*Updated* Samson – cylinder block construction progress…
David is focusing intensively on Samson’s cylinder block construction at present, hoping to trail fit the completed block onto the boiler shell next week, enabling work on the slidebars and motion bracket to progress – greatly adding to the amount of metal bolted together as one lump!
Below: We have already seen the machining of the block in earlier posts. A big job that was outstanding was the machining and fitting of the cylinder liner. The fitting of a liner, rather than machining the block directly, enabled a steam jacket to be incorporated into the design, without very complex core boxes being needed at the casting stage. The liner is seen on our Dean, Smith & Grace lathe during a break in work. The liner is over-length at this stage to enable it to be gripped in the chuck. Note the ‘steady’ to prevent oscillation. In this photo, the inside surface of the liner was being bored out.
Below: This view shows, from left to right, the mark for parting off the excess length then the step down in the centre of the liner – this steps up further to the right. The thinning of the centre section eases the assembly process, which would entail a lengthy pull into the block, ultimately relying on an interference fit but still needing to slide while being fitted.
Below: Options for fitting the liner included shrinking the liner by cooling, expanding the block by heating, a mix of both or a mechanical ‘pull’. The latter method was employed and the liner is seen here fitted into place. The interior has been honed and rebated (as seen earlier) to take the cylinder end cover.
Below: Looking down through the safety valve hole the liner can be seen in place. The oblong aperture is the regulator face and port, the valve sliding atop this.
Below: Also completed is the exhaust outlet for steam from the valve chest – seen here with the bronze gland in place. The hole to the right leads through to the steam space below the cylinder bore and is for the blower feed.
Below: Back to the Dean, Smith & Grace and we see the front cover for the cylinder being machined. The raised area fits into the bore of the cylinder itself – we saw earlier the rebate in the liner to accept this. A very accurate fit is required, and it gives the required alignment as well as sandwiching, with the front cover, the liner within the block itself. Hopefully the photographs make this clear!
Below: Back on Samson himself, the reverser reach rod has been machined and test fitted (seen near to the top of the photograph). This has a very precise route to the motion bracket, passing between the eccentric sheaves and straps as seen here. The pump connecting rod has also been machined and fitted, this being the larger diameter rod visible further down. The pin at the pump end has a spigot to prevent it turning, the movement being contained within the pump plunger jaw which is precisely machined to take the thrust directly, not just via the pin.
The front cylinder cover is more complex to machine as it also locates the slidebars and therefore great precision is required. This work is in hand, along with pattern making for the crosshead. Off site, the foundry has cast the flywheel and also have the axlebox patterns to cast. These can be readies for the arrival of the wheelsets once these have been manufactured. We would love to have the engine wheeled for April’s event – the first anniversary of the first metal being cut for the project…
Update Monday 27th January
I thought an update on this post was worthwhile, as the cylinder block made some impressive progress today…
Below: The front cylinder cover, machined and set up on a dividing head in order to correctly index the six holes required for the securing studs/nuts.
Below: The drilled cover and corresponding drilled and tapped holes on the front of the block.
Below: David, after trial assembling the cylinder block temporarily (borrowing studs from the chest for the cover!) – a proud moment and one to reflect on the huge amount of thought and work to reach this stage.
Below: To some of us, this is art! A couple of photographs of the assembled block…