Heisler Main Frame Design III
Nelson Riedel, Nelson@NelsonsLocomotive.com
/2005, last updated 02/23/2007

This page is a continuation of the Frame design II page and shows the design of the front sill and associated parts and the boiler supports.

Front Sill & Associated Parts:  The photo above shows the front sill on Cass 6.  While preparing this design I reviewed the photos of Cass 6, MRSR91 and parts from a slightly smaller late Heisler.   The drawings I did for Cass 6 show both the locomotive front sill and the tender rear sill are 10" X 13".   The review of the photos confirmed that tender sill as 10" X 13".   The locomotive sill was also measured as 10" thick.   However,  the height was measured as 14.5" at the center and 13.5" at the ends.    The photo above shows the bottom of the sill is flat between the vertical foot board supports and slopes up slightly toward the ends.   I never noticed that before!   All the photos and drawings of other Heisler Locomotives suggest the sills did not have tapered ends.   Possibly the tapered ends were done when the sill was replaced a couple yeas ago.  I decided to make the model locomotive and tender sills identical at 1.375" X 1.875" X 16".   Hopefully I'll be able to find a suitable piece of maple or cherry.

Sill Brackets: This photo of a late Heisler with the sill removed gives a good view of the front side of the sill brackets and the coupler support casting.  That dangling rectangular plate was probably a shim on the back side of the sill.
This photo shows the back side of the sill bracket on Cass 6.   Rather than making individual brackets for each side I decided to make a single bracket spanning the two frame sides. Once the sill is in place it will appear to be identical to the individual brackets.
Coupler Support: This photo shows the coupler support casting on an upside down Heisler tender frame.  The structure of the locomotive coupler support is identical.  The plan is to fabricate the support from plate and bar stock.
Tray:  The photo on right shows a nearly empty tray on a smaller late Heisler.   The boiler is off this locomotive so the entire tray could be photographed easily.   The plan is to copy this casting using 1/8" thick plate & bars.  



Front Sill  Bracket:  Drawing above shows the front sill bracket design.  The main piece is a 12.5" length of 1/8"  X 1.5" bar stock.   The smaller pieces that protrude from the plate will be cut from bar stock and silver soldered in place.   This drawing was updated 1/9/2007 to reflect minor changes made when the piece was fabricated.

Front Coupler Support:  The front coupler support shown above will be constructed of  1" thick and 1/4" thick bar stock.  The plates on the ends will be screwed and silver soldered to the central bar.

Frame Tray:  The tray will be made from 1/8" plate and 1/8" X 3/4" bar stock.   The parts will be silver soldered together. 
Coupler Pocket: This photo shows the coupler pocket and coupler on the MRSR91 tender.  The front coupler and pocket on the front as well as those on Cass 6 appear to be the same. Note that the coupler shank is slotted and fits into two of the three pocket openings.  All the couplers I've seen used on 1.5" - 1.6" gauge live steam models have a solid shank with no slot.  

The block between the pocket and the sill is 17" wide and 6" thick  which scales to 2.25" X .5".


The initial plan was to use the same type coupler pockets as on the shay.  However, after more though and seeing the coupler pockets Bob Reedy machined for his Climax (Live Steam March/April 2002) I changed my mind and decided to machine a pocket like the prototype.   The pocket design is shown on the right.  It will be machined from a block of aluminum. 

The plan is to machine the coupler shaft so that it is split and fits into two of the pocket slots.   

Boiler Supports:  The photo above shows the rear boiler support on a late Heisler.    The end pieces are castings and the cross piece is a steel bar.  The dangling thing in the center is a piece of wire.  The photo has been edited to white out background clutter around the support to make to show up better.   The bottom of the boiler (mud ring) sets on the castings.  The bar probably keeps the castings from twisting under load and also holds the dimension between the frame sides.  The rear support is hidden under the cab so this piece on the model can be made a bit simpler.  The outside of the castings are visible on the front mount as well as mounting facilities on the center stiffener that I'll want to reproduce on the model.  The cross bar will interfere with the oil burner nozzle so it'll have to be repositioned slightly.

Rear Boiler Support:  The rear boiler support is made from a piece of 1.75" X 1.5" X 3/16" angle.   I'll probably have to buy 2" angle and cut it down.  The support bolts to the bottom of the lower frame bar just in front of the rear stiffening plate. The bar will be positioned such that there is a 1/4" gap between the vertical side and the back of the boiler.  The boiler will be bolted to the saddle so any expansion will cause the back of the boiler to move to the rear.  I expect at most 1/16" of movement between hot and cold. 

The top of the vertical part of the support also serves as a support for the cab floor.  The rear of he boiler doesn't seemed to be clamped down on the prototype.  For the model, I plan to screw a couple 1/4" bolts into the back of the mud ring and run the bolts through holes in the vertical part of the support. The bolts will extend beyond the support and not be tightened against the support.   This arrangement will permit the boiler to move back and forth slightly to accommodate expansion and contraction but will restrain the boiler from moving side to side or to lift off the support vertically.  

This boiler support is also a brace for the side channels.  The ends fit under the channels.  There will be a 1/16" gap between the boiler support and the channels which will be filled with suitable shims.  Screws up through the support into the channel flanges will secure everything.

Front Boiler Support: The front boiler support will be a length of 1/2" X 1/2" X 1/8" angle machined at the end so that it can bolt to the under side of the lower frame bars.  A much smaller anger is used at the front than the back to avoid interference with the burner nozzle and the blow down valve.  The bottom front 1/4" of the boiler will rest on the angle.  However, the major front support will be via the side supports  described next.   The  primary function of this support is to control the separation of the bottom frame bars.  

Boiler Side Support:  The drawing above shows how the center stiffener is modified to accommodate the the Boiler Side Support.  The modification consists of cutting off the lower part of three of the vertical bars and silver soldering on the machined bar shown in blue.  Note that the bar is positioned off center so the stiffeners for the two sides become mirror images rather than identical.  The Boiler Side Support shown in red is made to closely resemble the standard Heisler front boiler support.  The cross bar is not used because it would interfere with the burner nozzle.  The HM416 Front Boiler Support replaces that cross bar. 

The photo on right  shows the lower part of the left center stiffener and the boiler support on MRSR91.

This photo gives a better view of the underside of the left stiffener and the boiler support  Note that the part of the stiffener that mates with the boiler support hangs down below the frame bar.  I decided to make the lower edge of the stiffener align with the lower edge of the frame bar.

I assume the chains are to keep the drive shaft from dragging should a universal break.  I have a lot of faith in my universal design so think I'll skip the chains on the model.  

This photo of the MRSR91 right front boiler support gives a good perspective of the stiffener, frame bar, support and the edge of the boiler. 

One of the challenges of designing a working model is to hide the deviations from scale as much as possible.  Most of us run four or five times scale pressure which necessitates thicker boiler material.  The frame bars are 4" wide.  The boiler lower edge in the photo seems to be about 75% the bar width or  maybe 3" which would scale to ~0.4".   On my boiler layout, the plates are 1/4" and the water jacket 1/2" which makes this dimension 1" --- 250% over scale. 

Stiffener Modification Bar: The stiffener modification bar will be machined from 3/8" X 1/2" bar stock and silver soldered to the stiffener. 
Boiler Side Support:  The drawing at right shows the  boiler side support.  The support will be fabricated from 1/8" and 3/8" thick stock silver soldered together. 

This sketch above shows the frame with all the parts in position.  This beats the frame design to death; time to start making some chips.

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