1/3-rd scale Myrick Model H vertical hot tube engine
- Thread starter myrickman
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I always like pouring main bearings instead of brass sleeves to make fitting easier and to ensure alignment. Here is the fixture I use to align the axis of the bore with the mains. For the initial pour, a sleeve goes on the opposite side to center the crankshaft mandrel in the saddle. I had this fixture made for another restoration so all I needed to change was the white plastic cylinder which fits in the bore.
Finished pour with caps and saddles dressed for a test fit. Still need to drill the caps for the oil cups and make the oil grooves. We're getting closer; the rod is at the foundry and should be done by next week. The rod will also get a poured main journal bearing.
Since the cam is a simple symmetrical one, it was made on the rotary table. This profile is similar to the original. I used a lift angle of 100 degrees to give me some leeway with the lash and holding the governor latch in. First I made a trial piece from blue proofing wax and it looked AOK. Still some angst about putting the cutter to the metal.... Zero degrees on the table was the high spot and the diameter of the stub on the gear side. Then the table moved 0.165 in. The table rotated to 50 degrees and a horizontal cut made. Then the table was rotated to the 310 degree position and another horizontal swipe made. From then on one rotates the table until the two flats meet up and viola. This is the profile on the original...not very elegant is it?
I was pleased with how it turned out and when installed on the engine, the little 3/16 lift rod had no problems following it. Actually, the bottom of the lift rod gets a rectangular shoe, so that should make the lift smoother.
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Spent this weekend making nuts and bolts and working on the governor pick and latch block. The lollipop weight on the flywheel rotates the brass sleeve and moves it left/right on the spiral slot. The left side of the sleeve rubs the pick arm which moves it into the catch block (hidden from view). This pick arm is a mock up which is soldered together. The permanent one gets welded and will be all steel. A small compression spring on the top of the pivot point keeps the arm against the brass sleeve shoulder.
A good friend of mine got me making all my fasteners from 303 stainless hex. They just look so nice and they stay that way. I can knock to a 1/4 inch bolt in about 10-15 mins...easier when they are small as I use a threading die in the lathe to cut the threads. Most of the larger ones are 1/4-20s, the small ones are 10-32s.
Old girl weighs in at about 60 lbs... Hope to get the rod in and finish up the valves next weekend. Should not be long now. For working from an undimensioned print I am pleased how it is turning out. The big IF will be can I get it to fire on the hot tube. I have several larger hot tube engines and have a decent grasp of what makes them work (or not). A tin shroud goes over the fins.. That is coming. A groove gets cut in the left flywheel to drive a cooling fan.
Here is a trial gas cock I made from a 5/16 cross casting and some 5/16 tubing I bought for PM Research. The handle needs some cleaning up but I'm happy with the way it works. This sort of valve was a staple item on gas-fueled oil patch engines. I made a jig to hold the raw pipe fitting castings which is just intersecting 45 degree slots in a piece of aluminum.
When I installed the rod assembly, horror of horrors, the rod hit the side of the crankcase. Had to use one of the rods from kit #2 and re-machine it. This time I took a quarter inch off each side and put the cap nuts in from the bottom. Somewhat of a departure from the original, but I think it'll pass.
The nice thing about doing this over was I have all the jigs made so this part was easy. Improvement over rod #1 was to put dimples in the shells to hold the bearing tight. Way easier than trying to tin it and get everything to stick. In the top right corner you can see rod #1. After dressing the corners, the rod fit nicely in the engine and will be final shimmed for running. The only big hurdle now to getting it running is getting the exhaust valve seat to seal; it is being stubborn.... :wall:
Finished up the running bits today and got the exhaust valve to seal so-so.. Took it out to the garage and dialed in the hot tube burner. Turned on the propane and it fired right up. Once I re-make the exhaust valve with a cast iron head, I should get it to seal better. When I try to lap it in, it cuts the head and not the seat. The hot tube is about 2.5" long made from quarter inch stainless tubing. When I get the valve to seat properly, it should hit harder and get up on the governer latch. Still, it will run nice and slow like I prefer.
[ame]http://m.youtube.com/watch?v=RktbcVtR3bw[/ame]
[ame]http://m.youtube.com/watch?v=RktbcVtR3bw[/ame]
Big congratulations!!!-----Brian
Finished up some of the minor bits today. I made a fan and hub/pulley which goes with the shroud. Still scratching my head at trying to do the stretch out for the shroud where a 3 inch cylinder intersects a 3.5 inch cylinder. I have some references on how to do it.... Made the fittings from PM castings and installed the gas line. Then there is the issue of paint. I am hedging towards using some Penetrol with lampblack in it. I'd like to keep the Oil patch look. Got the exhaust valve seating much better now. Using a cast iron head was the ticket. The lapping compound now cut evenly into both the seat and valve. Before, it was cutting only the valve. She is at least presentable to take to Cabin Fever. I best get some sort of cart or park close as it weights every bit of 70 lbs.
Pix of the fan and some of the plumbing. BTW, that is what the original fans look like. Kinds cheesy without a shroud. I have to scare up some 1/8 rubber tubing this week to finish the fan belt. Maybe some RC black fuel line??? Maybe some 1/8 O-ring stock?? Ideas??
Finally got around to making the shroud from some old galvanized steel. I turned a 3.5" round nylon and then bored a 3" pocket in at right angles. Then a 3" piece of round nylon was inserted into the pocket. I traced the intersection of the 3" with the OD of the 3.5" using a sharpie. To get the patterns for the sheet metal, I wrapped transparent plastic film over the two mandrels and traced them out with an exacto knife. From there it was a simple matter of cutting and soldering. That water-soluble plumbers flux I picked at home despot was the only thing which would successfully solder the old sheeting. Here is the result. I'll post what the original looks like in a follow up post. Thanks for all your kind and encouraging comments. Cheers, MM.
