Welcome to
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 22 - Tender WPU Gear, Steps, Brake
1. Brake Hanger Brackets    
I have made the brake hanger brackets from 1" dia brass bar but because they are inside the frames and completely out of sight, I have changed the design to ensure that the bracket carries the brake hangers, not the shouldered bolt as designed. On the drawing, I have pencilled in an extension to create the pivot point. As with the spring hangers, the holes were drilled first and the work supported on pins to mill the outer form. I have also done away with the as-cast shaping in favour of simple turning, followed by counterboring clearances for the nuts to fit on the fixing screws. The spigot is turned to 6mm dia and just over 1/8" long, and the hangers, which are from 1/8" material, have a 6mm reamed hole to match. A simple screw and washer will retain them.
2. Brake Hangers    
The brake hangers have been made from 5/8" x 1/8" EN3B bright bar and I have changed quite a lot of the dimensions. I started by cutting the material 1/8" longer than drawn because I have increased the hole sizes and made the outer dimensions to suit. All the holes were marked out then drilled and reamed 3/16" diameter, although the upper hole was opened out to 6mm later. A pair of 3/8" dia filing buttons with 3/16" stems were made and these were used to help produce the forms at the ends and also to act as filing guides for the centre hole. A small amount of roughing out was done on the mill but most of the shape was hand-filed
3. Brake Beams    
Rather than make new ones, I modified a spare set of loco brake beams to fit the tender. I don't like shoulder bolts as I find they are prone to break at the root of the thread so I designed the brake beams to be spigoted, with a 4BA tapped hole at each end for retention similar to the brake hanger brackets. I had to adjust the lengths to suit what I was planning and this is when it became obvious that the draughtsman had made numerous mistakes which could have resulted in a load of scrap work. Each beam was held in the independent 4-jaw chuck and he spigot turned to 3/16" dia and a tad over 1/8" long. At the same time, they were drilled and tapped 4BA. When assembled, the hangers will be retained by simply screwing in a short 4BA bolt to full depth.
4. Brake Blocks    
These are the brake blocks, as supplied, cast in threes. First, I cut the blocks into individual pieces and marked out where I wanted the brake pin hole to be in each blocK. The hole size in my blocks is specified as 3/16" so I drilled and tapped these holes at 2BA, this being the largest thread that is SMALLER than the finished hole (you'll see why in a minute). The next job was to face front and back of the blocks for a flat and level finish. Facing off in the lathe seemed the easiest way so a means of holding them was needed. Because I have soft jaws for my chuck, I made a carrier plate onto which I could bolt the brake blocks and then load to the soft jaws.
I happened to have a mild steel blank of 1.7/8" dia x 1/4" thick but any old bit of steel would do. After facing off and turning a dia for trueness, then reversing and facing the back, I have drilled a 2BA clearance hole in it to mount the brake block, bolted from the back, and also added an anti-rotation pin to hold it firm against the cut. Once both sides were faced, the next thing was to get the length of the block machined which I did in my small milling machine. Each brake block was placed in the vice using the bottom slot of the vice to centre it and then aligning the block by eye. There will bound to be a more accurate way but I don't think it matters that much.
Because the width of my vice (1.618") is less than finish size of the brake blocks (1.750"), I was able to mill one side to size (0.066" from side of vice) and then do the other side to finish at the required size. Next I had to clean up the outer edges of the brake blocks so it was time to open the tapped holes up to their finished size. One of mine was a bit adrift so I opted to mount the blocks in the vice, holding on the milled flats, and use a 3/16" slot drill to align the holes more accurately. Some of the blocks have a slight witness of the thread but it's not important - there's a pin through there on assembly.
I had forgotten to take a photo at that point ,so that last picture was taken at the end. Most castings have a draft angle and I bolted mine together in pairs with the smaller faces together and then started to clean up the profiles using a carbide burr in my hobby drill...
...and finishing off with a small drum sander for the internal radii and my belt linisher for the external radii.
That only left the wheel-form part of the job to do and the slot. Using the same soft jaws as earlier, I drilled and tapped a 2BA thread in the top of each jaw and loosely bolted three of the blocks to the jaws. Then I gently clamped the jaws onto a finished wheel to align them and finally pulled the bolts up tight. I used cap screws because they are normally high-tensile and you can get them good and tight.
Then I wound the jaws down onto an adjustable ring (normal soft-jaw accessory) to leave about thirty thou to come out. I also set the compound slide over to about two degrees to enable putting a slight taper on the blocks. I would have liked to have included some sort of anti-rotation pin to the setup but decided that all would be okay with small cuts and a gentle touch. I took five thou depth of cut from the cross-slide and used the wheel as a gauge. Once to size, I used the compound slide to take a final cut to match the wheel profile. The brake blocks are symmetrical so no special attention has to be paid to orientation, unlike the loco blocks.
Finally, it was time to put the slot in. I don't have much in the way of slitting saws so opted to mill them out using a 1/8" slot drill (of which I have plenty). However, they are not deep enough so I freehand ground a bit of the shank down and milled the slots in two hits, saving my home-made long-series slot drill to finish the depth.
5. Brake Linkages    
There is quite a collection of parts that go together to actuate the brakes. I have made a couple of variations to the drawings to suit my tooling; the rods are all threaded M4 and the eyes have been replaced with threaded bosses so that I can adjust for any variation in the brake block sizes. With the forks, I prefer to make the slot first, milling to within twenty thou or so of the bottom, then removing the underneath support and finally plunging the slot drill through at the end of the slot and working outwards till the cutter breaks free. This prevents the cutter grabbing the work and bending it inwards.
Next I drill the cross-holes using packing to stop the part collapsing, and finally to mill away the opposite end if it's double-ended or drill and tap through on the lathe in the 4-jaw chuck if it's a rod end. There are two of the adjusting linkages, three components needed for each one or five if one counts the forks but the drawing only calls for one set. I have used M4 right-hand and M4 left-hand to create the adjuster.
The other variation I have made is how I fix the brake shaft levers to the brake shaft. The drawing suggests a 6BA grub screw but I felt this was far too flimsy and have pinned mine with 3/32" taper pins. To set up the drilling, I mounted the shaft in a tiny Vee-block on the milling table. I only set it by eye, not worth getting the wobbler out for, but a quick check with the old ruler trick seemed OK
They were then set up with a bar through the eyes and resting on parallels to make sure they were level and the holes were then drilled with a 3/32" dia drill as pilot followed by the taper drill. For any who have not used taper-forming drills before, you need to be aware that they have a tendency to grab the material and pull themselves into the hole, resulting in a stalling of the drill for larger sizes (and probable damaged workpiece) and a broken drill for smaller sizes. It is very important that one uses a short, sharp pecking action to keep breaking the cut when using these drills. And they need to be held extremely tight in the chuck.
6. Tender steps    
The front and rear tender steps are both made from 20 swg brass sheet and are fairly simple affairs. After cutting out the the main upright section, the two large holes were drilled and then filed to size and shape. This was followed by drilling eight 1/16" dia holes for the rivets holding the treads, the single hole for the bracing stay and the three holes for fixing to the platform. The treads were marked out, cut to shape and the treads dimpled with a centre-pop. The two outer holes were marked out and drilled 1/16" next and finally the tread sides and rear were bent. The treads were riveted to the uprights and the other two holes in each tread drilled through and riveted. The rear steps were made in a similar fashion, the main difference being the hand-hold at the top of the steps. The handrail is a piece of 3/32" dia brass bar turned at each end to 1/16" dia and set in place using the natural spring of the material to retain it. The mounting holes beside the top large hole need to be left hand side and right hand side respectively. Otherwise, the steps are symetrical.
7. Brake Adjustment updated 26/04/20  
While setting up the tender brakes, It became obvious that a better means of adjustment was required if they were to function effectively. I decided to make four more turnbuckles and set them between each of the pull rods. As before, these were made from 3/8" hex mild steel, one inch long, drilled 3.3mm through and tapped M4(RH) at one end and M4(LH) at the other. The pull rods were cut and 5/16" removed from the longer half. This effectively meant that I had adjustment of the brake on each wheel. I have also settled on how to operate the brakes. First, I made another lever arm to mount at the centre of the brake shaft and a bracket to fix to the underside of the bottom plate. This bracket has a slot to allow adjustment and a pin to hook a strong spring to.
I'm not modelling the handbrake system as drawn, it relies on the tender chassis and it's tank being permanently joined. I do, however, want a handbrake and have knocked my own version. It relies on a strong spring to hold the brakes on when in the steaming bay, for instance, but a cam operates against a lever to free the brakes for normal operation. I also wanted a means of clipping the extra water pipes to the chassis and the picture on the left shows milled cutaways for the 1/4" pipe in the new crossbar. These are for the handpump and the axle pump return. A little gearbox was made to move the operating point to a location clear of the wheels. The gears came from the "useful one-day" box.
This view on the left shows the cam with it's locking flat, the position that holds the brakes off. The spring is an old bed-frame spring. The final view shows the thing assembled with the pipes in place and a T-bar Allen key poking through a hole in the side of the tender chassis. Once the turnbuckles were adjusted up, it works well and holds the tender on a five degree incline. No chance of rolling off the rails in the steaming bay.
8. Spring Hanger Brackets    
There are castings available for the tender spring hangers but I felt they made an interesting little project to machine from solid bar. Twelve are required and this lends itself nicely to some sort of production-line technique. Material is unimportant and I have chosen to use EN1A mild steel. On the drawing, I measured the minimum dimension needed to make the parts from round bar and it appears that 1.1/16" dia would suffice. I had 1.1/8" dia in stock and twelve billets were cut from this and faced to the given length of 13/16". I have transposed the circle onto the drawing to determine the best way to mill the rectangular shape, and have added dimensions that are either scaled or calculated to help with this. This is the starting shape.
Next, I drilled the four mounting holes, and an extra hole not shown here (explained later), 1/16" dia x 3/16" deep. The billets were then turned over and the three front holes drilled, not as drawn but also 1/16" dia and by 1/4" deep. The holes are for dummy 10BA bolts so can be opened out later and the bolts set with adhesive or tapped with very little effort to give a shallow thread. I didn't fancy having to thread thirty six full-depth holes with all the inherrent risk of tap breakage when it is unneccessary.
Drilling the holes at the start made it easy to do the subsequent milling operations and the first of these was to machine the upper angled faces. I had calculated that I wanted 0.085" from the edge of the holes to the outside, seen on the drawing in the picture above. Using two 1/16" drills, the hangers were set in vice and the cutter just touched on to one of the drills. the DRO on the quill was zeroed, the quill lifted by 85 thou and the DRO re-zeroed. Now I was able to mill the whole of the top profile. Using a single drill, I then set the hangers at various angles to rough out the radius at the top and these would be finished with a file.
The back of the vice had been set as the "Y0" zero datum and by working down to the "Z0" depth and to the calculated "Y" position each time, there was no need for a workstop on the "X" axis and the rear inner face was blended as work progressed. Next, I machined the shape of each of the lower sides in turn. I calculated that the angle should be twenty five degrees but I didn't have two holes avaiable to copy the earlier operation so an angle block was used in conjunction with a single locating pin. The workstop is being used to prevent the angle block moving whilst setting the workpiece into the vice but location is unimportant.
Since I'm still using the same cutter, the "Y" dimension stays the same as does the quill setting of zero. Once all twelve were done, the angle block was reversed and the stop moved to the other side of the vice. The other sides were now machined to size. In a similar manner, the spring housing was cut away next followed by the necking on the sides of the brackets, using 10mm and 6mm dia cutters respectively.
Then it was time to create the lower shaping and this is where the extra hole came in. When I realised what was needed, I went back and drilled the extra hole in all twelve, it needing to be 112 thou up from the base, or 0.763" from the top, and on the centre line. This was drilled 3/16" deep to ensure it didn't break through, but would probably be hidden by the spring if it did, so maybe not too important. So, once again, I was able to support the work on pins and create the required shape and was also able to take a little off the front section. Finally, I set a workstop and reloaded them on two pins to enable drilling and tapping of the 6BA spring-mounting holes. From this point on it was all hand-work, filing and linishing the radii.
All that is required now is some time spent polishing them, and fixing the dummy 10BA screws into the three face holes. I have made these to conform with the Warnett drawing but, as a colleague pointed out a while back, they don't look much like the prototype except head-on. However, they could be machined further using the same system by milling away material on top and at the sides to create a more authentic look but that's a detail too far for me. This has been quite long-winded but I was hoping to demonstrate that, by drilling the holes first, all the subsequent operations became so much easier. And when there are twelve to make, this style of manufacture is quite efficient.
9. Tender Springs    
The springs should have been gunmetal castings but aluminium ones have been supplied instead. Because of this, I have made a modification to the item by using a brass liner in the spring housing. There was just enough room to drill and ream a 7/16" hole in each and press in the liner. The other parts are as drawn and quite straightforward. I've cleaned up the area of the buckle and filed the underside of the springs but I'm not particularly impressed by the quality of these castings and may consider binning them and making real ones once I have seen them painted.
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