Heisler Truck Construction I
Nelson Riedel, Nelson@NelsonsLocomotive.com
1/30/2010, last updated
01/30/2010

The  Wheels sets and all the gearing were completed several years ago while waiting for the truck castings.   The redesigned castings arrived last fall and were immediately attacked with the machinery.   Now it's time to go back and show how some of the parts were machined.  Unfortunately, some of the photos of the machining process have been deleted.  So where necessary, I've remounted a finished piece to show how the machining was done.  

 

Truck Side:  The truck side is the largest casting and also most critical in that it sets the spacing of the axels.

The first step was to put some spacer bars in the bottom of the milling vise to support the bottom of the truck side casting on each side of center.   
The bottom of the truck rests on those spacer bars.  The surface which mates with the bolster cap is then machined to the correct length (4.313") and correct height (1.875") above the surface where the bottom of the springs rest.   This machined surface becomes the reference for the next operation.  
The spacer shown on the right is placed in the bottom of the vise.  This spacer will support the just machined surface when the  truck side is mounted upside down.
Note that  a heavy bar has been added to  the back of the vise opening to provide additional support to the casting.   The first operation with this setup is to mill the bottom of the truck side to the correct distance ( 2.563") from the reference surface on the top.  Next, the recesses for the lower cross cap and the axel bearing caps are machined.

 
Lower Cross Cap: The lower caps were fabricated from aluminum bar stock.  Two parts were mounted together in the 4-jaw chuck and drilled 1/2"
Next, the caps were moved to the mill and the lip machined on the surface that mates with truck side. 
The mounting holes were drilled into the cap and the cap was then used as a template to drill and tap mating holes in the truck side.   The truck side was then mounted in the mill as shown and the hole for the lower cross sleeve bearings drilled into the cap & side.   Normally I'd use a boring head to make this hole but a  sequence of drills taking small cuts worked fine.    The last step was to mill the ends of the cap and nearby area of the the truck side to the correct dimensions.  
Axel Bearing Cap: The axel bearing caps are made from aluminum bar stock.  The photos shows two caps held together and a 1 1/4" hole drilled into the pair.  The holes for the attachment screws were drilled and counter bored next.   
The axel bearing caps served as guides to locate the mounting holes in the truck side which were then drilled and tapped.  The caps were then attached and the bearing holes enlarged to the correct size plus ~0.051" oversize to permit the truck side to flex as necessary to follow uneven track.  The mill table indexing was used to accurately  locate the axel bearing holes relative to lower cross bearing hole.       

Lower Cross:   The truck side was set aside to be finished later and the lower cross was machined next.   The photo above shows turning the ends of the lower cross.   The piece was rotated in the 3 jaw chuck until a spot was found where the the far end was roughly centered as determined by a dial indicator (that area of the casting is rough with a significant parting line).   There was insufficient material to make the ends 5/8" diameter so they were turned down to 19/32" and the sleeve bearing was changed from 5/8" ID to 19/32" ID.  The shaft end was drilled and tapped and the shoulder at the inner end was turned to the correct dimensions using this same setup.   

The photo above shows a finished lower cross with associated parts.    When I'm satisfied that no modifications will be required, the end caps will be secured with Loctite (after the bearings are slid onto the shafts).  

This shows the HM315 Swivel Bearing Block secured in place by a pair of HM323 Swivel Bearing Block Clamps.   These parts are described in the Outside Truck Gears and Shafts section.  The original plan was to use a sleeve bearing inside of the bearing block.  When I got around to making the block I found some bronze bearing stock scraps left over from making the engine rod bearings so that was used eliminating the need for a separate sleeve bearing.  The HM315 drawing has been updated.         

This photos shows how the the slot in the low cross was  milled to accommodate the Swivel Bearing Block.
HC207 Bolster Cap: The next thing is to machine is the Bolster Cap castings.   The under side of the cap that mates with the top of the truck side is milled smooth and square and the ends are milled to the correct overall length.  Six holes are then drilled in the cap.  I used the angle fixture shown in the photo on the right to drill the holes. (After looking at the result I changed the drawing slightly to move the holes closer to the outer edge.) The main fastener for the Cap is the long 8-32 bolt shown on the right side of the photo.  The bolt was made of stainless threaded rod and a 1/4" hex nut silver soldered to one end.

 

Back to the Truck Sides: After the lower cross was completed, the trucks with lower cross and axels were assembled and everything checked to make sure it fit together and verify that the sides were straight.  The sides were then removed and the final machining of the sides completed.   The image above lists the tasks.

HM206 Bearing Retainer:  Slots 1/32" deep by 1/2" wide slots were milled in the truck side at the proper location for the bearing retainer.   The bearing retainer was used as a temple to location the holes in the truck side which were then drilled and tapped for the plate attachment  screws.  

HM207 Upper Cross:  The Upper Crosses are  simply lengths of 1/8" X 3/8" CFS bar stock with a hole in each end.   The ends of the bars fit into the slots shown on the image above.  This slots were milled and the cross attachment holes were drilled and tapped at this time.

HC207 Bolster cap Attachment Holes:  The Bolster Caps machined earlier  were clamped to the truck sides and used as templates to locate the associated attachment holes.   The vertical hole for the 8-32 bolt is over 2.5" long ----care must be taken to make sure the side is held vertical in the drill press and the drill pulled out often to clear chips.   Drilling a short hole and tapping it requires less effort but has the risk that the attachment screw becomes rusted in place.     

Slots for the Brake Shoe Hangers:  These 1/4" wide slots were cut using a Woodruff Key Slot cutter.    The truck sides were clamped in the milling vise with the side facing up for this operation. 

Holes for Brake Shoe Hanger Pins:  I made a fixture to locate these holes but have misplaced it so no photo.  The fixture has a slot that fits over the bars on the side of the casting.  The holes for the pins were drilled all the way through the casting so that a pin rusted in place can be driven out from the inside. Long pins are used to reduced the probability the casting will break if the brakes grab.

Axel Pump Bracket: The truck side next to the axel pump requires an additional bracket as shown in the photo at the right.  The bracket was made from a scrap piece of aluminum angle (steel, brass or bronze could also be used).  The bracket must be made and located to match the specific pump.   
     

This is a good spot to break.  The truck fabrication will be continued in the Truck Construction II page.

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