Main Frame Design II
It's been over a year since the Frame Design I pager was first published. The boiler is being fabricated and the foundry is in the process of casting the engine parts. It would be nice to make the frame now so that there would be a place to mount the engine when it is finished. Normally the frame sides would be constructed and jointed together with the frame bolsters. Unfortunately, the frame bolster castings will likely not be available for many months. An alternative is to fabricate the saddle, sills and associated fixtures and use them to hold the frame together until the bolsters arrive. So, it's time to finish the design of the diamond frame and then design those sills and associated fixtures.
The drawing above shows the saddle design. The plan is to assemble it from stock bars, plate and a piece of tube. The center will be a steel block sandwiched between 3/16" thick steel plates silver soldered to the front and back. The vertical passages will be drilled from the top. The horizontal passages will be milled from the bottom. The bottom will then be covered with a 1/8" thick plate. The sides and bottom plate as well as the 1/2" angles on the bottom will be silver soldered in place, The two flange like exhaust openings will be separate pieces silver soldered to the center block. More detail will be shown in the construction page. This drawing was updated on 1/9/2007 to reflect minor changes made when the saddle was fabricated.
Rear part of frame: Much of the rear part of the frame is obscured by the coal bunker on Cass 6 and the oil tank on MRSR91. The photo below shows the rear part of the frame of a late Heisler. The MRSR91 frame has an identical structure albeit a bit larger. Note that the seam between the two frame bars is even with the top of the rear sill, the bolster and that cross piece. The upper frame bar extends about half way across the top of the rear sill. The bottom of the cab sides and the bottom of bunker/oil tank sides are also even with seam between the two frame bars. The bottom of the oil tank rests on the top of the upper frame bars. I decided to not have the cross piece on the model: I want to keep that area as free as possible to accommodate oil, atomizer and feed water plumbing. The plan is to have the bottom of the oil tank about 2.5" above the top of the bolster. The igniter circuit and coil as well as a sealed lead acid battery will housed in the space between the bottom of the oil tank and the top of the frame.
Rear Sill: The drawing above shows the rear sill design. The sill will be made from 1"X1.75" bar stock. The angles are attached with 6-32 screws. The nose pieces are attached with a 4-40 screw each from the rear to hold the pieces in position while they are silver soldered to the bar. (This drawing was updated 1/9/2007 to reflect minor changes made when the sill was fabricated.)
Swivel Pocket: This piece will be made from 1/2" X 1.25" HRS bar stock The two 3/4" pieces between the long bars are held in place by a pair of 10-32 socket head cap screws and then silver soldered. The pocket is attached to the frame bars with four 10-32 socket head screws .
This drawing shows the tender coupler link design. The main part of the link will be machined from 1.25" square bar stock. The disk will probably be cut off a length of 1.25" diameter bar stock.
Frame Side Channel: The frame side channel shown in the drawing above is a length of 1.5" X 1/2" X 1/8" channel. The only machining required is to mill out the fillets on the inside corners for about 1/2" back from each end. This is done to provide a good mating surface for the angle brackets that are used to attach the channel to the rear sill and the side channel support.
Side Channel supports: The side channel supports are cut from 2" X 2" X1/8"angle The support bolts to the frame side bars. A 1.25" length of 1/2" X 1/2" X 1/8" angle will be used as a bracket to connect this support to the side channel.
The sketch shows the spacing of the rear bolster, center stiffeners and the side channel supports. Note that there is a 3/32" gap between the stiffener and channel support for the front of the cab. This matches the design of the MRSR91 cab front.
The front sill and boiler support designs will be described in the Frame Design III page.