Pennsylvania A3 Switcher (Kozo)

[crueby]

A clear coat will definitely help on the 12L14. I used 12L14 for the wheels on my Kozo Shay, and they started to rust pretty quick. Sprayed them with clear lacquer, had some the kind sold for brass door knocker hardware, worked fine. After that started using 303 stainless for just about all steel parts.

[Kim]

Thanks Chris! 
Kim

[Kim]

Chapter 17.6 – Union Links

Today’s project was to make the Union Links.  What are Union Links you might ask?  I found this chart (compliments of Wikipedia) that helps define all the elements of the Walschaerts Valve Gear.  And interestingly enough, Kozo is using all the standard terminology.  Go figure!  So where I said “I’d call it this or that” I was wrong.  Well, not wrong that I’d call it that, but I’d be wrong in what I called the part   This Kozo guy is pretty smart!

Anyway, the Union Link is part number 11 in this drawing, which can be found, along with a nice writeup, at: https://en.wikipedia.org/wiki/Walschaerts_valve_gear

As you can see, I’ve still got a LOT of mechanism to go!

The union links were made from 1/16” sheet steel.  I have been using 4130 for my sheet steel.   I had a scrap piece I was able to cut these two pieces out of. Here I’m getting ready to sticky tape them together to make them both at the same time.


I added another 1-72 hole to the jig and shaped the pair of them, like so:


Then use a filing button to round the ends, reamed the holes to 5/64” and there you have it.  Couldn’t be simpler, right?


That was an easy one.  Not sure there are too many more easy parts remaining!

Thanks for stopping by!
Kim

[cnr6400]

Might be simple, but they sure look good! 

(the designers in the days of steam may have called it a union link because "sausage link" was already taken)

One thing's for sure, Kozo did his research, and knew his model subjects.

[samc88]

Nice work, how did you do the stress relief, did you just heat up and let them cool or did you have to hold them at a certain temp for a while?

[Kim]

Thanks CNR!

Nice work, how did you do the stress relief, did you just heat up and let them cool or did you have to hold them at a certain temp for a while?

My unscientific method was to bring them up to a cherry red for about 5 min, then let them cool down slowly.  Since these were fairly small pieces with very small crosssection, I only did about 5 min.  But for larger, thicker pieces I hold them at temp longer.  I'm sure a more controlled high temp and a slower cool-down would be better.  Clearly, it's not as controlled as a heat-treating oven would be.  But I have found it to help significantly, regardless. That's how I learned to do this step - actually, people on this forum told me I needed to; that's why some of my parts came out looking like a potato chip!  And after doing this stress relief it really improved!

Kim

[samc88]

Thanks Kim, I'll give that a go when i next machine some valve gear bits, I got lucky when doing my coupling rods I think!

[Kim]

Chapter 17.7 – Link Bracket

The next part is the Link Bracket which will connect the union link to the crosshead.

The blanks were cut from 1/16” steel (4031 same as the union links).  Here I’m getting ready to double sticky tape them together.


After they were connected, I drilled three holes – two for attaching the bracket and one for the union link.


Then on to the jig.  Had to make a few new holes for this part.  In this position, I trimmed the parts to length then milled the neck on the bracket and trimmed the round part down so it would take less filing later.


Now at an angle in the jig to cut the sloping sides of the bracket.  Here’s the first side done.


After doing the second side I rounded the corners with files and then we’re done!


Thanks for looking in!
Kim

[RReid]

I'm impressed by your work on these small parts, Kim. Valve gear links aren't as sexy as some other parts, but they're just as critical to the smooth operation of the whole. Plus, they are among the parts that "get looked at" the most! It's obvious from the care you take that you understand both points.

[cnr6400]

 

[Kim]

Thanks Ron and CNR,
I do try to take the same level of care with all parts.  I kind of look at each part as its own project, and I'm sure it shows in my snail's pace.  But as long as I'm having fun, right? 

Kim

[Roger B]

Lots more fiddley and important parts        I have also found slitting saws better than end mills for slotting the ends of rods.

[Kim]

Chapter 17.8 – Radius Rods

The last several days have been spent working on the Radius Rod. This is another part of the valve gear that connects the curved expansion link bracket to the rest of the mechanism.  I assume that’s why it’s called “Radius Link” because it follows the radius of the curved expansion link part (which will be coming up shortly), but I don’t really know.

This was made along the same lines as the combination lever with just a few differences.

After bringing the part to a 0.200” square cross-section, I drilled the holes at the appropriate locations.


Then used a slitting saw to cut the slit in the end of the rod.  This part has a much deeper slit than the previous part.


Next, on the jig, I plunged the mill down at the right spots to create the neck of the small end.


Using the 5/32” mill thinned the length of the part except for the very end where the screw was holding the part in place.


Then I added a clamp to hold it down and removed the screw.  That allowed me to complete the thinning job to the end of the piece.  I got smarter and for the second part, I took down the end first, then did the long middle section.  I had no mishaps, but having the thicker neck holding it in place made for a little less chatter while milling the end, and perhaps most importantly, it made me feel more secure!

Here I’ve completed the thinning job.  It looks like there’s a big thickness difference between the previously completed section and the tip that was just completed.  But honestly, it was barely noticeable in real life, and after a little filing/sanding to remove the tool marks, you can’t tell at all.  I think the picture is seeing a ‘grain’ difference in the direction it was milled or something.


Apparently, I didn’t get any pictures of tapering the radius rods, but I did do that.  I used the jig, same as on the other part, though the angle was VERY shallow for this. But it worked well.

I made some 3/16” filing buttons to use in rounding off the small ends and used the 0.200” filing buttons from before for the split ends.


And after a little buffing to clean up the tool marks, here are the completed radius rods:


Still, a dozen or more parts to go in the saga of the valve gear!  And most of them are fairly complex little parts too.  So I’ll still be doing this for a while.

Thanks for checking in on my progress!
Kim

[crueby]

Great job on the parts, following along...

[Don1966]

Awwww a craftsman at work, nice work Kim……


 
Don