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Discussion Starter · #1 ·
I was asked to show more build detail in my next build so I will attempt to do that. I sometimes get involved in what I am building and forget to take photos but I will try to do more in this build.
If it seems like too much or to too little, let me know
The Casper was a 2-6-6-2 lumber engine on the Mendocino coast of Northern California hauling monster redwood logs. It was a compound Mallet
From a book, I scan a drawing which I will use for the general dimensions. It was a standard gauge engine but we will be doing it in 1/20.3 as it will be a better looking engine and fit in with the narrow gauge logging cars which it will pull
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I then paste it into Delta Cad, level it up and draw my parts over it. I use my general design but make sure everything is in scale
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I then break out the frames and CNC parts that Dennis will cut out on his CNC mill
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I will be doing all of the machining on the cylinders. The front LP cylinders scale out to 13/16" bore and the rear HP ones are 5/8" bore. The stroke is .9375 on both.
The engine had piston valves but I will be using slide valves so I need to draw out cross port plates. Here is the bottom of the plate which reverses the steam flow. On the cad program, I can lay out the end mill positions using a center start point of half the end mill diameter to the left and to the top of the piece.


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The top of the plate will have the timing ports of the valve.
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The valve chest cutout is also drawn out for both cylinders
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I'll post the build photos in the next posting. Please let me know if this is something useful to you.
 

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Bill, that's wonderful. We are grateful for anything you can post about your builds - always educational and interesting.
 

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DIDO! I always look forward to your posts with so much good information. I also like your articles in SitG.
 

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Accucraft Ruby, Accucraft 1:20.3
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I really appreciate the increased detail into your process. Especially this step of scaling and designing your plans. It will prove most useful once I have all the equipment to build on my own.
 

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Discussion Starter · #5 ·
Thanks guys
On scaling, I find that using the scale cylinder bores and strokes seems to work the best for me, They are usually a little bigger than manufactures use but my ceramic burners don't have any problem keeping up and the engines seem to run more effortlessly. This also makes it fit in with the scale outside dimensions of the overall cylinder size.
The HP bore scales out to .640". I will use .625" or 5/8". Using the 1.7 : 1 cross section ratio used by JVR and Aster, my LP cylinder bore is 13/16" and my cylinder stock will be 1" and 1-1/4" square stock. I will only need less than 3" of stock but I get 6" lengths which are easier to handle and leave me enough to do another job or replace a part if I screw up.

I set up the router table with 1/2" and a 5/8" round over bits. The fence is moved incrementally so I am only taking off 1/16" or less each cut. The bit has a ball bearing which keeps it from cutting too deep. I use a push tool to keep it down and feed it in and a piece of plywood to keep it against the fence
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The piece comes out with very slight ridges (about .001" deep) which are easily sanded out.
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The cylinders are then cut on the table saw. My saw is perfectly square and I can cut to within a couple of thousands but I cut the pieces .040" oversize and then trim to the exact size on the lathe.
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Here are the two router bits and the cylinders
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While I was at the metal yard, I picked up the material for the valves. I need 1/8" material for the cross plate and the cover and 3/8" material for the valve body. I cut them out while I have the saw set up
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Now I set up the self centering four jaw chuck and square off each end and then drill out the bore to 1/2"
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I don't have any drill bits over 1/2" so I bore the small cylinder to .615 and then ream it out with a 5/8" reamer.
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I don't have a 13/16" reamer so I boore the large cylinder out to .812 and clean up the boring marks with a piece of 600 sandpaper wrapped around a wood dowel.
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So here are the cylinders ready for the mill.
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Bill,

Thanks for taking the time to post in more detail. It's very enlightening to see your process.

Roger
 

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Discussion Starter · #7 ·
The mounting holes for the cylinder heads are done on the mill. I have a bolt circle program on my DRO but first I need to find the center of the cylinder. I have made up these tool as I have different bores to center and keep them around I have a perfectly centered 1/4" chuck and have made the tools for that use. Here are the two ones I will ise here.
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And mounted in the mill
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When I turn out the cylinder heads, I have holes for the piston rod and the center screw for the front head cover. I use this centering tool to find the center as it is split just above the pointed end and will wobble if off center
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I then use a centering bit to start the holes.
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After the holes are drilled, I tap them out on my tapping jig.
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I have various wedges of wood that I use do position things for angled drilling here is a 45 degree one I am using for the steam ports.
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I start the hole with a 3/32" end mill to get a flat and then use a centering bit and finally a 3/32" bit.
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The valve parts are drilled and milled with use of the digital readout DRO
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The various parts are laid out
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The sliding valve surface is then made flat on a glass pane and a series of 220, 320, 600, 800, 2000 wet sandings
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Accucraft Ruby, Accucraft 1:20.3
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I liked the clarification in your previous post about the router table being done in small cuts. I was baffled by the thought of doing that 1/4 round cut in one pass. Are they high grade wood router bits? Or do metal bits exist that I didn't realize?

Tyler.
 

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Discussion Starter · #9 ·
Tyler
Any carbide wood bit will work
I bought my bits on ebay years ago and I think it was $50 for 50 bits
The common thought at that time was to buy a set like that and when a bit goes bad replace that bit with a better one but In 15 years of use I only had a couple of bearings go bad and chipped one from misuse
I just looked it up and saw 35 bits for around $55 and this roundover set for 13
 

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Bill thank you very much for those posted details, great job
Thanks and with best regards Igor
 

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Discussion Starter · #11 ·
The wheels are rough castings from Walsall. They also sell finished wheel sets
The wheels are mounted in the external jaws of the three jaw chuck. Even though they are rough castings, the outer rim is very true. I drill and then ream the center hole for the axle
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I then cut the back to expose the spokes and measure the cut depth to make sure I can get a 6 mm rim thickness
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I then turn it around and mount it in my arbor to machine the front rim to 6 mm
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I rough out the tread profile leaving it about .010" oversize
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Not shown is where I then mount it back in the external jaws to turn the hub down to ,250"

It is imperative that the crank pins are all exactly the same distance from the axle. To do this, I have a piece of 5 mm axle stock pressed into this block which is then mounted in the mill vise
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The dimple on the axle stock was done on the lathe so it is perfectly centered. I use this to zero out the mill and then advance it half the length of the cylinder stroke (.468")
I then lock the X and Y movements so as to eliminate any mistakes and center drill, drill and tap the holes to 4-40. I do the same procedure for all of the wheels moving them in and out of the jig in a production line sequence.
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Then down to Dennis' to do the tread with a plunge cut. The counterweights are CNC cut and attached with JB Weld and they are painted.
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Discussion Starter · #12 ·
While I was doing the cylinders and wheels, Dennis was CNC cutting the frame rails and axle boxes.
I drew out the parts on Delta Cad and sent them to Dennis to cut.
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The axle boxes need a #30 (.128") hole drilled in them to accommodate the 1/8" suspension spring. I center drill it and then drill it through to the axle bearing hole. When the bearing is installed, the spring will bottom out against it. The bearing hole is cut out on the CNC mill to just under 10 mm. I then run a 10 mm reamer through the holes to get a nice slide fit and set the bearings in with 680 loctite. Notice how I use a parallel to set the inner face even to the mill vise
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The axles are 303 stainless close tolerance and I cut them to just oversize and then trim them to size on the mill and put a center dimple with the centering drill which I use on the quartering jig.
With the axle boxes setup and the eccentric for the axle pump done I am ready for assembly. I set one side in with loctite and let them set overnight. The next morning I check each wheel to make sure the bond is secure. I then set the opposite wheel in the quartering jig.
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The side rods need to have a pivot to allow the wheels to rise and fall independently. A three axle chassis needs only one per side. I use a fork and blade setup and do the slicing with a 1/16" slitting saw in the mill.
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The pilot and pony wheels are very similar. The axle is held in place with a three piece frame
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A stainless rod is inserted in the axle bearing holes to keep it true and the assembly is silver soldered together.
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I didn't get all of the photos of the build but you can see the frame in this photo of the front engine. You can see what looks like a rod going down to the frame but it is actually two rods, one which is drilled out and has a spring in the hole and the other which slides in the hole against the spring thus giving the wheels a spring support.
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Here is a photo of the frames to date.
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Accucraft Ruby, Accucraft 1:20.3
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That is excellent Bill. If I understand the suspension correctly, the #30 hole holds a spring on top of the bearing. The bearing box then slides up and down in the frame slot. With the top of the coil spring against the frame. Is the bearing box sides slotted and inserted from below? Or inserted from the outside like a Ruby?

Tyler
 

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Accucraft Ruby, Accucraft 1:20.3
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I just looked at the Cad drawing again, you must have a retainer that attach to the bottom of the frame, and the bearing box is trapped on one side by the frame. Are the box flanges assembled inside the frame? Or outside against the wheels?
 

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Discussion Starter · #15 ·
The Hole is for the 1/8" cut to length spring. You are correct that the axle box then slides up and down in the frame slot. The spring is compressed and fully within the axle box under normal conditions and it pushes the wheel down when it goes over uneven track. if you look at the drawing above, you can see that the slots in the frame are open at the bottom and there is a 1/8" cutout at the bottom of the frame for a 1/8 square strip which is screwed on holding the boxes in place.

The photo bellow is from another build but you can see how the boxes fit in the frame. The spring holes don't show as gravity has them all on the bottom. The outer lip acts as a spacer between the frame and the wheels and allows the axle box some lateral movement for going around curves. As the ball bearings have a close tolerance fit to the axle, the lateral movement is best allowed in the boxes. If I were to use bronze bushings which need a loose fit, slotted boxes would work also. The other advantage of this design vs a slotted one is that these boxes are done on CNC in one operation making the sliding edges and axle bearing hole in one operation. With a slot, the box needs to be repositioned in the mill to do both and that can lead to inconsistencies.
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Discussion Starter · #16 ·
Here is something I always do to the pistons. I cut a slot in the top with a Dremel cutoff tool which allows easy installation, removal and adjustment of the piston.
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The crosshead brackets are cut from a 1/8" flat stock on the CNC mill. 1/8" x 1/16" deep notches are cut for the mounting on the frame and the crosshead bars. In the past I have silver soldered 1/8 x 1/16" flat stock pieces into the notches. This works ok but you can never get it perfect so some bending is necessary to get everything true. This time I decided to try something new. I used 1/8" square stock and then on the mill, I cut the soldered on stock to be even and true to the main piece.
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Here you can see the frame mounts that have been milled and the crosshead bar mounts being soldered on. Note the snippets of solder at each joint.
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And the two finished and bead blasted units
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Here is the crosshead bracket for the rear engine. The large hole is for the ball bearings supporting the eccentric link and the upper small hole is for the reverse arm rod

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And here is the front unit with the holes in the same place but with a different supporting setup.
You can also see the crosshead and crosshead guides in place. The front of the crosshead guides have a 1/16" round nub turned on them which goes into a hole drilled into the rear cylinder head
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On the front pilot deck assembly, I start with a Trackside Detail pilot and coupler. The coupler doesn't fit in the recess in the pilot so I have to cut it down and solder it in place but I think it looks ok. The steps are shaped n the mill and soldered on to a strap which is bolted on to the buffer. The photos and drawings show a wood buffer which seems to go right through the main frame. In order to maintain strength and a scale look, I have a brass buffer bolted to the front of the frame and a hardwood piece glues to the buffer on each side.
The headlight is an Accucraft one from the EBT kitbash I did with the lower mount changed to match the prototype
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The step sides were cut on the CNC mill by Dennis slots were made for the steps. The assembly was held together with music wire pins and clamps and soldered together.
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A grab bar is made per the prototype and the steps and upper platform are set in place.
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Finally the sand box is made and attached and everything is disassembled for painting
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Brilliant idea Bill where you put a slot onto the front side of your pistons for easy removal. Saves a great deal of hassle and time when a piston decides to unscrew itself from the crosshead that has happened to a few of mine, let alone easy piston ring replacement. When I have pistons removed for what ever reason I will do that.
Thanks Russell
 

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Discussion Starter · #18 ·
The crossheads seem to be different shapes and sizes on every loco. As they are something that is clearly visible and a vital to the cylinder performance and life, I take care to reproduce them to scale and shape.
I start with 1/4" brass stock and cut the overall dimensions on the Table saw crosscut sled.
Then on the mill, with a 1/8" end mill, i cut the slots for the crosshead guides
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I then rotate it 90 degrees and do the slot for the drive rod
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Here is the Cad drawing for the crosshead
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And the milling
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In the above photo, you can see the 5/32 hole for the shoulder bolt which acts as the drive rod pivot. It only goes through one side of the slot for the rod. On the other side a 4-40 threaded hole holds it in place
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Here is the crosshead which has been tin plated and has the drive rod set in place.
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Hi Bill, I am curious about the tinplating, how do you do it or get someone else and does it stand up well to wear as I assume that's why you do it?
Russell
 

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Discussion Starter · #20 ·
Hi Russel
I use Liquid Tin which is real easy. You just dip a clean piece of brass into it for 3-5 minutes and rinse with water. It holds up real well. I have eight year old jobs that still have the look they had when first done.
The last bottle I got was $11 now I see it is $27 but it will do many platings
 
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