I now have the loose-jaw L1 chairs working fine:
I couldn't get less than 5 degrees, and still retain enough bash-fit strength in the plug, or still provide some minimal additional support so that they print properly.
But spot the very slight design change?
There is now a very short vertical section to the slot and pin through the base of the chair. It hardly seems enough to make a difference. But it has done -- it causes some slight friction in inserting the pin, and causes the key to snap nicely under the rail head. And not easy to pull out without a tool, just like the other chairs.
When I release the next program update with these L1 chairs, they won't match any existing timbering bricks you have made. The plugs and sockets are not in the same position relative to the rail gauge-face. They will require new bricks. See my previous note about making enough of the old L1 chairs for your needs before updating -- or at least, creating the required files to print them later. Alternatively, if you have made the L1 chairs but not yet the bricks, create the files for the bricks before updating. Or discard the the old L1 chairs and make new chairs and bricks. This applies for both loose-jaw L1 chairs and solid L1 chairs.
Usual cruel close-up. All the chairs on this test piece are loose-jaw. They don't need to be, because they are all separate L1 and S1 chairs, so could be solid slide-on chairs. It will be optional. (FDM timbers from the Neptune printer. EM.)
The best thing about loose jaws I'm finding?
Not having to threa
d them on the rail, or sort them into the correct order first is great -- you can just drop them in their sockets as you cut them from the raft. Then a quick tap with a pin hammer, using a cocktail-stick punch on the rail seat, and they are home.
But the best part is not having to fiddle about filing a lead-in on the rail ends, or trim the rails after sliding the chairs on. You can just touch the cut rail end against the sanding disc, getting a nice flat prototypical square end, and drop it on the chairs. Some blobs of Blu-tack between the timbers keep it upright while you get the first couple of loose jaws in.
Having square flat rail ends, not only looks prototypical where they are exposed. It also means we can have very close isolation gaps of only a few thou, which will hardly notice. With a smear of epoxy on the rail end to ensure isolation long-term. And some prototypical-looking fishplated joints -- 3D-printed fishplates applied from the side with a thin rear tab which fits between the rail ends. With randomised fish-nut rotations, of course.