Building Kozo's New Shay locomotive

[ths]

A few minutes? Surely that was only a few seconds. Hugh.

[crueby]

A few minutes? Surely that was only a few seconds. Hugh.

Only when hours seem like days, Spock!

[crueby]

Been a fun day in the shop today - got the eccentric followers mostly done. They started out as blocks of brass, taken down to a stepped shape with the mill. This step will form the bolt hole section of the followers. The bottom half is a shallow step, the top half has a post sticking up that will attach to the connecting rod. The curved part of the followers will be done later. (photo 1)

Once the steps were all done, the two halfs were clamped together, and a series of holes drilled down each side. The holes in the bottom half were opened up to 2-56 clearance size, the holes in the top half were tapped 2-56. The sharp-eyed among you will notice that I drilled 7 holes - the block was long enough for a spare set. (photo 2)

Next up was to round over the bottom of the bottom half. The block was clamped in the 4-jaw, on the rotary table set vertically. The inner edge of the block was centered in the chuck so that the milled surface would be concentric with the hole drilled later. A pass was taken with the mill down the piece, the table turned slightly, and another pass taken. This was repeated till the curve was done. On one side, the mill was offset so that the edge of the mill met up with the step. This whole process is simaler to what Kozo does in the book, except that he used a lathe bit on the late cross slide as a shaper bit, where I used the end mill. Same end result though. (photo 3)

Then, on the other side of the piece, the mill was offset the other way to match up with the step on that side. Then, the piece was turned around in the chuck so that the 1" at the chuck end could be curved like the rest was. (photo 4)

With the bottom half done, the top was bolted back onto it, the jaw against the inner surface moved out, and the block reclamped in the chuck. The same process was done on the upper curve, the only difference being that a smaller mill was used since the space was so narrow. (photo 5)

Next the chuck was switched over to the lathe. I center drilled for the tailstock, then slotted between each piece with the parting tool. It was only taken down though most of the posts. These slots will be guides for cutting off each piece later. (photo 6)

With the slots all done, a starter hole was drilled through the center and a boring bar used to open up the hole to match the eccentric cams. I left the fit a little tight, will let the lapping compound take it to a smooth sliding fit. (photo 7)

Last steps were to hacksaw apart the pieces one at a time, turning the face left on the chucked piece down smooth again and the proper distance from the bolt hole (final pieces are 4mm thick, so took it to 2mm from center of the hole and sawed off the next one). With the individual parts chucked back up in the lathe, the sawn face was taken down to make the part 4mm thick. Last photo shows the followers so far. Last step will be to notch them for the connecting rods and drill for the mounting bolts.

[crueby]

Getting close to having the eccentric followers/rods done. Continued on by notching the tops of the followers to take the connecting rod. The brass plate behind it in the first photo was just to keep it from flexing at the top during milling.

Second photo shows the set of followers all notched.

Next parts to make are the valve connecting rods. They are milled down to rectangular size with the fly cutter, then I started notching in the sides. The first side just has a shallow recess. (photo 3)

The second side has a much deeper recess - this has the effect of moving the clevis end out, so that the pairs of rods will line up in the center of the reverse gear link later. (photo 4)

After recessing the sides, the ends will milled for a slot to fit over the link. The cross hole in the ends will be drilled later with a jig, so that they all have the same distance from cam to link. (photo 5)

Last step for now was to drill/tap/countersink the bases of the rods into the followers. (photo 6)

Last photo shows the first pair done. After drilling the end hole, the sides will get tapered in and the ends rounded. Before that, I need to finish up the other two pairs...

[ths]

Phillips head screws!!! I guess they'd be rivets in another time. Good going on that, but why are there seven eccentrics for three cylinders? I've probably missed the obvious. Hugh.

[Roger B]

Great work as ever  How big are the slots you are milling in the forks at the end of the eccentric rods? From the ruler it looks to be around 2mm.

[crueby]

Phillips head screws!!! I guess they'd be rivets in another time. Good going on that, but why are there seven eccentrics for three cylinders? I've probably missed the obvious. Hugh.

The obvious is over there, behind you. No, other side... Oops, it moved again!

Couple posts back when I showed the followers milled out I mentioned there was a spate. The block was just long enough for 7, so got an extra out of it in case of a mistake while making them. I can throw it in the locos' trunk with the spare wheel I made way back!

Oh, and the phillips heads - only countersunk head 2-56 screws that I have. If original, just imagine the size the screwdriver would have been for the train!

[crueby]

Great work as ever  How big are the slots you are milling in the forks at the end of the eccentric rods? From the ruler it looks to be around 2mm.

Thanks!  The slots are 1/8" to match the links, so closer to 3mm. My tools/material are mostly inch based, though the book is all metric, so its a mix.

[Roger B]

Thank you. Did you have problems with deflection causing the slot not to be parallel? I also work with small machines and find that the end mills tend to push off to one side.

[crueby]

Thank you. Did you have problems with deflection causing the slot not to be parallel? I also work with small machines and find that the end mills tend to push off to one side.

Not on this one fortunately. I fed very slow, and had the cross slide locked down. Have had that issue before.

[Florian Eberhard]

Good Morning Gentlemen

That Problem does exist on any kind of milling machine (though the rigidity of a machine certainly has influence on how bad it is)
The problem seems to be that the milling flutes do bend easily. And that is getting worse with longer flute-length to diameter ratio.

There are some things that can help:
-cutting less deep in one pass
-using a smaller endmill for rough machining the slot
-using carbide endmills (they are around 3 times more rigid than highspeed steel endmills though they need a machine which is rigid enough or they will break very fast)
-drill the material away so the endmill only has to "finish" the slot

I sometimes also use the plunge-Milling technique but that also requires a finishing pass afterwards.

Cheers Florian

[Jo]

You can also use a slitting saw by cutting from the side

Jo

[crueby]

I got the other two pairs of the valve connecting rods for the followers milled out like the first set, and moved on to finishing them. First up was to drill the hole in the top end for the pin that goes through the tabs on the reverse gear link. To make sure all of the were the same distance from center of the followers, which is critical to make sure that the forward/reverse settings both give same valve movement positions/distances, a little jig was made with a plug to fit in the follower hole and a hole the proper distance out an arm. All six of the rods were drilled with this same jig.

Then it was time to taper the connecting rod arms - took a quick look at what it would take to hold them steady for the milling machine, and decided it was easier and quicker just to take them up to the grinding wheel and taper them that way. Last photo shows them after tapering and rounding the ends, ready for final filing/sanding them pretty.

At this point in the book, Kozo goes on to the linkages for the reverse gear actuator. Naturally, after all this time, I am going to take a side trip and get the followers installed, the valves timed, and make up a test stand and some temporary plugs for the piston drain holes so I can test this puppy on compressed air! Got a bunch of other things that will take up a lot of time the next couple days - league shoots, getting outside now that it is finally warming up and melting all that snow, etc., so it will be a couple days till next post which hopefully has a video of the first air powered run! Stay tuned....

[crueby]

I have not been able to get into the shop the last couple days, finally got going on installing the valve gear. Started out by lapping the eccentric followers to the eccentrics on the cranks. That all went well. I did run into one interference issue between the reverse gear pivot bolts and the conn rod tips - had to take off about half a mm from the hex heads on the pivot bolts. Once that was sorted, things started flowing. I started with the center piston, since to get the cover off the valve chest for that one you have to remove the right end cylinder. Below are a few pictures with the center pistons' valve gear all installed and timed. Lots o stuff in a very tight space - tough to get all the parts in and get the bolts started, but it is coming along nicely. Two more pistons to go, and I'll make up some temporary fittings so I can test run it on air (need to retain the reverse links at one side, plug the drain holes, make a block to hold the engine on the bench with the u-joints guided, and hook up the air hose - sounds like a lot but should not take too long. I hope. Maybe.)

[90LX_Notch]

crueby-

It's coming along nicely.  How much more until it is done?

-Bob