|Jul 24, 2005, 03:34 PM|
L-39 Albatros, 1:25 Scale, Microfan, CD-ROM
finally I am posting my current project. It is a tiny L-39 Albatros. It is built from balsa, glas and some carbon. And it is scale!
Wingspan: 38cm (15'')
Weight: 145g (incl. battery)
EDF: WEMOTEC Microfan 50mm modified (shroud has been removed), pictures will follow...
Inlet / Outlet Diameter: 35mm
Motor: CD-ROM, 6 stator poles, 8 magnet poles (stock), 10 windings (I believe), turns up to 33000rpm, then gets out of sync (it's the controller limit I think). New motor with 6 magnets and standard stator in progress for higher rpm...
Battery: 3s Li-Poly 520mAh
Functions: flaperons, elevator, throttle, lights
To be discussed in this thread:
Optimization of fan, motor and ducting for top speed
Comparison with other nano scale models and setups
Best launching strategy
Have fun, and don't hesitate to give me feedback...
|Jul 24, 2005, 10:08 PM|
It is beautiful. You're quite a craftsman. Yeah, I'd be interested in the launch technique. Looks to me as a solid, but VERY fast bird. Getting up to the best speed....bungee?
I see no cheater, and even with the nice-sized intakes I wonder if you're going to grab all the thrust you can get.
Do you have a static thrust number as mounted?
|Jul 24, 2005, 11:21 PM|
What stator are you using for the rebuild?
On my EDF-50's in my A-10 im running a 17mm Stator with 10 turns of 26gauge wire with 6 magnets per motor. Thrust is in excess of 150g per motor drawing 5.5A each.
|Jul 25, 2005, 03:05 AM|
dapple63: static thrust as mounted is 70g at about 31500rpm. Power is around 60-70W (have to measure again). Static thrust goes up to 100g, when wing is removed -> big cheater hole at the bottom.
I intend to go up to 100W with new motor. Do you think cheater hole kills high speed performance?
There is still a gap between the rotor and the side wall as you can see in the photo (up to 2.5mm). That will be fixed and I expect thrust to go up more.
Static thrust seems to be low, but related to the total size of the plane and its weight, it is considerable. On the other side, a very high efflux velocity is created due to an outlet diameter of only 35mm and considering the slim aerodynamic shape, high top speeds are expected.
I wonder if I need the cheater hole at top speed. To my opinion it destroys more the aerodynamic than it helps the dynamic thrust. I will test it...
Inlet diameter is 35mm effective.
|Jul 25, 2005, 04:30 AM|
Robbie d, stators of both motors are 20mm. I will use 5x5x1mm magnets for the rebuild. Motor is integrated inside the rotor of the fan... fan and motor weigh roughly 1oz. (30g).
|Jul 25, 2005, 05:51 AM|
|Jul 25, 2005, 09:53 AM|
kdk, the 3-view is all you need to build it. I didn't use any other drawings. The body was built from 1mm balsa, that was bent over ribs. Then everything was coated with glas and in the end the ribs were removed using some brute force (didn't use so much glue here). So the duct was cleared. I think, this is a good method for prototyping (certainly not for mass production)...
|Jul 25, 2005, 10:34 AM|
...sorry Phil, no construction photos. But I will try to explain, how I did it...
... and I will show some close-ups so things get clear...
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