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| Slowly casting up parts for a steam twin marine engine |
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| Artie:
This project has evolved over on HMEM, apologies to the guys who frequent both sites. Basically my project is a reversing horizontal twin loosely based on My Westburys design, an example, which I believe belongs to Don-tucker over at HMEM. Mine is destined for a large side wheel paddle steamer called the PS Pevensey which still operates today out of Port Echuca, australia largest inland river port. She will be 7'6" and radio controlled which poses a few issues for a steam engine. And the scale plans... The changes to the design are simply making the cylinders level, mounting them on either side of the boiler cover (more on that later) and making the crank a stand alone pylon type with 4 individual pylons, 2 in close next to the throws and 2 out wide as this will a long crank shaft. I am a caster of metal so it was decided early on to make and cast the components and this thread is my journey so far... yes it would probably have been easier to use billet... but where is the fun in that? Ill go through this quickly with a few pics per post... to break it up... firstly I have Mr Westburys plans but really dont refer to them much, its all in my head. To make this a sloooow revving engine set Ive increased the bore size from 19mm to 25mm (3/4 to 1 inch).... on with the show! |
| Artie:
The cylinders, for a simple item it ended up being quite a complex (and touchy!) cast. The plugs in manufacture.... I hate the wood lathe...scares the hell outta me! A mate, John is doing the dangerous stuff, Ive got the camera.. This was made up of 2 pieces which were screwed together outside the machining area, so when it was parted off it fell apart... Steam chest mounts and cylinder mount added... |
| Artie:
Brass for the cylinders. Ive never cast brass before so this is a steep learning curve. I decided to do what I know and cast a few in aluminium first to test the casting procedure and also work out the machining steps before I cut into a lovely lump of brass.. ended up casting 4 ali cylinders. before i was happy. Had a bit of sink back due to the larger volume of metal around the steam chest area. Solved that though, used a larger core. Core mold.... simply split steel tubing... Cores already baked... these are high clay content sand... ended up using a sugar based core which set harder and darker.. The foundry.. (shes showing off... doesnt normally do this...) Packing the cope... Ready to pour... You will notice that I ve fitted a reducer plate to reduce the volume of the flask (box holding the sand together..), any bigger is wasted effort.. |
| Artie:
This is what came out of the sand... still smoking hot..... Here you can see the sinkback that I mentioned on the right cylinder but problem solved on the left one. Its simply moving the holes that the molten metal comes in and goes out (sprues and risers)... |
| Artie:
So with the design and procedural stuff out of the way..along came the brass.... It doesnt look very pretty when it emerges from the sand. In fact it looks like it was salvaged from the Titanic.... But use your imagination because this... Can become this.... And it did, same cylinder a few days apart..... but Im getting ahead of myself here... casting brass.. it actually isnt a lot of fun... I much prefer working with aluminium.... Ali melts at approx 630 degrees celcius, brass at approx 950. I use steel crucibles for this and I have 2, a large volume unit which will pour about 3 litres of melt and a smaller unit of about 1.5 litres. Ive had these since I built the foundry some 26 years ago. Not any more. The extra 300 or so degrees increases the strain on the equipment enormously, I burnt those two crucibles out in 4 pours and the new unit is looking decidedly second hand already. I dont think I will do much brass work after this! |
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