by John

It seems months since I made any progress on the triple expansion steam engine.  It is such a complicated build, at the limits of my abilities (or maybe beyond the limits), and many  components have been partly made and put aside to be completed later, that I was unsure just where I needed to resume.

But, Xmas/Saturnalia, New year, several exhibitions, several competitions, and an intervening Stirling engine build all conspired to “force” me to put aside the difficult triple build.  Then it was just too bloody hot to venture into the workshop.  But we now have some milder weather, and I have some free time, so back into the workshop to inspect the triple and see where to resume.

I decided to do some easier components, to ease back into the build.  So I started by making some of the steam pipes,  CNC’d the flanges, and silver soldered them.  Only to discover that there was inadequate access to tighten some of the flange bolts.   So a quick redesign of the flanges to use only 2 bolts per flange, CNC’s some more flanges, removed the bad’uns, and silver soldered the new ones.   All good now, except that I need to fill some unused threaded holes in the cylinder castings, and drill and tap some new ones.


Checking the fit of the copper pipe, prior to machining and soldering the flanges


The pipes with flanges all made and ready to be fitted.  Except that these 4 hole flanges had to be replaced with 2 and 3 holers.


Inadequate clearance to fit the bolts.  So the flange was replaced with a 2 holer.


Today I made the bearings for the yokes on the Stephenson’s reversing mechanism.  These are made of gunmetal, quite small (9.5x8x4.7mm), need some precision drilling and reaming, and there are 12 of them.

After considering the “how to” options, I decided to use the recently installed 5C collet chuck on the lathe, having machined the gunmetal to fit neatly into a 3/8″ square collet.

The following pics were uploaded and the order was totally mixed up in the process.  From previous experience I know that trying to re-sort them will result in chaos and losses, so I will leave them as is.

Bolton 9 - 5

This is the final photo.   The 14 bearings (including 2 spares) are threaded onto a bright steel rod and the side decorative waist is milled.

Bolton 9 - 8

Showing one of the reversing mechanisms, with 4 new gunmetal bearings bolted into position.

Bolton 9 - 3

The square 3/8 x 3/8 lathe collet, about to accept the bar which has been accurately sized, drilled and reamed.   I used a parting tool to cut off the bearing at the correct thickness.

Bolton 9 - 4

Parting.  The blade is only 1.5mm wide.

Bolton 9 - 6

One of the yokes, with bearings bolted in place, and 2 loose bearings about to be fitted to the other yoke.

Bolton 9 - 2

precision drilling the bolt holes (1.8mm diameter) using the high speed spindle on the mill, at 6000 rpm.

Bolton 9 - 7

The three pairs of valve eccentrics, and reversing mechanisms.

Bolton 9 - 1

This should be the first photo.  It shows the gunmetal bar machined to size, drilled and reamed, ready to be drilled for the bolts, then parted on the lathe.