Engines > From Kits/Castings

Double Tandem Compound Horizontal Mill engine.

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This set of castings was generously purchased for me  :whoohoo: by my company for my 21 year long service award. I have never seen one of these model engines complete the nearest I can provide is this drawing of half of the engine:

The casting set came from Brunell Steam Model Engineering. I seem to recall paying ?325 for the casting set in 2002, today it will set you back ?441. 


What I got for my money as a set of gunmetal and aluminium castings:

I chose not to buy the aluminium baseplate as I was concerned about cleaning it up and possible ?slumping? in the casting and opted to use a sheet of 1/8? brass

I started the engine in 2003 and turned up most of the casting by the end of 2004 when I started painting and assembly:

This is where it all went wrong: The paint I had chosen was a Maroon used for Volvo?s, I foolishly only purchased one tin of the colour and by the time I got ? the way through the painting and went to buy another can I found that the colour had changed and everything I had done needed repainting :facepalm:. (Did I mention I hate painting? :paranoia:) The long and short was the delay in getting suitable paint saw the engine shelved, then I did my PhD which changed my perspective on everything so now I am going through all my half-finished engines and finishing them, this time I am finishing off this engine. This is what she looked like when I picked her up again.

Before anyone goes out to buy a set of castings a few words of warning: I don't know how I am going to run this engine when she is finished, as the swept volume of her cylinders is as big as my 5? Super simplex :Doh: and I am aware that getting things out of Brunell has been a challenging of late.

Next installment I will look at some of the challenges of the casting set.


Hi Jo,

Beats a gold clock  :ThumbsUp:

I wish I'd thought to ask for something like that.

Best Regards

As you will have seen from the previous photo?s there was lots of flashing on the castings. I prefer this than have someone let loose with an angle grinder and it was easily cleaned up using an old 12? hand file.

Most of the castings were easy turning/milling jobs so I was not going to go through these. The trouble makers were the two cylinder spacers, which had to first be turned on the narrow end, then turned around to have the wider end turned and the parallel taper, inside and out. The reinforcing bars on either side of the tail rod guide prevented use of a three jaw chuck so the tail rod guide was turned up using a 4 jaw self-centring chuck.

So far so good; ha but, the cylinders are separate from their mounting plates. It was necessary to first clean up the curve on the cylinders and then fly cut the top of the mounting plates. Sounds easy? Well no. there is a lot of jiggery pokery to make sure that all of the centre lines of the cylinders are at the same height. The mounting lugs on the mounting plates were horrible, I chose to mill them all off and turn up some brass buttons and silver solder them into position: It was much easier than cleaning up the originals, they are all the same size, a trick that I must remember on other models. This left the relatively simple (???) problem of soft soldering the cylinders and the mounting plates together such that the valve chests were square to the base. It took a couple of attempts for me to be happy with this.

Now came the next problem: It is necessary to mount all of the cylinders, guides and the crank support brackets together into a single assemble before attempting to mount them of the base plate?.. We will be returning to this problem later.

When we put the engine together you get the following assembly:

(Yes  :agree: that is a Steeple in the background, it is happily now finished).

The base is an assemble of aluminium angle screwed inside some wood cladding which has the brass mounting plate screwed to it using the various engine mountings: 

Now for what is happening today:


I am now armed with two tins of Maroon paint (it may be a bit bright but I claim it matches the sofa, which means I have the excuse to keep it in the lounge :Lol:), another two of grey primer. So let the painting begin.

First up that sheet of brass, the reason it is being sacrificed as the base is that it has some nasty marks in it which the engine parts will cover up and it is thick enough to cut threads into. Speaking of which I began at the crank end making some 5BA/6BA studs which happily screw through the brass into the aluminium underneath providing a nice secure mounting at that end:

One crank mounting in place, second about to be bolted down, trunk guides covered in paint?.and it dawned on me,  :hellno: I have to assemble the entire length of the cylinders together before I start bolting it down.

About this point I realised that there is more than just painting to go  :thinking: . You get some idea of her size from the ruler.


Question, for you boys: What can I do to make this flywheel more interesting? I was thinking that big Mill engine flywheels were often clad in wood to stop them causing drafts. I have also seen some clad with sheets of I assume thin metal.


Hi Jo!

Quite a project!   As the engine is a Double compound, it'll be self starting, so you could get away with cladding the spokes in.   Because of the twin crank configuration, you would obviously have to take power from the OD of the flywheel

The flywheel appears to be aluminum.....You could polish it but I doubt it would stay that way for long.

Flat belt the OD to a generator....or perhaps a rope drive to a countershaft?   Neither is real attractive, as I don't think the base is big enough......unless you went vertical....like a two story Mill diaorama perhaps.....seems to be a bit much.

I don't have a photo of "wheel cladding" though I could understand it's use...hmmmm will have to think on that.



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