Heisler Frame Construction Part II
Nelson Riedel, Nelson@NelsonsLocomotive.com
7/30/2006, last updated 02/23/2007

The locomotive frame side shown in drawing above is the next construction challenge.   The design details are at Frame Design I .

Side Bars:  The side bars are 9/16" square CRS.  The first challenge was to make the bends in the bars.  The technique that worked was to saw about 75% through the bar, bend the bar to the correct angle and then fill in the gap with weld.  The photo shows adjusting the bend angle of a lower bar against a print  of a part of  the drawing.
This shows adjusting the second bend against the drawing.  Once all four bends in the lower bars were finished they were positioned against a straight bar and the bends adjusted as necessary to give the 7/16" offset with the horizontal parts straight.

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.)     

Front Stiffener Plates: The next step was to add the stiffener plates.   The drawing  shows the location of the the rivet holes and for the front stiffener.  The 1/8" thick plates were cut slightly oversize on the band saw.    The 1.25" wide front part was then smoothed on the mill.  The ends were also squared and machined to the exact length on the mill.
Button head cap screws (6-32) were used instead of rivets.    Clearance holes were drilled in the frame bars first.  The outside plate was then clamped to the bars and the bars used as a pattern to drill the holes in the front plate.  The inside plate was then clamped to the bars and a clearance drilled used to mark the position of the holes on the inside plate.  The holes were then drilled through the inside  plate with a tap drill and the holes tapped 6-32.
The photo above right shows the front stiffener on the left frame side. Note that the edges of the plate extend beyond the frame bars.  The photo on right shows the plate after the edge was filed to match the side of the frame bars
Rear Stiffener Plates:   The rear stiffener were cut on the bad saw and then the edges finished on the mill using the same procedure as the front stiffener plates described above.  The drawing on right shows the position of the rivet holes.
The rivet holes were drilled in the bars first and those holes then used as a pattern to drill the holes in the plate as was done for the front stiffener plate.  Photo on right shows the finished rear stiffener plate on the right frame side

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. 

There was an identical problem with both frame sides ---- the top and bottom bars were about 0.05" too close together.  When the slotted stiffener was forced into position the bottom bar bowed down slightly.  This was fixed by cutting the top bar at the corner under the top of the center stiffener plate.  The slotted stiffener was then bolted in the correct position and the center stiffener plate attached to the bottom bar.  The top bar was then clamped to the top of the plate as shown on the right.  The inside of the bar was welded with this setup.  The clamps and plate were then removed and the weld finished.

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. 

The side channel support was than attached to the frame bars with a couplef 6-32 button head cap screws.  The slotted stiffener is attached with 6-32 hex head screws and nuts.  The slotted stiffener is positioned with a 3/32" gap between it and the side channel support.   The photo on the right shows that a length of 1/2" angle was attached to the frame  side as an additional cab floor support.

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.