While we wait for the plasma cut boiler plates and housing to arrive I went back to a job that’s needed doing for a while on the engine; the Lubricator.
Approaches to lubrication
There are several approaches to lubricating a steam engine, from a hand-held oil can (tends to be a bit erratic, and you chop the end of the spout off in moving parts) thru oil wicks, to pumped lubrication. I felt that a pumped system was the way to go.
There are 11 bearings that need lubrication in the engine (3 main bearings, 2 big ends, 2 little ends/crossheads, and 4 eccentrics). Actually, there is cylinder lubrication as well, but we are going to deal with that via a separate displacement lubricator which injects oil into the incoming steam (a sort of 19-century “posi-lub”!
There seems to be two approaches to pumped lubrication, either a single pump producing a pressurised rail, and then a set of individual needle-valves or calibrated jets. Or individual pumps for each bearing. Memories of failed cam-shafts on Ford Pinto engines in the 70’s steered me towards the latter approach, so that is what we decided upon.
A V11 pump
So, the conclusion is a 11-pump lubricator. These are normally arranged as a “V” to reduce the overall length. I have previously built one to Jim Ewing’s design (see pic) which worked very well on the loco. My first plan was therefore to build a set of these and then drive them from a set of cams.
However. for reasons I can’t remember I thought I only needed 10 pumps so, when I drew these up in ViaCAD I drew them with 5 cams driving these in pairs.
The cams are driven by a pair of “sprag clutches“, which are small needle roller bearings which only allow the shaft to turn in one direction. So, by holding one still in the oil tank and putting the drive arm on the other, one gets effectively a fine ratchet mechanism that will convert any to-and-fro motion into a rotating motion to drive the cams.
However, I concluded two things 1) making 10 (actually 11) of these pumps would take a while and 2) you could buy similar pump assemblies from Lubetec (these are Interlube AC pump units) ready made… So that was what I did – here are some pictures of the final lubricator with 11 of the LubTec pumps fitted – smaller capacity (red) ones for the eccentrics and larger (yellow) ones for the mains, big & little ends….