The
first model building activity was to drill the brass sheets for the frame
and the frame distance holders. This was a Saturday afternoon project and
included also the gearbox parts drilling.
The
first model building activity was to drill the brass sheets for the frame
and the frame distance holders. This was a Saturday afternoon project and
included also the gearbox parts drilling.
The task was nothing special, just the same as it was for the former models.
The only enhancement was that in this case I designed pilot holes for all
corners of the sheet cutouts. These small, 0.5mm (0.02") holes have no importance
for the model itself, but made the scribing of the shapes much easier. Earlier
it was always a hard task to find the
cor
rect
positions for the outlines measured from the existing holes for the openings.
With the pilot holes the scribing was a simple task just connecting the pilot
holes with the ruler.
The
vertical spacers are also the boiler support sheets, thus they were made
from 0.5mm (0.02") brass sheets, while the other parts are from 1.0mm (0.04")
sheets. The framesides include two rows of 0.4mm (0.016") holes. These are
for rivet rows. Unlike in the former projects, where these rivet rows had
no mechanical task, in this model I decided to use the short brass wires
in the holes as mechanical support for the soldering. This also means that
these wires should be soldered first, before soldering the frame together.
I
used the same flame soldering technology to solder the frame as before, for
the former models. This time, however, not the distance holders determined
the frameside positions for the soldering. A soldering jig was used instead.
This was a brass rod turned to exact 10.0mm (0.4") length having a threaded
hole in the center. The framesides were fixed to their ends at the openings
for the first and third drivers'
bearing
slots. The structure was carefully aligned both vertically and horizontally
and the screws were tightened. Only after this the vertical and horizontal
spacers were put to place. The first vertical spacer needed an extra fixation
by a hairclip to remain in place.
The
soldering
happened as usual, first putting solder grease to the joints and small pieces
of tin were placed there. The joints were heated by a butane torch.
The model is equipped with a Compensation Rod in the centerline
of the frame. This is a rod made from 1.0mm (0.04") brass sheet. It has two
dimps that touch the bearing tube upper surfaces. This was made by cutting
and filing to shape. The compensation rod itself also uses a tube bearing.
This
is a 2.0mm (0.08") external diameter brass tube with the hole reamed up to
1.2mm (0.048") diameter. A steel rod with the same diameter serves as axle.
This is plugged through the frameside hole.
The tube bearings were turned from brass. They have an internal hole for the axle with exact 2.0mm (0.08") diameter. This was drilled from both sides in order to have the hole exactly in the center of the bearing rod. After drilling it was reamed to size. The external diameter of the tube bearings is 5.0mm (0.2"). They have a shoulder on both ends with a 4.0mm (0.16") external diameter. This fits into the axle slots in the framesides. The axle slots were made by filing thus they were not very exact. The shoulders were turned one-by-one to exactly fit into their final slot. This also means all bearing tubes are a bit different, they are not fully interchangable, they can only be used in their own axle slot.
The
gearbox is indeed very similar to the Class 342 model's second gearbox. The
main difference is that this has one gearset more and the new one has a rather
tight fit inside the firebox. It was made by drilling, cutting and filing
the sides and the spacers. The soldering was again made using a soldering
spacer jig. This was, however, only 8.0mm (0.32") long,
2.0mm
(0.08") shorter than the spacers for the frame soldering. When soldering
the second gearbox a small problem arised: the soldering jig, made from brass,
also got soldered to the gearbox. It was impossible to remove, the whole
gearbox needed to be unsoldered. I decided to make soldering jigs only from
aluminium in the future!
The
gears are again soldered on tube bearings. These are tubes with 2.0mm
(0.08") external and 1.2mm (0.048") internal diameter. A steel rod is the
axle going through inside the tube bearing's hole from one gearbox side to
the other one. I needed two gears with 14 teeth and 0.4 mm module, but I
only had them as plastic gear. I hope this will not influence the model's
lifetime. On the other hand the plastic gears are supposed to be less noisy.
With the ready made gearbox I made a very unpleasant discovery. The gearbox
could not mounted inside the frame as planned, from the top.
The distance between the two last horizontal frame
spacers was smaller than the gearbox width, with the gears mounted. The only
way is to mount the gearbox plugging through from the bottom. This, however,
cannot be made if the screws fixing the wormshaft bearings are there. Thus
the only way to mount the gearbox is without wormshaft from the bottom, and
the worm with the wormshaft and bearings can only be inserted later.
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This page was updated last time on 13th January 2007
© János Erö