Use these links to jump to the section you are interested in on this page :-
Drilling the tube plates Drilling the Smokebox Tubeplates Forming the Wrappers Attaching the Firebox Tubeplate Making the Crown StaysOr try one of the other pages on building Spencer :-
Machining the Driving and Coupled Wheels
Spencer Start page, frames, Axle boxes, painting wheels
Luckily the firebox tube plate had the position of the holes marked out on it but to double check I scanned the drawing into TurboCAD and printed it out at full size. This confirmed they were in the correct position so I drilled through from the back into the copper.
The firebox Tubeplate will be used as a former when drilling the Smokebox tube plate so I tried to keep the holes as accurate as possible.
Here's the plate with all holes drilled to 3mm.
The plate and former were transferred to the lathe face plate to bring the holes to size. I did this for accuracy and because I had drill of the correct sizes! First job is to centre the 3mm holes using a centre in the tailstock.
The clamps are tightened and then the hole is drilled to size 3/8" in this case.
The flue hole is drilled 3/8" first and then 3/4" to size. One of the benefits of building a smalled boiler - I don't have to bore the flue holes! Note the firebox plates are much longer than they should be (I trusted the former was correct!) so I have bored a 3/4" hole in the spare so I have a practice piece. See section on Silver Soldering
Here's the drilled plate next to the drawing.
The two plates were marked out and then sawn to size.
With all the holes drilled I then had to make them all 0.1mm oversize to give plenty of room for the Silver Solder to run. This follows the guidance of Johnson-Matthey rather than the usual practice of having a tight fit an filing a couple of nicks to allow penetration.
I cleaned up the joint area with some emery.
After a couple of days practicing Silver Soldering I made a start on the Smokebox Tubeplate. First job is to mark out centre lines and position of flue tube. I had to create my own drawing of the Smokebox Tubeplate as there wasn't one included in Model Engineer, luckily TurboCAD allowed me to use the scanned drawings as reference so this was quite easy.
Here is a close up of the plate notice the flue tube centre is slightly below the centre line of the plate.
The Stay holes were drilled to correct size and the others to 3mm. Note I have only drilled a couple of the holes for the tubes.
This is because I can use the firebox Tubeplate as a jig.
This saves some time marking out and guarantees the two plates match.
Again I drilled the tube holes on the lathe. Starting with centring.
Then drilling 3/8".
And finally the flue hole is at 3/4".
Here is the plate after all holes drilled. Conveniently the bush for the wet header needs a 3/8" hole too!
The final job is to slightly counter sink each hole and file oversize. Here it is Loosely mounted in the boiler tube.
The wrappers are fairly complex shapes and again I was lucky enough to have wooden formers already made (they came with the castings). First job is to mark out the rectangular pieces of copper. I added about a inch onto each end to allow for inaccuracies in measuring and to give myself some slack when forming the shapes. Hermaphrodite calipers proving their worth.
The bench shears really speed up cutting out of sheets.
Here's the two sheets ready for forming.
The plates were annealed which left them pretty soft, they could be wrapped around the formers by hand. Then they were mounted in the "Workmate" clone and a large (orange) pipe was use to start forming the curves. Just like rolling pastry!
Here's the two wrappers after the first forming.
After an annealing here's results after a second forming.
After the third go the outer wrapper was getting close.
The inner with it's tight radiuses needed some more persuasion.
The last stage required careful use of the Planishing hammer on both inner and outer.
The inner is now a close fit to the former, unfortunately the former isn't exactly the same shape as the flanged plates so they did need more work later on.
Once the inner wrapper had been fitted to the Tubeplate it was time to rivet and Silver Solder the joint. First the holes were drilled and countersunk.
I felt three rivets would do the trick.
The wrapper and Tubeplate were pickled for an hour then dried and fluxed.
The two were then assembled and riveted using a flat rivet Dolly. See my Silver Soldering page for more info.
I tried to silver solder this using a Sievert 2943 nozzle (43Kilo Watts), Tenacity No5 Flux and SilverFlo-24 Silver Solder. Unfortunately I couldn't quite get enough heat into the assembly to get the Solder To Flow.
I hadn't trimmed the excess from the wrapper so I did this next. To reduce the amount to be heated.
After cleaning the old flux off using boiling water and elbow grease I tried again with SilverFlo-55 using two burners a 50mm nobrand rated at 28kW and a Sievert Cyclone burner rated at 10.5kW. My Girlfriend wielded the 50mm burner for background heat on the outside and the cyclone burner applied inside. The second attempt was okay but there were gaps at the top corners and bottom corners left due to incorrect tolerances - Silverflo-24 can fill a bigger gap. This was soldered as you see it here with the Tubeplate uppermost sat on a kaowool blanket (From CupAlloys). Most of the flux and all of the carefully placed pieces of Silver Solder slid off the top and down the sides and ended up on the bottom edge damaging the blanket.
Third time lucky! I closed up the gaps with a planishing hammer and this time rested the piece with the Tubeplate facing down on firebricks (no blanket) the radiant heat from the firebricks seemed to help get it up to temp quicker.
The el-cheapo 50mm burner is not great so I'm going to buy another Sievert handle so I can use a 2943 and the Cyclone burner at the same time, or the 2944 (84kW) plus 2943 43kW) when extreme heat is needed!
After the stress of Silver Soldering I had a couple of days off and then made a start on the Crown Stays, again the drawing was missing a few dimensions so it was TurboCAD to the rescue I started by cutting out 4 pieces of copper 2" x 3 13/16" using the bench shears. I then marked out the chamfer using a protractor and trimmed these off too. The all four were clamped together and cleaned up with a Bastard File. I have centre punched the holes for the 5 Cross Stays and holes for three rivets.
I should make things a lot quicker making them all together. First off the holes were drilled to be a loose fit on the rivets. (2.5mm for 3/32" rivets).
Then the 5 stay holes are opened out to 17/64".
A set square was used to mark from the edges of the holes to the bottom.
The slots were cut out using a hack saw 14 T.P.I. blade made light work of this.
A quick clean up with a file and they are ready to rivet together. Spot the slight mistake on one of the slots. Very pleased with this a quick and easy job. Just the thing to renew my enthusiasm!
Next the inner sides are cleaned up with emery.
The plates are held face to face in the vice and a bolster chisel was used to start off the bend.
The crown stays needed annealing before they could be shaped with a hammer.
A quick visit to the pickle bath and the stays are ready to rivet together.
The plates were fluxed before riveting this gives a slight gap for the Silver Solder to penetrate.
Several pieces of SilverFlo-24 were placed as the vee will hold them in position.
As it happened the Solder floated on a bed of molten flux so it took a while for it to flow I used a 2944 and 2943 burner to do this, sop was guaranteed enough heat! These are ready to be riveted to the firebox wrapper.
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