This part of the build seems to have taken forever. Mainly because I had to build up the structure in the boot to provide the rear roof supports. However, then I finished the roof before coming back to the boot.
I used the same extruded aluminium profile from Motedis that I used for the roof. I wanted the frame rock solid, especially as it would also support the roof and that meant it needed tying into the subframe. After exploring a lot of options, I decided to use the bolts that fix the boot panels to the subframe on inside and count on the weight of the battery to help stabilise the structure.
2 bolts holding the right panel
So I started by building a battery tray. I’ve got two 110Ah deep discharge leisure batteries from a robot I was building called Frank that was based on a wheelchair. I never quite finished him, but he only needs one battery anyway. I built the tray to hold both batteries which would be complete overkill, we will see how much space there is later.
I built a frame for the batteries by tapping through the ends so it was rigid and allowed me to sandwich two 5mm polycarbonate sheet left over from when we were turning RC cars into fast off-road robots. The gap is about 6mm so fits well, then the idea was the weight of the battery would be evenly distributed across the whole frame. I backfilled the underside with two hardboard sheets and sealed it all up in black tape. That way the weight of the battery is firmly applied to the whole frame without putting undue stress on the polycarbonate. The tap covers the hardboard up and stops it falling off but it also gives better lateral friction between the base and the floor of the boot.
I fixed side supports directly using the existing panel bolts to the subframe. I then dropped down to connect them to the battery base.
I then continued to build the frame in situ, the idea was three levels:
- The battery and power distribution
- The px2 drive, plus anything else that can fit in
- Sensors and other electronics
I’d do the layers later as I needed to get up to roof level to support the rear of the roof rack. Once I got near the top, I doubled up the profile and bolted on two 8mm lengths of stud which came out of two holes I cut in the roof. I used cable glands around the stud in the hope that this would stop water ingress. If it leaks, I’ll stick some silicon in them. I also tied my framework into the subframe at the top of the door using one of the bolts that fixes the boot interior to the subframe above the door.
After finishing the structure of the roof, I came back to build the final layers. First the px2 layer.
I left this as an open frame to help air flow around the px2 but put a small rectangle of polycarbonate on the right so either the usb or network hub could be mounted there.
The top layer was a full width polycarbonate shelf but I kept a good 6 inches at the back open for airflow.
On the right hand side, the interior frame verticals go higher, as the boot is asymmetrical. So there is future scope for a half size 4th shelf, if needed.
So although the power distribution still needs building, the frame is pretty much done. It was a hell of a lot of sawing and filing alu profile.
Time to start installing things.