Hovercraft B/C

[windu34]

I've been looking for a thrust fan. Would this one fill the niche?

https://www.youtube.com/watch?v=rLmxUP4Dku4
http://www.digikey.com/product-detail/e ... ND/5209819

Same fan. One is a video I found of it.

looks good to me

[sciduck]

Do I have to know gas laws for the test? Not sure if it's w/n the fluid mechanics topic or not...

[windu34]

Do I have to know gas laws for the test? Not sure if it's w/n the fluid mechanics topic or not...

No

[RJohnson]

What are people using for shielding their fans? I've been using gutter protectors because I had them laying around, but the performance loss is significant... Has anyone had any success with other materials that they're willing to share?

Thanks!

[windu34]

What are people using for shielding their fans? I've been using gutter protectors because I had them laying around, but the performance loss is significant... Has anyone had any success with other materials that they're willing to share?

Thanks!

I have tried a few materials, but in the end, the loss is pretty much the same. Bottom line is the fan needs to be powerful enough to overcome it

[Patrick Yepes]

I did an estimate by scaling down larger hovercraft propellers and found that you'll need about 50 CFM to go full speed with a 2kg craft. Does this sound reasonable?

Very reasonable, but keep in mind our hovercrafts will not be very comparable and youll likely need much more CFM. There is a fan on amazon with 200 CFM for a reasonable price.
I attached a grate/mesh over the propulsion fan that I laser-cut out of acrylic. Reduces thrust by ALOT. Might have to look for a different solution.
What have you guys tried as far as materials for the grate?

Isn't it against the 'rules' to laser cut something for the hovercraft since the students don't have a hand in the design, programming, or using the machine to cut said part?

Asking for a friend...

[bearasauras]

I think windu does the laser cutting on his own. NSO has policies for how much adults should be involved: https://www.soinc.org/building-and-tools-policy

[windu34]

I did an estimate by scaling down larger hovercraft propellers and found that you'll need about 50 CFM to go full speed with a 2kg craft. Does this sound reasonable?

Very reasonable, but keep in mind our hovercrafts will not be very comparable and youll likely need much more CFM. There is a fan on amazon with 200 CFM for a reasonable price.
I attached a grate/mesh over the propulsion fan that I laser-cut out of acrylic. Reduces thrust by ALOT. Might have to look for a different solution.
What have you guys tried as far as materials for the grate?

Isn't it against the 'rules' to laser cut something for the hovercraft since the students don't have a hand in the design, programming, or using the machine to cut said part?

Asking for a friend...

I complete the entire fabrication without any assistance from my coach which includes 2D and 3D modeling in AutoCAD, exporting the file to the Retina Engrave software, calibrating the laser cutter, and supervising the actual cutting of the acrylic.
Glad you are familiar with the policy

[SPP SciO]

With propulsion fans: has anyone had experience with removing the propeller from a CPU fan and attaching it to the shaft of a DC motor? We were able to grab a bunch of old CPU fans from an e-waste recycling center and are thinking of experimenting. We've tried DC motors with a drone style propeller (on a simple alkaline 9v circuit) and it doesn't do the trick.

Basically - would we have more luck switching the drone prop for a wider, steeper pitched prop? Or trying to attach a computer fan prop to a motor? Or should we use the computer fan for propulsion "as is" because the propeller is optimized for that particular motor? The 12v fans don't seem to produce much airflow with 9v batteries.

[windu34]

With propulsion fans: has anyone had experience with removing the propeller from a CPU fan and attaching it to the shaft of a DC motor? We were able to grab a bunch of old CPU fans from an e-waste recycling center and are thinking of experimenting. We've tried DC motors with a drone style propeller (on a simple alkaline 9v circuit) and it doesn't do the trick.

Basically - would we have more luck switching the drone prop for a wider, steeper pitched prop? Or trying to attach a computer fan prop to a motor? Or should we use the computer fan for propulsion "as is" because the propeller is optimized for that particular motor? The 12v fans don't seem to produce much airflow with 9v batteries.

I don't have much experience working with any of those types of propellors/fans so Id recommend trying all the combinations. More importantly, you must transition away from 9V batteries and use either 7.2/8.4 V NIMH or 7.4V LiPo BATTERY PACKS. The amount of current a alkaline battery produces is nowhere near what you need to supply to the motor