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Building the Skookum in 1/32

21K views 93 replies 29 participants last post by  OldNoob 
#1 ·
Skookum is the world’s only operating 2-4-4-2. Skookum returned to operating service this year after a 15-year overhaul at the Oregon railroad on the former Southern Pacific Tillamook Branch. The 1909 locomotive has an amazing story that starts with its rejection by a Tennessee logging railroad, its acceptance in the Pacific Northwest, and its tragic derailment that left it abandoned in the woods. Enthusiasts saved the locomotive and over more than 60 years moved it to safety and eventual restoration. Here is a photo of the “Skookum” unloading logs at a mill pond in 1953.



And after the derailment and abandonment.


And the current restored version now running at Niles Canyon Railroad in California



Text and photo found on the web

This is a small but complex loco. It is a true Mallett with compound cylinders. I will be building this in similar fashion to my N&W Y6 builds but will be showing more of the machining and metal working procedures. I will be making three locomotives.
 
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#5 ·
Thanks Bob
Maybe some day.
Or, You can come to Sacramento. The meet and accommodations are great and lots of track time available.

My build will be a little different from the Ruby one as having the engine nearby, I should be able to get a real close scale model with the correct size spoke wheels and Walschearts valve gear along with the different size low and high pressure cylinders.

Searching the web, I found this pretty good spec drawing. I also have a large blue print of just the engine. Neither was absolutely correct but good enough to start my plans



From this drawing, I drew out the frame rails and gave them to Dennis to cut out on the CNC mill.
This can be done without CNC as I did before Dennis converted his mill but this makes things more accurate.




The wheels come from Walsall and you can get them in rough castings or finished and quartered on the axle shaft. I prefer to get the bare castings and machine them myself
Below, the rough castings are on the rt and on the left are wheels which are ready for the tread profile which will be done with a plunge tool to be shown later.



I start by mounting the wheel in the outside jaws of the three jaw chuck and drilling the axle hole out to 3/16"


I then ream it to 5 mm


It is then mounted on the arbor and the tread width is cut to 6 mm wide


Still on the arbor the tread detail is roughed out leaving it .010" oversize for profiling.


finally the hub is turned to .250"


The pilot and pony wheels are the same and are turned in the same manor


So. here is what I have so far, the frame rails and wheels for three engines.
 
#6 ·
Thank you for posting about the details of wheel profiling. I have seen it described on the Mark Woods Wheels website but if I recall correctly, it shows a larger, more rigid lathe at work. I am very interested in how you manage a form tool on a mini-lathe for the final profile.

If nothing else, I did not know about Walsall. At least I will be able to purchase wheels pre-machined.
 
#11 ·
Kevin
Yes I plan on having them done for Sac
Jim
It would have been fun to do it in 1/20.3 but since it was and is a standard gauge we are doing it in 1/32
Our tools are just ground from 5/16" tool stock with a grinding wheel and dremmel cut off tool

Here are some photos of the process




 
#12 ·
The axle boxes are critical as if a hole is off center, The wheels will bind when the side rods are installed. Dennis does them on the CNC mill which gets them correct every time.

Being that each chassis only has two drive axles, I could mount the axles in fixed positions but by springing them, I ensure true tracking through the roughest conditions.
Here I set up the first one in the mill vise for drilling. They are set up so the flat is in line with the left side of the vice so that after the first hole is set up, they can all be drilled the same. First I center drill them all and then drill them out with a #30 drill bit for the 1/8" springs.



A spring is checked for fit. Springs will be selected for compression later


Before I mount the wheels on the axles, I have to make the axle pump eccentric. I will be using 12x18 mm ball bearings so I turn a length of 12 mm from 1/2" stock. My axle is 5 mm and I want as much throw as I can get so I measure in from the outside .110" and center pop it there


I now mount it in the four jaw and adjust it by mounting a length of music wire which has been turned to a point in the tail stock. I adjust the four jaws till there is no wobble in it,


I will be parting off three eccentrics so I put a dot on the piece so that each time I slide it out it stays in the same position in the chuck.




I then drill out and tap the set screw hole. My mill is adjustable down to 50 rpm or less but it still maintains full torque so to prevent the tap from bottoming out and breaking, I put a piece of tape where I need to stop.


So here are the three finished eccentrics


Here are the front and rear chassis with the wheels just slipped on. You can see the front and rear crossmembers where the buffers will be attached and the round crossmembers I always use. These give the frame tremendous rigidity and keep everything perfectly aligned as I add other cross members. I will probably need to remove the rear on on the rear frame to fit the axle pump in but the pump itself will act as a crossmember.
 
#13 ·
I am moving about with this build. It helps in doing three so that I don't get too bored with repetitive operations.
The crank pin on the wheels has to be accurate for the cylinder stroke and the same for all wheels. I have a length of 5 mm rod pressed into a brass block mounted in the mill vise. I center on it and then go .350" out for the .700 stroke and drill and tap all wheels.


The counterweights are attached with JB weld. You can just make out that the front ones are a little smaller per the prototype


Things are tight on the rear truck. I will be using a ball bearing scotch yoke but I need a really short piston & cylinder


Here are the axle pumps in place. The crossmember on the lower frame is for the rear truck


A closeup of the bypass valve


Because of the small wheels, there isn't enough room for a long shoulder bolt and coil spring. So I came up with this spring which will keep the pony truck on the track and the two raised portions will keep it from flopping around when picked up.


The cylinders start with a square bar rounded off on one corner in the router and then cut to .020" oversize on the table saw.


Then they are trimmed to length on the lathe


They are center spotted


They are then drilled out to 3/8" and then bored out to .500 and .650"


The 2" pipe is cut to length and squared off with the 12" disk sander


A former block is cut out from a 4x4


And the firebox is formed.


And checked for square


Throat sheet and front sheet are drilled out




Here is a video My friend took of the soldering of the first boiler. It went pretty good but I got it a little too hot on the sides and it didn't flow that well there because the flux broke down. I redid it later and it came out fine.

Not sure id MLS has fix YOUTUBE vids but if you don't see the vid click on the title and it will work. It is 6 minutes.
 
#15 ·
Sean
The counterweights are 1/16 hot rolled steel sheet
The torch is a Sievert. Not sure of the model number
Here is one at Amazon but it has the air holes closer to the tip. The holes close to the handle allow you to put the tip close to the inside of the firebox. Siefert has a handle which accepts different tips. It says Siefert Pro on the handle.
https://www.amazon.com/Sievert-Indu...hvlocphy=&hvtargid=pla-4584207577679761&psc=1

Harbor freight has several at lower prices but you would have to go down there to see the torch head size the one in the vid is 1-1/4" OD
 
#16 ·
The Sievert tip you are referring to is the "cyclone" tip. It is available in several sizes, the medium size is my standard "go-to" for most work.

Grainger sells them, this web page shows several sizes:
https://www.grainger.com/category/welding/gas-welding-equipment/brazing-and-soldering-torch-tips?attrs=Item%7CBurner&filters=attrs

The big advantage of the cyclone tip is that you can insert the torch tip inside of close spaces without affecting the flame. This is important for things like silver soldering inside of a boiler firebox.

The Sievert brand handle and torch tips are expensive, but work without complaint. I have never regretted the purchase.
 
#19 ·
There is a lot of machining to be done on the 12 cylinders for the three engines. I start by drawing out the dimensions and settings i will use on the mill. A couple of things changed but you can get the idea.


The cylinders flange out to support a larger valve body. I cut a 1/8" x 1/4" strip on the table saw to get the triangular transition pieces and solder them to the cylinder, I then fill any gaps in the seams with JB weld.


All of my machining will be done on the left side of the mill. I hold a parallel against the side to make sure each part is in the same position.


On the lathe, I turn out a tool used to center the cylinder bore in the mill. It is exactly the samd diameter of the bore so it gives me a true center.




The circle program on the DRO is used for the end cap bolts. You can see the mounting and exhaust holes on the left side of the cylinder also.


Then the holes are tapped out on my Micro Mark Tapping tool


I want the cylinder drains to be as close to the end of the bore as possible to ensure total drainage so I first drill a .040" hole .040" from the end


I then center drill and then drill a 4-40 tap hole(.093) at a distance of .080" from the end.


This solves my problem of having a hole at the end without having the drain mount hole too close to the end.


 
#22 ·
Working around putting up Christmas decorations, I was able to get some work done on the Skookum

I took this shot to show how the steam flows into the cylinders. you can see that the outer ports go at an angle to supply steam to the cylinder and how the middle one goes through the block to what will be the exhaust pipe.


Here are the cylinders showing the various holes that have been drilled in them.


The side rods for the chassis need a bolt which has a low profile head for clearance and looks. 1/4" stainless hex is turned to 4-40 for this


I finished up the boilers. Here I am ready to solder the inside of the firebox and boiler mount studs. Although all three boilers are almost exactly the same dimensions, I have them numbered for the best fit.


Here they are after soldering


Two boilers were leak free after the first soldering but one had two leaks and had to be resoldered. This shows the before and after pickling and clean up.


And the finished boilers


The cylinders have covers on the end caps. I turn them out to .050 over the cylinder diameter and bore them out to the diameter. this gives a .025 thickness to the cap material.


I check the bore diameter and depth on each cover.


Before I fully part them off, I round the end off with a file.


Here I am drilling out the valve body which has been milled to accommodate the valve.


So here is a good day's work of milling and drilling.


And a box of parts for final assembly which will probably be after the holidays
 
#25 ·
Here is a photo of the front of the high and low pressure cylinders, The LP cylinder had a front piston rod guide which I don't need here because of the crossheads but I duplicated the look. The cyl cap has a stud turned to 10-32 which received the extension an holds the cover in place. the HP cyl cap has a raised portion which equals the cap bolt head height thus giving me enough room to tap it to 0-80 and use the 1/8" long screw to attach the cap.




The rear covers will be held in place by the piston rod gland nut. the two extra holes are for the crosshead guides.
 
#27 ·
yes, the cylinder end of the guide goes into the hole in the head. I haven't designed the rear attachment yet. I usually have similar holes drilled into the bracket or sometimes I drill a hole through the guide and attach it with an 0-80 stainless screw.
 
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