Welcome to
Steve's Britannia
1.1/2" scale Allchin Traction Engine
Steering, Brakes, Plumbing etc.
  1. Steering Axle and Brackets  
Apart from the steering axle brackets, very little had been done in the steering department and I had to make most of the components. The first of these was the steering axle that is supported between the two brackets at either side of the hornplates. Unfortunately, one of the brackets had been machined so far out of true that a new one had to be made. Rather than buy a new casting, I fabricated one from some bronze offcuts. Here is the original perched on the end of the steering axle, clearly showing the level of error.
The axle itself, made from mild steel, was straightforward turning plus a couple of flats and drilled holes for fixing the steering chains to. It also needed a keyway machined in the nearside end to take the wheel gear.
  2. Steering Worm Gear  
The steering worm was cut from some EN8 steel bar and was screwcut at the lowest speed my machine can handle. It was still a bit fast for comfort, though. I also made a gear hob at the same settings with some silver steel.
A wheel blank was made from bronze on the lathe, as well as a mandrel to load the wheel on, then set up in the mill ready for hobbing. First job was to gash the basic form onto the outside of the wheel using a small end mill. This allows the hob to pick up and auto-rotate the wheel on the mandrel. However, although I managed to harden the hob, it obviously wasn't silver steel and wasn't hard enough. A rogue piece of material had found it's way into the silver steel drawer. Unfortunately, the hob soon destroyed itself trying to cut the bronze. Instead, the wheel was made using the rotary table on the mill with the head pivoted over. First, though, I needed a means of relocation so the keyway way was cut and a matching one in the mandrel.
It was a slow process keep taking the wheel off to check the fit but once I had a stiff fit, I lapped the two in with grinding paste, driving the worm shaft with a pistol drill. It would have been better to have a slightly steeper angle on the wheel but this is the final fit of the two parts.
  3. Brakes  
The brake bracket had been cleaned up externally and the mounting holes drilled but that was all. I mounted it to the side of the footplate to check alignment and all appeared OK so set up to finish the bracket and make the other parts of the assembly. To start, I aligned it in the milling vice using a 1/8" drill down the spindle guide. Once clamped, a No5 centre drill was used to make the 60 degree cone at the top of the guide. This was followed with a 3/16" dia drill all the way through.
Leaving the drill in the chuck, the bracket was upended and aligned at the end of the vice using the drill. Then a home-made tapered reamer from another job was used to create the underside coning. The brake lever was made next using offcuts of 1.1mm mild steel plate. Two random pieces were clampled together on the mill and the various holes drilled using the DRO for accurate positioning.
Three single-use filing buttons were cut from 5/16" dia bar and bolted in position. I don't bother hardening these, just bin them when filing is complete.
The brake spindle was next. Bill Hughes recommends making the square thread as per the prototype but at 16tpi on a 5/32" dia I really can't be bothered. An M4 thread was cut onto 5/32" dia stock bar then parted to length and a 5/16" dia collar silver-soldered into position. The spindle was cleaned up and the 30 degree angle machined onto the collar first, then the spindle was reversed in the collet and the top turned to take the handwheel. A 10BA thread was cut for the retaining nut and the next section will be filed to 3/32" square.
In a moment of thoughtlessness, I drilled a 1/8" dia hole through the handwheel, not much use for a 3/32" square spindle. So I silver-soldered a piece of 1/8" brass bar into the hole and started again. A ring of 1/2mm solder around the top and heat from below to pull the solder down through. This time, a 3/32" dia hole was drilled through. To create the square hole, I loaded a needle file into the tailstock and just kept sliding the tailstock back and forth until the spindle just started to enter. Then the wheel was reversed in the chuck - I leave the lathe out of gear so the chuck floats radially - and started from the other side. It's a long, slow process but saves making a broach to press through.
After turning the brake strap pins, I made a drill-jig for drilling the 1.3mm diameter split pin holes. I think a jig gives much better support to the drill on these small diameters and, being made from hexagon bar, gives me five other places for different length 1/8" dia pins in the future. This is the collection of parts that go to making the assembly. I can't believe that I just turned and parted off a couple of 10BA washers!
These two pictures show how it all assembles together and, finally, mounted on the the side of the engine.
  4. Water Pump  
The water pump had been milled on the top, bottom and end, and the pump gland made, but that was all. The mounting holes were drilled first together with a dowel hole. Then the underside of the water supply flange was milled and the associated holes drilled. Setting up to drill the passageway to the pump chamber entailed mounting the pump body at at an angle.
The various bushes and ferrules were made to suit the pipes required and a small valve was made for the water outlet from a piece of brass hex. The little silver-steel tapered reamer will be useful for a few more valves. The various parts were then mounted in position waiting for me to make the eccentric and pump arm. I will tidy up the casting a bit later when the pipework is ready.
  5. Blowdown Cock  
Another item that I made between boiler sessions was the blowdown cock that sits on the lower right-hand side if the firebox (from the driver's point of view). I started making this from phosphor-bronze but part-way through the first operation I broke a 1/16" dia drill up the hole, scrapping the part. I swear, I'm never going to make anything from phosphor bronze again unless it's absolutely neccessary; bloody awful stuff. Starting again with a different, unknown grade of bronze I polished the stock diameter first, then turned the 3/8" diameter shoulder and the 3/16" diameter for the thread. A small undercut was made at the back, a button die run down using the tailstock die-holder and the 1/16" diameter hole drilled for a depth of 7/8". There was no problem with drilling this material although I still brushed on lots of suds.
A threaded bush was made from a piece of 3/8" dia material next and the blowdown cock screwed into it. Then the 5BA hole was drilled and tapped to depth, followed by turning the outer form of the cock.
1/8" dia stainless steel stock was used for the spindle, simply running a 5BA button die down to length and turning a 80 thou spigot on the front along with a 45 degree point. After parting to length, the spindle was held in a collet block and the square head milled. The collet was just nipped up tight enough to hold without damaging the thread. The blowdown cock offered up to the boiler bush before marking where the outlet needed to be. The outlet was turned from some 3/16" diameter brass tube and silver-soldered to the body. I haven't made my mind up yet whether I will bother with the dummy studs and nuts.
  6. Pump Feed Clack  
I made the pump feed clack from an offcut of bronze plate so that I could make the main body as a single piece, rather than silver-soldering a three-part assembly together. It ended up as three pieces, though. The billet was held in a four-jaw chuck and the front faced off to set a datum.
Then the upright section of the clack was turned to 3/8" O/D, the bore drilled 7/32" dia. by 3/8" deep to the point for a 1/4" x 40 thread and followed with a 3/32" drill right through. A 7/32" slot drill was used to flat-bottom the hole before tapping 1/4" deep. Finally, the neck of the clack was turned to 5/16" dia using a tool that leaves a 45 degree angle at the back. The chuck was then swapped for a collet and the work held on the turned diameter to allow facing to overall length. I screwed a threaded plug into the body first to protect the thread from being squashed down.
This is how it looked after the first two operations. Back with the four-jaw and the other leg of the clack was machined next. The three faces that are in contact with the chuck jaws all have further machining to be done but the bung protecting the thread is clearly visible. After facing to length the 5/16" dia was turned to depth, just short of the other leg. A 1/4" dia by 1/8" long spigot was turned on the front and a 3/32" diameter hole drilled until it broke into the other leg.
The job then moved to the mill where the sides were milled down to just over 5/16" thick. The cross-hole for the branch was drilled next, followed by a tiny recess to locate the branch pipe and flange. A 1/4" diameter slot drill was used for this.
The branch and flange were made next, just straightforward turning on the lathe. Hughes shows the flange bolted to the boiler bush but my bush is threaded 1/4" x 40 so I made my fitting to suit. This is the second operation with the work held in a collet, turned and threaded to 1/4" x 40 and drilled through.
A few other simple parts were made which I didn't bother to photograph. A bronze washer was made to act as the flange on the inlet side of the clack and I also made the injector-feed clack at the same time but that was a very simple item. Both clacks needed a top plug and these were made from 7/16" diameter bronze. After turning, they were screwed into a hexagonal block and the spanner flats milled. Doing it this way, the work is always being tightened into the block.
After silver-soldering the various components together, I decided to add the dummy nuts and bolts to the two flanges. Holes were drilled and tapped 10BA on a 7/16" dia PCD and long screws inserted from the back. Nuts were tightened onto the fronts and the rest of the screw cut away at the back. This way, I get to use the screws on another job. Another flange was made for soldering to the 1/8" dia delivery pipe, 1/8" dia silicon nitride balls were pressed into the seats of each valve and the caps fitted using plumbers washers to seal. These are the two completed valves, ready to fit to the engine.
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