This is the second part of a three-part series:
This part covers drawing the:
- Running plate (Includes creating a bespoke hole shape)
- Cab sides (Includes creating a bespoke hole shape)
- Cab front and rear (Includes creating a curved roof support)
- Cab roof (Includes using the above to make a roof shape)
- Firebox (Includes making a hollowed arch shape)
- Backhead (Includes curve-bevelling cylinders and boxes)
- Boiler
- Saddle tank (Includes adding a curve to a hollow box shape)
- Smokebox (Includes making a concave curve to a hollow shape)
- Smokebox door (Includes making a simple spoked wheel)
- Chimney (Includes concave curves on a cylinder)
- Cylinder (Includes placing rivet heads evenly around a cylinder)
- Slidebars
- Sandbox (Includes rounding the edges of a box shape)
- Steps (Includes usng the above to create a square hole with rounded corners)
- Springs (Includes slicing a ring shape to make a leaf spring)
- The complete model (Test-fitting all the parts)
My rationale for setting the build out like this is in case you want to
start using
Tinkercad to draw your own locomotive and need ideas for a particular part. I do not
profess to be an expert but having used Tinkercad for the past five years to
design and print a range of rolling stock and locomotives, I have found a few
techniques and short-cuts which might prove helpful. Like most things, there
are several different ways of reaching the same end-point. If you have
discovered another method or clever short-cut, then please share them in the
comments at the end of this post.
Tinkercad is a fairly basic 3D drawing package which was
designed for children to use and develop their 3D drawing skills. Having tried
a few 3D CAD packages with mixed success, I was immediately drawn (sorry about
the pun) to Tinkercad as it had a more gradual learning curve
and, as a self-confessed scratch-bash bodgeller, it appealed to my way of
constructing models. Unlike other 3D CAD packages, which tend to start with 2D
drawings which are then projected into the third dimension,
Tinkercad uses a range of three-dimensional shapes which are
combined to make new shapes. A bit like construction with basic building
blocks. For more information and a tutorial on basic
Tinkercad techniques see -
How I drew and constructed a 3D printed Southwold Railway open wagon
So, let's get started!
The running plate
The running plate was drawn by simply combining a series of various
sized cuboids together. I have coloured the cuboids differently here to show
the various components.
The most complicated parts were the green fillets at the corners of
the plate.
These were made from a green wedge shape, to which was added a small
curved wedge (shown in red). The top of the wedge was made into a curve by
combining it with a hole shape made from a cuboid .....
..... with an elliptical hole nibbled out of it.
These fillets were drawn by eye to more or less match what I could see in the
photo. Had I been making the running plates from plasticard, I would have done
something similar, using a knife and neeedle files to create the fillets.
However, in
Tinkercad, once I have made one, I can duplicate it.
To accommodate the motor, which projects above the
Bachmann chassis (See
Part 1), I replicated the body of the motor using a cylindrical hole shape which
was then combined with the main component of the running plate to form a
motor-shaped hole.
Similarly, holes were 'drilled' into the leading frames below the running
plate using a 3.5mm diameter cylindrical 'hole' shape to accommodate the
locating lugs on the cylinders (see below)
The finished upper section of the running plate.
The lower running plate / footplate section was made in the same sort
of way. I have coloured the various components to show how it was drawn.
Here's how that looks once all the components have been combined.
The Cab Sides
The sides of the cab were simply a 2.5mm thick cuboid with three holes
nibbled away from its edges.
The upper part of the doorway was made by creating a template from a
couple of cuboids and a couple of cylinders.
This shape was then turned into a hole, which was used to punch the
required shape into the upper part of the side.
The curved front edge of the bunker was simply a strip of "round
roof" added to the edge of the cab side.
The ledges on the top edges of the opening were a couple of cuboids
with rounded edges .....
..... created using the radius and
steps features in the shape properties drop-down window.
Once one side had been drawn, it was duplicated and flipped horizontally to
create a matching opposite side.
Cab front and rear
The front and rear of the cab started off as a 2.5mm thick cuboid, 5mm
shorter than the width of the cab to allow the front and rear to be glued in
between the 2.5mm thick cab sides.
An enormous 385mm diameter x 2.5mm thick cylinder was laid over the top of the
end, its size being adjusted until the correct height and 2.5mm overlap of the
ends were achieved. A larger cuboid hole was then superimposed over it and the
two combined ......
... to produce the curved roof section (Note: I made the cylinder
transparent so I could see exactly how much overlap there was between it and
the lower cuboid section of the end).
Two 12mm diameter x 3.5mm thick cylinders were then positioned where the
spectacle rings were located. These were 3mm larger in diameter than the
spectacle windows to allow for a 1.5mm wide spectacle ring. Two 9mm diameter
cylindrical holes, the diameter of the spectacle windows, were then placed in
the centre of each spectacle ring cylinder and all the shapes were then
grouped together, .....
... to produce the cab rear
To make the cab front, the rear was duplicated and a 6mm strip was removed
from the base to allow for the step between the lower footplate section and
the upper running plate section
A copy of the firebox (see below), turned into a 'hole' shape, was then placed
over the top. It was increased in size by 1mm at the top and the sides to
ensure the firebox itself would fit easily into the space. The firebox 'hole'
was then increased in height by a few millimetres to ensure that it would
punch a clean hole in the cab front
The two shapes were then grouped together
The firebox
The firebox started off as a 61.5mm diameter x 45mm tall cylinder.
A certain amount of informed guesswork was required to determine
these dimensions as, of course, the firebox is largely hidden on the photo.
A 61.5mm x 25mm x 45mm cuboid was then superimposed over the cylinder, lining
up the top edge of the cuboid with the centre line of the cylinder.
The bottom of the cylinder was then sliced off with a cuboid 'hole' lined up
along the base of the superimposed cuboid.
A 56.5mm diameter cylindical 'hole' was then centred over the original
cylinder and raised up 2.5mm to allow for the 2.5mm thickness of the hollowed
out firebox.
Then all the shapes were grouped together (and re-coloured grey)
Finally, a 56.5mm wide cuboid hole was positioned and raised up by 2.5mm to
tidy up the hollowed out inside the firebox......
.... and I reverted its colour to red.
The boiler and tank
Because I wanted the tank to be removable to allow access to the
electrics inside, I drew the boiler and saddle tank in tandem - adjusting each
as required to ensure a comfortable fit.
The boiler was carved from a 46mm diameter x 100mm long cylinder
This was hollowed out with a 41mm diameter cylindrical 'hole' shape
- to give 2.5mm thick sides.
4mm was removed from the bottom edge of the boiler using a cuboid hole
shape. ......
.... and the top half of the boiler tube was removed with another cuboid hole
Two pieces of 9mm x 2.5mm x 100mm strips were added to each side as shown. The
width between the verticals matched the internal dimensions of the saddle tank
(see below)
These were then grouped with the boiler and coloured grey
A 2.5mm thick cuboid was then added to the base of the boiler to act as a
floor and unify the two side pieces.
A 2.5mm thick cuboid was added to one end of the boiler to fill the gap
between the firebox and the boiler. It dimensions were decided by marrying up
a copy of the firebox to the end of the boiler. A 41mm diameter cylindrical
hole has grouped with the filler piece to hollow it out in line with the
inside of the boiler.
At the other end of the boiler, another filler cuboid was fitted to bridge the
gap between the boiler and the smokebox (see below). This was done
retrospectively after the smokebox had been drawn, using a copy of the
smokebox to guide its dimensions.
The tank was formed initially from a cuboid, 45.7mm x 100mm x 2.5mm
To make the curved edges, a 17mm diameter x 100mm long cylinder was
drawn.
This was hollowed out with a 12mm diameter cylindrical hole (to give walls of
2.5mm thickness.
This tube was then sliced in half with a cuboidal hole.
And then sliced into a quadrant with another cuboidal hole.
This was duplicated and flipped and the two curved pieces attached to the
sides of the original cubiod which will form the top of the tank.
Two 100mm x 28mm x 2.5mm sidewalls were then added.....
.... and all the shapes grouped into a single unit.
A 59.5mm x 22mm x 2.5mm thick end wall was added.
To shape its protruding corners, a cuboid was drawn and a 17mm
diameter hole nibbled out of one corner. .......
The resulting piece was then turned into a hole, ..........
..... and then duplicated and flipped, and the two pieces moved to the
corners of the end-piece.
The end piece was then duplicated, and the other piece moved to the opposite
end of the tank.
All these pieces were grouped together. A 55mm diameter cylindrical
hole was then positioned over one end to allow the tank to sit on top of the
firebox. Its exact position was determined by test-fitting the boiler and tank
on to the 3D model of the loco which was being pieced together as each new part
was drawn (
see below).
The hole was grouped with the tank assembly to make the required
cut-out.
Finally, a 4mm diameter hole was made in the exact centre of the top of
the tank using a 4mm diameter cylindrical hole.
The smokebox
The smokebox was drawn in a similar way to the firebox above, albeit
slightly smaller.
The infills between the smokebox and the boiler were shaped by marrying
copies of the two together and using the boiler as a 'hole'.
The concave indentations on the lower part of the smokebox were achieved by
creating a large elliptical cylindrical 'hole', duplicating it and using them to
shape the indentations on either side of the solid smokebox assembly. The
ellipse was drawn by eye, as I had no scale drawing or photos of the front of
the loco to guide its dimensions.
I turned the smokebox on to its base before exporting the .STL file to
facilitate printing.
Chimney
I used one of the chimneys I had drawn previously for another of my loco
builds, simply re-sizing it to match the dimensions of Anita's chimney. The
chimney is probably the most complicated single shape on the loco.
Shaping the complex curve at the base of a chimney or steam dome in
Tinkercad is tricky. I'm not sure that I've completely mastered
the technique, but this is the approach I use. Owing to its complexity, I've
gone through the process in fine detail but, basically, the chimney is
constructed from a series of tubes combined with torus shaped holes used to
give the concave curves.
Step 1 started with a
tube....
Its dimensions were changed to match the diameter and height of the chimney.
Step 2: Another tube was drawn to match the diameter and height of the brass cowl
on top of the chimney
Step 3: A torus was drawn, twice
the height of the ring just drawn. Its inner diameter is the same as the
inner diameter of the ring and its outer diameter is twice the outer
diameter of the ring. This is can be harder to achieve than it sounds
because the parameters for the shape shown in the drop-down properties menu
don't always seem to match the dimensions of the shape. Some degree of trial
and error might be required.
Step 4: A cuboid, half the
height of the torus was superimposed over it .......
..... and they were grouped to chop the torus in half horizontally.
Step 5: The torus was turned
into a 'hole' shape and superimposed over the ring ......
..... and the two shapes grouped to create the concave curve.
Step 6: The ring was now
added to the chimney. I decided some adjustment to its shape was needed and
so I sliced it in half by combining it with a cuboid hole shape. My fault, I
measured the height and width of the cowl wrongly. However, I've kept this
step just in case you have similar problems.
Step 7: This process was
repeated to make the ring at the base of the chimney - you'll see why I was
constructing it upside down later.
Step 8: A cylindrical
'hole' shape, the same diameter as the smokebox was then placed over this
base ring (which is why it's upside down). I elongated the cylindrical hole
slightly to exaggerate the curve to help ensure a snug fit. I also inserted
a solid cylinder into the base to give it a bit more strength .......
Step 9: Once grouped
......
.... I added a 3.8mm diamter peg in the centre to help locate it into the
4mm hole in the top of the smokebox.
Step 10: You'll notice a
couple of whiskery parts left over from cutting the curve for the
smokebox. Again, I've left them in to show the process isn't perfect.
These were removed by placing a couple of cuboid holes over them and
grouping the whole thing together.
Cylinder
Inevitably, the cylinder started with ..... a cylinder, in my case it
was 17.5mm in diameter and 21mm tall.
A 3mm diameter x 19mm tall cylindical hole shape was then grouped
centrally with it to act as a guide for the piston rod. The piston rod on
the Bachmann chassis was slightly under 3mm in diameter.
Another cylinder, 6mm in diamter and 2.5mm tall was then mounted centrally
on top of the other cylinder.
A 2.36mm x 2.73mm hexagon shape was then mounted near one edge of the
cylinder. It protruded 1.5mm above the main cylinder.
This was duplicated and moved across to the opposite edge. Then the two
hexagons were grouped together.
The two grouped hexagons were then duplicated and rotated 45 degrees.
The duplicate button was pressed twice more and the rotated grouped
hexagons automatically appeared in their final locations. At this point I
grouped everything I'd drawn together to avoid accidentally moving
something.
A 1.5mm diameter half-sphere shape was positioned just below the top of
the cylinder
This was duplicated and reflected, and moved to the opposite side of the
cylinder. The two 'rivet heads' were then grouped together.
They were then duplicated and rotated through 22.5 degrees.
The "Duplicate" button was then pressed five more times to complete the
rotational riveting around the top of the cylinder.
All the rivets were then grouped together. I did this by highlighting the
complete shape and then holding down the shift key and clicking on the
cylinder to remove it from the group. The ring of rivets was then duplicated
and moved to one side for use later (see below).
A 10mm x 16.6mm x 15mm cuboid was added to the side of the cylinder to form
a mount. Its size was determined by measuring the distance from the frames
to the inside of the cylinders on the Bachmann chassis to
ensure the new cylinders would be in the right position for the motion on
the chassis.
A 3mm diameter peg was added to the centre of the block, using the alignment
tool.
The cylinder assembly was now grouped together
So I could follow my policy of keeping things simple in terms of printing
on to the build plate with the minimum of supports, I now started work on
the other end of the cylinder.
On reflection, I could have saved myself work by duplicating the
cylinder assembly, removing the support, and simply reducing the height of the
cylinder body (after ungrouping it). However, I decided to make the end piece
from scratch.
A 17.5mm diamer by 2.5mm tall cylinder was drawn, to which was centrally
added a 6mm diameter by 2.5mm tall cylinder.
The bolt heads were added as above.
A 3mm hole was made in the centre using a 3mm diameter cylindrical hole
shape
Once grouped, the ring of rivets made earlier was positioned.
And, once these had been grouped with the rest of the assembly, ......
....two 2.6mm square rod hole shapes, 10mm apart, were grouped with the end
cap, to provide locating sockets for the slidebars.
Slidebars
These, as you might expect, are little more than a few cuboid shapes
linked together. However, I needed to tilt them slightly to line up with the
cylinder and the motion.
The first stage was to draw one of the slidebars, 52mm x 2.5mm square.
This was then turned through 5 degrees. This was an estimate based
on the angle of tilt of the cylinders shown in the photo. I reality, I might
have to adjust this slightly when I come to construct the model, to ensure the
motion moves freely.
The slide bar was then duplicated, moved 10mm away and reduced in
length to 50mm
Although reducing its length after being rotated will distort the
shape slightly, I decided it would not be significant.
A 2mm x 27mm x 9mm end piece was now added. This should be much thinner,
according to the photo, but I decided to over-engineer it for
strength.
A 9mm x 2mm x 9mm cap was then placed on top.
The assmbly was then grouped, duplicated and the duplicate flipped
horizontally.
Cab roof
The drawing process for this is actually quite easy now that the ends
of the cab have been drawn. What is trickier is trying to decide how it
should be printed (see Part 3).
The first thing I did was create a duplicate of the cab rear, then ungroup
it until I could isolate the section which forms the curve of the roof.
This was copied and pasted into a new drawing. It was then duplicated.
Having made a note of its dimensions, I increased them on one of the
pieces, making the section 8mm wider and around 2mm taller. If you want a
thicker roof, increase the dimensions accordingly.
According to the photo, the roof overlaps the ends of the cab by around 7mm,
so I stretched the roof upwards by the length of the cab plus 14mm.
I now rotated the roof through 90 degrees so it was lying flat on the
workplane.
I then aligned the original curved section from the cab end along the
centre line of the roof and increased its length (so it was more than the
7mm overhang)
The piece was turned into a 'hole' and duplicated (moving the duplicate to
the other end of the roof). The 'hole was then moved in so it was 10.5mm
into the length of the roof (I nudged it in using the arrow key in 1mm and
then a 0.5mm steps). Why 10.5mm? 7mm overhang + 2.5mm cab front thickness
+ 1mm to allow for an easy fit. I made the roof section transparent so I
could see what was going on underneath.
The hole was then grouped with the roof to make the overhang. This process
was then repeated for the overhang at the other end of the roof.
3mm was then trimmed off each side of the roof, using a couple of cuboid
'hole' shapes, to give the roof some apparent depth when viewed from the
side.
The roof is now complete, though I might add a couple of alignment strips
under the sides of the roof when it comes to fitting it in place on the
model (see Part 3)
Smokebox door
Fairly straightforward - a disc and a dome - plus a hinge and a
handle.
A 40mm diameter x 1.5mm tall disc was drawn first.
Over which was placed a 36mm diameter x 2.5mm tall dome (or half-sphere as
Tinkercad calls it)
The two shapes were grouped and a 25mm x 2mm x 4mm cuboid was then
overlapped with the door, as shown
The was duplicated and moved 10mm away from the first.
The two cuboids were then grouped and centred on the door, using the
alignment tool.
A 1.5mm diameter x 16mm cylinder was then attached to the two hinge
plates as shown, ....
.... and a 3mm x 2mm x 4mm block, with its edges rounded off, was attached
to one end of the hinge rod.
This was duplicated and the duplicate moved to the other end of the rod.
A 2mm diameter cylindical hole was positioned in the centre of the door
(using the alignment tool).....
..... and everything was then grouped.
For the handle (which on this loco appears to be a small wheel), a 1.5mm
tall tube was drawn, as shown.....
A 1mm x 1mm x 8mm cuboid was then laid across its centre (using the
alignment tool)
This was duplicated and rotated by 45 degrees.
The "Duplicate" button was now pressed twice more and the other spokes
added automatically.
The wheel assembly was grouped and a 1.5mm D x 3mm L peg added to the
centre.
One finished smokebox door plus handle.
Backhead
I cheated with this loco by simply copying and resizing a backhead
from a previous loco build (See
Progress Report 98). However, I will take you though the design process in case you want to
create something similar for one of your own loco builds.
Backing
The backing for backhead was extracted from the firebox (see above) which
was duplicated then disassembled into its two main components.
The edges of the cylinder and the cuboid were then bevelled and rounded,
using the properties settings for each shape.
The bottom of the cylinder was then sliced off with a cuboid 'hole'
shape.
Then all but the top 2.5mm was sliced off with another cuboid 'hole' shape.
The regulator
As can be seen below, this was constructed from a series of
parts. Hopefully the screenshots will be self-explanatory:
At this stage, a trapezoid shape was used. Search for 'Trapezoid' in the shapes toolbox. It was 17.5mm tall and 1mm thick with a 3mm wide
base and a 2mm wide top.
For the spindle shaped handle, I used a multi-point cylinder. Again
this was searched for in the shapes toolbox. Its eight radii and six
heights are shown in the Shape Properties drop-down box.
Sight glass
This was drawn directly on the surface of the backhead.
Rivet heads
Sandbox
Step
Spring
The complete virtual model
As has been mentioned above, as each component was finished, I
test-fitted it on to a model of the finished loco. This enabled me to check
how the various parts fitted together and make adjustments as necessary.
Once satisfied, I exported the parts as .STL files so they could be printed
and then assembled (See Part 3)
Introduction
