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Steve's Britannia
5" gauge Britannia
Assembly & Alignment Drawing Errors 1. Mainframes 2. Pony Frames 3. Main Axles 4. Coupling Rods
5. Bogie 6. Pony Truck 7. Brakes, Sanding Gear 8. Cylinders9. Link Motion 10. Oil Pumps, Saddle
11. Smokebox 12. Boiler Detail 13. Boiler Fittings 14. Superheater, Ashpan 15. Valves, Pipework 17. Cab Fittings, Clothing
18. Cab & details 19. Footplates & details 21. Tender Frames, Axles 22. Tender WPU, Brakes 23. Tender Body 24. Tender Body, Filter
Drawing 7 - Brake and Sanding Gear
1. Brake Blocks    
I have covered the tender brake blocks in much greater detail on drawing 22 so this is just a shorter description of the main brake blocks. As I described previously, I first cut the strip of brake blocks into the indivdual components followed by drilling and tapping 2BA at the position where the pivot pin goes, this being the nearest thread size under 3/16". Then they were bolted onto the carrier plate and one side faced before reversing and facing the opposite side. To produce the wheel profile, I bolted some extensions onto the soft jaws and mounted the blocks as before, using 2BA cap screws tightened up very firmly.
I had previously made a wooden former the same diameter as the main wheels and this acted as a gauge, saving me from having to remove a wheel or axle from the build. I also approached the job of milling the slots differently as I now had my new mill. This time a slitting saw was used, loading the blocks in pairs in the mill vice and plunging directly to depth gently by hand. To finish, the 2BA tapped holes were drilled and reamed 3/16" to accept the pivot pins
2. Pull Rods    
The two pull rods, along with most of the other brake components, were made twenty years ago and no photos exist of the making of these parts although I remember that the eyes and forks were brazed to the rods taking care to get the alignment correct. However, I have since found that they do not pull up evenly on all wheels and have now cut them in two, removed 1/4" of metal and made a turnbuckle for each one using M4 left-hand and right-hand threads respectively. The turnbuckle is from 5/16" hex mild steel at 1" long. A locknut on the right-hand end allows fixing after adjustment. There is another picture in the "overview" section of the complete linkage.
3. Sanding Gear    
The sanding gear is non-functional and made from various bits and pieces. The sand pipe is from 3/32" dia brass tube, the dummy steam line from copper wire taken from some 1.5mm twin and earth carth cable, the combining nozzle and nut from 1/4" hex brass and the bracket from 16 swg brass sheet offcuts. The machining of these parts is mostly straightforward and needs little explanation. However, the drawing does show a forty-eight thou hole at 30 degrees in the combining nozzle to fit the steam pipe to and for this I made a simple fixture to screw the nozzle into. A 1/4" x 40 hole was tapped in a piece of hexagon brass and the hexagon rotated round and held in a vice. This allowed the nozzle to be screwed in, a tiny flat filed where the hole was to be and then centre-drilled and drilled 1.5mm.
The 3/32" dia pipes were bent freehand using a bending spring and the various parts were soldered together with silver-bearing soft solder. There is also a photo on the "overview" page that shows one set fitted to the loco.
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