I am inexperienced with fabrication of cylinders and wanted to ask you a question regarding materials of construction. In your photos on this thread and "machining from solid" thread, indicate you are using bronze / brass materials which silver solder well. What about other materials for cylinder assembly, such as CI? I know CI is difficult to solder due to the graphite present and mild steel would present rusting issues when not in use. What are your thoughts?
Hi David. Cast iron will silver solder, but it's not so easy to get a good joint. I usually use bronze - which I get as offcuts from the local scrappy. A better proposition might be mild steel, with a CI liner pressed or Loctited into the bore.
In the first pic - where the flash froze the motion, it was doing 250 - 300 rpm, still a bit sticky. Yesterday morning (the 'action' shots) I had it down to about 50 rpm - I expect that running on steam, and with a bit of a load, I can do considerably better than that, hopefully down around the 20 - 25 mark.
Post by classicsteve on Sept 19, 2009 11:28:41 GMT
Nice job Tel, and under 60rpm sounds great as it gives you time to see the motion.
Now you can tell us the answer about whether half-beam engines are always self-starting due to the dead weight of the beam.
I have a question regards running on steam - presumably the cylinder would be lagged at full size, but there must still be a lot of condensation from a cold start. I expect vertical double acting cylinders usually have a drain cock on the bottom of the cylinder - but what do they do about condensation in the top half of the cylinder? Surely the water will sit on top of the piston, and you risk a hydraulic lock at TDC.
I suppose the steam port will take the water away providing the first TDC is slow enough. Maybe the 'owners manual' tells you to turn it over by hand after warming up - but I bet a cold start is a little bit more involved than just turning the steam on.
You always leave a little slack between the valve and the nut, so the valve can lift of the face a few thou and pass the condensate. Doesn't take long, most of my engines have no cocks, and it's only a flick or two to set 'em running
Post by classicsteve on Sept 19, 2009 19:24:57 GMT
The reason I ask is I am curious about full sized practice as much as running a model.
I was absolutely stunned when I visited the Forncett steam museum and found they needed to heat the beam engine from cold for 24 or more hours before it could be steamed. It had never occurred to me before just how much it takes to heat the metal up so that steam doesn't immediately condense to water.
This all means that the condensed water is quite an issue. If I am over there for there last Stema-Up of the season I will ask them some more about that. Its a side of things you don't realise when you just turn up and see the engines running.
And if you have never been there - then it really is worth a trip (not for you Tel, but I can always pot some photos). Nice people and they host a Model Engineering display for the steam up in October.
But if there is something specific, then I might be there before they close for the winter (I am hoping to visit for the Oct steam-up when they have local model engineers). Also I have photos from previous visits.