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.
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Final Design for Main Frame Centre

Right after modelling the main parametrics of the frame, I’ve gone on to make it ready for 3D printing.

First, I have added screw holes in the bottom of the frame for attachment of a battery holder, and I slightly thickened the top of the walls on the long sides to allow room for embedded nuts for attachment of a lid.

Here’s the bottom:

8 screw holes on the bottom for attachment of a battery holder.
8 screw holes on the bottom for attachment of a battery holder.

I may not use all 8 screws, but I have put all the holes there in case I do need to.

For the top I have modelled in four hexagonal cavities for nuts to be embedded in, as you can see in this section analysis:

Section analysis of top of frame
Section analysis of top of frame – the long walls had to be thickened to make space for the nuts

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