Up one level Neidrauer Adventures and 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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?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
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