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Could use some Electronics help- 3d printed (maybe) B-25 using Gremlin electronics.

IcedStorm777

Well-known member
#1
So i have a gremlin that i really never fly i haven't flown for a long time. I thought, dang it would be really cool to use two of the motors and a 3s 450mah battery to build a B-25. My question is this. How do i do it? So as far as designing the 3d printed plane and assembling it and servos, i can handle that but what soldering etc do i have to do to convert the gremlin into what i need. So i assume i would have the motors attached to the ESC's, the ESC's attached to the PDB, and than the PDB would be attached to the receiver (how would i solder that?) and than i might have the camera attached to the PDB to just for fun. So if i do that is there a way i could the the receiver/ flight controller and use it as a RC plane controller or would i have to un-solder the drone receiver and than somehow attach the PDB to an airplane receiver. Also with this motor prop combo: https://emaxmodel.com/emax-rs1104-5250kv-brushless-motors-with-prop-t2345-combo.html using two motors what would my maximum AUW be? I figured i might be able to sneak one or two other motors on the plane for added thrust if needed. I am thinking wingspan could be about 15-17", do you think that is too big? Thanks for the help!

-Gracen
 

IcedStorm777

Well-known member
#2
So i have a gremlin that i really never fly i haven't flown for a long time. I thought, dang it would be really cool to use two of the motors and a 3s 450mah battery to build a B-25. My question is this. How do i do it? So as far as designing the 3d printed plane and assembling it and servos, i can handle that but what soldering etc do i have to do to convert the gremlin into what i need. So i assume i would have the motors attached to the ESC's, the ESC's attached to the PDB, and than the PDB would be attached to the receiver (how would i solder that?) and than i might have the camera attached to the PDB to just for fun. So if i do that is there a way i could the the receiver/ flight controller and use it as a RC plane controller or would i have to un-solder the drone receiver and than somehow attach the PDB to an airplane receiver. Also with this motor prop combo: https://emaxmodel.com/emax-rs1104-5250kv-brushless-motors-with-prop-t2345-combo.html using two motors what would my maximum AUW be? I figured i might be able to sneak one or two other motors on the plane for added thrust if needed. I am thinking wingspan could be about 15-17", do you think that is too big? Thanks for the help!

-Gracen
So i think i am actually going to use foamboard to design it as it is lighter. It looks like each motor puts out around 160g of thrust on 2s which would put the thrust at about 320. With this in mind i would like my maximum AUW to be around 200-250 grams as i want to be fairly aerobatic. The design will be loosely based on a B-25 but not exact. I just can't figure out how to turn the quad into an rc airplane setup so please let me know if you know how to.
 

FDS

Well-known member
#3
You don’t use the FC, all you need is a PWM capable receiver and an esc, then you use a couple of servos for elevator and ailerons or rudder. You will want a very light plane to run that motor on, it would be not much cheaper to just buy electronics for something bigger.
 

IcedStorm777

Well-known member
#4
You don’t use the FC, all you need is a PWM capable receiver and an esc, then you use a couple of servos for elevator and ailerons or rudder. You will want a very light plane to run that motor on, it would be not much cheaper to just buy electronics for something bigger.
I am planning on a 16" wing span as the electronics weigh about 90 grams and 1 sheet of foam is about 120 grams so that would leave about 40g for hot glue. So i guess my questions is i see two parts on the quad that i can't differentiate. I see the motors, esc's, and camera. Than there is what everything connects to. The ESC's connect to it, the camera connects to it, the JST port connects to it, and a micro USB (I think thats what it is) Connects to it. I assume that is the PDB? Than their is a grey red and black wire that connects to something that i assume is the reciever. So if this is right than all i would have to do is unsolder or just snip the two of the esc's from the PDB? AKA could i use the same reciever and just change it to a plane mode?

Or would it be possible to just un solder everything from the PDB, and than i could solder the ESC into a servo plug and than just plug that in to an aircraft reciever? That seems like the easiest way and than i could just use an aircraft receiver.

IMG_0429.JPG
 

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FDS

Well-known member
#5
You could use one of those ESC’s with one motor. You will need a BEC to provide power to the servos. You need control surfaces to steer your plane, they need servos to power them. Servos use PWM signals to power them, the flight controller cannot generate those signals. Hence you will need a PWM source, either a PWM adaptor connected to the SBUS receiver or a PWM receiver. What transmitter are you using?
That RX looks like an SBUS one, check out SBUS to PWM adaptors, there’s a few around, they are relatively cheap.
There’s no FT designs that weigh under 200g. You can fly things with under 1:1 thrust to weight ratio, because the wing makes lift. However the lower the thrust to weight ratio for a given wing size the lower the performanc.
 

ElectriSean

Eternal Student
Mentor
#6
FC's most definitely can generate PWM and run servos, but the servos will need to be powered by a seperate BEC. Betaflight/CF/iNav all support fixed wing, though iNav is probably easiest. No idea if it will run on that Femto though. Easiest would be to get a seperate PDB with a BEC built in and a standard fixed wing Rx.