Cowl support structure:
The final cowl supports are a square tube structure tied to the cage as described earlier, but the initial concept was a bit different: a 1.5" round cage tube running from the A pillar to the firewall positioned inboard and above a separate cowl support part that the cowl, windshield , and body side panel would attach to. I liked the round tube part of that idea, but the rest didn't work out, so it evolved to the square tube design.
This shows the parts made for that initial concept:
When these supports were fitted up with the windshield, cowl, and firewall, the idea ran into some problems:
- The windshield pivots on the windshield frame made in the last post were not sufficiently aligned to each other - particularly the mounting boss faces weren’t adequately parallel to each other. The all-thread clamping during welding didn't work as well as I initially thought. This misalignment created too much binding against the cowl side mounting bosses when lowering the windshield.
- When the windshield mounts were tightened to the mounting bosses on the cowl supports, the cowl supports didn't line up to the cowl angle very well. In other words the windshield mounting bosses on the supports weren't aligned accurately relative to the body angle face of the support.
- I needed to change a bunch of things about how I built the cowl supports to assure better angular placement of the windshield mounting bosses on the cowl supports, and alignment of the supports to the firewall and tapered cowl sheet metal.
First up was fixing the windshield pivots:
The stock "squashed tube - stamped bracket" mounts are more forgiving of angular positioning on the cowl. Willys made a smart move for production ease! The bosses in my design are less forgiving in placement. But I liked the less cluttered idea of the new mounts, and the removable cowl concept, so I changed some things to make at all work better.
The initial windshield bosses were cut off:
Cleaned up the cut to fit new bosses with the same initial design.
To set the spacing of the pivots on the windshield frame more accurately, and keep them better aligned and parallel through welding, the all-thread fixturing idea was ditched, and a more rigid support was made out of 1 1/4" bar stock I had around.
My little lathe can't fit that diameter of bar stock through the headstock to turn the ends square... so I cut the rod with a saw, then filed the ends checking with a square, and checking the length for correct boss spacing. When close with a file, the ends were lapped square by spinning them against sandpaper stuck to the top of my table saw, with a little fixture mocked up to keep the rod square to the sanding surface. The little v clamp piece in the foreground was used to press the rod against the angle blocks with one hand while spinning the rod with the other. Took a little time, but the ends were flat and square to the shaft. Holes were drilled using a drill press, and tapped using a tap guide in the press - to mount the pivot bosses on the fixture rod. Not as accurate as a lathe, but was able to do pretty well.
New pivots, with new fixture rod in place, ready to weld:
Welded the new bosses in and the alignment was good as checked by rotating the assembly on the fixture rod afterwards.
Cowl supports:
The first attempt at cowl supports shown above was fabbed out of flat stock. Welding the full edge length of the parts caused too much warpage, contributing to their alignment issues. Into the scrap bin they went.
Another iteration was started using a 1" x 1.5" x 0.120" tube instead. Working with that idea, another issue became more apparent. The initial idea was to place the cage A pillar so it integrated with the dash - either aligned with or behind the dash panel. This would look clean, and enable a nice mounting of the fixed dash panel and cowl support structure. However, mocking this up lead to the realization that with the angled flat fender body sides, putting the A pillar that far forward really cramped the footwell space…
So the concept changed some more to have a conventional flat fender A pillar position - set back a little ways from the dash to gain more lateral foot room.
The A pillar to firewall cage plan changed as well. I originally was going to run a 1.5" round tube from the A pillar to the firewall corners (to tie in to the engine bay cage) above the separate cowl supports. This became more complicated with the new A pillar position.
To simplify things, I decided to make larger 1.5" square tube cowl supports that run from the planned A pillar to the firewall to tie into the engine bay cage tubes- so they serve as the short cage tubes to the firewall while also providing flat mounting/sealing surfaces for the cowl and body side panels. The supports visually replace the "filler panel" on the side of a 3B, and are mostly hidden by the windshield frame. The cowl panel and bottom body panel will attach with screws/nuts in through-holes with crush tubes. Also the cowl support windshield pivot boss design was changed to provide an easier way to assure alignment of the pivot bosses.
Here are the final design cowl support tubes, partially completed. The bend in the shape aligns to the dash panel/body door opening, and the lower parts of the tubes will be fit to the 1.75” cage A pillars.
The new cowl side windshield pivot bosses have smaller diameter inside ends that insert in holes in the outer wall of the cowl support tubes. This lets the boss angle float a little at the cowl support prior to welding - so they can be tacked while the cowl support, cowl, and windshield are all positioned in place at the firewall. This made it much easier to get the alignment and positioning right. The smaller diameter boss also provides more clearance to the back edge of the hood. The bosses are blind tapped so water doesn’t enter the support through it. Here they are tacked (with the patched cowl attached to insure correct positioning, and then final welded to the cowl support tube (with the cowl removed):
As shown above, to wrap up the removable cowl mods, the patch panels with mounting flanges were added on the cowl sides.
Before fitting the patch panel, the cowl edge was trimmed to a point that would replace some warped areas around old windshield bracket holes and some old dent patching. Here's the cut, and the fitted patch panel. These next photos are tipped sideways to show the parts better…
After bench fitting the patch panel and flange, then it was final fitted on the rig. This made sure that the cowl sides matched up to the firewall flange across the front, and both cowl supports. Once tacked, they were removed and fully welded. They were then clamped to the side supports again to mark the mounting holes on the cowl side flanges using a transfer punch through the cowl support mounting holes. Here's the flanges with mounting holes drilled - viewed from the underside of the cowl:
I'll trim the dash side of the cowl assembly later on when the dash panel comes together. What currently looks like the dash panel on the cowl assembly will be cut back to make a 1" flange that will overlap the upper part of the dash - like the factory design but attaching to the dash panel with button head screws rather than spot welds.