Frame Construction Part II
The locomotive frame side shown in drawing above is the next construction challenge. The design details are at Frame Design I .
Before the upper bars were bent they were attached to the lower bars with a pair of 6-32 screws running vertically between the two bars to the rear of the bends. Next, the upper bar was detached from the lower bar and the saw cuts for the two rear bends were made and the bar bent close to the proper angle. The two bars were fastened together again and the center stiffeners positioned between the two bars, minor changes were made in the bend angles and then the stiffeners clamped in place. The bends were then welded with everything clamped. The weld at the bend adjacent to the lower bar could only be partially made with the bars fastened together. Next, the bars were separated and the welds finished and ground. The next step was to make the cuts for the front two bends in the upper bar, make the bends and then fasten the bars together again and clamp the stiffeners between the bars as shown in the photo above. The last two welds were then made in the upper bar while it was fastened and clamped as shown in the photo. The bars were then separated, the welds finished and ground. The bars were then fastened together again and the ends straightened slightly if necessary. Once the shape of the bars was correct, weld was added to the bends as necessary to allow the joints to be ground and filed to resemble a bar that had been bent rather than cut and welded. It's especially important to make the second bends from the front as nice as possible since those bends won't be covered with stiffening plates.
The next step was to fasten the upper and lower bars together with the screws at the rear and to camp the bars together at the front. The bars were then welded together at the front and rear at the points where the bars split. After the welds cooled the sides were ground flat. This area of the sides will be covered by the stiffening plates which is the next task. The photo above shows the two sides after the bars were welded together. (Those center stiffeners are just setting on the bars at this point.)
Center Stiffeners: There are two center stiffeners on each side, a center stiffener plate that will be inside the cab and the slotted stiffener just in front of the cab as shown in the above drawing. The side channel support is positioned in front of and against the center stiffener plate. The slotted center stiffener is located in front of the side channel support with a 3/32" gap between them. The center stiffener plates are only on the outside of the frame; there are no inside plates. The center stiffener plates and side channel supports are attached with button head screws simulating rivets. The slotted stiffeners are attached with 6-32 hex head screws and nuts.
The weld was then ground and filed before the plate was reinstalled. Since there is only an outside plate for the center stiffener the holes for the 6-32 screws in the bars are tapped. In this case the plate bottom and sides were finished on the mill and the holes drilled in the bottom edge of the plate first. The plate was then used as a pattern for the holes in the bottom bar. After the bottom was attached and the top was filed smooth to match the bars and clearance holes were then drilled through the top of the plate and then tap holes drilled into the bar and the holes tapped. The button head cap screws holding this plate are ~5/16" long.
A finished frame side is shown above. This part of the project should have taken less than a week but I managed to stretch it over 6 months ------ I was having too much fun working outside. Winter has come so the rate of progress should increase. The sills and saddle are next.