A recent project was to manufacture and build a
tender for a Fowler B6 road locomotive. An original full size drawing
obtained from the Rural history center at Reading university was
provided by the customer. This drawing was re-drawn full size using
AutoCad. This allows easy scaling to any size required for the present
and the future. Even full size if required. Selected items were
copied and scaled to half size for the six inch engine tender. Where
possible all holes were added to the tender sides, floor and reinforcing
plates. The drawings were e-mailed to our Laser cutting sub-contractor.
Several day's later we received a pre-cut set of parts.
Bitmap of the drawing created in
Autocad that was used for Laser cutting. Note the fold extensions
Fowler designed tender and Belly tanks using various
methods. Some Tender's had flat sides with the flange radius on
the tender wrapper, others had flanged sides with a plain flat wrapper
as commonly used. The early B6 tender's had this type of tender.
The bend radii is 1.5 inches. Quite a large radii to fold, forming
using the coining method in a brake press was not acceptable due
to the fact that the finished radii would have an appearance similar
to a twenty pence piece! Special radii forming tools were made to
allow the brake press to cold form the radii to the correct dimensions.
Bunker top extension and the spare
radius parts used for construction
After forming the flanges the corners needed to
be added at the correct radius. For parts that are visible internally
and externally you need to provide a good finish both on the inside
and outside. Flanging the plates is the obvious method but formers,
heat distortion and hammer marks in the finished product render
this a difficult choice. To overcome this solid steel billets were
turned in the center lathe. A radius gauge was made from the pre-formed
tender sides. The radii were machined into the billets using the
home made radius gauge as a template.
Laser cut and formed Tender sides with added radii
Tender tank front plate. Only the external
radii is visible on this plate!
For instances where Radii or filled sections
are used I choose to use a wire frame method to produce the filled
in sections. I use 6-mm diameter steel rod. This is easily formed
to the correct radii, tack weld both ends. Each part that is added
is at a slightly smaller radii. Then you have to weld along the rods
both on the inside and the outside until the whole corner is one solid
part, the heat generated during the welding leaves a nicely annealed,
solid corner radius. Care full use of an angle grinder to dress the
welds will prepare this into a nicely formed corner. See below!
During manufacture and after dressing
made up radii
Partially assembled B6 Tender
During manufacture it is important to
keep checking progress and the fit of each part into the assembly.
I find this gives vision to progress and allows thought into what
needs to done next. The photo above is where I trial fitted the front
of the tank. This part has a large radii in the vertical plane that
blends into the 1.5 inch radii of the tender side. Quite tough to
get it all lined up correctly! Note the tender reinforcing plates
are pre-attached before final assembly of the tank!
Draw bar fitted to the rear of the tender for spacing
the wrapper rivets
One of the problems we face during construct
is the need for another part of the assembly that is needed to allow
progress. In this case the Draw bar assembly is need to allow the
rivet spacing to be determined. Seen here on one of the many trial
fittings. But the final dimension of the Tender is required before the draw bar can be made. Chicken & Egg situation.
This tender is of fully riveted construction.
Riveting a large assembly that weighs around 75 Kg's can be a tough
job. Here I am reaching down inside to rivet the front lower edge
View of the riveted tank construction
Mr Heath and Mr Robinson here again!
Supporting a large assembly and the rivet
snap in a position that allows you to move and manipulate it during
riveting can be difficult to arrange. This method allows me to lift
the tender tank and loose rivet carefully over the rivet snap without
pinching my fingers to many times. Also it is possible to damage the
metal surface if you are to rough with handling. Care needs to be
taken! In this view the right hand side panel is being riveted to
the tender wrapper.
Fitting half round Beading to the Bunker
The half round beading is 3/4" x 1/4". I bend this to the correct radii by heating it carefully with a Welding torch, when it is just becoming red hot it will form easily to the radii. Take care with the heat, it is very easy to melt the brass. I fix the brass to an edge at the begriming where the beading starts. Then by clamping and moving around it is possible to get a nicely formed beading. The beading is attached with equally spaced rivets.
It is difficult to write how to make and assemble, the main things to be careful with are to get everything as square as possible, Side plates and wrapper distances need to be equally spaced. Rivet spacing need to equal and in nice straight lines. Always assemble;e with several bolts. Check square ness then proceed to add more holes as you go. Finally riveting the whole assembly together.
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