Building Kozo's New Shay locomotive

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Nice work. Silver soldering is fun isn't it?

Todd

Once you figure out the basics and learn what to look for, it is! I love adding a new skill to the toolbox, especially one that opens up so many model possibilities.

I just picked up a copy of W M Harris's book 'The Steam Donkey Engine' from Village Press - looks like that could make a really fun project, though I think I'll scale it down a little bit. I was looking at PMR's vertical boiler kit, that could make a good way to do the boiler, scale the rest of it to suit. Something to think about in another year or so after the train is done...
 
The wheels are almost done now (just need to drill for the gear bolts and paint the spokes/hubs).
Got the wheels faced off to final width and the axle holes bored/reamed to size,
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then mounted the wheels on an arbor (turned to a sliding fit on the wheels, and left in place in the chuck till all were turned so it was absolutely true) for turning the tread and rim to size.
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Then, the headstock was turned 3 degrees so I could taper the tread surface,
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then 10 degrees the other way to taper the rim. The corners were rounded with a file while turning.
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That completes the main fabrication on the wheels. The right side hubs will be drilled/tapped for the bevel gears, and all of them will have the hubs/spokes painted black. The rims stay clear, just polished.
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As it turned out, I am glad I made one extra wheel assembly - one did get botched somehow in the axle hole, think it slipped in the chuck or the drill wandered a touch - came out slightly wobbly. So, that one goes in the trains trunk as a spare...!
 
Those are some beautiful wheels! Keep up the great work! I hope to get back to my A3 soon.

Todd
 
Too hot to do anything outside recently, so been spending some time in the shop playing with the Shay model.
I drilled/tapped the right-side hubs for the bevel gears, and got them painted. The holes were drilled using a drilling jig to keep them all the same, same jig will be used to drill the gears. The center hole in the jig was already in the scrap piece of brass, has nothing to do with the jig...
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Then got the axles done - pretty straightforward turning of a shoulder on steel rods, with two axles having eccentrics added (held with set screws) that will power pumps for oiling the engine/shafts, as well as the boiler water feed pump. The wheels are held on with high strength loctite.
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Here is a shot of the wheels set under the frame to see how the overall progress is going - almost looks like a train...
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Next up are the bevel gears - I have cut lots of normal flat gears, this will be first time for bevel gears. I have a book on gear cutting plus some articles, looks like a straightforward extension of the normal method, with some extra fiddly steps to keep it interesting. This engine needs 4 pairs of gears, one per axle. Stay tuned for progress pictures, hopefully none of the gears get turned into projectiles for the ol' flintlock!!:eek:
 
Nice! How long is the frame? Looks like a pretty big loco. Of course, I've been following Ed Hume's Gauge 1 version of this model. That makes yours look huge. :)

Todd
 
Nice! How long is the frame? Looks like a pretty big loco. Of course, I've been following Ed Hume's Gauge 1 version of this model. That makes yours look huge. :)

Todd

The frame on this one is 32" long, 6 1/2" wide. Definitely not HO guage!
 
Well, I was going to wait and post the making of the bevel gears for the Shay all in one post, but it turned out I did not have any brass large enough diameter for the ones attached to the wheels so had to order some more (found a chunk of 1-5/8" bar as a drop at a commercial supplier, it should be here later today according to the tracking).
So, I got started with the smaller gears, a 20-tooth gear at 26.57 degrees. These are being done with a 44 tooth-range cutter, module 0.7. First up was to turn the blank on the lathe, with the bevel done with the compound slide
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and the rest done with the normal slide. Since the teeth will intersect the post of the gear, the gear is first made with the post on the large side, which later on will be turned off after a new post is hard soldered on the small side of the gear.
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With the blank turned in the end of a brass rod, the chuck was moved over to the rotary table, which was set at a 26.57 degree angle to the mill bed. Since that did not leave enough travel on the bed, I got out the heavy plywood extension that I made several years ago for cutting large clock gears.
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The teeth were cut in three passes, one normal pass to cut the slot between all the teeth, then two more passes to take a slight wedge off the side of the large end of each tooth to give it the final shape - this is needed since the teeth and the gaps between them need to be tapered on a bevel gear, and the cutter will only do a parallel-sided gap in a single pass. I used the formulas from Ivan Law's book on gear cutting (with the correction from Sine to Cosine that I learned from other's posts - that saved the day!). I tried to get photos showing the process, but they did not come out well enough to show - will try again with the larger gears, hope they show the difference between passes.
As each gear was completed, it was cut off the bar, and the process started again for the next one - 4 gears needed in total.
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Once all the gears were cut (they mesh very well with each other, so that is a hopeful sign I did it right, will know for sure once the large gears are made) it was necessary to make a new post for the small end. The posts were turned to the final diameter, with a smaller end that fit snug into the holes in the gears. They were then silver soldered in place.
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After soldering, the gears were chucked up in the 4-jaw, and trued using the original post. They were then redrilled through the new post, and the old post turned off. Again, this was needed since the final post coming out of the small end of the gears would have been in the way of the gear cutter.
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Once the gears were done, a setscrew was drilled/tapped into the post to hold them on the line shafts. Once the trucks are done, the positions of the gears will be adjusted to mesh well, then the posts will be cross drilled for final pins - the setscrews are just to allow that adjustment before pinning.
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Those gears are works of art. You are demonstration some serious skills with this build. Awesome work.

ROG
 
Okay, got the larger bar stock for the 40-tooth bevel gears, and got the first one made tonight (weather was good during the day, so got the canoe out for a paddle first!).

Took the 1 5/8" round stock, and cut down four discs, then center drilled/reamed for the axle, and using the drill guide made for the screw holes in the wheels, drilled out some 3-48 clearance holes. Then bored out the recesses in the center of the gear, which provide clearance for the bearing holders.
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Then, made up an arbor with the same drill guide,
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and turned the outside of the blanks to the bevel angle.
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With the chuck/arbor moved over to the rotary table on the mill, cut the teeth using same constant-depth method as the small gears. Must have gotten my calculations correct, since they mesh very nicely. Just need to make up the other three....
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This was my first build of bevel gears - they seem intimidating to make, but once you have been through it and see the changes each cut makes, it really is a straightforward process. Glad I had made some normal gears first though....!
 
Great job! I love watching your progress. Could you give a quick link to what was meant when you talked about the Sin Cosine correction to Law's book? Thanks Todd
 
Great job! I love watching your progress. Could you give a quick link to what was meant when you talked about the Sin Cosine correction to Law's book? Thanks Todd

Hi Todd,

I dont recall which posts I read about the error originally, but doing a search for "ivan law bevel gear cosine" found quotes like:
.................
In fact there is an error in Ivan's maths concerning the OD of the small end of the gear. He has :

OD small end = PD + 2 x Addendum x SIN pitch cone angle

This should be :

OD small end = PD + 2 x Addendum x COS pitch cone angle

Likewise the effective number of teeth on the back cone for selecting the No. of form cutter should be N/COS pitch cone angle not N/SIN pitch cone angle

It becomes obvious if you consider a gear of pitch cone angle = zero degrees which is of course a spur gear.

It makes no difference, for his example mitre gears because SIN 45 = COS 45
,................

Hope that helps, it is a critical correction!

Chris
 
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Oh, and in my copy of the Ivan Law book it is on page 106 where he does the formulas for bevel gears.
 
Got a start on the trucks for the Shay - The lower bolsters are bigger than any rectangular stock I had, so I made the bars from a couple lengths of round rod. In the past, I've run into trouble doing this, having the bars warp on me as I took down the first side. So, before machining, I did a stress-relief session in the oven (500F for an hour) first, let them cool down, and there was absolutely no warping problem. As I understand it the bars get work hardened during the rolling process as they make them, and if you cut one side off the internal stresses built into the bar will cause them to twist to the side. Other alternative is to take a little off one side, turn it 180, take some off the other, and so on. Baking them first to relieve the stresses let me mill off one side down to desired dimensions at a time - easier, and came out dead straight.
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Once they were milled to overall length/width/height, I milled the steps in the right ends (which let the drive shafts pass by).
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Then, using the tilt table and machine vise, milled the ends and the angled slots in the ends (3 degrees, to give the suspension room to tilt on uneven track). Kozo did this with angled blocks in the vise, but having the tilt table made it an easier setup for me.
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After milling, laid out all the attachment holes and spring-end holes, and did a long session of drilling/tapping. Both lower bolsters are the same, except for the mount holes in the center for the brake levers, which are opposite on each bolster.
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Finally, made up the bronze bearing blocks and adjustment screws which pre-tension the springs on each axle (there is a sprung vertical movement on the left end of each axle, then the entire truck has springs for movement of the axles as a pair - slick setup they did on them).
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Next up will be the rest of the framework for the trucks.... but first, off to the local steam fest later this week! Here is a link to thier site:
http://www.pageantofsteam.org/
 
Wow! You work fast. I spent two hours in the shop last night and only got two parts started. That all looks beautiful. Good job!

Todd
 
Wow! You work fast. I spent two hours in the shop last night and only got two parts started. That all looks beautiful. Good job!

Todd
Secret is being retired and spending an entire rainy day in the shop!!!:D
 
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