A few pieces under way so I thought tha a few photos would be of interest. Hopefully it will goad me into accelerated action. Consider this content as alternative and/or supplemental to the information previously posted by Brooks and Engels.
First up is the frame for the seat.
I have made 5 or 6 seats so far for different projects but this is only the second seat frame, first for a D VII. Jeff hit several challenges in making his frame and before I weld in the primary cross tube I will be travelling to Ottawa to double check the frame on their Fokker built D VII.
The D VII seat is unlike most homebuilt aircraft seats that are fixed into position. The Fokker seat is easily adjusted vertically utilisng a sliding seat frame locked into position by the use of two pinch clamps that use 'wing nuts' to adjust tension.
A few things going on in this photo.
The jig is made from MDF scraps. I like mdf because of its unwillingness to burst into flame as I weld. The vertical piece locates the forward tube that runs transversely under the front of the seat. The top of the frame is closest to the camera so the orientation of the jig is with the seat lying on its back.
There are two short lengths of tube located on the base to represent the vertical tubes that the seat frame slides on. The narrow dimension of the jig base equals the distance between the bottom of the top seat clamp and the top of the bottom clamp.
The clamps were made first. They are of 0.060" mild steel sheet that I cold formed around a steel bar. The extended tubes will sleeve the clamping bolt that pinches the clamp shut. This was made from bushing stock and, after welding, only requires final reaming for the bolt.
The tubes are 0.035" 4130 of various diameters which most closely equate to the original metric dimensions.
The forward trasverse tube is cut to length +10mm to ease welding, and clamped to the jig. It is then a simple matter to cut and file the side bracing tubes to length.
Here is the apex of the two port side tubes at the transverse.
When finish welded, I will trim the transverse ends down to the correct OAL, approximately where the silver mark is.
The long tube lying on the jig is the primary transverse that runs between the port and starboard upper clamps. This is the piece that I need more information on: exactly how it mates to the clamps and whether there is a slight bow in the middle of the tube.
FYI, there are 15 parts in the seat frame not including the hardware.