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Discussion Starter #1
The two Uintahs #50 and # 51 were built by Baldwin for the Uintah railroad in Utah in the '20s. They were the largest and most powerful narrow gauge locomotives ever built with 44,000 lbs. of tractive force.
LGB made several electric models which were very nice but not prototypical in dimensions. Bachman has a 2-6-6-2 which is smilar in looks but is not a Uintah.
Mine will be live steam and to the correct 1:20,3 scale.


Baldwin photo

The full Walschaerts dimensions were ploted out on Dockstader's program available on the web The termilology is generic for all valve systems so the drawing above ties the various parts to the dimension input boxes
As I will be using 5/8" cylinders, it is important that they are as efficient as I can get them so much detail has gone into this design
  1. www.billp.org//ValveGear.htm


    The cylinder and valve design is different from most. As I will be using piston valves, I will be able to have all of the porting in the valve body (per the original) this makes the valve assembly fully contained and attached to the cylinder with four screws. This makes the cylinder simpler and less massive.


1" square bar is rounded off on one corner on the router table with a 1/2" rounding over bit . Cuts are done 1/8" at a time at slow speed.

Top shows radius
Here the cylinders are cut to length in the table saw cross cutting jig


The cylinders are cut about .040" oversize and then faced off on the self centering four jaw chuck

Cylinders are bored out. Boring tool is ground from an old end mill

A piece of scrap wood is cut to 45 degrees and used to ser the cylinders in place where they are clamped in.

A 1/16" end mill is used here to get a large volume oval port without going too far into the cylinder bore

The port is then finished off on the top of the piston

Holes are drilled for mounting the cylinder to the frame and for mounting the valve to the cylinder
 

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Bill, so far, so good! Looks great. Does the boring bar give you a clean enough surface inside or will you need to hone it?
 

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Bill
Will be following this build as with your others. This one in particular is of interest as it is a favorite narrow gauge locomotive..great project.
 

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Discussion Starter #5
Dave
The boring bar gives me a very nice finish. I grind it to a point then put a very small radius (2 or 3 thou) on the point which keeps it from having a threaded appearance. I make the last few cuts at only a couple of thou deep to make sure it comes out round with no taper and only cut on the in stroke with the automatic feed. A couple of swipes with 600 sandpaper wrapped around a dowel evens everything out.
Ray
This was done with an 80 tooth carbide tipped blade but any carbide blade of 50 or more teeth will work. It is amazing how much better the cut is than a that of a power band saw
 

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This looks like an interesting project to follow.

Larry
 

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Discussion Starter #8
The valve will be a piston type spool valve with a SS spool and a bearing bronze sleeve. Per the prototype, the steam will enter from the side (inside face) and the exhaust will exit from the middle of the top face. The pipes will be attached with flanges.
The original had massive steam and exhaust pipeing which will allow me to ensure free breathing for the cylinders as I match the scale size of the piping.
I didn't get many shots of the valve machining but I will try to explain as I go through the photos

The heart of the valve is the bronze sleeve which is turned out of 1/4" stock and then drilled out to just under 5mm in the lathe.
The ports are cut with a 1/16" end mill and using the DRO the distance between the outside edges of the ports is exactly.750". This is critical.
The sleeve is then rotated in the mill and the steam and exhaust ports are cut in the same manner. The holes in the valve body are 3/32" for steam and 7/64 for exhaust
The main hole in which the sleeve is pressed is drilled out with cobalt bits to keep it straight and true and finally reamed with a 1/4" reamer. This gives me a tight press fit.
After the sleeve is pressed in, it is cut with a 5mm H-7 reamer and finally lapped with a 5mm SS rod and metal polish (lapping compound is too coarse for this)

The valve body is made from a 1/2" x 1" x 1.3" brass block.
Mounting holes and countersink as well as all through holes are done on the mill using DRO

The valve and cylinder are nearly finished here. The hole in the center at the top is for exhaust and a flange will attach with bolts (holes not drilled yet)
The hole in the front connects the two exhaust ports (holes on the outside ) with the hole on top. They will all be plugged
The notch at the bottom of the sleeve is for registration to ensure the sleeve doesn't rotate while being pressed in.
You can see where the cylinder will be mounted to the frame, I will be using SS spacers to reduce the heat transfer from the cylinders to the frame

The piston is turned to a few thou oversize and parted off. Once it is attached to the rod, it is mounted in the chuck by the rod and turned to size

Here are the component parts, The bottom of the valve is shown with it's oversize porting. Rings are turned from Florogold a Rulon type material
 

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Pretty good project. I have intentions of buildng one for myself one day. I do have all the engineering drawings along with a 20.3 scaled elevation drawing I mocked up. Its a giant beast.
 

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Discussion Starter #12
Posted By bille1906 on 03 Nov 2012 05:38 PM
While I was working on the cylinders, I was also doing some frame work not necessarily in this order

The side rod holes are drilled out using the DRO to ensure the spacing is the same as the frame axle block spacing
The blanks are then set in the mill with a rod and a drill bit through the holes to keep them aligned.

The jig with the pins in it is the same one I use to drill the holes. The rod is placed over the pin and the end mill is lowered and the rod id rotated to get the proper radius

The edges are trimmed off on the band saw. The plywood piece is a stop that makes sure all of the slots are the same depth.

The linging pin is turned out on the lathe

Here is the outside and inside of the bars

Here is the joint cut out on the band saw The cuts are made slightly oversize and then the saw marks are cleaned up with a file

Here is a drawing of the prototype rear frame. as you can see it is two piece. My frame will be similar in design. I made a slight change to allow a little more room for the firebox

Here is the frame joint using half-lap construction. In addition to the nine bolts, the pieces are JB'ed together


The axles are sprung with 1.6 lb. per wheel in the bottomed out position. This will run in the bottomed out position and there will be the 1.6 lbs. force on each wheel to keep them all down through any track condition

Here is the completed rear frame with the front frame in the background

This gives you an idea of the size of the thing. There will be another inch or so added to the front and rear
 

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The front truck is articulated,are you connecting the steam admission prototypical in the center of the swivel bolt?

Manfred
 

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Did you plate the side rods? the last photo they look steel but obviously brass in the earlier photos. If so, what did you use?

What are you using for drivers?

Well done on the frames too! looks like it will be an interesting project.
 

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Discussion Starter #15
Manfred
I haven't done that design yet
It is very hard for me to determine just how the front piping is on the original.
It looks like the exhaust comes out the top of each cylinder then "t"s at a swivel joint and then goes to the bottom center of the smoke box via a sliding joint
It then looks like the admission line "T"s and goes down between the cylinders but none of my drawings show where it goes from there. I assume it makes a "U" turn at or near the pivot point which would be the best point to make my connection.
I believe there will be enough room to install a dog-bone fitting and thus eliminate the need for flexible tubing.
If you or anyone else has seen any more descriptive literature on this loco, I would appreciate the input.
 

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Bill

I know that the 3 ft. gauge Uintah 2-6-6-2T's were a design unto themselves so I don't know if the following will be of any use to you, but just in case.


Catskill Archive - Baldwin Locomotive Works - Mallet Articulated Locomotives[/b]


The Home Machinist - Live Steam Forum/Topic: Uintah Railway locomotives[/b]

Curtis_F - Posted Reply: Mon Jul 09, 2012 8:10 pm

Uintah_No. 20-21_BLW-Spec-Sheet (PDF 3.84MB)[/b]
Uintah_No. 50_BLW-Spec-Sheets (PDF 8.49MB)[/b]
Uintah_No. 51_BLW-Spec-Sheet (PDF 13.22MB)[/b]
 

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The Uintah engines were simple articulateds, not true "Mallets" which were compounds as described in the diagram and article above. All four cylinders on the Uintah engines were the same size, and steam was only used once.
 
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