Section 11 - Valve Gear

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Neidrauer Adventures and Photo Album » Building a Live Steam Locomotive - the Mikado Project » Section 11 - Valve Gear

Completed! Valve Gear. Lots of little levers: Link Trunion, tumbling shaft lever, eccentric crank, eccentric rod, radius rod, combination lever, union link, lifing link. July 2008-January 2009

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Don't they look nice? The link blocks fit nicely into the Expansion Links.

1-Sept-08 Machining the Link Blocks to correct height. This was the last setup for the rotary table.

Using the slitting saw to cut the link blocks from the hunk of bronze stock.

The low-tech method of separating the the link blocks! We'll change setups on the table and finish machine them to size.

Boring the .251 holes.

Using a tapered pin to center the expansion link. Two of the links we machined were Tim's. His pieces has a slightly larger slot so we couldn't use the same locating pin we used on mine. We also had to put one piece back in and machining it larger to match the other piece, thus the use of the tapered pin.

Using a small bore adjustable feeler gage to check the slot width. Tricky things to use because you have to hold them perpendicular to the part in two axis (l-r and front-back) and rotate it between your fingers, also judging by feel the amount of 'drag' the gage has on the part. Then you measure the gage with outside micrometers, going for the same amount of drag to get your reading. I still have some practicing to do before I can repeatably read it like Bill can.

27-Aug-08 Cutting the link blocks from a piece of bronze.

With the stock clamped down, a skim cut is taken from the top to true it to the table surface.

27-Aug-08. Without disturbing the table, we re-use the same setup from the expansion links to cut the link blocks. The bronze stock is clamped to the table and centered under the cutter. This unique curved piece of bronze was actally a scrap piston ring segment from one of the Frisco 1522 overhauls. A Very Cool connection for me personally, since I crewed on the big mountain when she ran.

What a nice batch of Expansion Links!

20-Aug-08 Although I only need the two expansion links for my locomotive, I agreed to machine Tim's expansion links since I already had the setup in place. Here Bill is checking the diameter of the bored hole from the bottom of the part. We need the hole to be .251 (not .250 or 1/4

The finished expansion link. I'm very happy with the finish inside the slot - you can see the reflected surface in the picture. A good finish is important since this is a bearing and moving surface, a rough finish will wear out the Link Expansion Block which goes inside it.

Here's a pretty broad shot of all the tools and support things for this fixture.

Another part, another fixture needed to hold it! In order to get a smooth and parallel inside surface on the expansion link, we build an extension table on the rotary table. The aluminum plug is a snug fit into the center of the rotary and the sacrificial top. Two holes in the top are aligned with the t-slots in the table to clamp it down. The rotary table is dialed in using the coaxial indicator and the DRO axis' are zero'ed. I love my coaxial dial indicator - just chuck it up, put the machine in slow backgear and move the table handles until the indicator needle stops moving. Bingo! you are over the center!

30-July-08 While we had the link in the vise to bore the bolt hole, we moved over .797 and up 3.250 and instead of landing in the middle of the link, we were on the edge. That's not good.

Further investigation revealed the 40 degree notation was incorrectly referenced on the print. The machine shop correctly followed the print resulting in the 'leg' of the link ending up like a dog's hind leg at the top and not the front leg. The part is thicker than needed at the 3/8

Checking the bored hole with and oversized (.251) dowel pin. The hardened stainless finished up nice and smooth, which is good since this hole is also a bearing surface.

The waterjet process leaves a tapered edge, like plasma or flame cutting can. With the expansion link clamped up, we center on the bolt hole to bore it out.

30-July-08 Putting the squeeze on the Expansion Link. My friend Tim M. who is also making a Heavy Mike had his expansion links cut from Stainless Steel by a local waterjet cutter, All Cut, Inc. He gave them a call for me and they were able to fit my job in with one they were working that day! I got my parts in 24 hours!

Waterjet cutting does not leave a hardened edge like Laser or EDM. My pieces has a slight curve to them, probably in the original stock. A couple of spacers, a dowel pin and some pressure in the vise took care of that.

Without changing the setup or the most importantly the center zero, we move out and drill the four bolt holes, but not the two locating dowel pin holes. We'll do those later.

We decided not to follow the assembly instructions provided and do our own thing. Setting up a stop in the vise for all the parts, we center the reamer and zero the DRO on center.

23-July-08 We start a new section! Yeah! Starting with the Trunion Link Supports, we trim the sprue end off and machine the ends to a uniform height. Like all castings, these thin brass castings are slightly warped, but a few hits with a soft hammer strightened them out before clamping in the vise.