Bonding Trailing Truck Spring Parts to Rear Frame

The trailing truck rear spring frame attach cross member at right on top of rear frame behind trailing truck wheels and the spring saddles from the rear cross member around the trailing truck journals to the front of the trailing truck wheels and the equalization lever mounting boxes towards the front of the rear frame at angles to the frame were glued in place aligned to the trailing truck.  The truck was attached to the front pivot to provide alignment.

The rear view of the trailing truck spring mounting parts attached to the rear frame above the trailing truck are shown above.

Each trailing truck spring sits on a saddle bar that freely rotates vertically to allow compliance with undulations in the track.  The rear of the spring is pinned to the crossbar at the hole shown at left while the center of the spring sits on the middle of the saddle bearing down on the top of the truck journal and the front of the spring is aligned with the small "U" cutout at the right of the saddle just right of the front of the truck wheel in this photo.  A lever will couple the front of the spring down past the "U" slot to the long equalization lever that will be located just in front of the truck "U" frame that passes under the rear frame.

The long equalization lever pivots are near the front of the rear frame and are angled to position the equalization levers from the spring front down link levers to the rear driver down link levers of the main frame.

Number 3-48 screws will serve as pivots and retainers for the equalization levers.  The inside portion of the lever box severs as a nut for the screw and requires threading.  A 3-48 tap in a hand tap handle is used to do the threading.

Avove the 3-48 threading is completed prior to removal of the tap.  The ABS material is soft and easily threaded by hand.

 After threading the levers are inserted in the boxes and screws inserted and snugged down.  Sufficient clearance inside the box permits free movement of the levers which were drilled out for a 5 mil clearance to the OD of the screws.

 Above pix shows the alignment of the levers which terminate at the small "U" notches on the spring saddles at the upper ends of the levers in the above photo,

After connection of the equalization levers at each end to the down links and insertion of the rear frame into the main frame a completed path of equalization exists from the center of the main frame at the top of the main drivers in the top of above photo, through that spring, downlinks to reversing lever inside main frame, up link to rear driver spring, across rear driver to cross equalization lever at rear of back driver, down links to two trailing truck equalization levers, up links to each trailing truck spring front, across trailing truck journals to trailing truck spring rear cross mount on rear frame.  The combined effect of the overall equalization linkages and springs is to transfer force between drivers and trailing truck to maintain approximately constant spring force on all wheels.  All the moving parts of the equalization system described operated on the model.  Everthing wiggles up and down when a driver or the trailing truck moves up/down.

Trailing Truck Spring and Equalization Fit Check

 The front cross support and trailing truck pivot and the rear cross support and tender tow bar mount were glued to the rear frame side assembly prior to removal of the sacrificial inner support structure.

 The inner support is like a ladder assembly attached to the side frames with short posts.  Those will be cut away to remove the ladder assembly.

The Dremel tool is equiped with a cut-off blade to remove the posts.

After cutting away part of the posts prior to completion of removal of the ladder support stucture.

Shown above almost all the posts are fully removed.

 After final post remoal the ladder support structure is removed leaving some residue of the posts still to be removed by grinding.

A round sanding wheel was used in the Dremel tool to grind away and smooth both the inside and outside of the rear frame assembly.  Much of the outside will have attached parts for the trailing truck spring and equalization lever attachments.  The inside is clear for the firebox clinker chutes which will drop down through with the exit doors below the frame bottom.

 The finished rear frame is ready for installation of the trailing truck pivot, spring and equalization attachements along with the rear firebox mount and external cab mounts.

The trailing truck pivot is attached to located the training truck position.

The trailing truck rear sping mount, spring saddle mounts and equalization lever mount with lever are shown loosly set in position for a fit check.  Later those parts will be glued to the rear frame.

An above view shows the opening down through the frame and trailing truck where the clinker chutes will pass to a point below the trailing truck frame.