a newbie's take on the A3 switcher

[Kim]

No, I haven't run it on Steam yet   

But I have run it on air many times! And that's a lot less messy.  Maybe someday...

If you have any other questions about my cryptic drawing or how I did something, feel free to ask.  I'll do my best to decode what I think I did, as much as I can remember anyway! 

Yes, it is a complicated part that's hard to place in the bar stock.  And it requires MANY steps to compete. But they are REALLY cool once you get them done!

Good luck,
Kim

[Pogo_proptie]

i did not thrust myself to understand everything to offset the oversize, just i just thinned it to 2inches and will follow the book. but your order of operations seems logical so i'll steal some of that 

POGO

[Kim]

That should work too.  It just seemed like more work to me to turn it down to 2" when every side is being machined anyway, but that was me.  I have no doubt that will be quite successful for you!

Keep us posted...

Kim

[Pogo_proptie]

on fig 14-4 i clearly see the bottom shaved a 3/64th. but neither you nor blondihacks seems to have made the cut.. i think i'm going crazy here.. what am i missing.

I made it already, and I turned to go nogo going from 272 to 276.5 i think. so tomorow i put the 4 jaws and yolo this but i'm still happy to ear your call on the flat bottom

POGO

[Kim]

If you look at my diagram, that 1/16" allowance I leave at the bottom is the same as Kozo's 3/64", I just chose to make it a little bigger (1/64" bigger) because my stock was 42 thou bigger than his.  And I chose not to mill the 3/64" off the bottom (or the 1/16", in my case) and make a flat spot on the bottom because I didnt' need to, and I just cut it off when rounding the cylinder in that later step.

Or, at least, that was my theory.  In actual fact, I ended up needing to make the bottom of the cylinder flat, which I did in post #1071.  If you look about 5 pictures down in that post, you can see where I figured out I needed the bottom to be flat in order to use it as registration for some of the required steam passage holes.  So there you go, Kozo was right, yet again! 

Although, in my defense, it saved me some angst and worry in that I didn't have to worry about cutting down too far on the bottom.  Because by the time I flattened the bottom (i.e. cut that 3/64" off) I already had turned the 1/8" diameter circles at each end of the cylinder, so I knew exactly how far down I could trim the bottom.  Made me feel like I had a little more insurance that I wouldn't botch the part - at least not in THAT spot... 

So go ahead and take off the 3/64" on the bottom. I did, I just happened to do it later in the build. 

Kim

[Pogo_proptie]

cool cool cool, today is bore day.. i made my plug and as soon as the kids leave or school, the 4 jaw is going on

Pogo

[Pogo_proptie]

one other thing that's trickling my brain, why is the ''left over 10 thou for truing'' taken from the far side(exterior to the train). i feel like i can't really do something if the bore was done to .875 at the start ?

again i feel kinda dumb and don't see the final picture yet but you are so helpful that i'm letting loose

thanks kim

POGO

[Kim]

Not sure I can help you with Kozo's thinking here, but I can tell you mine.

The 10 thou is left on the overall dimensions.  But once you've made the two main flats - the mating surfaces for the Valve and the Steam-Tee, the center measurement for the 0.875" bore is taken off of that.  The references for everything are now based on those two flat surfaces, so any remaining truing allowance is, by definition, on the outside and bottom of the cylinder.

For me, the "turning allowance" was for measurement error and machining error while creating the machined surfaces.  Once you have machined flat surfaces to use as reference, it becomes just extra material to remove.  It may be more than then thou, or it may be less by the  time you have the reference surfaces machined flat.  But it gave you some wiggle room.  And after you've got reference surfaces, you don't need wiggle room anymore.

Kim

[Pogo_proptie]

I want to validate one more thing. Here is where i am so far
https://imgur.com/a/iXp6IlG

2 cylinder blank. Or wall-e's cute little face you decide.

Next step is the steam channels and such. I'm not perfect on the dimensions of the tip shelf. So my thinking is not make the features relative to the top surfave(wich seems to be what the plan requires) but to 0 my things on the same 2 flats that indicated the bore itself. And remake all the holes with the good dimensions. That way they will line up with the rest of the valve and things all attached to the frame.

I hope this is clear. Thanks again

[Kim]

2 cylinder blank. Or wall-e's cute little face you decide.

Definitely Wall-E!   

Next step is the steam channels and such. I'm not perfect on the dimensions of the tip shelf. So my thinking is not make the features relative to the top surfave(wich seems to be what the plan requires) but to 0 my things on the same 2 flats that indicated the bore itself. And remake all the holes with the good dimensions. That way they will line up with the rest of the valve and things all attached to the frame.

I hope this is clear. Thanks again

That should work fine, assuming your actual dimensions of the valve face aren't dramatically off, which they likely aren't.
But do keep in mind that the valves aren't centered over the cylinder bore.  They are offset to the outside edge of the cylinders.  One of the many reasons the cylinders stop being interchangeable.

And of course, the steam passages on the inside flat of the cylinders (the side that mates with the steam-tee) aren't centered on the bore either.

Kim

[Pogo_proptie]

Yea i saw that. My intent is to 0 on the same edges the bore was made and then offset to where the plan has them. And not to find the center for x and y on the top edge wich turned out not as good as i had hoped. That way the errors should stop there instead of propagating and messing up the cross head and valve alignment

[Pogo_proptie]

well i'm long between posts but not gone.

here is my progress so far.

the cylinders were making me very nervous and i bough enough bronze to scrap but made it work.




the shapper operation


so far so good

steam chest was next



no such thing as too much solder


then it was the multiples cylindre ends with the fixture to make the 6 hole patern


and new toy i got a powder coat going in what was formely my observatory,


first test was encouraging

next is the steam manifold


this part was not really fun noise wise. notice the chuck in a chuck for cool points


after all that work and making the second hole i saw WD40 coming out of the 1ST hole.  woops my silver joint was bad.

so this was the only solution

managed to get it hot enough to separate it and made it again the next day (the joint, not the piece)


i love those skecthy old school setup

i'm pretty pleased with this one


i'll post the rest soon but it's late now,

hope to see more action in here it's been slow lately
thanks for coming by

POGO

[crueby]

Thats a lot of parts and work!   

[Kim]

Wonderful work!  The cylinders look great, as does the steam-tee.   

Great save on the solder job on the steam-tee.  That is always a bad feeling when you think you've got something done, then realize, you don't...  But you handled it, and it looks great!

Those are all very tricky parts!
Kim

[Pogo_proptie]

a couple more

 this is the cross head start, very cool process by kozo here. such a clever dude


my less than great fixturing solution


family picture of the piston and xhead. as always, nothing i hate more than thin stainless parts.

for the locking the piston rod part i just dremeled a 1/16th drill bit and superglued it in the piston.

this is the part where adult langage was used

the cut was too agressive on annealed brass and it grabbed on the last pass...

bracket continues




this one was fun. i went with the boring head until the scribbed line and measuring the diametre on the aluminium


family reunion of parts


i am a bit farther and about to start the valve train but it will be the next big update (this is getting very difficult i think) and i fear this is when my newbie status will come home to bite my ass.. we'll see

POGO