A 3D printed beam engine

 Having recently acquired a (very) cheap 3D printer new for £80GBP (see How I assembled my 3D printer), I have pressed it into service producing a range of items both downloaded and original (eg see How I drew window frames for 3D printing with TinkerCAD). My present project is a boneworks for Bulkeley Station (see How I changed the layout at Bulkeley and How I constructed the boneworks - pending). My model is based on the Etruria Bone and Flint Mill in Stoke on Trent which boasts an engine house with Watt beam engine to power the grinding machinery. The windows of the engine house are quite large and so the beam engine will be visible inside it. I therefore needed to find an appropriate model beam engine to sit inside. A quick search of the Thingiverse website revealed a suitable candidate - https://www.thingiverse.com/thing:1350988.

The 54 parts needed to make the model were duly downloaded and printed out - which took nearly 48 hours of printing time.

Fortunately, the download includes a comprehensive set of assembly instructions and so I was able to follow them. However, I ignored the recommendation to use epoxy and defaulted to my usual Vitalbond thick superglue.

The first task was to glue together the two halves of the flywheel. It was at this point I recognised the wisdom of using epoxy as it provides far more wiggle-time to ensure the two halves are perfectly aligned. The two halves of my flywheel are a few millimetres out of alignment and I was unable to correct this as the glue had set.

The next task was to glue the two base sections together. As the firmware on my printer has a bug which prevents me from printing anything taller tan 36mm, I had to slice the two sections in half vertically (using TinkerCAD) and then rejoin them before gluing the two base sections together.

The upper surfaces of the base sections were then glued in place.

The two halves of the crankshaft were then joined with the crankpin, onto which had been threaded the main crankshaft. A jig was provided in the kit to ensure the two halves of the crankshaft are properly aligned.

The bearings for the crankshaft were then screwed to the baseplate with 2mm screws.

The valve actuator arm was then threaded into the upper half of the valve chest........

..... and held in place with a butterfly shaped retainer which was fixed with a small dab of glue applied with a cocktail stick.

The two halves of the valve chest were then united.

The beam bearings, bearing plate, pillar and base ring were then located ......

..... and joined together with glue and screws.

Two short linkages and two long linkages were then interlinked with the piston rod using one of the bolts. A nut was glued to the end of the bolt with a small dab of glue.

The other two short linkages were then threaded on to the linkage pivot pin which in turn was threaded through the ends of the long linkages.

A small dab of glue held the two linkage pivot arms in place.

The two halves of the beam were then identified, together with the large bolt and nut which holds them in place.

The linkage assembly was attached to one end of the beam with another bolt and nut.

Another bolt and nut was used to connect the other end of the linkage assembly to the beam.

The beam with its linkages ........

.... was then joined to the pillar with the large bolt and nut for the main pivot and two short bolts and nuts for the linkage assembly.

The cylinder top plate was then glued to the cylinder and the piston and inside of the cylinder filed smooth to allow the piston to slide up and down inside.

The piston was then glued to the end of the piston rod.

The two halves of the cam were then threaded on to the end of the crankshaft, sandwiching the valve connecting rod between them. Small dabs of glue held the cam sections in place and then a pulley and end-cap were attached to the end of the crankshaft. The flywheel was similarly attached to the other end of the crankshaft.

The other end of the valve connecting rod was linked through the valve actuator and fixed in place with a small nut. The pressure gauge and control levers were glued to the valve chest.

The flywheel was then given a few spins to make sure everything was functioning as it should.

The steam pipes and flanges were then glued to the valve chest and brackets, ......

..... and the cladding for the cylinder slipped into place. These are removable, partly to help with painting and partly to allow the piston to be viewed inside the cylinder.

The main structure for the beam engine was now complete.

Although the quality of printing which is achieved by my printer is not the best - particularly in the vertical (z-axis) plane, I had decided not to spend a lot of time smoothing down the parts as the beam engine would only be visible through the engine house windows and hence not attract too much scrutiny.

I was pleased to find that it was very smooth in operation and quite robust. I accidentally knocked it off the workbench and on to the floor on a couple of occasions and it survived this maltreatment well.

Now I was satisfied with its construction, I turned my attention to motorisation. A small 3v motor was clipped into the motor clip and a AAA battery holder and switch wired up. The motor arm has been carefully designed to allow these to fit snugly in place.

 The pivot for the motor arm was then glued inside the base section and a piece of shrinkwrap tubing threaded on to the motor shaft and shrunk on to make a tight fit. The motor shaft bears directly on to the outside of the flywheel, and allowed to pivot to compensate for any undulations in the flywheel circumference.

However, even when using a 1.2v rechargeable cell, you can see the speed at which the beam engine operates is far too fast, so I experimented with a couple of alternative solutions.

Eventually, I designed, drew and printed out a sleeve which allowed me to put a small 12v geared motor into the motor bracket. I added a few pieces of lead flashing to act as a counterbalance. I found that a plastic wheel from a cheap plastic model car provided about the right speed when bearing on the outside of the flywheel and so this was forced on to the end of the motor shaft.

The pivot for the motor arm needed to be shifted and another hole drilled beside the flywheel.

A PWM motor controller was acquired (£3.65GBP from eBay) and wired up to three AAA 1.5v cells to allow me to fine tune the speed.

The model was then painted with acrylic paints. As you can see, I opted for green for the main components .....

.... and red for the minor components.

The bearings and piston rod were picked out in silver

.... and the bands and bolts for the cylinder picked out in gold. The cladding was made to look like varnished wood and the stonework for the plinth was painted brick colour with grey/cream mortar courses.

I am now very pleased with the way it has turned-out. As you can see, I can vary the speed at which operates and may eventually link it to a 12v supply which I intend to install for station and building lighting at the station. The PWM controller can cope with up to a 16v supply.

I congratulate the designer of the beam engine who I think has done a marvellous job and then shared his hard work with the rest of us for free. All I need to do now is finish off the building in which it will be housed!