A bit of work now needed to be done to the two buffer beams. The front one needed the top outer sections reducing in width to match the bottom of the front section of the running boards and also the ends needed the rear corner milling to take the end of the valances. The rear beam just needed the ends milling for the valances.
Mods to the front buffer beam
The valances will be made mostly from 1/8" square brass as this is much easier to bend to the complex shape required than angle. The shaped ends that fit up to the buffer beams will be made from brass strip.
As a matter of interest I borrowed my brother's bathroom scales (I haven't got any!) and weighed the loco as it is so far. Funny enough it's not as heavy as I thought. With the boiler and bogies in place it weighs about 28lbs but I reckon that when the tanks and cab etc are fitted it will clock in at about 40lbs. Still pretty heavy for a 2½" gauge loco I suppose.
Work on the valances commenced at the front end with the short curved section just behind the buffer beam. A length of 1/8" aquare brass bar was annealed and bent around a piece of bar, 'adjusted' to fit the underside of the running board and trimmed to length. A recess was then milled in the front end to take the shaped part which butts up to the buffer beam. These 'fancy' bits will be cut from 18swg brass. The brass bar was then clamped in position and soft soldered in place in situ using a needle flame on the gas torch and ordinary 60/40 electrical solder. I thought it would be easier to solder the valances in place as I went along. The needle flame puts the heat just where you want it and means you can solder one bit without disturbing another.
First section of valance soldered in place
The shaped piece was then cut out roughly to shape and also soldered in place taking care not to solder it to the buffer beam as well! The final shape will be trimmed after the valances are finished and the running boards cleaned up. I dont think it will be necessary to fasten these bits to the buffer beams at all as they will be quite rigid.
Shaped part soldered in place
It was then just a case of cutting and bending more pieces of 1/8" square brass and soldering them in place. The long rear section was made in two pieces to make it easier to get the two double bends in the right place.
Next section fitted
Rear section completed
When both sides are completed I'll take the running boards off and fit a few 10BA brass screws in strategic places and then resolder any joints that need it.
Note - The bogie wheel castings have just arrived! (Thanks Roger!) I can now get on and finish the bogies and complete the chassis.
After fitting the valances to both sides, the running boards were removed for final soldering. As it happens only a few joints needed 'touching up' and I didn't think it necessary to fit any more screws. Any imperfect joints were just clamped, some flux applied, and the joint reheated until the solder flowed. The running boards were then given a good scrub with soapy water to remove the flux and cleaned up with a piece of scouring pad. They were both then temporarily fitted to the chassis again for the final pieces to be made and fitted. These consisted of two short lengths on top of the buffer beams to fill the gap between the running boards and a cover to fit over the middle cylinder in front of the smokebox. It was decided to leave this cover loose as I may fit an oil resevoir under here to lubricate the inside motion.
The completed running boards
I'm still waiting for the brass tube for the smokebox to arrive but I picked up a three foot length of 4" diameter by 14swg brass tube off Ebay recently. If it comes to the worst I can use a piece of this and cut a strip out to reduce the diameter, then silver solder it back together as I did with the tube for the Flying Scotsman.
I think the next job will be to turn the bogie wheels and complete the bogies. Then finish the boiler so I can get it tested and do a proper steam test!
The bogie wheel castings were very clean with very little flash and machined easily with no tough skin or hard spots. I think they are the new ones for Ayesha II currently being described in Model Engineer. The first operation was to face the back of the wheels and drill and ream the bore for the axles. Measuring the castings showed that the inner edge of the rim was truly concentric with the tread and so the castings were simply chucked by the tread in the three jaw and about a 1/32" taken off the back of the casting. One thing to check when machining wheel castings is to see how much needs to be taken off to bring the wheel to the correct finished thickness and split this amount between the front and rear of the casting. It's easy to take too much of the front and machine the flared ends of the spokes off!
After facing the rear of the wheel the bore for the axle was drilled and reamed 1/4" Diameter. This operation was then repeated on the other seven castings. It's much easier to carry out one operation at a time on all the castings rather than try and finish each wheel individually. By using the micrometer dials on the lathe it is easy to ensure all the wheels finish up the same thickness and diameter.
Facing the back and drilling/reaming the bore
The castings were then reversed in the chuck (gripping them by the tread) and the centre boss faced to the correct length. I could have also faced the rim to the correct thickness at this time but decided to leave that until the wheels were mounted on the jig to turn the treads etc.
Facing the wheel boss to length
I next required a true running jig to mount the wheels on for the final turning operations. This was simply a length of aluminium bar slightly smaller in diameter than the finished wheel diameter held in the chuck, faced off, and drilled and fitted with a piece of 1/4" steel bar threaded at the end for a nut to secure the castings in place.
Simple jig for finish turning the wheels
Each casting was then mounted on the jig in turn for the remaining operations. First the rim was turned to thickness, then the flange turned to diameter, and then the tread and side of the flange turned to finished size using a tool with a 1/16" radius on the end to give the correct radius between the base of the flange and the tread. The side of the tool was angled at 20 degrees to give the side of the flange the correct taper. Care was taken to ensure that all the treads came out at the same diameter! All the books say to take the final cuts on the treads at the same micrometer setting but you may find, as I did, that the diameter increases slightly with each wheel, probably due to the tool wearing with each cut. Cast iron is very abrasive stuff and wears even carbide tools quite quickly. Best to check with a digital vernier just to make sure.
Facing the wheel rim to correct thickness................................Turning the flange to correct diameter
Turning the tread and side of flange
As with the driving wheels I decided to cone the wheel treads at 2 degrees although a lot of people say it is not necessary in the smaller gauges. This was done by setting the topslide over by 2 degrees and taking a skim over the tread making sure all the wheels were done at the same setting. The amount removed was very small so I didn't bother checking the tread diameters again. The final turning operation was to turn a small step on the the inside edge of the rim to trim it up. At the same time a small chamfer was put on the edge of the tread with a file and the edge of the flange rounded.
Trimming inside edge of rim
The bogie wheel axles are 8mm silver steel with the ends reduced to ¼" diameter to fit the wheels. Getting the axles all the right length can be a fiddly job if you have to keep taking them out of the chuck to measure them so an adjustable stop that fits inside the lathe mandrel is useful here. This ensures that the axle is always inserted to the same depth in the chuck and all of them can be made to exactly the same length using the micrometer dial on the leadscrew. I keep meaning to make such a depth stop but for now I use a length of bar to fit down the lathe mandrel with a clamp to butt up against the end of the mandrel and control how far it goes in. In use the bar is inserted in the mandrel up to the clamp and the axle inserted in the chuck and pushed up against the end of the bar and the chuck tightened. The stop is of course removed before the lathe is started. The axle is then turned to length and the dial reading on the leadscrew noted. All the other axles are then turned to the same reading using the stop to position them.
Improvised depth stop
Stop in use to position axles in lathe chuck
The ends of the axles are then reduced to fit into the wheels, again using the leadscrew dials to measure the diameter and the length of the shoulder. The wheels are loctited on so the shoulders were made an easy push fit in the wheels.
Back to the bogies and the needle roller bearings were pressed into the axleboxes and a wheel and axle asembly tried in place. One problem became immediately apparent. The diameter of the rear bosses on the wheels were only very slightly larger than the bores for the bearings. The bearings are recessed into the axleboxes to accept an O ring seal (as on the driving wheels) and so the ends of the wheel bosses tended to jam in the recesses! Oh @xx??! The problem was eventually solved by replacing the O rings with turned washers made from Peek of such a thickness that the outer edge was slightly proud of the axleboxes. The bosses now bear against the ends of the washers. The axles were then fitted and the wheels loctited on permanently.
The ends of the equaliser beams tended to move from side to side due to play in the spring pins so the ends were drilled and tapped for 8BA bolts, the ends of which locate in shallow drillings in the top of the axleboxes and hold the beams parallel to the bogie frames.
Next job was to find some suitable springs for the side control of the bogie. I needed eight of these (four per bogie) and didn't seem to have anything suitable to hand. You'd have thought that with all the junk etc. that I've acquired over the years I would have found something to do the job! I didn't fancy winding some as they need to be fairly accurately matched in order to centralise the bogie properly. In the end I purchased a box of mixed springs and found some that should be ok.
Top and bottom views of the bogies showing the side control springs
The bogies were then fitted to the chassis and it was obvious that, as suspected, the springs on the equaliser beams were much too strong. All the weght was carried by the bogies and none by the driving wheels. In the new Model Engineer series on building Ayesha II it recomends using cut down ball point pen springs but, of course, I only had about two! Retractable pens using the springs seem rare nowadays. In the end I wound some up from some old 0.017" guitar strings. I wound two long lengths on a piece of 3/32" rod and then cut each length into four pieces for each bogie. These are a lot weaker than the originals and seemed much better when fitted. It's difficult to judge until the loco is finished and the weight on each wheel can be measured. I want to get as much weight as possible on the driving wheels where it is most needed.
Another problem that had showed up earlier was that the front tiebar on the leading bogie fouled the front cylinder drain cock on the middle cylinder. This was solved by drilling new mounting holes for the bar and lowering it in the frames by 3/16".
Bogies fitted to chassis
That's the chassis virtually complete now so time was taken to get rid of all the swarf and dust collected over the last few weeks during the fitting of the running boards. This was done using the airgun on the compressor which blasts away anything not securely fastened down!
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