- Part 1 - Scaling down and deconstruction
- Part 2 - How I drew the various parts
- Part 3 - Printing and constructing the loco (pending)
This part covers drawing the:
- Running plate
- Cab sides
- Cab front and rear
- Cab roof
- Firebox
- Backhead
- Boiler
- Saddle tank
- Smokebox
- Smokebox door
- Chimney
- Cylinder
- Slidebars
- Sandbox
- Steps
- Springs
- The complete model
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 severasl 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
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 .....
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 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.
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 .....
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.
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.
.... 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.
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 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 tube was then sliced in half with a cuboidal hole.
.... 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, ..........
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.
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'.
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.
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
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.
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.
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)
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
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.
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.
Firebox door
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)
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