The saddle and the Burrell boiler have been on the bench for a while. Most of the delay was down to me struggling with the design and location of the steam valve.
The Saddle
The saddle was designed to allow me to split the cylinder and ports to make it all easier to make. This was especially important at the 1/20th scale of this model.
Making the saddle took sometime:
However, the part that stopped me in my tracks was the steam valve. This should be integrated into the saddle and then operated with a long lever from the driver’s position.
Steam Valve Block
Fitting a steam valve into the edge of the saddle would be quite difficult. I did quite a lot of research to get inspiration for this steam valve.
However, I had to concede that it just wasn’t going to fit. Room for a steam valve was squeezed significantly by the fixings for the cylinder. Therefore the decision was made to make the steam valve remote.
Hopefully that gives the background to the delays and the design process. Has the design is just me it sometimes takes time to sort the wood from the trees. This now means the saddle is complete and I can now fix it to the boiler shell.
Silver Soldering the Saddle
Over the last few weeks I have been trying some different silver soldering techniques.
Coupon testing of a copper and phosphor bronze bolted joint gave me options for application of the silver solder.
Applying silver solder around the bolt flowed better than applying it around the edge of the phosphor bronze.
In the final joint I applied silver solder around the edge and around the bolt head. Maximising the capillary action from both directions.
I also looked at what worked as a masking tape for silver solder. I found the best and easiest to apply to be a graphite pencil.
This reduced the amount of silver solder that ran away from the edge of the saddle.
For such a tiny boiler the heat input and insulation required to get it up to the right temperature was significant. However, I got there and I’m very happy with the result. I will have to wait for hydraulic testing to prove it, but I think it’s looking good.
Finally I just had to reassemble the engine to look at it as a whole.
