Chassis Construction - Counterweights

The next step was to mount the counterweights on the axles.  The key here was to get the counterweights flat and parallel to the plane of the chassis.  After filing each counterweight to remove burrs, I reamed the holes to fit the 1.2mm axles from Aspen.  I then carefully mounted each counterweight and bonded it with CA on the top face and on the bottom around the seal to the axle.  Some holes were not exactly perpendicular to the counterweight face... but for this part you only need to get the counter weight roughly correct - worst case you can file the front - because you really only see the front the counterweight (however the filing causes an aw shucks moment in a few minutes...).  So I mounted the counterweights on one side, and then set the chassis on its side with the counterweights up, I file them flat to each other and parallel to the chassis.  This eliminated some extra CA and generated a lot of brass dust.  The results of the mounting are shown in Photo 6. (Yes the two middle counterweights stick out about 0.010", there is some play in the axles and I didn't make them equal on the backside before taking the photo, which you can see because the wheels are out from the frame as well.).  I think I got the surface parallel to 0.005" without much difficulty.

Mounting note #1:  The K28 has only one large counterweight, it is on the third axle from the front, which you can see in photos or in a larger model.  The K36 has all large counterweights.  Note #2:  When the large portion of the counterweight is pointing up on the fireman's side of the cab, to correctly quarter the drivers, the large portion of the counterweight should point forward on the engineer's side (90degrees different from the fireman's side). Difficult to see that in a photo of only one side, that's where a larger model comes in handy.  The Aw Shucks moment:  it turns out that alcohol doesn't take off paint very easily, but combined with a 3 minute ultrasound soak to remove all the little brass filings, it took off some of the paint on some of the chassis.  This was a surprise to me because I have not had a problem with alcohol before, see Photo 7. 

While painting the counterweights, I touched up the chassis by hand.  I used Floquil engine black for the counterweights since they will be seen more and should match the engine body.  The finished chassis are in Photo 8.

 Chassis Construction - Frames

The Aspen kit comes with flat chassis frames that you need to bend 90 degrees to form the outside frame on the left and right.  I used a bending tool to do the job, but found it very difficult to get the bend exactly the same on both sides.  Getting it 90 degrees isn't hard (keeping it 90 degrees is another story) but if you don't do it exactly on the dividing line then you form a parallelogram and the frame has a little tilt to it...  In reality, the model interface is the flat unbent surface.  So as long as you are pretty close, you won't notice the difference when the model is assembled.  The outside frames could be a little higher on one side and won't see that even in a head on look.   The bent frames then need to have the pilot attached and the cylinder casting attached.  Assembly Note:  The bent frames are easy to unbend, but then are easily bent back.  If you do that more than once, it's easy to tear the brass sheet.  Because there isn't any interference issue, I ran a bead of solder on the inside edge of the bend.  That fillet makes the bends much stronger and after soldering you can visually bend the frames square (check in all directions), the fillet can be seen in Photo 9.

Before assembling, I modified the pilot to be able to take a real coupler.  I cut two of the support rods, bent them to match the existing bent rods (and they can be soldered to a support rod underneath if you really want, and filed down the pocket so that it will accept a Micro Trains coupler, see Photo 10.  I soldered the pilot onto the frame.  This was a little tricky because you need to make sure the pilot is flat and square to the frame.    It was within my soldering skill set (not novice, but not great).  I used a resistance soldering tool, held the pilot in vice with an alligator clip and held the frame using pliers.  It was very fiddly to get the parts to be flat, and square, and centered on the frame, during the heat application, and I had to unsolder/re-solder once or twice, but it worked.  If anyone has a better solution, I would really like to hear it!  Assembly Note:  you need to file the pilot frame to accept the cylinder casting in the next step.  It's not clear you need to do that (and the pilot doesn't extend that far back in the real engine, so you are filing away something that doesn't exist...), but a rectangular chunk of the two rear corners need to be filed - you can see that in the photo of the finished frame assembly below (look at the back corners of the pilot on the chassis that is holding up the chassis being photographed (lower left).  These I didn't make exact, they are hard to see in the model.

The cylinder assembly is pretty easy.  First I filed the back edge of the pilot (resting on the frame) roughly square to the frame, and then mounted with CA.  If the casting doesn't lay flat, you probably didn't file enough of the corner away!  Assembly note:  make sure the cylinder front faces front, don't ask me how I know...  I then added the castings that go in the holes in the rear of the cylinder casting, also with CA.  Make sure that the slit in the top casting is vertical, and make sure that the bottom casting has its two holes lined up vertically, with the smaller whole above, and either right above, or slightly to the inside.  [These parts only approximate the real valve gear linkages and pistons, I think that rotating the hole slightly inside will make valve gear assembly and operation easier, but I tried to assemble them perfectly one over the other.  We'll see later...]  The final chassis parts and frame parts are shown painted in Photo 11.