This isn't the kind of thing that we should be doing in the days before the trip departure, but for whatever reason I felt compelled.
First was the solar roof. The aluminum structure that has been on all along is supporting two 200W panels that I got from EVTV here
(actually from a suggestion from Warren
on this thread)
But on reading the suntrip rules more carefully I realized that Tandems are allowed up to 550 watts of solar on the bike while moving, and that extra 37% could be useful especially on cloudy days. After some inspiration from a guy Mark Havran who I met recently at the maker faire I decided to have a stab making a new roof using fiberglass reinforced construction foam. As something that could be stiff and light and support the panels over their entire surface so that they aren't subject to microcracks from all the flexing under vibration.
This here is just one of the new roof structures.
There are two that will go end to end, and stacked together like that we're almost 14 feet long, it's a HUGE structure when you see them together, but by doing it in two pieces like this we'll be able to ship it in a basic oversized box OK, while the single piece aluminum roof was too long.
Unfortunately I can't put 3 of these 200W panels end to end since that's over the limit, but I also couldn't find any 150 or 50 watt panels with the right dimensions. I ordered a bunch of spare Maxeon solar cells some weeks ago but they haven't arrived yet, so in a pinch I took two of these 100W Sunpower panels with the cells in a 4x8 grid
and then cut off two rows of cells to make them into 75 watt panels in a 4x6 cell grid. We used some carving tools to access the cell contacts from between the layers of EVA and then solder new terminals to reconnect the cells on the end. I just finished these today and it seems like the trick worked OK!
The other major change was to the rowing pendulum/pulley structure. The prototype I've been using has 2 pulleys but the string goes very close to the rear wheel and there is no way to fit either a fender (certainly a good idea) or a larger tire (probably a good idea in bumpy terrain). So I rebuilt this last night using thin walled 4130 tubing with 3 idler pulleys to direct the string further to the side of the tire and give fender room clearance.
Initially it was a much simpler structure, but tests showed it was too flexible when rowing hard or when the bike was cornering, and so I kept adding tubes and tig welding them to make it stiffer until getting the pretty wild shape above. We also upgraded the pulleys themselves.
Warren wrote:The block pulley was nylon, from McMaster-Carr, with a sealed ball bearing replacing the original bushing.
Our order of these pulleys from McMaster-Carr came in yesterday. The groove depth and diameter of these pulleys is just perfect, so thanks Warren for pointing them out to us. I didn't have a lathe tool that would make a nice curved groove contour from the string and these totally fit the bill once we made a ball bearing hub for them.
I'm still now up all night making a plywood cargo box for holding our stuff between the two seats, and then tomorrow we really do need to box and ship it all to France!