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"Notes from the Unit Shop"

Kevin O'Connor's advice for the beginning small scale live steamer



Putting the Spark in Old Faithful: Improving a Classic


In 1976 the Aster Hobby Company of Yokohama, Japan released their sort of scale rendition of a 0-4-0 tank locomotive called Old Faithful. It was based on a style of Japanese logging locomotive found operating in the Kiso forest in the northern part of Japan, near to where the 1998 Olympic Games were held.   The original locomotive was wood fired, and so was fitted with a spark arresting diamond stack as well as an impressive “cow catcher” out front.  The kit box for this locomotive has a top cover illustration showing an alternate outline that features a shotgun type stack and a front drag beam with a link and pin coupler. 


I called Toyoki Inoue of Aster to inquire more about the model and its origins.  Toyoki told me of the Kiso Forest, and that Aster produced 1200 of the little locomotives, more or less split evenly between the two outlines. 


During the last few years I was lucky enough to purchase two excellent examples of this locomotive.  One was a factory built unit while the other was kit built: both were the diamond stack variant.  I ordered the spare parts need to turn one of the locomotives into the straight stack version, and while I was waiting for the conversion parts to arrive I decided to steam up the kit built version for the first time.  The locomotive’s wheels had no sign of wear and there were no wicks in the burner, though there was evidence of some soot in the boiler flues.


Down to the shop we went and out came the steam up kit.  I packed the wicks (more later) and checked the tightness of all the fasteners.  Then I headed to the track for a test run.  I will not bore you with all the frustrating details.  Suffice it to say that my exasperation index was topped out in less than an hour and I repaired to the house to spend some quality time with a Wild Turkey.  


As I pondered the problem I came to the conclusion that biggest issue besetting me was excessive condensate upon start-up.  Clearing the condensate caused the locomotive to jerk its way down the track, with the result that the condensate trapped in the smoke box sloshed down the two lower fire tubes, thus extinguishing the front wick.  Prior to retiring for the night, I jotted down all my thoughts concerning the locomotive.  When I wakened the next morning I had a plan of action.  After breakfast I headed for the shop and disassembled the cab, boiler, and firebox from the chassis and set to work. 


To fix the excessive condensate in the smokebox problem I did two things.  First, I drilled the hole in the base of the smokebox that the exhaust tube passed through oversize to 9/64” dia.  This enlarged hole now acts as a condensate drain.  It does not degrade the performance of the exhaust jet in producing sufficient vacuum to draw the fire up the fire tubes.  I know that sounds like heresy to the Al Cohols of the hobby, but it does work.  My theory is that the departing condensate, following the call of gravity, seals off the annulus just enough to maintain a vacuum.   


Secondly I opted to shield the fire tubes from the spray produced by the exhaust jet as it vented up through the petticoat.  To do this I fitted a short piece of 3/8” dia. K&S brass tubing up into the stack’s threaded extent ion into the smokebox.  The 3/8” dia. tube is just a light press fit into this extension; no machining is required.  I set the brass tube’s lower length at 1/8” below, and overlapping, the nozzle of the exhaust jet.  This may be all that is required, but not having done anything like this before, I decided to file away the FRONT of the brass tube to half way through the tube’s diameter, from where the brass tube enters the threaded extension down to 1/8” from the end of the tube.  A 5/32’ chain saw file was used to remove this material.  I finished up this part of the job by reinstalling the stack and the smokebox cover.


Paste pipe dope from a tube was used for a sealant for the smokebox doors.  The newer stuff contains Teflon, but any kind will due.  I like the pipe dope approach because I don’t like cleaning up after silicone goo.  The goo gets all over and subsequent wipings only serve to thin out the unwanted coating, but never really remove it.  And beside, the stuff irritates the eyes.  Pipe dope cleans up on the first swipe and it doesn’t feel icky.   


The steam regulator assembly was removed from the boiler’s backhead.  I found that the long copper tube that fits into the boiler was straight as a die.  The meant that if the boiler was more than half full that the pickup end of the regular was in the water.  I had noticed that, when the locomotive was assembled, the regulator gland nut was positioned right against the rear cab bulkhead; actually contacting it, and that the nut was screwed down all the way on the regulator body.  Even so, the gland nut was leaking ever so slightly, but would not pull up; more packing was needed.  A problem … if more packing was added, the glad nut would no longer fit within the cab.  I hack sawed 1/8” off the threaded end of the regulator and ran the M 7 x .50 thread further down the regulator’s diameter to allow the gland nut to move out of the way of the bulkhead.  Aster’s graphite yarn was removed from the glad nut and replaced with three turns of Teflon coated valve packing. 


I like to have gauges on my boilers so I drilled out the side of the regulator body between the valve seat and the backhead flange and soldered in a 1/16” dia. siphon, to which I attached a 0-50 psi x 3/4 “ dia. pressure gauge.  Prior to reinstalling the regulator into the boiler’s backhead I removed the dummy sand dome (box?) and its stud from the top of the boiler.  I filed the steam end of the copper pickup tube in a 45 degree angle and then bent the business end of the copper tube to poke up through the sand dome boss as the regulator was slide into place and screwed to the backhead.  


Since the copper tube now stuck up into the boss that the sand dome stud screws into, something needed to be done to make room.  I wanted the tube in this position in order to pick up steam from a point the greatest distance from the surface of the boiling water.  This was intended to cut down on condensate carryover.  The threaded end of the boss was drilled 5/32’ diaa. x 5/16” deep, which allowed the copper tube to nestle within the stud at assembly and formed a tiny, but effective steam dome.  The 45 degree angle insured that there was no chance t hat the copper tube would seal itself off from steam flow.


Modifications were made to the valve spindle.  Its steam-metering end was drilled and bored out to accept a .065” dia. insert, which protruded 1/8”.  This insert was turned to .058” dia. with a 45 degree chamber for steam sealing purposes where it meets the stainless steel spindle.  A 6 degree included (3 degrees per side) angle is machined onto the .058” dia. right up to the 45-degree chamfer angle.


The addition of this machined insert “tames” the throttle settings and allows for easily adjusted prototypical speeds under varying, especially light, load conditions.  I turned the brass valve wheel to 3/8” dia. and chucked up a piece of ½” dia. hard wood dowel, faced it off, and counter bored it was a 3/8” dia. endmill about 1/16” deep, then parted off the end of dowel about 1/8” thick.  A tiny amount of JB Weld™ was sparingly applied to both the brass valve wheel and the 3/8” counterbore in the wooden disk.  The brass wheel was inserted into the counterbore and firmly pressed together.  Black Magic Marker was applied to the wood disk to blend it in with the cab’s interior.  Now there is no chance of burning fingers while fiddling with the throttle.


The stock steam supply line runs from the backhead forward to the steam cylinder distribution valve via the outside of the firebox.  This line is not only very long and in unlagged, but it also runs through a large displacement-type lubricator that presents ample area to radiate heat into the atmosphere.  Since the locomotive’s operation suffers from an excess of steam condensate in the smokebox and exhaust, I decided to reroute the steam line forward through the firebox.  To do this two slots have to be filed in each of he left hand firebox baffles right at the level that the steam line passes along.  A 5/32” dia. chain saw file is perfect for this purpose.  The slots are just deep enough to let the steam line snuggle in.  IN rerouting the steamline, some additional heat energy from the firebox is imparted to the steam passing within, but not enough to be considered superheat.  AT this point the locomotive was reassembled.


The last thing needed is wicks in the burner.  This locomotive likes to have both its wicks made from fiberglass and very tightly packed into the burner’s wick cups.  I don’t think that you can pack them too tight.  Tight wicks use fuel sparingly and promote long runs.  Trim both wicks no higher than ¼” above the burner cup tops and contour both til they resemble the business end of a .45 caliber dum-dum round.  Attention to this detail will pay dividends later I the proper combustion.  If the wicks are higher, or loose, the flame will burn too hot and the safety valve will lift and shorten the run. 


I have found that this locomotive likes to be steamed up on blocks.  Any thickness block will work as long as the wheels are above the track’s surface.  Steaming up on block allows he locomotive to clear its exhaust of condensate (it’s a real “slobber stack” without jerking its way down the track.  Once the locomotive’s exhaust is running clear at a slow throttle setting just lift the locomotive off the blocks and send it on its way.  If you are pulling a consist, it is necessary to shut down the throttle and add the cars/vans prior to moving it off. 


One might ask, “Why go to all the trouble?”  To me the answer is clear.  It is because the locomotive runs so much better after the attention.  This kit built locomotive, depending on temperature (my runs were in the 40F to 50F degree range), runs 30+ minutes pulling two Aster #51 four wheel gondolas weighted with 4oz. each of fishing sinker, over a distance of 3700’ to 4000’.



This article originally appeared in Issue No. 47 (Vol. 8. No. 5) of Steam in the Garden.  appreciation for permission to reproduce it on SouthernSteamTrains.com is expressed to Kevn O’Connor, author; and to Ron Brown, Publisher / Editor of Steam in the Garden.


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