Trevithick Dredger Engine- bronze brazing and some milled parts.
by John
The copper tube which I am using for boiler shell has 6 holes, intended for another project by the previous owner. Here I am trimming the length, so 2 of the holes will eventually be removed. Using a drop bandsaw, with a wooden plug so the tube is not bent by vise pressure.
Bronze brazing the domed boiler end to the boiler wrapper. The assembly absorbs a huge amount of heat before it reaches brazing temperature. Showing the temporary forge, and the torch head for the oxy-propane fuel. The join has been completed in this photo.
The join in progress. Note the positioning copper rivets, and the tacking points. At this point I ran out of oxygen and had to finish the braze on the following day.
And today I made some parts for the boiler’s removable flat end. My CNC mill is out of action, so GSMEE President Brendan kindly allowed me to use his machine.
CNC spotting 3.2mm brass plate.
The almost completed firebox door base. Spotting did not allow for the removed material in the rebate, and the drill ran out in one hole- some repair required. I will plug and redrill that hole.
The manhole cover. It will eventually be painted.
Sitting in intended positions. Fastener holes spotted, yet to be drilled and threaded.
johnsmachines 
Hi John,
This looks amazing. It would be good if you put something re cognisable in the photos for scale.
Peter
Sent from my iPhone
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The disk is 184mm diameter.
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Interesting… I was advised to use 45% silver solder for all joining. Brazing would have been ENORMOUSLY cheaper than silver…albeit stronger. I have seen some British boilers utilising TIG.. very neat. But again, the retail price makes its prohibitive to buy….
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I used bronze brazing because that was required by the boiler inspector, but now that I have got the hang of it, I will use it more often. Certainly cheaper and stronger than silver solder, but the narrow window between melting the bronze and melting the copper workpiece makes it a slighlty nerve racking exercise. In my next post I cut through the bronze brazed joins, and I remain impresed. John
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