Tuesday, September 25, 2012

Repairing the Running Gear on EBT No. 14

In my last post I explained how I managed to replace the broken valve gear on EBT No. 14.  The early EBT mikados (12, 14 and 15) used slide valves, while the later mikes (16, 17 and 18) were ordered from Baldwin with Southern, or piston style valve gear.  The slide valve gear is actually quite similar to the Walschaerts type gear, which is well documented. 

After having repaired the gear, using photo etched nickle silver replacement parts from Phil Light, I finished installing the Tsunami TSU-750 in the tender, with a 20 mm high bass speaker in the tank, as shown below.

As you can see, fitting in the decoder, speaker, capacitor and associated wiring required extensive modification of the tender shell.  All this cutting, nibbling, soldering, filing and fitting wires into the tender and locomotive, required a lot of handling.  After picking up the locomotive for the umpteenth time I noticed that another rod had popped loose.   What came loose were two connected rods or links, with a set of pincers on one end of the assembly, and a bracket on the other than slipped a pin holding the main rod in place.

Just to be safe, I checked the other side of the locomotive and found that while this assembly was still attached, the clamp that held it to the drive rod pin was loose and slipping.  So I was faced with repairing the damage on both sides of the engine!

Since I am not an expert in Walschaerts valve gear, I once again emailed my friend Phil Light, with an explanation of the problem and a photograph of the damage.  Phil replied that the small link that connected to the third driver was called the eccentric crank, and that it was connected by the longer eccentric rod to the expansion link.  Here is a diagram of the basic Walschaerts valve gear, which shows the eccentric crank and rod and its connections to the rest of the valve gear.


The names of the various rods and links are less important than how to reconnect them so that the engine works as it was designed.  Snapping the eccentric rod back on the expansion link was straightforward.  I simply had to use tweezers to tighten the pincers around the pin.  The real problem was reconnecting the eccentric crank to the crank pin on the third driver (see above).

With the piston fully inserted into the cylinder and the rods in a straight line as shown, the crank should be fixed to the pin at a specific angle (25 degrees), and soldered in place so that maintains its angular relationship to the wheel as it rotates.  This makes the eccentric rod move back and forth to rock the expansion link.

Once the eccentrics were arranged with the crank at the proper angle, the clamp was soldered to the crank pin using the same method as I did replacing the broken valve gear in the last post.  A small square of paper is perforated with a sharp pin (I enlarged the hole a bit with a toothpick) and slipped over the crank pin to prevent the solder from fixing the drive rod to the wheel.

With the paper in place, the eccentric link clamp is pressed over it.  Using a protractor, a 25 degree angle is measured and cut from paper, and used to set the correct angle for the eccentric link.


 I then carefully applied a small amount of TIX liquid flux to the top of the eccentric pin.

A hot soldering iron with a very small drop of solder is applied to the top of the pin, being careful not to hold it on the pin too long.

With the repairs made to the running gear, the engine was reassembled and run without incident.  Here No. 14 takes the siding at Rockhill while a coal drag chugs by on its way to Blacklog.  You can clearly see the eccentric link and rod successfully operating on the engineer's side. 



Wednesday, September 5, 2012

Repairing Broken Valve Gear on EBT No. 14

Back in July, I lost the use of my only operating steam engine, EBT mikado #14.   I should have seen it coming.  The slide valve gear on the fireman's side had been giving me fits for some time.  The various links and rods were connected with snap on pincers that fit around pins on the connecting parts.  One link in particular (I later learned it was called the radius rod) kept coming loose, and I had to watch it carefully to prevent a disaster.  The disaster came in the person of my 7-year-old grandson, who likes to run trains fast ... VERY fast!  In this case, #14 was roaring around the dual gauge wye at a significant fraction of the speed of light, when the rod came loose, dropped and dug into the ballast alongside, causing the locomotive to derail and the thin nickle silver rod to bend.

When I had a chance to sit down and work on the engine, I found that another rod (called the combination lever) had come loose from the valve slide crosshead.  This second lever was forked on one end to fit around the crosshead with a pin to hold it fast.   In trying to snap the lever back onto the crosshead, one side of the fork broke off.  While trying to remove the broken pieces, a small rod at the other end of the combination lever (called the union link, connecting with the driving rod crosshead) broke in two, leaving me with a royal mess!  Here you can see the broken parts.

The long vertical shaft is the combination lever.  You can see the broken fork head at the top (with the broken piece next to it).  The pin to which the radius rod connected is right below the broken part. At the other end of the lever is the broken union link.  Clearly this was a major disaster.  I could run the engine without the valve gear, but it would look rather odd.  This is a picture of the left (fireman's) side of the locomotive with the broken parts removed. 

Here is a view from the other (engineer's) side for comparison:

I was in a panic!  The Hallmark EBT mikados were produced back in the 1980's by Samhongsa, and had been out of production for decades.  There was no one to contact for spare parts.  With the encouragement of friends on HOn3 and HOn3 Chat lists on Yahoo! I decided to try to make repairs myself.  The first idea that came to mind was to cannibalize parts from another locomotive -- in this cast, a massive Pere Marquette steamer that had been sitting in my scrap box for years.  I dismantled the valve gear in hopes of finding something usable, but as you can see, the standard gauge parts were much larger than the tiny narrow gauge valve gear on #14.

Clearly, I was not going to be able to make repairs on my own.  In desperation, I put out a call for help on the internet and was overwhelmed when, within days, I had received replies from a number of fellow model railroaders offering to help.   One of those responding was Phil Light, owner of Light Scale Models, who has expertise in photo etching parts in nickle silver.  (You can check out his website at www.lightscalemodels.com -- he does exquisite work!)  Phil offered to make CAD drawings of the damaged links and arrange for them to be reproduced by a professional firm for a reasonable price.  After we exchanged emails, I felt comfortable contracting for the replacement parts.  Phil then send me PDF files of the CAD drawings.

Parts A and B are two options for the radius rod, one that includes a snap connction on one end, and the other which is designed for rivets at both ends.  C and D are options for the union link.  G1 and G2 are the two halves of the combination lever, which are designed to solder together to form one piece with a fork at the end, as in the following drawing:

 After we agreed on the work to be done, it was only a week or two before the etchings arrived in the mail.   The parts were on a sheet of nickle silver with four or more copies of each part, just in case.

Removing the replacement parts was (literally) a snap.  A few cuts with a hobby knife held against the part were enough to sever it from the sprue. 

I approached the repairs with trepidation.  I had never worked with such precision before.  The various rods and levers were connected with tiny 7 mm nickle silver rivets from Scale Hardware (www.scalehardware.com), a wonderful company that sells a wide range of tiny nuts, bolts, washers, rivets, and other hardware for the fine scale modeler.  The rivets are so small and delicate that Phil recommended soldering them in place, rather than crimping or tapping them closed.

With my heart in my throat, I laid out the tiny parts on the work bench.  The rivets are so small, that most of the work had to be done with magnifying glasses, just to see what I was doing!  Soldering the rivets turned out to be simpler than I had feared, thanks to an instruction sheet from Phil.  A paper bushing about 1/4 inch square is poked with a pin to make a hole large enough for the rivet to pass through.  The rivet passes through the first component, then the paper bushing and finally through the second component to be riveted. 

A small amount of flux is applied to the rivet tail where it contacts the component.  A tiny bead of solder is brought to the joint on the tip of a clean, hot iron, which neatly flows around the joint to secure the end of the rivet.  Amazingly, the paper bushing prevents any solder from seeping through the moving joint. 

I assembled the parts as a single subunit, consisting of the valve spindle crosshead, the combination lever, the radius rod, and the union link, all connected by 7 mm soldered rivets. 

The final step in the project was to install the valve gear assembly on the locomotive.  I carefully lifted the valve gear hanger and slipped the valve crosshead over the slide and inserted the piston rod in the cylinder.  The next step was to connect the radius rod (the long horizontal rod above) to the expansion link, which rocks up and down in operation.  The radius rod and expansion link are connected by a hex head pin that passes through both of them and holds them in the valve gear hanger assemble.  The pin is not threaded.  It is simple bent on the back side to hold everything in place. 

The union link (the short piece on the bottom of the combination lever, above) connected to a pin on the valve gear crosshead.  Unfortunately, In trying to snap the lever onto the pin, it broke off, forcing me to file the crosshead flat and bore a 7 mm hole through for a rivet to hold he union link in place.   Not wanting to disassemble the entire drive train to secure the rivet, I took a chance and decided to solder the rivet in close quarters between the crosshead and the drive rods.  To prevent solder accidently dripping on moving parts, I covered everything with blue masking tape, then carefully applied a small amount of flux to the end of the rivet.  Holding my breath along with the soldering iron, I gently inserted it between the back of the crosshead and the drivers, and applied a tiny drop of solder.  The rivet held, and the installation was complete.  All that remained was to put the engine on the layout and give it a test run.  Eureka!  No. 14 (minus boiler and cab) chugged back and forth, whistle sounding and bell clanging!  I won't say it is as good as new.  In fact, it is BETTER than new!  The rivets look a lot better than the old pegs, and the solder holds everything together more securely.  I was almost (I say, almost!) inspired to redo the valve gear on the engineer's side.  But there are enough other projects to keep me busy for a long time.  I'll put off a complete rebuild for another time.....