Up one level Neidrauer Adventures Photo Album » Building a Live Steam Locomotive - the Mikado Project » Section 11 - Valve Gear
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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 Successful clamping #2 - a backing bar against the lever, and only taking cuts from the left works.  Clamping attempt #1 for the left Tumbling Shaft Lever.  This did not have enough support to keep the part from moving under the cutter.  With the machined ends down and under the clamps, we take light cuts on the unsupported end.  Machining the lever for the engineers side. The problem with this clamping setup is that any twist or differences in height between the two legs results in us cutting the ends to the wrong height, the part unbends (moves) when the clamps are removed.  12-Nov-08 We start work on the Tumbling Shaft Lever.  There's no place to hold these castings! Everywhere we want to clamp we have to machine.  The completed milling operation on the union link.  Unfortunately we machined away the rod detail on the casting, it looks like one continuous piece without the step detail in it. We should have cut more from the other side in the first machining step, thus moving the centerline down. Oh well. The joys of working with castings. The casting measures to print...  With the union link flipped over and the machined surfaces on a parallel, we machine the other side.  Union Link: The machined reference surface.  Union Link: like every casting, the first step is establish a machined reference surface.  We decide the backside of the link will be ours.  We finally resort to clamping the combination lever in the vice. It is setting on a parallel and pinched between the vice jaws with two pins to insure a good line contact with the casting surface.  You can also see at the rod and how much was machined away, the centerline of the casting was offset more than we figured, so some of the rod body ended up getting machined to make the finished dimension.  29-Oct-08 Holding the end of the combination lever, setup number 2. With the inside corner angle plate confining the left-right motion and a jack screw to keep it from pushing down we try a skim cut on the top.  We'd like to clamp over the part, but the only clamping place is right where we need to cut, so that won't do.  clamping along the lever just bends the lever, we'd end up with a tapered surface if we tried it.  The part twists and flexes too much, this setup also does not work.  Taking a guess where the relative centerline is inside the casting, we machine the rod end to one-half the finished thickness. Now with both ends having a machined surface, we can turn the part and drill the holes in another step.  With the rod end machined, setting on a parallel and clamped in the vice, we need to machine the other end. We first try clamping it against the angle place and skimming the top surfaces with the cutter, but things moved around too much. It was also very hard to clamp the part without moving or introducing bend into the setup. This setup was no good.  29-Oct-08 Next: How to machine the Combination Lever.  Trusting the part is relatively straight along the casting parting line (the drawing show it as straight), we clamp the part in in the vice and machine the 'ears' of the rod end parallel.  ?Are we there yet?  How to measure the thickness of a part without disturbing the setup - measure over the whole thing and subtract the angle plate from the dimension.  If we unclamped the part from the vice to measure it we would lose accuracy since it would not locate the same way again.  Without any support, the cutter was pulling the rod up and would break it if we continued.  We bolt a stop to the inside corner plate which prevented this from happening.  Finally we were able to finish this machining operation.  With two parallel machined surfaces clamped in the vice, we try to machine the other end.  Leaving the rod end unsupported we not acceptable, so we take and inside corner angle plate to confine the motion.  With this setup the end cannot move front to back (relative to the table) but the cutter can push it down or if it grabs, pull it up.  We take very light cuts.  Taking our best guess where the centerline of the Radius rod is inside the casting, we clamp it in the vice, skim cut until we just barely touch the other end.  22-Oct-08 There's a lot to be said for machining the valve rods out of solid instead of using castings. For one thing, there is no straight surface anywhere on a casting to help get you started.  The castings have taper (draft) molded into them and that's when you have a good part that does not have coreshift or flaws in it.  ?Where do you make the first cut to reference all the other surfaces from? How are you going to hang onto the casting?  We spend a lot of time thinking and discussing how to proceed.  The finished Eccentric Cranks with the pins pressed in. We put the end of the crank on one of the shop lamps to warm it up and make it easier to press the pin in. 15-Oct-08  The finished eccentric crank pin.  We added a shoulder on the back to keep the pin from being pulled through since it is only held with a very light press fit in the soft aluminum casting.  Here's how we we make sure we hit the right length on the pins.  Usually we'd use a carriage stop but I don't have a micrometer on mine and who has a .781 long piece of material?  Instead we use the depth mic and measure from the end.  Threading 4 - After returning the crossslide to zero, advance the cross-compound and start the next cut.  Threading 3: At the end of the cut bring the carriage back to the beginning of the cut,  advance the crossslide back to zero.  Threading 2 - a two-handed operation. Left hand on the cross-slide to quickly retract, Right hand on the threading lever to dis-engage at the end of the cut. At the end of the cut simultanously disengage the half-nut and retract the cross-slide.  Threading the 5/16-24 thread.  Turning the eccentric pins.  I love working that 12L14 leaded steel, it gives such a nice finish on my small lathe.  If I had used regular 1018 cold-rolled, the finish would be rougher.  1-Oct-08 The finished eccentric cranks  Using a slitting saw to cut the slot in the crank.  We had previously lightly scribed the centerline of the holes accross the casting and used that line to clamp the part horizontal.  Drilling the clamping holes in the crank with a favorite setup - angle place, locating plug (under the clamp) and C-clamp.  With the crank located on the plug mounted on the angle plate, we use a scriber to check the scribed line and make sure the crank is horizontal before clamping it. 1-Oct-08  The crank on the close-fitting plug, which is bolted to the angle plate.  We will use a couple of larger spacers to mount over the bolt/plug and hold the exccentric to the plate with a clamp.  The plug mounted on the angle plate.  When mounted on the milling table, we can indicate the plug to locate the centerline of the hole.  The eccentric crank after the drilling and boring operations. 1-Oct-08  Using a larger end mill to enlarge the hole and speed up the next boreing operation.  Pilot drilling the holes. After enlarging we will bore the crankpin and main pin holes. 23-Sept-08  23-Sept-08 One last thing - drill the roll pin alignment holes and now the parts are ready for paint!  16-Sept-08 Four sets of trunion blocks. Two for me and two for a friend who is also building a mikado.  16-Sept-08 With the trunion gently pressed onto a pin held in the chuck, and the live center holding the other end we maching away the excess and lumpy solder making the pin smooth again.  By the time we got to the last one, My silver soldering skills had improved. Here I've hardly wasted and silver but have a nice neat joint.  The silver solder filet looks okay, but I'm still having trouble getting things hot enough with the plumbers torch and MAPP gas.  16-Sept-08 The results after silver soldering one: the alignment pin is stuck. After removing the pin with a hammer, we think this very close fitting pin carburized in the heat, jamming it up.  We switch to a slightly smaller pin for the rest of the parts.  Using two parallels to seat the pin flush in the back of the trunion.  10-Sept-08 Assembled Expansion Link assembly.  The 1/4  10-Sept-08 Turning the trunion pins from oversize 7/16  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.  13-August-08 Finish machining the Expansion Link Block slot in the expansion link.  We used the table extension on the rotary table to achieve the correct radius.  The 4-flute cutter was brand new and razor sharp when we started. By the fourth part, it was already dulled.  This hardened stainless steel is tough stuff!  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.
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