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How many servos can it handle?

#1
So, been in the process of upgrading my FT Storch's electronics and I was curious on servos and what the ESC can handle. I have a 50A ESC with a 5A BEC, 900KV brushless motor, and will be going from 4 to 6 servos (all 9g plastic gear analog)...I have decided to add separate flaps. While I'm assuming the ESC can run all this, I just want to make sure. What is the max limit of servos the ESC could handle in a situation like this? Also, is there an electronics tool possibly that can show me this information? Thanks!
 

Arcfyre

Well-known member
#4
I agree with Merv, should be fine.

Out of curiosity, what can size is your motor? What prop? I've had a couple Storches and am still a huge fan of the model.
 
#5
Yeah I'm a big fan too...so much I'm working on souping it up. :)

It's a Power up 25 Sport 900KV from HeadsUp Hobby

http://www.headsuphobby.com/Power-Up-25-Sport-900kv-Outrunner-Brushless-Motor_p_1601.html

Prop not sure yet...probably 11 or 12, just depends on ground clearance. Doing a 4 channel plus flaps setup (used to just run it as a 4ch), and adding 4S power. On the first few flights with the new upgrades I'll probably do 3S until I get the kinks worked out. Oh, I have done away with the old wire landing gear and picked out some more traditional landing gear (got tired of hot gluing the old ones back on after about every flight).
 

kdobson83

Active member
#6
So, been in the process of upgrading my FT Storch's electronics and I was curious on servos and what the ESC can handle. I have a 50A ESC with a 5A BEC, 900KV brushless motor, and will be going from 4 to 6 servos (all 9g plastic gear analog)...I have decided to add separate flaps. While I'm assuming the ESC can run all this, I just want to make sure. What is the max limit of servos the ESC could handle in a situation like this? Also, is there an electronics tool possibly that can show me this information? Thanks!
For the lower draw servos like the 5g and 9g analog servos your using, the rule of thumb is .5a per servo. So, if you have a 3a BEC it should be able to power up to 6 servos. But keep in mind the RX will will draw power too, plus if your using 3 or 4 cell battery, the BEC has to bleed off that excess voltage to drop it down to 5v to power your stuff. Basically the BEC takes your 12 or 14 volts your battery is giving and dropping it to 5v producing heat. That heat adds up and is compounded by the heat produced by your esc as well. All this heat can add up to brown outs. Thanks is why I always make sure I have atleast an extra amp over what it may require.

But, looking at what your doing, you want to power 6 servos with a 5amp BEC. So you've got two amps to spare. Meaning you could add a servo powered bomb drop mech too. 🤔😉

Anyway, just wanted to give you a little tip for your future builds.
 

quorneng

Active member
#8
The only issue you have to be careful with is to avoid "stalling" a servo either due to flight loads (unlikely with a Storch), stiff linkages or exceeding linkage travel limits.
This can be an issue with flaps as the servo has to travel (and stay) at a particular setting whereas control surfaces only rarely travel to their limits and then only briefly.
Even a 9g analog servo can draw close to 1 A under high load or stall conditions so remember vigorous "waggling" of all the control surface servos simultaneously can work the BEC hard and possibly drop the Rx voltage to a critical level at the same time.

Just make sure as much of the force generated by the servo arm is efficiently transmitted to the control surface. ;)
 
#9
She's going to be a monster!

May I suggest you get some 4" tires or so. It'll be a go anywhere/do anything kind of airplane.
Oooooo good idea. :D I may look into that.

I just hope the current airframe can handle 4S power once I get to that point. I'll find out shortly though if it can't. It probably wouldn't bother me though, I like the Storch so much I'd build another. Kinda surprised I haven't built a backup airframe yet of it.