Hovercraft B/C

[chalker]

So.... I'm pretty sure most people will think this is a stupid question, but the rules specify the dowel's height "above the lowest vehicle surface". Isn't the lowest surface of the vehicle the part that runs on the track? (In which case why didn't they just say above the track?) I know that sounds wrong, but it also seems odd to me that it would refer to the upper surface of the vehicle when it says the lowest surface.
And yes, I'm aware that this is not the place for official clarifications, I'm just looking for someone to tell me why I'm not seeing this right.

Technically, if the hovercraft levitates without a skirt, the 'lowest vehicle surface' is going to be a few mms ABOVE the track surface when in operation.

Alright, I'll give you that, it just seemed like an odd distinction to make. If the purpose of the dowel is to break a photo gate, why not base it on something that won't vary from team to team?

Because we don't want to have to force the teams to turn on their motors to measure the height - it drains the batteries and might pose a safety hazard.

[Soccer123]

What is the part number of the motor from digi-key that suffice? We have been there and must have missed that.

Here is the link: http://www.digikey.com/product-detail/e ... ND/2560506

That is a really good looking blower! Specs are definitely above the requirement

Is the blower in this link legal based on the 2016/2017 rules for SciOly hovercraft event - i.e. the rules say "propeller" and would this blower have what would be considered a "propeller"?

[windu34]

Here is the link: http://www.digikey.com/product-detail/e ... ND/2560506

That is a really good looking blower! Specs are definitely above the requirement

Is the blower in this link legal based on the 2016/2017 rules for SciOly hovercraft event - i.e. the rules say "propeller" and would this blower have what would be considered a "propeller"?

Yes

[Elastaro]

If I use a 7.2 V battery rated at 3000 mAh to power a 12V DC fan rated at 1.8-3A (for thrust), will the fan be damaged? Does anyone have any suggestions on maximizing the fan output? Thanks!!

[antoine_ego]

If I use a 7.2 V battery rated at 3000 mAh to power a 12V DC fan rated at 1.8-3A (for thrust), will the fan be damaged? Does anyone have any suggestions on maximizing the fan output? Thanks!!

I doubt it'll damage the fan, considering you're running under the voltage limit. If you want to maximize fan output, I'd actually recommend using an 8.4 V battery, because that'll significantly increase the power.

[MrGood]

What was Christopher Cockrell's theory?

[sciolyqa]

Is it safe to connect a 2s lipo battery with 4600mAh to a 12v fan with 24awg wires? If not, what is a safe connection to be made?

[RJohnson]

If I use a 7.2 V battery rated at 3000 mAh to power a 12V DC fan rated at 1.8-3A (for thrust), will the fan be damaged? Does anyone have any suggestions on maximizing the fan output? Thanks!!

I doubt it'll damage the fan, considering you're running under the voltage limit. If you want to maximize fan output, I'd actually recommend using an 8.4 V battery, because that'll significantly increase the power.

One thing I'd be careful about with this idea is the change in internal resistance of a battery as current draw increases. For example, I started using rechargeable double A cells to get a theoretical 8.4 V, however, the LiPo batteries I had for EV proved to be much more useful, as their internal resistance remained very low at the necessary discharge rates for the fans. With the 8.4 V battery, the voltage drop over the motor was about 4.7 V, with the 7.4V LiPo battery, the drop was about 6.9 V. Ultimately it is the drop over the motor that is important, not the drop across the battery.

Is it safe to connect a 2s lipo battery with 4600mAh to a 12v fan with 24awg wires? If not, what is a safe connection to be made?

I would not add a connection with 24 gauge wire. If the connections to your fan are with 24 gauge wire, then it should be safe so long as you don't exceed the ratings of the motor; additionally, the shorter the length of 24 gauge wire, the less efficiency loss (assuming you still have solid connections) and with the higher efficiency comes less heat generated by resistive heating. Thicker wire can be found in a lot of places. Try scrap electronics, scrap/excess piles at Home Depot/Lowes. There are quite a few inexpensive options and there may also be other events on your team that you could get some from.

Good Luck!

[geniusjohn5]

I have a couple questions. 1) I've read the Hovercraft Clarification rules but I'm a bit confused. So all I need to know is this item ok to use in the competition?(Click link: https://www.amazon.com/Ultra-Strong-DC1 ... B0054S92FW) and 2) does time have to be controlled? I'm thinking about using a potentiometer to control the speed of the hovercraft but I need to know if that's acceptable or not. Thanks.

[windu34]

I have a couple questions. 1) I've read the Hovercraft Clarification rules but I'm a bit confused. So all I need to know is this item ok to use in the competition?(Click link: https://www.amazon.com/Ultra-Strong-DC1 ... B0054S92FW) and 2) does time have to be controlled? I'm thinking about using a potentiometer to control the speed of the hovercraft but I need to know if that's acceptable or not. Thanks.

Yes you can use it, but you can not use any external integrated circuits outside of what is in the housing of the fan. Time is variable at competition so yeah....
It is legal to use a potentiometer (assuming it is not digital)