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I'm just finally getting around to posting some of my recent modifications to my Aristo Mikado.  Around the end of October, as the cooler weather started bringing out the steam plumes again, I decided it was time to do something about the weak plume coming from the Mikado's stack and the billowing steam coming out of just about everywhere else.  The problem was the lack of a seal between the boiler and smokebox, and the crimp at the top of the exhaust tube which caused the exhaust steam to fill the smokebox rather than shoot up the stack.  Following Larry Herget's example, I sealed up the interface between the boiler and smokebox using high-temp silicone.  I also cut the crimp off the top of the exhaust tube, and tapered the top of it slightly by chucking the tube into the drill press and turning it while gently squeezing it between a pair of needlenose pliers lubed up with a few drops of oil.  The idea of the taper was to act as nozzle to give the exhaust steam a little more velocity as it shoots out the stack, resulting (in theory anyway) in a higher steam plume.  I didn't take any photos of the process, but here's a video of the results (running on Larry Mosher's layout)...

http://www.youtube.com/watch?v=i_j-RtSxDQQ

The enhanced chuff is actually coming from the burner rather than the stack exhaust. I found that if I turn off the gas and run on residual steam, the chuff sounds pretty much the same as it did before (which I thought was pretty decent anyway). The modifications have given it a stronger draft, so I guess it's drawing more air through the burner when it chuffs, causing the burner to make sort of a "woof" sound with each exhaust beat. It's a cool effect, but I'm not sure if there are any negative effects in terms of burner operation. It certainly doesn't seem to have any trouble keeping up with demand for steam, and as far as I can tell the flame isn't licking into the smokebox when it chuffs (though it was pretty hard to be sure since I was looking down through the steam plume).  

The downside is that the engine has become more finicky when it comes to lighting and staying lit while the cylinders are clearing.  If the stack is blocked even momentarily with water, the fire goes out.  When I sealed the smokebox, I did leave some space at the bottom, but apparently it's not getting quite enough air through there.  However, I have learned to avoid the problem by clearing the cylinders of residual water from the previous run before lighting her up, and not filling the boiler quite as full to start with.  I tightened up the nut on the Goodall valve (which also functions as a secondary safety) as tight as it would go so that it no longer weeps steam and is actually usable as a Goodall valve again.  Now all I need is a better pump bottle to replace the wimpy one that came with the engine.

While I had the smokebox apart, I decided to give her a bit of a facelift too.  The plan eventually is to bash the engine into a 1:32 scale model of a Northern Pacific W-3 (I started to build a new tender for it in brass, but then I got distracted with rolling stock projects so I haven't made a whole lot of headway on it lately).  For now I just decided to give her a few simple touches for more of a NP feel (the stock above-center headlight mounting was already a good start in that direction). I moved the bell from the smokebox front to the boiler top between the domes, moved the marker lights up a bit, and flattened the bottom of the handrail that goes around the bottom of the smokebox front.  I filled in the old mounting holes for the bell and marker lights, then painted the smokebox with a mix of 2 parts Floquil Graphite and 1 part Floquil Old Silver.  Here are some pics (running on Andy Brauer's layout):





She's still wearing the Santa Fe lettering, I'm not sure whether I'll go ahead and re-letter the current cab and tender, or just wait until I build the new ones as the bash project progresses.

After the smokebox mods, there was just one little problem left to fix, and that was a non-working pressure gauge. It worked the first time I fired up the engine, and maybe once or twice randomly since then, but most of the time the needle never came off the peg. I have been able to get by without it, but a working pressure gauge is a nice thing to have, so I while I was in tinkering mode, I finally decided it was time to do something about it.


Like the throttle control and the fuel valve (problems I solved with a Spektrum RC unit and Accucraft K-27 gas tank), I'm sure Aristo would have fixed it for me if I had gone to them with my problem, but instead I looked at it as an excuse to make a change. I wanted a smaller pressure gauge anyway to free up some space inside the cab, since there won't be quite so much room in the 1:32 cab . I ordered a new pressure gauge and syphon from Accucraft (part # AP-21151). Designed for installation on a Ruby, the syphon has a union at each end, one end attaches to the gauge, and the other one attaches to a fitting (included) that screws into the Ruby throttle manifold. The stock Aristo syphon has no unions, it's simply soldered to the gauge at one end and a banjo fitting at the other, so I needed a way to splice the two syphons together.  I cut off the Aristo syphon about 1" from the banjo fitting, drilled out the Ruby manifold fitting to go over the end of it, and soldered it on. Then I attached the Accucraft syphon and pressure gauge using the unions on the syphon.  Here's a photo of it installed:




A stationary test-firing on the kitchen countertop (there were 2 feet of snow on the ground when the pressure gauge arrived) confirmed that I now have a working pressure gauge on my Mikado. It also led to another interesting discovery. Although the safety valve started venting steam at around 45 psi as expected (it has been adjusted from the 30psi stock setting), the pressure kept on climbing. The needle on the gauge was approaching 80 when I shut off the gas, with the safety blowing the whole time. I suppose it's not really so much of an issue if the engine is running and using up steam (I didn't open the throttle at all during the test), but it's still a little scary that the safety valve isn't keeping up with the steam production. Has anyone else noticed this, or is there just something wrong with my safety valve?
 

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Great work RW, you should post these mods on Aristocrafts site also. Great Photos, thanks for the full discription of your work.
 

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RWJENKINS;
I just again want to say "THANK YOU"  ;) for sending me your unused limit switch to get my Mikado back on the track. Your FACELIFT looks very nice.   I have included a photo of my FACELIFT.  While I had the plastic shell off to seal the smokebox, I removed the mold line down the center & repainted the shell.  I also installed a set of airpumps on the front deck w/rock shields, added a front coupler for doubleheading and at the top is a Nathan feed water heater with the markers mounted on it.  This loco also "POP'S" out of the top where it should.

SEALING THE SMOKE BOX, SEE; http://www.mylargescale.com/forum/topic.asp?TOPIC_ID=42907

 

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Nice work indeed. Like Larry, I also sanded the seam down and used several of his articles, as you did, to improve my Mike, including the front coupler. Still searching for a second Mike to double head with. I have the only one in Neb, I guess. Couple of others had them, one sold his with out unpacking it, other ran his once or twice and sold it. I'm lonely! :) Jerry
 

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RW
Very impressive look to your engine.  As in the past, the brass version and updates will upgrade this engine to the level that the rivet counters will be intrigued with.  If only Lewis would take notice of how well a Mikado could present itself and the different version he could offer.
 
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