Inq
Elite member
I'm kind of enjoying some design, CAD work and printing for my Inq'd Trainer. I finally decided to put the servos in the back with the rudder and elevator and was working out how to do it. The easy way (and probably the smartest) would be to just hang the horns outside the fuselage and have short connecting rods to the control horns. Eventually, I want to design and build some war planes and I'd like to experiment with putting all the guts inside so the scale aura bubble isn't burst when I see all those horns and rods flapping in the wind.
At one point, I thought, I could just directly connect it to the surface, but I'd loose any torque multiplication using the control rods. GEARS - I've printed 3D plenty of gears in the past - Involute Spur, Herringbone, Worm... etc... so... why not?
Here's the first attempt. The design starts out using a 9 to 27 tooth ratio for a 3:1 torque advantage. When the servo moves through a full +/- 60°, the control surface will do +/- 20°. Since the gears don't fully turn around I removed the un-needed teeth to help it fit in slender fuselages. It also is custom fit for SG90 servos.
I didn't want to fiddle with critical placing within the plane to mate the gears, so I also designed a gear box that keeps them in contact and aligned. This way the whole unit would just be attached to the control surface first and then slid into place in the fuselage. That's the dream at-least. Here's the CAD drawing...
Total weight of the gears and gearbox using ABS is 4 grams. Here's the first printed version... waiting for the plane to put it in. I used the translucent filament hoping to be able to see the gears in action... but I haven't quite mastered getting it clear enough to be useful.
At one point, I thought, I could just directly connect it to the surface, but I'd loose any torque multiplication using the control rods. GEARS - I've printed 3D plenty of gears in the past - Involute Spur, Herringbone, Worm... etc... so... why not?
Here's the first attempt. The design starts out using a 9 to 27 tooth ratio for a 3:1 torque advantage. When the servo moves through a full +/- 60°, the control surface will do +/- 20°. Since the gears don't fully turn around I removed the un-needed teeth to help it fit in slender fuselages. It also is custom fit for SG90 servos.
I didn't want to fiddle with critical placing within the plane to mate the gears, so I also designed a gear box that keeps them in contact and aligned. This way the whole unit would just be attached to the control surface first and then slid into place in the fuselage. That's the dream at-least. Here's the CAD drawing...

Total weight of the gears and gearbox using ABS is 4 grams. Here's the first printed version... waiting for the plane to put it in. I used the translucent filament hoping to be able to see the gears in action... but I haven't quite mastered getting it clear enough to be useful.
