E-snake

My Feedback: (2)

Hey,
I a looking at building a VTOL airplane using a ducted fan on a joint. The Gws fan I am looking at can put out about 7oz of thrust with the batts I will use. If I were to put a kind of funnel on the duct to preasurize the air, would it give me more thrust? If not, Is there any other way of increasing thrust without more volts or a different fan?

Thanks
Ethan

Fly-n-3D

Will you be using a brushless setup? And this might work. Neil Guildford did this with his Bobcat-E-Cat-D/F.

E-snake

My Feedback: (2)

it willl be brushed unless i can find a fan for a Himaxx 2025 motor.
That is exactly what I am talking a bout.

hypersoniq

which GWS fan? I have a 75mm "EDF-75" and you can swap out the brushed motors for brushless ones. there are probably drop-in b/l motors that have been tested wth each of the GWS fan sizes already, the key is not to get rpms too high or the impeller blades will start rubbing against the fan housing (they could just break apart also).

to lift off, cutting the exhaust area won't help. you need to have exhaust at 100% of the fan area for maximum static thrust (like "low gear"... not too fast but lots of thrust). higher pressure can be had by the method you are interested in, this creates higher speed at the expense of power ("high gear" ) .

I am trying to work out some simple form of variable diameter exhaust nozzle for my current edf project(s) so I can have 100%FSA for takeoff and can clamp down to about 70% for high speed runs. the basic plan is to have a short tube (equal to fan area) at the exhaust of the fan that is within an array of exhaust petals that has a rubber band at the aft end. the tube will be on a rail that is driven by a servo. sliding the tube aft will spread open the petals and give max static thrust, while retracting it forward will allow the rubber bands to clamp down to about 70% of it's original size...hopefully. right now the biggest challenges ahead are petal design and making sure clamping is symmetrical so as not to alter the thrust line. also to construct a light tube that won't distort when opening the petals, probably have to use fiberglass.

check the diameter of the shaft on the motor in your GWS unit and try to find a motor that has that shaft already, otherwise you'll need to use some kind of adaptor to affix the impeller. I lucked out and found one at exactly the same size (GWS EM-400[2666 kv] has a 2.3mm shaft ,so does the golden horizons air power B/L [4700 kv] I am replacing it with... same size can (a bit longer but equal diameter) and will handle 10-18 amps (continuous) and give about 38,000 rpm @ 7.4 volts. a CC-25 and a LiPo will finish off my test system, and f it works I can put 2 of them in the next project, otherwise I will need to use the more expensive fans from WeMoTec.

rkflyboy57

My Feedback: (6)

hello. you guys seem to know about ducted fans. I need to know where I can get replacement motors for a GWS A-10 that my wife and son bought me for Fathers day. I am using a Castle Pixi 20 amp speed control with Thunder 2S, 1350mah batteries. I live at 4900ft msl in Oregon. My problem is for the first 5 flights the plane flew good except it needed more power for my taste. Next time out one of the motors quite working so I pulled it and tried running it on the bench, but it was rough and low rpm. It never seemed to get hot while I flew it BUT??? I called GWS and they promptly sent a replacement. I test ran it; installed it and headed for the field. I was ready to fly when I turned it on and throttled up and the other motor did the same thing. I've left it on the bench for a year now. As you can guess, I'm an old glow fuel burner. I'm not having much luck with this electric stuff. It sure seems to be a lot more hassle and expensive, when compared to glow fuel!? I've tried 4 other elecs with recommended (hobby shops and manufactuers) and am not yet impressed. It has cost me quite a sum with little pleasure. I live in a remote area and am going at this solo. I've been flying gas aircraft and helis for over 25 years so maybe I should keep at that. Anyway back to the original question--- I would like to find very good replacement motors by an aftermarket company that I can replace these cheap stock units with. Any ideas????? Thanks

hypersoniq

not sure if you have the edf50 (50mm) or edf55 (55mm) fans, but I think the HiMax 2015-xxxx is a suitable brushless replacement for the GWS fans of that size (xxxx = kv [rpm/volt] 3600, for example). of course the brushless motors mean you need a new speed control/esc (like a Castle Creations Phoenix)

if you are sticking with brushed, and you have a GWS fan with a 150H motor you could drop in a cheap gws 300H motor for better performance, but nothing close to the brushless setup.

bimmerland

Do you have any suggestions for the HK A10 that uses 75mm EDF units. The stock setup with a pair of 30XX-3900kv motors puts out about 970 grams of thrust for both engines running a 2650 3S 40C Lipo. Need a little more power for hand launching. Any advice greatly appreciated. Thanks

CoolerByTheLake

You might want to check out the post more carefully, it's over 7 YEARS OLD!!!!

bimmerland

Thanks for the heads up. Obviuosly someone was looking or would not have commented...