Pieces of my current project - Tich

[GWRdriver]

My current main project is a Double TICH, a 7.5" gauge locomotive which is a 2X size rendition of the LBSC Tich 0-4-0 locomotive which was 3.5" gauge. At the moment I'm working on the running gear, specifically the connecting rods; the material is 303 stainless, my first use of stainless for rods. I elected to machine the rods all over as far as a I could while still connected to the parent metal. I did this because any machining could be done all around by holding/clamping the parent bar, which would also act as a stiffener, rather than have to contrive ways to hold the soon to be flexible rod without damaging it. The rough machining would then be followed by some final machining, boring the journals, radiusing the ends, then hand finishing. So far so good.

HOWEVER. . . when the last tendons of metal connecting the rods to the bar were finally cut I was surprised to find that they bore a much stronger resemblance to this photo than any connecting rods I had seen before:

For size comparison, the rod journals are 8.500" center to center and are .500" wide at the thinsection and there was a bow at the center point of almost 1/4". I knew there would be SOME deformation but this was over the top. I think one of the reasons for this was that I took far more off the front of the rods than the back. I took equal amounts of material from the top and bottom of the rods and there was no deformation in that axis at all. In any case, some careful pressing with wood blocks in the vise and an occasional coaxing with a rubber mallet put them back into line, followed by radiusing the ends and boring. Hand finishing with files and emery will follow. So far so good.

 

[hitandmissman]

Very nice looking rods. You are off to a good start.

 

[tel]

Yep, very nice pair of rods Harry, and certainly an interesting way of winkling 'em out of the parent bar - one that I would never have thought of.

 

[gbritnell]

A nice looking set of rods. When I'm making something from a bar I work similar to what you have done. I'm really surprised that they sprung that much. Stainless is usually quite stable unless you weld it.
gbritnell

 

[hobby]

Looking Good..

Looks like in your above, photo, that you cut the ends square, did you file the ends to get the radius'?

I like how you got the smooth transistions, from the straight section, to the inside curves, and the outside radius' look very nicely done.

I am drawn very much to the transistions, it makes me want to start machining pieces with (non square) smooth transistions.

Nice progress...

 

[kcmillin]

Verry nice parts. I am intrigued by the outside radius as well. with it still attached to the parent bar, how was that cut?

Kel

 

[GWRdriver]

One of the things I find umm . . bothersome (?) about this format is that messages you might need to respond to can get right by you if you don't see them come up on the new message marquee. Thanks for the compliments guys, sorry to be so long to respond.

On the radiusing of various surfaces . . . one of the reasons I kept the rods on the parent bar was to able to hold them for thinning and radiusing. The transition radii on the top and bottoms of the rods were done with a boring head all at one setting of the mill. I worked out the exact center points on Cad. The transition radii on the faces of the rods were also done with a boring head, also figured out on Cad. The rods were then thinned down with a side cutting end mill and in the end came withing a thou' or two of fairing into bored radii. At this point all surfaces have a milled finish EXCEPT the end radii and at this point the rods were cut from the bar and straightend. It was interesting (and challenging) to find that much of the deformation took place just inside the end bearing bosses where it goes from full thicknss to thin web.

Once everything was straightened to my satisfaction the end bosses were bolted end for end, one at a time (through the bearing bore), to a rotary table which was indicated in and the outside radii were milled. They were only roughed in the first photo. The milled end surfaces also faired out to within a few thou' of the bored radii which all makes final finishing much easier. I am currently in the process of working out tool marks with Swiss files and emery cloth which is much more of a job than it appeared.