Heisler Truck Design II
Nelson Riedel, Nelson@NelsonsLocomotive.com
3/17/2005, last updated 04/09/2006

The main truck side casting, axel bearing cap and  cross piece retainer are the subject of this part.  Before starting the design of the truck sides the following photos of disassembled trucks were reviewed. .

The partially disassembled truck above has the truck bolster, upper cross pieces which hole the truck sides in place.  This is a later truck design which has a much simpler upper cross pieces than used on Cass 6.  The brake plank which holds the brake cylinder is used only on the outside trucks.

The photo above gives a clearer views of the inside of the truck side casting.  This is a middle truck where the brake cylinder is attached to truck side by the bracket identified on the drawing.   The brake cylinder is barely visible in the weeds.   The lower cross piece is still installed on this truck.  The bearing for the gearbox swivel on the lower cross piece is off center, another clue that it is the middle truck where the gear case and pinion shaft are off center to one side to make room for the line shaft on the other side.

 The  photo above shows a lower cross piece with the shaft on the left side is broken off.  The non symmetric center indicates that it is for a middle truck.

This shows the bottom  of the truck side where the shaft from the center cross fits.  The black stuff in the center might be hardened grease. Note the shoulder on each side of the of recess used to align the cap. (I had wondered how I was going to align that cap.)

This shows the under side of another truck side with the lower cross shaft cap in place.   The cap is held in place by four bolts fed through the bottom of the spring cavity area.   The bolt heads are visible on several of the previous photos. If you're wondering why I didn't lift the truck side up out of the weeds before taking the photo all I can say is I tried.  But, hadn't eaten my Wheaties.    That side probably weighs at least  500 pounds.

Photo above shows the part of the truck side between the wheels.   Sorry about the bright light across the top.   It was a chilly morning and the sunshine was welcome.  The brake hangers are held by pins at the top.   The flat cross bar above the brake shoes keep the hangers and shoes aligned with the tire treads.

The drawing drawing above shows the model truck side which will be cast in iron.   

The first step in making the pattern was to make the spring tower pictured above.  The main piece of the truck pattern was made from 1/2" thick aluminum bar stock.   The spring tower was screwed and then soldered to the  main bar.  The part of the spring base that protrudes toward the center was also made as a separate piece and also screwed and soldered to the main piece.   

The photo above shows the completed truck side pattern.  The slots in the front of the spring tower for the brake hangers will be machined in the finished casting to avoid using a core in the casting process.  The brass pieces near the top of the spring tower were used to increase the thickness where the bolts for the cap fit.   The holes for flat head screws were covered with Bondo body filler. 

This shows the inside of the truck side pattern.   The springs are the correct diameter but 1/4" too long.

Lower Cross Cap:  The shafts on each end of the lower cross piece are clamped to the truck sides with the lower Cross Cap shown in the drawing on the right.     The cap attaches with screws.
The photo shows the lower cross cap pattern  in position on the bottom of the truck side pattern. The cap will be cast without screw holes.   The holes will be drilled in the cap first and then the cap used as a pattern to drill the holes in the truck side casting.  The holes in the truck side casting will be counter bored for socket head cap screws, the screw heads being under the springs.  I think I'll try using an interference fit on the heads much like the square recesses were used on the prototype for square head bolts.
The axel bearing cap  is shown on the right. The cap and mating recesses in the truck side were machined to match the bearing OD.   There will be about 0.05" shrinkage.  Charly Wilkins tells me that the hole location will be consistent from part to part so I should be able to simply ream the holes to the correct size using an adjustable reamer.
This shows the axel cap pattern in place on the truck side pattern.  The caps will be cast without screw holes.  The holes will be drilled in the finished casting and then the cap used as a pattern to drill the holes in the truck side.
The axel bearing hole in the truck side has no shoulder or retaining ring to simplify the the casting and subsequent reaming of the holes.  The bearing retainer plate shown on the right will be attached to the truck side casting to retain the bearing within the side.  The retainer plate is simply a 1" length of 1/2" X 1/8" CRS stock.

The remaining truck parts are described in Truck Design Part III.