Miniature Traction Engine

[Nigel Taylor]

The black paint needs a mention. I needed a paint that could work at a high temperature for the chimney and the firebox.

I found this coal black paint, initially I thought this description was really describing the colour. However, this paint is designed for painting your fake coal on the gas fire....really.

I had a quick search and saw that this paint is also used for stoves, so thought I would give it a go on the chimney and firebox. I've now fired the boiler a few times and this black finish is growing on me.

So, if you need a high temperature black paint then this paint from Rapide Products is rather good and cost me just £3.99 at a small hardware store.

 

[Nigel Taylor]

After making the test boiler, fitting a DRO, adding a stiffening plate and sandbag damping to the milling machine....I'm back working on the Burrell traction engine. Today I roughed out a steering wheel whilst waiting for cylinder material.

Not quite perfect, but considering it is 22mm across I'm ok, I might make another one....but for now.

I then parted it off and machined the other side. A little bit of filing, emery cloth and tumbling this afternoon.

I need to add a handle so you can turn it fast

 

[Nigel Taylor]

The handle is now in place, it doesn't rotate, but that might be asking a lot for a 1/20th scale Burrell steering wheel

 

[donwatson]

Love it

 

[Nigel Taylor]

The cylinder is being broken down into a design that I can make and seal. A design that I can make work at this small scale.

The fundamental feature of this design is a saddle that will get silver soldered to the boiler. Here it is shown part machined.

 

[Nigel Taylor]

An overview of the miniature traction engine build to date:

 

[Nigel Taylor]

The steering system is a worm drive of a drum that then winds the chains in and out. These chains connect to the front axle beam.

The first challenge was making a 6mm diameter 2mm pitch worm and wheel

 

[pe2dave]

A man with patience!

 

[Nigel Taylor]

A man with patience!

I think my patience has improved with age. Also, I'm now happy to make the same part more than once as it is a great learning experience.

 

[Nigel Taylor]

I built up the bottom end of the steering system. The phosphor bronze bearing has a recessed section that the brass tag was rolled into and a flattened side with step that aligns on the edge. This angled edge was machined at 38.5° to align with the steering column.

I think I'm getting more confident when working with sheet metal.

The worm sits snugly into the gear wheel. There is no chance that this can jump a tooth.

The bearing at the top end is a simple brass post. The steering wheel hub was machined from brass with an 8BA thread to accept the steering wheel. The steering column works very smoothly, just need to add the chains and attach them to the front axle.

I had to reassemble the parts, I need to make the crankshaft as the flywheel is balanced on a much thinner rod at the moment, hence slightly too low.

 

[pe2dave]

How can lumps of metal seem pretty. But (to me) it is.
Please post a video of it running when complete.

 

[Nigel Taylor]

How can lumps of metal seem pretty. But (to me) it is.
Please post a video of it running when complete.

Thanks Dave, just lots of patience to sometimes make 3 or 4 parts before you get it right. Might be sometime before it's running, but will post progress. Best regards, Nigel

 

[Nigel Taylor]

A very brief clip of the steering wheel and gear being turned

 

[Nigel Taylor]

Not sure if everyone else is struggling in the heat in the workshop, it's definitely slowed me down.

However, I did managed to turn and mill the crosshead guide.

The inside surface of this is the bearing for the mid-point joint in the conrod. Thus allowing the sliding seal to work on cylinder and hence enable the double-acting operation of the cylinder.

 

[Nigel Taylor]

The crankshaft has been made so that it splits into two parts. The conrod big-end then doesn't need to split. Thus I can reduce the thickness of the design as it doesn't need to have a bolt through it. Overall I can increase the crank throw and hence stroke.

I managed to squeeze the throw out to 7mm and still clear the firebox.

Thus the engine is 12mm bore and 14mm stroke double acting.

 

[Nigel Taylor]

I've bolted the cylinder saddle to the boiler using two square head phosphor bronze bolts that I made:

One has a hole through as this is the pathway for steam from the boiler. This will be controlled by a valve that I will fix into the side of the upright that divides the cylinder and valve chest.

 

[Nigel Taylor]

I made the valve chest from solid brass and then added the pushrod guides as one piece initially

Once this was silver soldered in place I then milled out the centre section, leaving me an aligned pair of bearings.

Now I have a roughed out valve chest, need to now make holes for fixings and the shaft gland nut.

 

[paulrbarnard]

I made the valve chest from solid brass and then added the pushrod guides as one piece initially

Once this was silver soldered in place I then milled out the centre section, leaving me an aligned pair of bearings.

Now I have a roughed out valve chest, need to now make holes for fixings and the shaft gland nut.

That was cunning. I will try to remember that for the future alignment of bearing rods.

 

[Nigel Taylor]

That was cunning. I will try to remember that for the future alignment of bearing rods.

The only issue might be that it was stressed whilst being silver soldered and when I removed the centre part it might have moved. Hopefully not... I will report on how well this has worked.

 

[Nigel Taylor]

The engine itself is coming along, now I need to look at the options for the steam valve: