Building the 2.5" Scale Shay

[jcbrock]

My first attempt I tried pinning mine with taper pins, but that didn't go so well, the pins sheared. I was considering silver soldering but was a little concerned about warpage from heating, so I'll be interested in how it goes. I'm only about a month away from having shop space again, can't wait.

[Soot n' Cinders]

Yeah, I can imagine the taper pins might sheer anyway. Each cylinder on mine can put up to about 400 in-lb of torque on the crankshaft. Silver solder gets tricky as well, I attempted it but the amount of heat required in such a large piece was very hard to work with and caused warpage. I think heat shrink will work, I'll throw the pins in the freezer over night to get them down to about 2 degrees and I'll put the crankwebs on the grill or in the over to get them up to about 500 degrees when I'm ready to assemble.

[Soot n' Cinders]

The new crankshaft is made up! All that remains for it is to finish the counterweights and the straps for them.
The heat shrink wasnt working out how I wouldve liked, so the crankshaft is a 0.0005" interference press fit with 680 loctite retaining compound in each joint. After assembly I found the shaft was running about 0.015" out of true because the keyways broached were a little wider than the woodruff keys I had. So after some googling, I made up a crankshaft straightening jig like the one that used to be used for automotive crankshafts. I had 2 V blocks on top of some 1-2-3 blocks to get enough height to swing the shaft and had the whole thing clamped together on top of a piece of granite counter top I had measured as very flat with a surface run out gauge. From there, I would check the shaft with a run out gauge and the adjust accordingly using my precision crankshaft adjusting tool, my 2.5 pound hammer. After 30 minutes or so of beating and annoying everyone else in the house, I finally got the shaft running true within 0.0005". So Im calling it done and leaving it for the loctite to cure over night.

[John_S]

I made up a crankshaft straightening jig like the one that used to be used for automotive crankshafts..

This is one of the reasons I love this hobby so much. Everyone comes up with ingenious solutions to problems; there's never a single solution to any given problem.

Tristan, I can't wait to see you finally fire this beast up and run it!

[Soot n' Cinders]

I cant either John! I figured there had to be a way to make a crankshaft without doing Kozo's method of turning it from one giant billet of steel. That would have been a lot of work for this thing, whittling away all that steel from a 14" piece of 3.375" steel round stock

[Soot n' Cinders]

With the crankshaft straight, the next problem is the bad bearing. I have enough bronze stock on hand to completely remake split bearing from scratch but I don't think that's a good idea because the amount of time it would take to make the whole thing again. So my idea is to use the worn out bearing as a shell and either pour Babbitt into it or take commercial bushings and solder them into the halve and machine them to bring the bearing halves back to size.
The next question after that is wether or not to do which ever approach to the other two main bearings and possibly the crank bearings. They are all bronze split bearings as well so I'll have the same problem in a couple years when the bearings have worn again. I've got everything apart now so machining the other five bearings to take whichever fix wouldn't be hard. That in theory would make things either to fix in the future.

[jcbrock]

My 2 cents: try the commercial bushing first because it is only a couple bucks to experiment, but anticipate remaking a set - one for now and a couple for the spares box. It doesn't take that long to make them new and machining that bronze is fun and easy, it's like cutting butter.

[Soot n' Cinders]

My 2 cents: try the commercial bushing first because it is only a couple bucks to experiment, but anticipate remaking a set - one for now and a couple for the spares box. It doesn't take that long to make them new and machining that bronze is fun and easy, it's like cutting butter.

That's true, using commercial bushings would cost me about $7 per box from McMaster-Carr.

[Soot n' Cinders]

Well, while the thoughts of bearing repair roll around in my head, work on the crainkshaft continues. The first counterweight has been machined to fit the tennon on the crankweb and I whipped up a prototype strap to hold it in place, I think it looks pretty good and should hold up to the force of holding the weight on the spinning shaft.

[Soot n' Cinders]

As Christmas break nears for me I've been practicing my welding for the boiler. I bought some 3/8x4" flat bar and ground the mill scale off of it, set it on my magnetic welding squares with a 1/16" gap, and went to welding. Filler rod is ER70S-6 and I have my TIG welder set as high as it will go, 180 amps. Seems to have gone pretty well, but I am far from a professional welder so I wouldn't mind some feedback on what I have going. If all is well, I will finish welding it up into a box with a half coupling and I'll take it to the club to hydro test it and see what happens.
Heres the first one I did.

And the second, even to my eye this one looks better than the first.

[Trainman4602]

What no Stays? You need more practice welding

[Soot n' Cinders]

It's a 4x4x8" box. And my intent is to stress the corner welds