do i need a bec?

[romihensem]

hi guys, i have a question which needs yr kind assist with. i have a plane setup as follows. 3 retract servo + 2 ailerons + 1 elev + 1 steering = 7 servos. do i need a separate bec for this setup? i know that anything more than 4 servos recommends using a separate bec but since the retracts arent used often, basically just to on and off during takeoff and landings, is a separate bec really a must here? am using 2200mah on the TowerPro 40A esc. Hoping some kind souls can help me... thanx in advance...

[darenlsl]

I am assuming you are referring to retracts using 9g normal servos used for foamies. These Retracts servos although not always used, tends to have load even when fully retracted or extended. Ideally they should not. But as the angle that they operate in (not 180deg), I have yet to get a set of mechanical retracts that locks fully without loading the servos at all.

Except for retracts that works on 180 deg dedicated retracts servo In the larger models which you would need a external bec anyway, It is highly recommended u use an external bec as a safeguard.

[rt9]

TowerPro ESC is providing about 1.5A as seen from the website..

for money sense..

HWing 3A BEC is ~$25
HWing 5A BEC is ~$45
HWing ESC 40A with 3A BEC is ~$49
TowerPro ESC 40A with 1.5A BEC is ~$24

TowerPro 40A + HW 3A = ~$49 = HW 40A ESC :p

for me i usually uses a ESC with 5A BEC with 6 digital servos.
still safe for me till now.. bless.

CC 50A with 5A BEC is ~$115+gst
HWing 40A + HWing 5A = ~$94

so i bought the CC :p

*this is my indivivual experience and opinion..
some may like ESC with built-in BEC.. :p
some may like ESC with external BEC.. :p

[rt9]

:p sorry lost touch..

didnt know CC 50A is now selling ~$106 nett :p

[romihensem]

hmmm

thanx for the reply and advice guys...

@daren, yup i'm using the 9g servos. worst its only a 90deg servo but i notice it pretty much locks up the gears and doesnt have any load anymore but ya i know theres still current drawing at no load.

@rt9, thnx for the details bro. while both TP40A + 3A bec = HW40A, theres a lot of weight i can save by just buying the HW40A individually. Now i'm starting to regret my past decision....

btw this is the project i'm working on now... trying to save as much weight as possible.

http://www.youtube.com/watch?v=K1WraPKOLzI&feature=feedlik

[beefncake]

its best to separate power your retract servos with its own battery

hi guys, i have a question which needs yr kind assist with. i have a plane setup as follows. 3 retract servo + 2 ailerons + 1 elev + 1 steering = 7 servos. do i need a separate bec for this setup? i know that anything more than 4 servos recommends using a separate bec but since the retracts arent used often, basically just to on and off during takeoff and landings, is a separate bec really a must here? am using 2200mah on the TowerPro 40A esc. Hoping some kind souls can help me... thanx in advance...

hi bro, my suggestion is to use a separate battery for the retract servos, the idea is that should the retract servos bind due to retract gear not been able to retract up/down fully etc, it would not drain fully your main receiver/flight pack causing total loss of control. Even if you use seperate bec/battery for all your control servos including retracts, you still face the danger of losing control when your retracts get stuck.

You can use the ESC BEC as per normal to channel 3, but use a Y-Lead to connect Channel 5 to your retract servos.

Remove the Positive Live Red wire from the single male plug end of the Y-Lead. This male plug with live wire removed will connect to Receiver.

While for the 2 Female servo plugs (full wires intact), 1 to your battery and 1 to your servos (since you r connecting 3 retract servos, you will need to connect another 3 Y-Leads from this connection, or maybe is there a Y-Lead that splits into 3 Female Plugs from 1 Male Plug?)

In doing so, the receiver will only give out signal to the retract servos, and any power drain from the retract servos is only drawn from separate battery. You r rite though retract servos only consume minimum consumption as they are bang bang on and off only, if they get stuck, they can drain out the battery in a instant.

Take note also you can also use the above menthod to separate power any other control channel from your main receiver/flight pack.

[jansonfinn]

hi bro, my suggestion is to use a separate battery for the retract servos, the idea is that should the retract servos bind due to retract gear not been able to retract up/down fully etc, it would not drain fully your main receiver/flight pack causing total loss of control. Even if you use seperate bec/battery for all your control servos including retracts, you still face the danger of losing control when your retracts get stuck.

You can use the ESC BEC as per normal to channel 3, but use a Y-Lead to connect Channel 5 to your retract servos.

Remove the Positive Live Red wire from the single male plug end of the Y-Lead. This male plug with live wire removed will connect to Receiver.

While for the 2 Female servo plugs (full wires intact), 1 to your battery and 1 to your servos (since you r connecting 3 retract servos, you will need to connect another 3 Y-Leads from this connection, or maybe is there a Y-Lead that splits into 3 Female Plugs from 1 Male Plug?)

In doing so, the receiver will only give out signal to the retract servos, and any power drain from the retract servos is only drawn from separate battery. You r rite though retract servos only consume minimum consumption as they are bang bang on and off only, if they get stuck, they can drain out the battery in a instant.

Take note also you can also use the above menthod to separate power any other control channel from your main receiver/flight pack.

Wow, but the weight increased is , won't it be?

Although I have not fly a plane w/ retracts yet, but how high is the possibility that the retract servos will bind?

If in worst case scenario the retracts really bind in midair, land the a/c & rectify the problem again b4 taking off. Just like the real a/c situation of landing gears unable to be stowed up. Isn't this better than adding another batt?

[beefncake]

retract binding

bro its very common to get in situation where the retracts LG cannot fully shut into the retract wheel. If you are lucky, u can spot it and fully down the retracts & continuing flying for all of the flight or like u said land immediately and rectify problem b4 taking off. However there can be cases where you wun know the retracts is binding and continue flying till your flight pack get fully drained.

I know theres a weight penalty but its definitely worth it and u dun haf to keep using eagle eye to spot at your retract wells while flying to check if everything' ok. On my VQ Hien, I am using a 1300mah 4.8V NIMH batt for the retract but the capacity is well over-kill, after more than 10 flights in a weekend, i checked the battery voltage only dropped from 5.28V to 5.27V. I got that batt cos its cheap only S$20 from Rotor. Thus for your case any 2S Life or Lipo with step down regulator will do. A total of extra 30g to pay for the insurance should be okay lah...

[gpsnuts]

hi guys, i have a question which needs yr kind assist with. i have a plane setup as follows. 3 retract servo + 2 ailerons + 1 elev + 1 steering = 7 servos. do i need a separate bec for this setup? i know that anything more than 4 servos recommends using a separate bec but since the retracts arent used often, basically just to on and off during takeoff and landings, is a separate bec really a must here? am using 2200mah on the TowerPro 40A esc. Hoping some kind souls can help me... thanx in advance...

It is really no a good idea to use normal servo for retract. It is due to the fact that the servo must hold the weight of the retract when in retract position. I would suggest to use a separate battery for the retract servo. This is to prevent the retract servo from draining off the main battery that power your RX.

Perhaps, you want to consider replacing the retract with the servoless ones.

[beefncake]

It is really no a good idea to use normal servo for retract. It is due to the fact that the servo must hold the weight of the retract when in retract position. I would suggest to use a separate battery for the retract servo. This is to prevent the retract servo from draining off the main battery that power your RX.

Perhaps, you want to consider replacing the retract with the servoless ones.

bro i agree with you about using dedicated 180 deg retract servo vs normal servo, but Rohm's setup here is a small edf, so if he's gonna get retract servo he muz get the micro or mini size servo type. So far Ive not come cross 180 deg retract servo which length and width is the mini/micro servo size, maybe u can help by recommending where to get this type of smaller-sized retract servos?