The motor for our aircraft has been selected and ordered. As we wait for it to arrive we design the motor mount structure by creating a mock-up and then modeling our solution in CAD. Once the design is finalized we create the templates used to cope the tubes. Then we cut, notch, and weld the tubes up to the fuselage.
The process begins with 3D printing a model of the motor we will be using. We also created a mock propeller that will help us determine the largest size prop while maintaining ground clearance and clearance to the underside of the tailboom.
We can use another temporary 3D printed part to prototype the motor mount location with an offset from the existing horizontal tube on the fuselage frame.
This is a CAD rendering that shows a central tube surrounded by 4 perimeter tubes that will be used to hold the mounting plate in place. We opted for a design where the center tube mounts directly to the existing cross member on the fuselage frame.
Here's a view from the rear of the frame showing how we plan to attach the motor mount. The central tube is 1" in diameter and the outer supporting tubes are 1/2"
This is a drawing of the bottom tube flattened. This will be printed in 1:1 scale, cut out, and wrapped around the tube for notching.
The motor mounting tubes have been cut to length and notched per the flattened templates. The red circular part is a 3D printed model that was used in the prototyping process to ensure CAD accuracy.
We begin by welding the center tube to the motor mount plate so that we can do a fit check with the perimeter tubes.
The support tubes have been welded to the motor mount plate. This assembly is temporarily clamped and taped to the fuselage frame for a fit check prior to final welding.
The aft section of the motor mount is fully welded and the assembly is clamped to the fuselage frame to enable the forward section to be welded.
Prior to welding the forward section of the motor mount we will have to strip away the primer from the fuselage frame around the attach points.
