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| xo18thfa:
The flywheel is a two step turning job. Here is the drawing: Any metal, except aluminum will do for the flywheel. Aluminum is probably too light. The flywheel has to be a bit robust or the engine will run very "jerky" on the track. This flywheel is bronze. Chuck a 9/16" length of 1-3/4" or 2" diameter stock and turn the outside. Grip the flywheel by the inner recess to face the back and turn the rim. Break the sharp corners on the rim with a hand file. Polish the rim to VERY high luster. Everyone will see it. Clamp the flywheel in the mill vice and tap for a 6 x 32 set screw. Same operation as on the wheels. The crankshaft is a 3 piece fabrication. Here is the drawing. The first piece is the main shaft. Cut a 3-7/32" length of 5/32" diameter ground and polished stock. Drill and tap the end of the shaft with 4 x 40. Also cut a 5/16" length of 1/8" diameter ground and polished stock and tap with 0 x 80. This is for the wrist pin. "Loctite" machine screws into the ends of the shafts. Be sure to use high quality "ground and polished" stock for the crankshaft and axles. G&P is exact diameter, perfectly round and exceptionally smooth. Regular rolled stock will work, but G&P is superior. Use either free machining 12L14 steel or 303 stainless. Next, face off a 3/16" length of 1" diameter stock for the crank web. This web is bronze for a nice contrast. Center drill and tap with 4 x 40. Secure the web blank on a piece of scrap material in the mill vice. Tap with 0 x 80 exactly 5/16" from the center of the main shaft. Trim the 4 x 40 and 0 x 80 machine screws to a length of 5/32". "Loctite" the crank web to the main shaft. Chuck the main shaft and crank web in the lathe. Turn to final diameter and width. "Loctite" the wrist pin into the crank web and the crankshaft is done. Use Loctite #242 (the red stuff) for these applications. #242 is a high strength threadlocker for close, smooth finish surfaces. Autozone usually carries #242. Time to assemble the rolling chassis. Trim the length of the axles about 1/32" proud of the bearings on both sides. The back-to-back measurement on the wheels is exactly 1.574". While putting the chassis together, bolt on eight angle brackets for the footplate. The angle brackets are 1/4" x .025" brass hobby angle drilled for 0 x 80 machine screws. Put a drop of light machine oil on each bearing. It will roll like a champ. Next time is the start of the motor unit. |
| xo18thfa:
The motor for Regal is a single cylinder, single acting oscillator. The bore is 7/16" with stroke of 5/8". Oscillators are easy to build and very powerful. "Chip" is the first oscillating locomotive I built, its been running strong for years. Here is Chip at the National Summer Steamup, I think in 2013. https://www.youtube.com/watch?v=olNsRBN_M1I The first part is the engine standard. It consists of the portface and manifold. Here is the drawing. The first step is clamp some 1" x 1/8" brass to the milling table. Profile the sides and cut a shallow recess to receive the manifold. If you don't have a 1/4" ball end mill bit, hand cut the recess with a round file. The manifold is 1/4" diameter round brass. Drill and tap both ends with 3/16 x 40 as deep as possible, but don't break thru. Soft solder the manifold to the portface. Flip the standard over and drill all the holes. The two #43 holes at the top of the standard just break into the manifold. Cut the standard off the stock. The standard is not quite finish yet. The finish up comes after the cylinder build. The cylinder is a 1-5/16 long piece of 7/8" diameter bronze. It is usual practice to make mating surfaces from dissimilar metals. So the standard is brass with a bronze cylinder. There are several grades of bronze. Alloy #932 is the most common form. It is a general purpose bearing bronze that is vert durable easy to machine. Here is the drawing for the cylinder and top cover. Chuck round cylinder sideways in the lathe and machine one side flat. Machine the other side and port face in a similar manner. Clamp the cylinder in the mill vice to drill the port hole and tap for the pivot pin. Make a very small center drill on the bottom of the cylinder for the bore center. Since the cylinder is an odd shape, it will not chuck properly in a 3-jaw universal chuck. Use a "wiggler" center finder to center the cylinder in the 4-jaw independent. This is the wiggler I made many years ago. Use the wiggler to adjust each chuck jaw to center the cylinder. This is enough for now, so we will end here and finish the cylinder next time. |
| xo18thfa:
With the cylinder block centered in the 4 jaw begin drilling out the bore. Step drill with about 3 or 4 drill bits to 3/8". Then switch to a boring bar. Take several light cuts until the bore is about .010" under 7/16". To size the bore exactly to 7/16" use a reamer in the tailstock chuck. Feed the ream slowly with the lathe set at its lowest speed possible. They say you don't have to, but I heavily oil the reamer. Turn the bottom end of the cylinder to remove excess metal. Even though the ream leaves a very good bore surface, it's still not good enough. The bore need "lapping" to remove the microscopic burrs left by the ream. Turn a piece of wood, either maple or oak, to 7/16" diameter. Obtain some fine, #280 grit, grinding paste. Chuck the wooden lapping rod in the lathe chuck. Apply some grinding compound to the wood lap. Slip the cylinder on and start the lathe. Work the cylinder back and forth on the lap for about 15 to 20 seconds. That's all it needs. The process requires a lapping rod that is softer then the cylinder, in this case wood. The grinding paste embeds itself in the softer lapping rod in order to hone the cylinder surface. If a harder lap was used, the grinding paste would embed in the cylinder wall and cut the lap. The cylinder bore must be as true as possible before lapping. Lapping will not correct a bad bore. When finished, the bore will have a very smooth frosty surface. Now lap the portface on the engine standard and cylinder. Do this by taping a quarter sheet of #320 wet/dry sand paper tightly a flat surface. Oil the sand paper and gentle grind the port faces with a circular motion. Repeat the process with #400 grit and again with either #1500 or #2000 grit sandpaper. If you don't have the finer paper, #400 is good enough. It will just take a bit longer for the engine to "run in". When complete the portfaces are dead flat with a smooth frosty surface. Finally time for the piston. Here is the drawing: Fabricate the piston with 3 parts, the big end, piston rod and piston. The big end is the hardest part to make. It is 1/4" square stock. To get the big end stock centered in the 3 jaw chuck, make a split collet that fits over the square stock. Cross drill the big end with #30 to fit the wrist pin. Chuck the stock with collet in the 3 jaw. Drill and tap with 2 x 56, turn the end a bit then part the big end off the stock. The piston itself is alloy #303 ground and polished stainless steel. The G&P stainless fits perfectly in the reamed and lapped cylinder bore. Drill, tap and turn according to the drawing being careful not to mar the surface. Oil the cylinder and try a test fit of the piston. It should slide close but free. The piston should slide freely when blowing in the portface hole by mouth. If it's too tight, give the cylinder a few more seconds on the lap. When all is ready, soft solder the top cover on the cylinder and make the pivot pin. Assemble the motor onto the frame. The cylinder spring is 1/4" long, 1/4" diameter, 0.020" music wire. The exact spring is McMaster Carr part number 9657K259. An equivalent works fine. Oil everything in preparation for the air test. Put a drop of light machine oil between the cylinder and engine standard. Hook up a regulated air source to the manifold and block up the engine. This engine runs fast on 6 or 7 PSI. Run the engine for about 30 minutes on air. Stop every 5 minutes or so to disassemble the motor and clean it. Do a "dyno test" with a finger against a wheel. It will take some effort to bog the engine down. https://www.youtube.com/watch?v=2yZPM22uW80 Next time is the footplate and fuel tank. |
| xo18thfa:
The footplate serves as the basis for mounting the boiler, cab and burner assembly. It also provides additional rigidity to the rolling chassis. By this point a few errors have probably crept into the Regal chassis, making it difficult to fabricate the footplate in one operation. Do the footplate in stages, using "fit one part to the next" method. The footplate is from 1/32" sheet steel or brass. It is possible to mill the footplate as done with the frames. The thin material is just as easy cut with a fret saw and hand filed out. Break all sharp corners with a small chamfer or round over. Here is the footplate drawing to start: Remove the wheels, axles, gears and motor parts from the chassis. All that will need paint eventually anyway. Turn the frame upside down on the footplate and directly transfer the mount holes. Next part is the fuel tank. Regal has a single pot, gravity fed, alcohol burner. The goal is to hide the fuel tank as much as possible under the frame. It would be easier to make an over sized tank and install under the rear end of the footplate, but that's what I am trying to avoid. So the Regal tank is rather flat and as long and wide as possible. The flatter profile should also prevent starvation to the burner pot as the fuel level drops. Previous tests determined that Regal should burner about 0.8 milliliters of alcohol per minute. For a 5 minute warm up and 20 run, that comes out to a 16 milliliter capacity requirement. Doing the conversion, that is about 1 cubic inch. At first I thought that would be possible with a single tank. But math and theory usually never work out, so I went with 2 tanks. A large tank in back and a small one in front connected with a run-a-round tube. The tank is silver soldered from 1/32" thick sheet brass. The rear tank has an overall dimension of 2-1/8" wide, 1-1/8" long and 11/16" height. Cut a strip of brass 5/8" wide and bend into the rectangular shape and silver solder. Cut the top and bottom sheets rather oversized. The burner pot itself is a 1/4" nominal (3/8" OD) copper elbow. Trim the elbow so it is a smidgen above the top of the tank. The center of the burner pot is about 1-3/8" in front of the tank. When installed this will put the burner pot about half way between the rear axle and the center gear axle. Silver solder a length of 1/4" brass tubing for a fill tube. Silver solder two #2 x 56 machine screws for mounting the tank to the footplate. On the bottom of the tank, silver solder a length of 1/4" tube for an overflow. Cut the top of the tube at about a 30 degree angle and push it in until it hits the top of the tank. This will overflow excess fuel out of the tank at about 1/8" from the top. At this point I changed my mind and added the additional tank in the front. This tank is from 5/8" thin wall square brass tube with the ends silver soldered on. As an alternative, make the forward tank with the same method as the rear tank. Connect the front and rear tanks a run-a-round tube from 1/4" or 5/16" brass tube. The fuel tank is a real "cut to fit" job, so no drawings per se. It is actually easy to silver solder the tank. Once silver solder cools, it re-melts at a higher temperature, so there is no worry about the job falling apart on subsequent solderings. Finally, stuff the burner pot with wick material. Wicks are kind of an art, not too tight, not too loose. Insert the wick well into the rear fuel tank. Ordinary cotton candle wick is an excellent material. Just don't ever let the tank run dry. An alternative is fiber glass. Shape and trim the wick to get a 1-1/2" to 2" flame. Test burns show this tank will work. It's good I added the front tank, now it has a good 25 minute burn time. With a flame of 1-1/2 inch height, the fuel consumption is down to about 0.60 milliliters per minute. And it burns hot. Next time is the boiler. |
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