Heisler Frame Construction Part III
Nelson Riedel, Nelson@NelsonsLocomotive.com
Initial 1/08/2007, last updated


The fabrication of the locomotive front sill bracket, rear sill , and saddle are described in this page.  The design details for these parts are at Frame Design II  and Frame Design III.

Front Sill Bracket HM412:  I'd been working on those frame sides for so long that I decided to do this easy part to refresh my silver soldering skills. 

The little brackets on the ends of the sill bracket were made first.  The first step was to to silver solder a ~ 2" length of 3/16" X 9/16" bar  to a piece of 1/8" X  1.5" bar stock as shown on the right.  The space between the 3/16" bar and the upper edge of the 1/8" bar is 9/16" (a 9/16" square frame side bar will fit in there)    

The 3/16" bar is held to the 1/8" bar by two 4-40 FH brass screws as shown on the right.   Two 7/8" lengths were sawed off this bar.  The screws were located so that they were near the middle of the two pieces to be sawed off. 
This photo shows the finished brackets.  After they were sawed off the longer bar, the ends were milled to give a length of 0.812".  The next step was to make the angle cut on the lower edge with the band saw and then finish the edge with a file.      
The little brackets were then attached to the 12.5" long 1/5" X 1/8" bar with one 4-40 FH brass screw per bracket.  These screws hold the parts in the correct position during the silver soldering operation pictured on the right.  The screw between the two parts of each little bracket hold the brackets together during this second soldering operation.

The finished front sill bracket is shown below.  Note that the FH brass screw heads will be hidden by the wood sill and the Frame Tray       


Rear Sill HM407: The rear sill is a much heaver hunk of steel and looked to be a challenge for my small workshop. 

The two nose pieces were made first.  Both nose pieces have a 3.44" radius, are 3.5" wide and stick out about 5/8".  The upper nose piece is 1/4" thick and the lower is 3/8" thick.  I turned the radius on the lathe using the setup shown on the right.   The plates are 1/4" X 4" and 3/8" X 4" bar stock .  Each plate is about 3.5" long.  They were welded to a ~5" length of scrap 1.5" square tube.  The plates were positioned so that the outer edges were a little over 6.87" apart.    The tube was mounted and centered in the four  jaw check and then the outer edge was turned to 6.87" diameter.       

The next step was to saw off the two nose pieces --- each piece about 3/4" long .   Photo at right shows sawing off one of the pieces.  The two pieces were then mounted together (side by side)  in the milling vise and the long flat side milled to make the height (the amount the nose sticks out) 0.61".  The ends were then trimmed so that the pieces were 3.5" long (the side-to- side dimension of the nose).      

The main part of the sill is a 16" length of 1.75" X 1" steel bar stock.  An oblong hole was cut in the bar for the link to the tender.  The noses pieces were attached to the bar with one 6-32 socket head cap screw each.  These screws hold the nose pieces while the pieces are silver soldered in place.  The photo below shows the tender side of the finished sill 

This photo shows the frame side of the sill.  The holes above and below the slot are for the screws that held the nose pieces during the silver soldering.    The four pieces of angle were attached to the bar with 6-32 button head cap screws (left over from the frame sides).  The ends of the sill were rounded with a 1/4" radius corner rounding end mill.

I had dreaded making this part but it turned out to be fairly easy --- so I was ready to tackle the saddle which I was really dreading. 


Saddle HM406:  The center part of the saddle is made from a 9.25" length of 1.75" X 2" steel bar.  The top edge of the saddle slopes down on each side.  I was able to cut the slopes on my little band saw as shown in the photo at right. The saw made this task easy. 
The next step was to saw the notches for the fame bars on each end and then use the mill to finish the cuts and the slopes to the exact dimensions.  The upper surface was then smoothed on the belt sander to remove the milling marks.  This was also easier than anticipated.
The next step was to cut the sides from 9.25" lengths of 3/16" X 2" bar stock.  The pieces were rough cut on the band saw and then finished to dimension on the mill.  The sides were attached with four 4-40 FH brass screws per side. The screws are only partially countersunk.  After the sides are silver soldered to the center the screw heads will be filed off.  Enough of the head remains to hold the sides in place if the jointed are reheated.  On the other hand, enough of the head sticks out so that when smoothed, the screwdriver slot is removed.  
The next step was to machine the 4.25" radius in the top of the saddle.  I used the setup shown on the right.  There are spacers under the saddle to hold it off the table.  The tool speed was set very low (~100 rpm) and small cuts were taken (~0.01"-0.02").  This was the second dreaded task in making the saddle and it went very well.    
The next step was to cut the smoke box base from   the 1/4" thick 8" OD tube stock that will be used for the smoke box.  The OD of this piece should be 8.5" diameter to mate with the smoke box.   I put the piece in an hydraulic press and flattened it slightly so that it fit perfectly with with the smoke box tube.   (I actually bent it a bit too far and had to press it back slightly.  It's harder to bend back so it's best to do this operation very carefully.)      
The next step was to make the exhaust port pieces.  These pieces mate with identical pieces soldered to the exhaust pipes so a total of four pieces were machined.  The pieces were cut from 1/8" plate.  The plates have a 3/4" center hole and side holes made with a #33 drill.  I drilled the side holes in one piece and then stacked the four pieces on a 3/4" expanding mandrel and used the holes in the top piece as a pattern to drill identical holes in the other three pieces.  A pair of 4-40 screws through these holes with nuts on the back hold the four pieces together. 

The next step was to turn the 1.125"  diameter side edges.  This was done on the mill using the setup shown on the right.   That's a 5C collet holder attached to the rotary table. The side of the end mill was used against the sides of the plates as the rotary table is turned.  Worked neat. 

After the sides were finished on the mill, the edges around the screw holes were smoothed using a file and a sanding drum on a Dremel rotary tool.    The finished pieces are shown on the right.  

Unfortunately, shortly after removing the rotary table from the mill I realized that four more of these pieces are needed for joints in the exhaust pipes near the cylinders.   I leave that collet fixture attached to the rotary table so it won't be difficult to set it up again.

The next step was to attach the smoke box base to the rest of the saddle with a 1/4" FH screw.  The 3/4' diameter holes were then drilled for the input ports on the side and the output port in the center.  The side holes are drilled perpendicular to the  sloped sides.  A short length of 3/4"  rod was used to position one of the port plates as a pattern over the input ports to drill  the side screw holes.   The screw holes were drilled all the way through (#36 drill) and the top part tapped 6-32.   Stainless steel 6-32 studs will be screwed into these holes.   Hopefully any broken studs  will be easy to drill out from the bottom.  
The passages connecting the side and center ports were milled next.   The passages are 0.75" wide and 0.4" deep  Each passage was milled in two passes.  

Note that the sides are held to the center with steel socket head cap screws at this point.  I was concerned that the brass screws might shear due to stresses from the milling operations.  These steel screws were removed and replaced with FH brass screws before the soldering operation.  

The passage near the three holes were stepped with the mill as shown in the photo.   These steps were then smoothed with a rotary tool.  Sorry, forgot to take a photo after the smoothing.

The sides, curved base and the port plates were all silver soldered at  this time.   Two more holes were drilled in each side for screws and brass screws were used everywhere.  The port plates were also held in place with brass screws.   The parts were all pickled in preparation for the soldering.  The joints were fluxed and strip solder was placed between the surfaces along all edges.  This time I used an acetylene torch to do the soldering.  It was quicker than the propane torch.

A deflector  is needed to guide the exhaust gases from the horizontal passages up the center  hole.  The photo at the right shows machining the end of a 3/4" square brass bar with a 3/4" diameter end mill.  Both sides of the bar were machined.      


The deflector was sawed off the brass bar and positioned on the base plate so that it will be under the center hole.  It was secured with a single  4-40 brass  FH screw.  Photo shows the base plate with  deflector.   Once the position of the deflector was verified to be correct it was silver soldered to the bottom plate.    The next step was to solder the base plate and the angles at the sides to the bottom of the saddle.  Everything was pickled and fluxed and brass screws and strip solder was used again.   This time the propane torch was used to heat the joints. 

Photo above shows the top front of the finished saddle.  I forgot to mention that the holes to attach the smoke box  to the saddle were drilled in the curved base before it was soldered in place.  Several of the brass screws that held the port plates in position also got soldered in the process.    After all the soldering was finished the screws were drilled out from the bottom and the holes tapped again.      

This photo shows the finished bottom.  After everything was soldered the saddle was tested for leaks using water.  There were a couple small leaks around the base.    The saddle was pickled again, the areas around the leaks fluxed and pieces of a type of solder made to fill larger gaps (McMaster-Carr #7676A3) were laid over the leaking joins and then the joints were heated again.  That fixed all the leaks except small leaks out of the holes at the bottom of the holes from the port screws.  These holes will be plugged with stainless setscrews.      

After all soldering was finished, the saddle was pickled again to remove any remaining flux.  The surfaces were then smoothed and screw heads removed  using the belt sander, files and a sanding drum in the Dremel rotary tool.   The final step was to bead blast the saddle.  It is now ready to paint.   

This photo shows the rear sill mounted to the frame side bars. 
This is the front of the frame with the front sill bracket bolted in place.  The saddle is merely setting on the frame sides at this point.   

The tough frame parts are finished so now it's on to the easy parts.


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