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 ansd 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.
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