The roof rack's frame is primarily built out of 80/20 15 series aluminum profiles. To save weight, the lightest 'profile weight' possible (standard, lite, ultra-lite) was picked for each bar, based on its role.
And
that's when procurement hell started... No company was carrying all the
lengths and profile weights. Had to order from 4 different suppliers,
each using a different freight carrier. Months of shipping nightmare
ensued, with lost & damaged bars, bewildering tracking stories, and
lost driver. To be fair, Covid did not help...
Meanwhile, it was time to do a reality check on the pivot & slide mechanism from the CAD. Saw and screws to the rescue:
Miracle, it worked ! Only small adjustments for clearance and motion arc were needed:
Finally, all the 80/20 bars got accounted for. Time for the cutting to start !
The central pivoting arm that swings the panels is a 2" round bar with 0.5" walls. It pivots inside two 80/20 stanchions:
Based on the extremely slow rotation speed, about 135°
in 30s, I thought that a greased bare metal to metal approach would
work. But aluminum is too ductile for the 500Nm torque (=50kg load on 1m
lever) at play here, sometimes leading to high stiction. Moreover, my safety goal is > 1100Nm, so actual bearings will have to be used. When procrastination allows... 😅
The motor is based on the smallest / cheapest ATV winch
I could find, mated to a custom sprocket cage that fits my gear train
box. I fabricated it all with hand tools and a lot of filing. Bad idea.
Will have to redo some parts with an actual lathe from a Maker Space in
town, or something:
The first gear train I built was based on 2 stages, for a gear ratio of about 1:22:
Deployment needs to take about 30 seconds, to give plenty time to the user to react in case of an issue. So it will be redone as a 3 stage gear train with a ~1:35 ratio. Oh joy... 😢
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