda]

It says "The vehicle must be less than 20.0 cm tall when the propellers in motion when non-levitated." So if my hovercraft is 19 cm tall when non-levitated, but then goes to 25 cm when levitated, it's okay?

yep

[BDake]

The track is just going to change the coefficient of friction. If you test on a track with a different coefficient of friction, which we probably all will because we can't know 100% how he made the track, what the rails were and all the stuff that effects it, you just have to know how to account for different coefficients of friction in your math and calculations. Its a physics event after all ..

It also makes it the most fair if we are kept in the dark about the track until we have to run it. Every team that either checks the forum or not will be on the exact same page

Exactly this ^. I couldn't have said it better.

Lesson learned from States this weekend - just when you think you'd tested as many surfaces you can anticipate for the track, plywood shows up - would have never guessed this to be a possible surface, and cost us dearly. Others clearly pulled it off, so wasn't impossible by any stretch - just circles back to all the real world comments and advice in this forum to be as prepared as possible for variables in the events.