CAD Design for Arm

Now that the main body is done, the next step is the arms. Now I know exactly how they have to fit into the frame, because I designed the fitting earlier, and the female part of this is already built into the frame centre.

The first problem I noticed is that the radius of the propellers I’ll be using is about 130mm – the same as the length I had set between the body and the motor centre. The frame is angled so that motors this distance from the frame will be equidistant, but I obviously need some clearance between the propellers and the frame, and so I have regretfully extended the arm length to 160mm to allow for this. Because I don’t want to print the body again, this means the motors will form a slight rectangle instead of a square, but I think it will be close enough that it doesn’t really matter.

Here’s the finished CAD render of one of the arms:

The motor is angled slightly upwards as this increases aerodynamic efficiency and decreases turbulence, especially when taking off or landing.
The motor is angled slightly upwards as this increases aerodynamic efficiency and decreases turbulence, especially when taking off or landing.

The underside:

The two holes in the bottom of the arm are to allow the motor/ESC cables to run underneath them, for ease of access, rather than along a channel down the middle.
The two holes in the bottom of the arm are to allow the motor/ESC cables to run underneath them, for ease of access, rather than along a channel down the middle.

The attachment point:

The bottom three screw holes are countersunk because the screws will be inserted here from the inside.
The bottom three screw holes are countersunk because the screws will be inserted here from the inside.

Finally, I added a single layer (0.3mm as it’s the bottom layer) of plastic to the bottom of the arm to help bed adhesion, as it’s printing vertically (this way it looks the best as the curved edge is printed along the Z axis).

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