Steam Department Update January 2016

A very busy month in the steam shop that can best be described as “so far so good”.

In the last blog I outlined the plan for work on #1630 this Winter.  Thru January we have worked steadily on this plan.  The discovery in December that the valve chambers were worn to the extent that both need to be re-bored turned the program for this Winter from one that looked relatively simple in comparison the last year into one that will be a challenge to complete for May.

However, we have now completed re-boring the first valve chamber (engineer’s side), which is a huge step.  In this entry, I will describe what has been involved in getting this far.  What we have found so far does suggest that, once this work is completed she will be substantially more capable than at any time since she arrived from Eagle Pitcher.

The detailed measurements of the two valve cylinders revealed a great deal of wear.  The valve moves over a relatively limited proportion of the overall cylinder length (over and either side of the port openings.  This means that the wear is very uneven over the length of the bore.  In our case the worst area of wear (on the fireman’s side) was approaching 1/8^th inch larger in diameter than the unworn areas of the same bore.  This is well beyond tolerances that would have been acceptable during overhaul in steam days.

Wear on the FS cylinder liners

Each valve is a quite complicated assembly.  This shows one complete valve just detached from its rod.

A complete valve assembly

The seal between the valve and the cylinder at each end is made by two pairs of spring loaded rings.  Each ring is made up of 4 equal segments.  Between each pair of rings is a solid iron bull ring.  It is the bull ring that forms the bearing between the valve and the liners of the valve chamber.  When new the clearance between the raised section of the bull ring and the liner should be 1/32 inch.  Not visible when the valve is assembled is the fact that the bull ring has extensions on either side of the visible bearing surface and about ½ inch below it.  These form the base of the channels in which the spring rings fit.

At each end of the valve is a cast “spider” which has a central hole thru which fits the valve rod.  The spider has a machined cylindrical body the end of which fits into the fabricated valve body.  The spring and bull rings are fitted around the cylindrical body of the spider.  When the components are fitted to the valve rod and the not tightened the bull rings set the spacing between the spider and the valve body and so set the critical width of the slots in which ride the spring rings.  This is a very significant dimension as the spring rings must be free to move to maintain the seal but, as they are prevented from coming out of the valve only by small lips, excessive play can lead to a ring segment coming free and damaging the cylinder.  The machining of new bull rings will be a careful and accurate exercise!.

The whole valve is assembled on the valve rod.  The back of the valve assembly sits against a ring firmly attached to the rod.  When the rods are separated from the valve, the retaining ring can be clearly seen

Both valve rods

When assembled as below the ring is hard against the spider at the back of the valve.

Valve retaining ring

The various parts of the valve are fitted moving from back to front and then the other end of the assembly is clamped into place by a nut threaded onto the front of the valve rod so holding the parts together as a single assembly.  Here you can see the large castellated nut and cotter that clamps the assembly from the front.

Valve clamping nut

Once the clamping nut is removed the front spider can be carefully driven away from the valve body.  The amount of force needed varies depending upon the extent to which carbon has built up around the parts.  Comparing this view to the previous one, the spider has moved far enough away from the valve body to open up the slot which traps the rear pair of spring rings sufficiently to allow the spring and rings to be removed.  At this point the front pair of rings are still trapped in their slot between the bull ring and the spider.

Spider partly removed

Considerably later, the bull ring has been pulled off the spider releasing the front pair of rings and the old bull ring is now shown on top of the cast iron that is being prepared for machining to make the replacement.

Bull ring and replacement

With all rings removed the spider sits on its own and is in process of thorough cleaning to remove all carbon and allow the new bull ring and spring rings to be assembled onto it.

Spider being cleaned

Similar cleaning is required on the valve body, here seen with both spiders removed.

Valve body completely stripped

Both valves have now been stripped to their components and cleaning of the valve bodies and spiders is well under way.  We have new spring rings of various sizes that were obtained with the locomotive in the 1970’s.  These were made in 1/16^th inch increments between the nominal bore size (12 inch) and the maximum allowable re-bored size (12 3/8 inch).  We do not have a complete range so the actual size to which we bore the cylinders will be determined by both what is required to remove the wear and reach a smooth, true bore and the rings we have available.  The likely size is 12 3/16 as this is both slightly above the worst measured areas of wear and a size for which we have adequate new rings.

So far the ES valve liners have been bored.  First the substantial mounts, that hold the bearing ion which the boring bar rotates, must be firmly bolted to to each end of the casting.

Mount for the boring bar

Once the mounts are in place, the boring bar itself must be carefully slide into the mounts.  This is a fun exercise!.  The bar must be very rigid as the objective is to hold the cutters so that they maintain accuracy of cut to within thousands of an inch along it whole length.  This requires a bar of about 3 inch diameter.  It took 6 guys to move it along the shop.  So gently positioning and sliding it into position is no small task!.  Just to make it more fun, the cutter head must be placed over the bar as it is fitted thru the rear bearing and before the bar can be pushed along the length of the cylinder.

Loading the boring bar

Success.  Here the end of the bar projects thru the bearing at the other end of the cylinder.

Boring bar in place

The boring itself is very difficult to capture.  The gears that allow the cutter to be manually advanced and retracted, then locked to the screw mechanism to make the cut, have been attached to the shaft at the front.

An air motor then turns the shaft, with the cutter head attached, while the gears slowly turn a geared shaft running the length of the boring bar to which the cutter head is geared.  In this way the cutter head is advanced a fraction of an inch at each rotation.  Each cut takes about 30 minutes but it takes at least that long to accurately adjust the cutter head to required depth for the next cut

Boring in progress

Once the actual re-bored size is determined, we can start to machine the new bull rings.  These are required to be 1/32 under the bore size on their flat surface.

The bull rings and cylinder liners are made of cast iron, the wear properties of which were found most suitable for this application.  This makes the first stage of producing replacements unusual.  I suspect that, in steam days, blanks, from which the bull rings would be machined, were specially cast for the purpose and requiring limited machining to complete. Nowadays that is not economic on a small scale.  Suitable rings are not available so we must start from a disk.  The first step is therefore to produce the ring, of a suitable size for final machining, by cutting probably 75% of the total weight of the disk out of the center to produce a ring.  This is a long and tedious process on the lathe, taking several hours for each ring.  Brian has worked at this for several days and has now produced the 4 rings needed.  All this was accomplished amid a deal of comments from the rest of the team around him going into the mass production of iron filings!.

Producing a bull ring blank

In other areas

Works continued on producing the bracing that will allow us to rivet the smokebox of the Shay.

Good progress has been made on completing the cab of #428 to the extent that it is now being fitted with windows.

The large compressor for the new air system is now wired and was recently run in test mode.  This was the first time that this compressor has run under load since it was salvaged from the Milwaukee Road shops many years ago.  Testing allowed a number of adjustments to be made but also indicated the need to replace one valve and install an unloading mechanism.  This will take a couple of week but then we should be ready for inspection and commissioning.

Nigel