johnsmachines

Quite a few potential workshop days are being foregone because we in southern Oz are experiencing a very hot summer.  And the few more moderate temperature days are “lost” to essential jobs for SWMBO, and around the house.   Shouldn’t complain about the weather.   Townsville, Queensland, where my brother and family lives, has been declared a disaster area due to torrential floods…  1000mm (39″) rain in the last few days, with more on the way.  And the next ice age has apparently started in USA.

But,  back to the workshop for a few hours here and there, I have made the boiler water feed pump for the Trevithick dredger engine.   As usual, I grossly underestimated the time these few simple components would take to make.

The pump is driven off the crossbar where the stroke is 100mm (4″).  At the pump, the stroke is ~17mm (~5/8″).  The suction side has an 8mm (stainless steel) non return ball valve and the delivery has a 6mm non return SS ball valve.  The plans specified a dummy pump, for appearance only, but I have made it functional.

The 2mm ss cap screw is to limit the ball movement to 0.8mm travel.  Something less conspicuous will replace the cap screw.  Probably a ss grub screw.

The rod driving the pump piston is a piece of bronze brazing filler rod.  Just happened to be the correct diameter.

I will need to add a further pump, hidden somewhere, for boiler approval.  It will probably be a hand pump.

The next step is to design and make the stand for the engine.  The plans specify a large, and in my opinion –  ugly, wooden box.  So that is not on my option list.

Most of these “dredger” engines were used in factories and mills.  Some were used to drive mine pumps, and a few were used on dredgers.  In the factories and mills they would have sat on masonry or wooden bases, and on the dredgers they would have sat on the very solid decks.  (the dredgers in some cases were converted gun ships, designed to mount large black powder cannons,  mortars or seige guns, so they were very solid!)

Now, some pictures of other dredger engine models, and the reconstructed full size one, and their bases.  I have numbered the pictures, and I would be interested in my readers opinion about which would best suit my model.  Please leave a comment.

1. The engine as mounted in The London Science Museum, on large wooden blocks.

2. A Model Dredger Engine on a masonry base.  I could do something similar, but I would used aerated concrete.

3. A very simple wooden base.

4. A beautifully crafted model on a cabinet maker’s base.  Acknowledgement to fredyfredy42.                                              I like the colour scheme too!

5. Another simple wood block base, reminiscent of the gun boat decking and frame.

6. An elegant wooden base

7. And finally, the modern, aluminium base for the beam engine which I made a few years ago.  I like it on the beam engine, but I doubt that it would look OK under the Trevithick.  The dredger engine is shorter, taller, and narrower.