Disassembling 1385’s Pistons

Earlier in the rebuild of C&NW 1385, the cylinders were bored out to make them round once again. [See Nov. 26, 2015 post Driving Wheels and Frame Reunite].  The drawback of that operation is that now the pistons are a bit too small.  Usually the only way around this dilemma was to either build up the edge of the piston with bronze or make a new piston.  Fortunately for us, one of the decisions made over a hundred years ago is of great help to us today.

Location of cylinder/piston.

The C&NW decided to use a multi-part piston rather than a one piece casting in the R-1 class locomotive.  There are two cast steel follower plates that hold what is called a bull ring sandwiched between them and they are bolted together.  Once the bolts are extracted (or broken off) the front plate comes off and the bull ring slides off the rear plate.  The outside diameter of the bull ring determines the size of the piston and the bull ring also has 2 grooves in it to carry the packing rings that actually make the steam-tight seal against the cylinder wall.  A new bull ring for each piston will be machined to the proper size and fitted to the followers.

Both pistons tied down to the workbench for the process. Pete Deets photo.

One bull ring had been built up with bronze brazing rod as shown by the gold color in the below photo. One of the drawbacks in that approach is the heat needed to add the material can distort the shape of the bull ring which it did in this case and it made it difficult to remove from the rear follower.

Bull ring with bronze brazing rod buildup. Pete Deets photo.

An unanticipated find in this process was the bolts holding one piston together were quite badly corroded and several broke in the process of extraction.  As seen in the below photo, two of the bolts that didn’t break are severely necked down.  All new bolts are being produced to ensure the pistons hold together for a good long time.

Worn bolts. Pete Deets photo.


Washout Couplings and Plugs

An important part of caring for a steam locomotive is time-honored boiler wash. Performing boiler washes at regular intervals is mandatory to conform with Federal Railroad Administration regulations and ensures that the locomotive’s boiler is kept free from all corrosion and scaling which would otherwise lead to reduced operating performance and eventually cause damage to the boiler. Boiler washes must be completed after every 31 days the locomotive is in service and is one of the many steps of regular maintenance required to keep a steam locomotive operating. During a wash the boiler is first emptied and then high-volumes of water are flushed through the interior of the boiler and smokebox until no sign of rust, scale or other detritus is detectable in the drainwater.

In order to perform a boiler wash, it is necessary to have numerous access points to the boiler’s interior to direct the water into the boiler as wells as locations for the drainwater to escape. This is achieved through the use of removable plugs of a decent size that can easily be removed and put back in with a steam tight seal.  SPEC Machine is reproducing steam era Huron style [Huron Manufacturing, Inc.] couplings and plugs from certified materials for the task.

washout couplings arrayed on table

New washout couplings for C&NW #1385. Pete Deets photo.

sample washout coupling and plug

New washout couplings with sample plugs from the C&NW #1385’s old boiler. Pete Deets photo.

The couplings will be welded into the boiler shell and the two plugs shown in the above photo (which are actually from the 1385’s old boiler) demonstrate how the plug sits in the coupling and also shows the wide sealing surface that makes the Huron style so easy to use.  With a clean thread and sealing surface a gentle tap or two with the heel of your hand on the end of an 18-inch wrench is all that is needed for a perfectly steam-tight fit.  Much more force than that will only distort the plug and seat and ruin the sealing surface.

bronze rods

SPEC Machine’s Steve Roudebush opens a shipment of new bronze rods which will soon be formed into washout plugs for 1385’s boiler. Pete Deets photo.

Recently the steam bronze arrived for the new plugs and was photographed being unboxed by SPEC Machine’s Steve Roudebush.  Those two sticks total over 300 lbs. of material.  The next step is to whittle away anything that doesn’t look like a Huron plug.

Engineering calculations show the threads should be able to withstand pressure up to 13 times greater than the boiler’s design pressure but calculations alone aren’t good enough. One extra coupling was made to serve a dual purpose.  First, it will be welded into a piece of test material so we can gauge how badly the heat of the welding process will distort the coupling.  The test material will also have a fitting applied to allow the 1385 team to hook it up to the hydrostatic pressure test pump.  Once a plug is made, it will be screwed into the coupling and can be pressure tested as a system to further prove the safety of the design before it gets installed on the actual boiler.

Meanwhile in St. Louis, Missouri, Continental Fabricators has continued production work on the new boiler. This photo recently shared by Continental Fabricators’ staff shows the front courses welded together.

three boiler courses welded together

Welded front courses of Chicago & North Western #1385’s new boiler. March 5, 2018. Photo courtesy Continental Fabricators.

Lots and Lots of Staybolts

A brief update to yesterday’s discussion on staybolts:

SPEC has received the stock to be used for C&NW No. 1385’s rigid staybolts and is cutting it to the length, engraving the heat number and drilling the tell-tale holes per Continental Fabricator’s specifications. There will be over 1000 new rigid staybolts created in all, cut to five different lengths as required by 1385’s boiler.

Staybolts Help 1385’s Boiler Keep in Shape

The Flannery Bolt Company is long gone but their products live on as their staybolt and staybolt accessories are reproduced today for projects like the Mid-Continent’s Chicago & North Western No. 1385.  In the steam era staybolt production and replacement were a regular occurrence and such parts were readily available in large quantities. Even in 2018 there are at least two shops readily producing them as a specialty item, but for the 1385 project Mid-Continent has opted to keep it local, producing them in-house at SPEC Machine where the bulk of the locomotive’s overhaul and assembly is taking place.

1385 project volunteer Pete Deets explains, “We decided to have Steve Roudebush [owner of SPEC Machine] make them as the best way to control the cost and delivery schedule.” He adds, “The bolts to go with the sleeves and caps are on the way… there are 72 flexible staybolts on the 1385 but there are also a few hundred rigid stays that will go into the boiler.”

diagram of boiler showing staybolts

The majority of the boiler is cylindrical, a naturally strong shape, but there are also some flat and irregular surfaces within the boiler too, especially around the firebox. With the intense pressures up to 250 psi inside 1385’s boiler, these surfaces would weaken, bow, and eventually fail without staybolts to support them.

The flexability afforded by a flexible staybolt is critical to maintaining the boiler’s strength while still allowing for the expansion and contraction that occurs as temperatures change from one extreme to another within the boiler.  Deets explains:

A flexible staybolt has a ball shape on one end and is threaded on the other.  The ball end fits into and will be held by the cup shape of the inside of the sleeve.  The sleeve will be welded on the outside or wrapper sheet of the boiler above the firebox. The bolt is then dropped into the sleeve and the threaded end is screwed into a threaded hole in the firebox.  The bolt is hammered or “upset” to cause it to swell into the threads and form a steam tight seal and a copper gasket is applied with the cap to seal the sleeve end.  The ball end of the bolt can actually swivel in the cup shape of the cap and it allows the firebox to move in relation to the wrapper sheet of the boiler as the engine goes down the road.  [Locomotive designers] found that allowing that slight bit of movement was better overall for the boiler than trying to hold every bit very stiff and rigid. If things were too rigid the boiler would break the staybolts anyway.  It was also noted there were fairly specific areas of a boiler that were prone to breaking stays so the Railroad Master Mechanics Committee came out with recommended patterns of placement for the flexi’s to alleviate or at least minimize the breakage.

The photos of the staybolt caps reveal a series of numbers stamped on each one. The number represents the part’s “heat number.”  That is a jargon from the steel industry as they refer to every batch of iron or steel (or any metal) that comes out of a furnace as a “heat.”

Deets elaborates on the importance of heat numbers:

That number is vital because every piece of metal that goes into the pressure retaining portion of the boiler must meet very specific requirements of physical strength, mechanical properties and chemical properties and we have to be able to prove the materials we use meet those specs.  Every batch of steel made is tested for chemistry and physical properties and is assigned a unique number.  The records of those batches made for specific applications such as boiler plate follow the steel through the finishing process of the mill and each piece is marked with the heat number and other information.  Those records are the certification that this particular batch or heat number meets this specific set of requirements and we must get a copy of and keep on file the material certifications or “certs” for short.  That heat number represents the “pedigree” of each of those parts.

The below YouTube video produced by Wasatch Railroad Contractors while working on a different locomotive restoration provides a good illustration and explanation of how flexible staybolts work.

Last but not least, SPEC Machine has also been busy finishing up more work on 1385’s brake equipment. Brand new brake heads were cast last summer (see post from Sept. 1, 2017) and are now being machined in preparation for installation.

break head machining

One of the newly cast brake heads is machined to specification. Each brake head supports one of 1385’s brake shoes.

1385’s Boiler Assembly Underway

The assembly of C&NW 1385’s boiler began in earnest late last week at Continental Fabricators in St. Louis. Here are the latest photos from the shop floor, courtesy of Gary Bensman.