Section 12 - Smokebox

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Neidrauer Adventures Photo Album and Blog » Building a Live Steam Locomotive - the Mikado Project » Section 12 - Smokebox

In Progress! The 'face' of a locomotive. Custom smokebox support stays completed (Frisco used 4 stays, not the 2 like the USRA models), throttle modification and installation, a custom flaring tool - Winter 2011. Smokebox front, smokestack, headlight bracket, hinges, bell. February - June 2009.

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Using the wiggler to get the outside reference surface.

Using the milled surfaces for reference, we bolt the shell to the table and align it to vertical using the combination square. It is a pain clamping the shell down (on the inside), it rolls a little each time we tighten the bolt.

The 1/8

Using a larger ball-end mill, we finish the lower hinge support. We also skim the outside of the hinge to get a vertical reference surface.

We start by just skimming the outsides of the hinges to get reference surfaces

1-Apr-09 With the shell hinges temporarily bolted on and the smokebox shell held down on the table vertically, we use a carbide ball-end mill to cut the bearing surfaces on the hinges.

We figured the only way we could hold the shell hinge brackets was to rivet them to the shell then mill the slots, insuring parallelism to each other. Here we bolted the shell to the table again and using the wiggler to line the shell up with the top and bottom marks on the shell (back and front on the table).

The supplier now provides these brackets in aluminum only, due to the case-hard skin these thin sections have. We chewed up a HSS and a TiCN coated drill bit before finding a small Carbide ball mill we could use. Even though this little mill had one damaged flute, and really wasn't a center cutting mill, it chewed through the tough cast iron without complaint. Sometimes it is all about getting the right tool for the job, and in this case, it is carbide for cast iron.

Now to drill the rivet holes. We lift the brackets off the table with a parallel and clamp away from where we have to drill.

Using a ball-end mill, we clean up and machine the hinge tabs. Since these brackets are cast iron, we use a carbide mill. I think the results look good!

28-Mar-09 The smokebox front hinges are easier to clamp, just line up the straight side with a square to the vice.

Another clamping conundrum, how to hold the bracket to the shell to match drill the shell holes to the bracket.

25-Mar-09 These smokebox shell hinges are just plain hard to hand onto! Here we are making a cleanup cut on the shell bracket portion to fit nicely up to the end of the shell.

We have not removed the alignment block (left) from the table since drilling the other holes in the shell, so we just roll the shell around to line up the punch mark and then drill.

18-Mar-09 Laying out the decorative rivets the old-fashioned way: Layout dye, calipers and a center punch. 4 done, 116 more to go!

Success! With the handrail, headlight and bell holes drilled in it, the cover fits on the shell without needing adjustment.

Drilling the handrail holes.

Drilling and tapping for the headlight bracket.

Running the same bolt circle program with the same dimensions as the smokebox shell, we hope everything lines up during assembly. We find some radial differences in the placement of our holes and the casting marks, when all was done, the cover and shell lined up properly.

11-Mar-09 With the back of the smokebox cover marchined, it is time to drill some holes. Setting the cover on the table, we indicate the outside to center it. We tried this without clamping at first so we could swing the whole diameter uninterrupted, but we couldn't put the clamps on without moving it. This cover is also at the limits of my table travel, we had to move the Ram out to reach both front and back holes.

I've been running the numbers for the RRS heavy mike I'm building and finding differences between what is drawn and what I calculate. I'm not trying to second-guess the draftsman, just how to best set up my blast nozzle/petticoat.

I have done the calculations, drawn the 1:6 and 1:3 cones, and found significant differences making me wonder if I am doing something wrong.

If you don't mind, I'd like you to double-check what I have figured.
Cylinders: 2.375

The big question: Do all the bolts holes in the cylinder saddle fit nicely with the drilled and tapped smokebox holes? Answer: YES! we could start all the bolts by hand, indicating there was not interference.

Here's what the smokebox shell looks like after 24 iterations (about 4 hours) of align, drill and tap operations.

Two holes down, 22 more to go. Here's how it went: Using the pointed wiggler, line the punch point on the shell up under the spindle. After checking the front and side alignment with a magnifying glass, bolt the shell down and check the alignment again. We found the shell moved slightly each time we tightened the hold-down screws. Keep adjusting until things are tight but still true to the punch mark. Center drill a hole, Tap drill al the way through, Tap for for a 10-32. I wanted the extra security of a threaded hole in this nice thick smokebox shell instead of just a through-hole nut and bolt assembly. After that hole is done, loosen the clamps, rotate the shell until the next punch mark is on top and repeat: wiggler, center drill, tap drill, tap.

The transfer punch. For these holes under the cylinders, we put a piece of stout steel bar on the punch and the other end on the table. Using a 3 lbs. hammer, quickly strike the steel bar as close to the punch as possible, transferring the center mark.

With two holes drilled and tapped, we put temporary bolts in to hold the cylinders to the shell so we can punch-mark the rest of the holes, insuring the cylinders do not move during the punching process.

Using a homemade close fitting transfer punch, we mark two holes in the shell then remove the cylinders. We use the wiggler to line up the head exactly over the punch march, rolling the shell around until things line up. We do not ever move the X-axis (l-r) to position the hole.

With the right (or wrong) light, the scribed center line and casting halves mark almost disappear.

28-Feb-09 The painted cylinder saddle is brought down from the cold garage and into the shop to match drill it to the smokebox shell. We have scribed a center line on the shell to match the casting halves joint, and another line where the center of the front row of bolts should go to position the saddle front-to-back properly.

Another Saturday of bad weather means more time in the shop and less out at the track. Good for shop time, bad for getting the track ready for the April start of season run. Using the eyeball

We drill just the two holes perpendicular to the smokebox front at first. Our holes are okay, but the cumulative errors between the rotary head, the angle of the tilt and the not quite on center part cause us to adjust the holes with a small round rat-tail file.

How to lay out the hole pattern? I had a difficult time determining if the print was a straight overhead view (showing the curve of the smokebox) or a plan view. In the end we used a tilting rotary chuck. First we indicate the part to get it on center with the rotary. An adjustable chuck like the Buck 'Adjust-Tru' models would be nice here. Then we center the mill head over center and drill the holes with a small drill.

25-Feb-09 With the six-jaw holding the end of the smokestack and a boring bar in the toolholder, we turn the recess for the petticoat per the print.

Another good days work! The smokebox shell has the smokestack, blast pipe, steam pipes, handrail and boiler step holes in it.

When we advance to the next larger cutter, we have to look around to find a carbide cutter to put in it. We can run carbide twice a fast and take a heavier cut each time, speeding each boring pass up considerably. Unfortunately, this cutter which looked like it had enough clearance, did not perform well in this setup at all, producing lots of chatter and a lousy finish. We have to switch back to a HSS bit.

The high speed steel cutters are okay, but slow. We can't take very large cuts - about 0.010 each pass.

Having quickly reached the size limit of the boring head with boring bars, we start a progression of larger flycutters mounted in the boring head to enlarge the hole to the 2

All the holes (not counting rivets) are done except for the smokestack hole. We add a center bolt in the blast pipe hole to help secure the pipe and start a series of larger holes for the smokestack.

After a hole is drilled, we loosen the top bridging clamp, roll the pipe and line up to the next scribe mark. Here we are drilling the holes for the side step.

With a 4

Next to make a clamping fixture. My mill table is way too small to clamp over the shell by resting it in a slot, and I probably couldn't lift a vee-block large enough for the 12

21-Feb-09 It's lousy weather outside today, nothing can be done at the track so into the shop we go. Using the same DRO bolt circle program, we have made marks on the rim of the shell for the steam pipe, handrails, and smokestack holes to go on the side of the shell. Using the rim marks and the combination square, the hole locations are marked on the side.

A bit of figuring with the DRO bolt circle program and soon we are drilling and tapping the 5-40 holes for the smokebox cover.

With the bridgeport knee all the way to the bottom and the ram pulled out a bit more, we do our best to center the pipe in the mill. We discover the pipe is not completely round by about 15 thou. Not a problem since the boiler is almost 1/8

Finishing the centering operation with the dial indicator. Next we clamp down a nice sharp piece of high speed steel in the lantern style tool post and face the end of the pipe.

11-Feb-09 This old Rahn-Larmon lathe still has the factory-issued 14

The cutting was going well until we hit a piece of sand or a stone in the aluminum which destroys the edge of the HSS cutter. You can see the defect in the middle of the casting - the small black dot in the middle. You can also see the smooth finish on the left and the rough finish on the right which was after the cutter edge was ruined. We try switching to a tougher carbide bit, but it does not have enought relief clearance and the bottom edge drags on the metal, cutting poorly.
We end up digging the stone out with a pointed chisel which allows us to finish the work with the resharpened HSS cutter.

Running in open belt, about 258 rpm, we take light cuts from the inside working out with a nice sharp high-speed toolbit.

Here's how we chose to hold the smokebox front: Using a 6

Our 'live center' is a shop-made affair of many years ago using an open-cage tapered roller bearing. I had to dunk it in the solvent tank to clean out the gunk and dirt, then greased it up a bit. The inner race is not captive so if you back the tailstock off, the bearing will fall out, which also gets it dirty again. It needs to have a proper live center made. You can spend your time making tooling or making parts, this time it was parts.

4-Feb-09 We start a new section - the Smokebox! It's always fun to start a new one--fresh drawings to look at, new castings to puzzle out how to hold. We put the big Rahn-Larmon lathe to use to turn the OD of the smokebox front true, and clean up the back. Although we have the casting clamped from behind, we use the live center and a spacer block for additional pressure to keep it in place.

9-Feb-08 Thanks to my friend Tim M., who is also building a Mikado and having a boiler built, I was able to get a cut of the boiler pipe for my smokebox. It is 12