EDF Problems in SR71 Build.

From my thread on the other side As a rule of thumb, you will need 4000 watts of power (200Watts/Lb), if each fan delivers 2000+ watts, you should be OK. If the data above is correct, then you should even able to fly it well on just one fan, kicking out 4200 watts. Obviously to generate this you will either have high Volts of high amps. This does mean that you might be able to run the fans at slightly less than full throttle and preserve those mahs and get longer duration. Looks

Again from the other forum

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Asuming each fan is powered by its own 12S Lipo (44.4v), to get 4200 watts you would be sucking about 95A from the Lipo.

Therefore rough beer maths show that:

on a 4000mah you would get about 3.8 mins

on a 5000mah you would get 4.7 mins

and 5.7 mins on a 6000mah.

All assuming you were flying at about 70% throttle (which is generally 1/2 the Amps pulled at 100% throttle). 70% throttle, I think would be OK, since you have 2 fans/power systems each delivering enough power at 100% to fly the aircraft on its own.

so a 6000mah 12S Lipo per side, would give you a decent flight time of approx 6 mins.

Edited By Christian Ackroyd on 15/03/2012 19:16:44

Edited By Christian Ackroyd

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Plug-n-Play capacitor for Dean connector

3 x 180UF 63V

A new posting has been made on the thread Thrust v weight.

Posting:


SR71, mmm good question. Short anwser ( i think) is not really an difference. Assumming your talking about the same capacity and C rating.

I would think you would lose a bit of power with 4 x 3S each side (8x3S Lipos total), just because the additional wiring involved in connectition cables would have a slighter higher resistance and lose some power as its converted to heat in the cables, although I think this would be negligable and certainly not that noticeable with the reserve of power you will have.

Its a lot of 3S lipos to connect up and hence more wiring, but of course if you crashed you might be able to save a few lipos.

Personnally, i think that it would be more expensive to buy 8 x 3S 6000mah lipos, than 4 x 6S or 2 x 12S equivilents, and that for just one flight set. You would probably want 2 x flight sets unless you want to wait until all lipos have recharged between flights. You might want to use some online calcs and work out if you can get away with 2 x 10S or even 8S lipos, since you have more than enough power and shouldn't need to fly at full throttle - 8400watts is well over 400 watts/lb


Posted By Christian Ackroyd on 16/03/2012 18:27:54.

Read the thread online

Hi Klipy
they were recomended by a guy on the rcme thread im running ( thrust v weight )im getting some good info on it, there should have been a picture of them but it did not show up.
the lipo's will be in the fuse, and the esc's in with the fans so maybe i will need them, i dont know.
I have two Lander 120mm fans on the way here and im trying to find some 6s 6000 lipo's
Hope to restart the sr build again on monday, but still waiting for materials to arrive.

I have found an edf fan that gives the following thrust

12.5 lbs on 10s
16-21lbs on 12s
21-24lbs 0n 14s
24-27lbs 0n 16s

Now that opens up new doors

And would you believe on their smaller fans the 3900w they use Scorpion 40-35 630 motors the same as i used !!!!!

Hi Klipy the esc's that i have coming have a anti spark wire built into them, so did the ones i destroyed
and i did not get much of a spark with them.

Now that i have a spare scorpion 4035 - 630 motor from the sr71 im looking to put it in a plane.
can anyone tell me what size this motor is in ic terms, if it is around the .91fs size then i have a
model for it, and also the prop size please

Thanks Klipy i have a World Models Groovy it's a 3D 54" 6lb plane recommended motor 91 so the scorpion will be on the high side, should make it interesting though the next step up from my wot 4

Now one of my 6s lipo's has gone down to 5s can you tell me the reason for this latest mishap
Getting fed up with the leccy thing now, should have bought two turbines would have been cheaper

Ran the Lander fan today it was great
6,75 Kg thrust on 11s
99.9A
47.58 V