Hovercraft B/C

[Zioly]

I'm just throwing out ideas off the top of my head. Obviously, 3,000 mAh is a bit too much for your motors, which is why they burned out, so I wouldn't recommend trying to hook them up directly again. I'm assuming this is why you hooked up a resistor, so your motor wouldn't burn out. It's probably not spinning the motor because the resistance is too high.

We've discussed quite thoroughly some very good batteries, fans, and accessories previously on this thread. Feel free to take a look around, as it will answer many questions.

I could be wrong, but aren't mah just a measure of capacity? It would be the voltage that burns things out from what I understand. My friend has a 7.4V 5900 mah battery and it works fine

You are correct

Sorry about that. Hm, I'm not sure then. Good luck regardless!

[petermai6655]

So I have managed to levitate a craft of the max weight with pretty low friction with the ground, but I cant seem to figure out the propulsion aspect. Of course propelling a craft with relatively low mass (and thus inertia) isn't all that complicated, can someone work out the CFM requirements and/or explain how to calculate the propulsion fan requirements for a 2kg mass?

So how are you powering your hovercraft? What should I use to power my hovercraft?

[petermai6655]

Should I use a digital voltage meter along with a potentiometer to control the speed and time? If so, what potentiometer should I use? A multi-turn potentiometer? Also, Could I put an LCD digital voltage meter for the hovercraft? Is this against the rules or anything?

[petermai6655]

If I understand the parameter correctly, I could connect as many batteries together as long as the voltage at any point in the circuit doesn't exceed 9 volts, is this correct? Does this mean I could connect a bunch of 18650 batteries, or any other battery I choose, together for a max voltage of 9 volts right?

Also, are voltage boosters allowed?

[antoine_ego]

If I understand the parameter correctly, I could connect as many batteries together as long as the voltage at any point in the circuit doesn't exceed 9 volts, is this correct? Does this mean I could connect a bunch of 18650 batteries, or any other battery I choose, together for a max voltage of 9 volts right?

Also, are voltage boosters allowed?

If you made your own without any ICs, and the overall voltage was stepped up but was kept less than 9.0V, you should be fine. To be perfectly honest, I don't really see the point, you should just get a better battery.

[petermai6655]

so just read on the rules revision...

Brushless motors and integrated circuits are not permitted, unless they are an integral part of and are imbedded into a commerically available electronic or computer cooling fan. (9/12/16)

so in such a case where a commercially available fan is a brushless, it is allowed?
noticing some pc fans and it comes with 3 wires on all of the more standard pc fans out there...

oh, and slight typo on the "commercially" vs "commerically" as you have on the website.

thanks

Standard caveat that this is not the place for official statements....

Generally, the 3 wire connectors have an extra wire that serves as a tachometer signal that measures how fast the fan is spinning. Regardless, yes, brushless fans that are designed for pc cooling would fall into the allowed category.

How about brushless server cooler fans like the HP Bladecenter C7000, C3000 fans?

https://youtu.be/zT0GtztnaYU

[KILLERpanda35]

I'm just throwing out ideas off the top of my head. Obviously, 3,000 mAh is a bit too much for your motors, which is why they burned out, so I wouldn't recommend trying to hook them up directly again. I'm assuming this is why you hooked up a resistor, so your motor wouldn't burn out. It's probably not spinning the motor because the resistance is too high.

We've discussed quite thoroughly some very good batteries, fans, and accessories previously on this thread. Feel free to take a look around, as it will answer many questions.

I could be wrong, but aren't mah just a measure of capacity? It would be the voltage that burns things out from what I understand. My friend has a 7.4V 5900 mah battery and it works fine

You are correct

Is your friend useing those same motors (m370 dromida)

[andrewwski]

Could be a few different things going on.

It looks like those motors are fairly small, and they aren't typically run with that much voltage. It's possible that if the motor is running under no load (freely), it works fine, but will encounter issues if run under load. When you add a load to the motor, the current draw increases, and thus so does the power dissipation (causing it to heat up). In fact, a typical motor will draw the maximum current at stall - when it is not moving at all - and none of the electrical energy is being converted to kinetic energy. So even if you have two identical motors being supplied identical voltages, if used in different configurations, one may be subjected to higher loads.

Internal resistance in the battery could also be limiting the amount of current (by causing a voltage drop). The mah ratings of batteries are the capacity in milliamp-hours, which says nothing about the rate of consumption (current). This is dependent on the internal resistance of the battery. It's possible that if a motor is trying to draw too much current, you are creating a substantial voltage drop from the battery which then also reduces the current that can be drawn.

You mention that it's a 7.4 V battery they are using, which leads me to believe it would be a 2S Lipo, which should be able to supply plenty of current - so I doubt this is what is going on. But you could check for this by measuring the battery voltage under load.

I have seen a team that was using a large motor on a 7.2V NiMH, and created a substantial enough voltage drop that it cause their Arduino's voltage regulator to drop out when the motor was switched on. So voltage drops can be significant, but it doesn't sound like that's what's going on here.

There could also be poor quality control with the motors you are using, such that two identical ones behave differently. Not an expected outcome, but it can happen.

[Entomology]

Is hovercraft relatively about the same difficulty the same for both divisions? I want to know if my Div B resources and Div C resources for hovercraft are interchangeable.

[Adi1008]

Is hovercraft relatively about the same difficulty the same for both divisions? I want to know if my Div B resources and Div C resources for hovercraft are interchangeable.

In terms of building the device, much of it is the same. For the test, I'd expect Division C to usually be much harder than Division B