Jan 2013 - Oct 2019.



John R. Bentley 2013-19.


Fabricating stainless steel
Fittings for the Methanol Tank

for the burner of the model D-type boiler



First: the pressure relief valve



This relief valve is based on a design by Less Kerr that I saw in an article about a small methylated spirit burner in the 26 May-8 June 2006 issue of Model Engineer. Mine is larger due to a more sizable tank and proportions and materials are different, but the concept is the same.



I was off to a great start, carefully cutting the thread on the stainless steel body. I used my Craftex mini lathe with a spindle crank for human power which provides better control and gives a good finish when cutting threads. I paid very close attention since I wanted a good smooth fit into the fuel tank top bush as this opening also serves as the fuel filler. All this fancy talk about precision and finish is just fine but attention to the basics is more important - I cut a left hand thread by mistake!




On the second attempt I got it right :-)









Drilling the body







Making a sturdy threaded mandrel to hold the valve body for knurling






It seems to get an adquate grip






Profiled for the knurling operation with the outer end supported by the tailstock center






The valve body (center) squeezed between the two knurls in my Craftex mini lathe






Flattening the bottom of the hole with an endmill






The completed body removed from its mandrel






Threading the end of the valve spindle










Making an end retainer for the stainless steel valve spring








The few parts which make up the valve






The following views show the finished relief valve for the methanol fuel tank











Pressure is relieved around the central piece which is the valve spindle







Next: the methanol tank valve






As this will be the fuel regulator and main tank shutoff a large handle is appropriate





This valve is an adaption of a simple screw down needle valve





It is not really very big





The body was turned from stainless steel in a Taig lathe




A flat was milled and a hole drilled to mount the spigot







Milling a hex section at the base of the valve body





The completed hex





Valve body parted off from stock and held in a brass mandrel for drilling and threading






Making the spigot






Spigot and body to be silver brazed together






Starting to look like a valve (I hope)







Turning the valve spindle





Making the packing nut for the top






Turning the handle from naval brass






I copied a very common North American handle design






Milling the flutes






All the valve components (with the spigot already attached to the body)






The completed valve










Tank mounting: Saddles and Piers





The saddles are located and held against the shell by bolting into blind threaded bushes in the bottom of the tank

Drilling the positioning holes






Fitting the saddle curves to match the tank's shell
(the near one still needs a bit of adjustment)






Lower supporting ribs






Ribs silver brazed into position






Two small plates will be brazed on the sides of each assembly






Facing mill preparing aluminum stock for the piers






Piers to be drilled and tapped (on tops and bottoms)






Completed saddles and piers bolted to a steel baseplate









Next: the fuel level indicator




This is a pressurized fuel tank, not a steam boiler. The requirement of a water gauge in a boiler is to show only the safe range of water levels. However a fuel gauge has a somewhat different job. Like those in our cars, it must indicate how much fuel is in the tank regardless of the amount and therefore it must display the entire range from full to empty.

With this in mind I decided to simply use a very long gauge glass at the side of the tank with the visible portion spanning the complete distance from top to bottom. The fuel level of course will not give a linear indication of the volume of fuel since the tank is wider at the mid point. It also means that the very long glass is located where it will be suseptable to being smashed easily and so will require some physical protection.




A banjo joint at the top and bottom of the shell will suit this arrangement nicely





The upper banjo connection is visible in this view



Banjo connections are reasonably easy to construct and offer a couple of advantages over many other types. Orientation is easily set (or changed) as direction does not depend on thread tightness or washer thickness. The other feature is that banjos can be installed by simply sliding in over a suitable threaded bush. My fuel gauge grass assembly can slide in from the side over the top and bottom tank openings simultaneously as a rigid one-piece unit.




Turning one of the slightly oval banjo bodies



The oval shape was to aid in mounting a pipe on the side



Reaming the drilled hole through the body






Using an odd shaped tool to create a hollow body






Creating banjo bolts from stainless steel screws



Left: original screw; Middle: head reduced; Right finished banjo bolt




The holes in the heads are for a tommy bar to tighten the bolts
(hex heads would be a suitable option)






A length of tubing silver brazed to the body completes one banjo unit






Cutting silicone washers for the gauge glass from model airplane fuel tubing






A few extras for some future project






I have used this type of gage glass washer for years
- they work well without any problems






A stainless steel nut to slide over a silicone packing washer





Yet to be finished are elbows and protection rods for the glass





You are on Part 11














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