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Are there any good Division B study materials for the Hovercraft Test? The test exchange only has 1 test - are there any other options?

SciHC101 wrote:Are there any good Division B study materials for the Hovercraft Test? The test exchange only has 1 test - are there any other options?

For Division B, I'd recommend looking at an algebra-based physics textbook, such as Giancoli's. Additionally, you could look at AP Physics 1 exams/practice material

Adi1008 wrote:

SciHC101 wrote:Are there any good Division B study materials for the Hovercraft Test? The test exchange only has 1 test - are there any other options?

For Division B, I'd recommend looking at an algebra-based physics textbook, such as Giancoli's. Additionally, you could look at AP Physics 1 exams/practice material

Sure, if you can answer the questions in that textbook and the AP exam, then you'll be able to ace any Div B exam. I don't know many people in Div B who could do that, though. I guess the top teams will probably be at that level. Out of curiosity, what would you recommend to study in Div C? Have you seen tests with content at a higher level than an introductory college physics course?

petermai6655 wrote:How do you control the speed of the hovercraft? Whenever I try to add a potentiometer, it smokes up because of the high current draw of the motor. Whenever I add a MOSFET to the circuit, to enable high current support, the motor's speed is significantly reduced. I tried many potentiometers and different types of batteries and still can't control the speed. Am I doing something wrong?

You just have to have the right potentiometer. As far as I know, no potentiometers exist that support such high current LiPo/NiMH batteries. Either pick weaker batteries, add more mass, or use cover sheets or something.


-p

LittyWap wrote:

petermai6655 wrote:How do you control the speed of the hovercraft? Whenever I try to add a potentiometer, it smokes up because of the high current draw of the motor. Whenever I add a MOSFET to the circuit, to enable high current support, the motor's speed is significantly reduced. I tried many potentiometers and different types of batteries and still can't control the speed. Am I doing something wrong?

You just have to have the right potentiometer. As far as I know, no potentiometers exist that support such high current LiPo/NiMH batteries. Either pick weaker batteries, add more mass, or use cover sheets or something.


-p

There most definitely are potentiometers available that can handle the current from batteries. Check out this Digikey link and filter by power: https://www.digikey.com/products/en/pot ... ageSize=25

I am looking at computer fans right now and I found one that has a high CFM. However, when I looked at the operating voltage in the datasheet, the voltage range is from 10.8 to 12.6. I was wondering if this fan will still run or not. Will the fan still be powerful? I already ordered the fan, so if there is a problem, please let me know so I could cancel the order.

petermai6655 wrote:I am looking at computer fans right now and I found one that has a high CFM. However, when I looked at the operating voltage in the datasheet, the voltage range is from 10.8 to 12.6. I was wondering if this fan will still run or not. Will the fan still be powerful? I already ordered the fan, so if there is a problem, please let me know so I could cancel the order.

This is a problem that happened to our team. We tried to run the fan with a 8.4V NiMH that was a bit overcharged to about 9V, but it still wasn't enough voltage to run the fan. I would recommend cancelling your order and getting a different van with lower voltage requirements. If you ordered from Digi-Key, they're very good about returns and order cancellations in my experience.

dcrxcode wrote:

petermai6655 wrote:I am looking at computer fans right now and I found one that has a high CFM. However, when I looked at the operating voltage in the datasheet, the voltage range is from 10.8 to 12.6. I was wondering if this fan will still run or not. Will the fan still be powerful? I already ordered the fan, so if there is a problem, please let me know so I could cancel the order.

This is a problem that happened to our team. We tried to run the fan with a 8.4V NiMH that was a bit overcharged to about 9V, but it still wasn't enough voltage to run the fan. I would recommend cancelling your order and getting a different van with lower voltage requirements. If you ordered from Digi-Key, they're very good about returns and order cancellations in my experience.

Did you find any good fan from Digi-Key? Because Those with high CFMs from Digi-Key, that I found, didn't work with the low voltages that are allowed. Also, how did your team control the speed of the hovercraft, because I am experiencing a problem with using a potentiometer with mines?

Question about the scoring rule 6d. Our team has a hovercraft that works at 2 kg. To ensure full credit for the MS, there's a small container of sand ballast - the strategy is to adjust that mass at impound, to make sure the vehicle registers 2,000.0 grams on the supervisor's scale. Rule 5g leaves the possibility open that this mass check will be done right before a run. Re-reading the rule, I'm worried that they'd have 2,001 grams, have to remove a gram of sand before the run, and get the 0.7x penalty.

So to summarize, 1) has anyone used this strategy successfully, and if so, was the measurement during a pre-competition impound, or right before the run?
2) could the penalty be avoided if the vehicle was designed to weigh in at say, 1,995 grams, and the last bits of sand were added while the vehicle was on the scale, so as not to go over and get the construction violation?

Thanks!

chalker wrote:

LittyWap wrote:

petermai6655 wrote:How do you control the speed of the hovercraft? Whenever I try to add a potentiometer, it smokes up because of the high current draw of the motor. Whenever I add a MOSFET to the circuit, to enable high current support, the motor's speed is significantly reduced. I tried many potentiometers and different types of batteries and still can't control the speed. Am I doing something wrong?

You just have to have the right potentiometer. As far as I know, no potentiometers exist that support such high current LiPo/NiMH batteries. Either pick weaker batteries, add more mass, or use cover sheets or something.


-p

There most definitely are potentiometers available that can handle the current from batteries. Check out this Digikey link and filter by power: https://www.digikey.com/products/en/pot ... ageSize=25

I agree. This 5 Ohm beast -- which looks like it spent a decade in a Kazakhstan warehouse -- worked well for us: https://www.amazon.com/gp/product/B00K8 ... UTF8&psc=1