Double Tandem Compound Horizontal Mill engine.

[Jo]

This set of castings was generously purchased for me  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. 

http://www.brunell.com/product.asp?numPageStartPosition=11&strPageHistory=cat&strKeywords=&strSearchCriteria=&PT_ID=69&P_ID=131&btnProduct=More+Details

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 . (Did I mention I hate painting? ) 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 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.

Jo

[Maryak]

Hi Jo,

Beats a gold clock 

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

Best Regards
Bob

[Jo]

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  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:

Jo

[Jo]

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 ), 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,  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  . 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.

Jo

[steamer]

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.

Dave

[Captain Jerry]

That's a good looking project, Jo, and I really like the color.  I hope to see it run. Which leads to my question.  In estimating the steam requirement of a compound engine, is the swept volume of the LP cylinder considered in the same way as the swept volume of the HP cylinder?

Jerry

[sbwhart]

Cladding the fly wheel in would look great, and if you realy want the chalenge grooving it for a rope drive would add the icing on the cake for me.

Stew

[b.lindsey]

Can't help but notice the similarities between the main frame & cylinders to those of the snow tandem engine. Since this engine predates the snow, I am wondering if its just the nature of the "tandem" beast or whether the snow designers might have borrowed from the design of this and similar engines. In any case, its a fine looking model Jo !!

Bill

[NickG]

Will be watching this one as well Jo, very interesting. So you reckon the quality of the castings is good, wonder what's happening with their customer service, are they struggling to get casting sets done, don't have any in stock or what?!

Good point about the sheer size of it .... definitely deserves a boiler and some work to do this engine! 

Nick

[kellswaterri]

Hi Jo,
        that will be quite some engine when finished, I can see I will have to get a shufti on, just stocked up on some tooling from Arc Euro...a couple of long reach dial guages and mag bases also large and small Stevensons blocks...you asked about photos of ''cladding'' for the flywheel, remember ''Gugger'' over on Model Engine Proboards, he has photos on his,
http://s89.photobucket.com/albums/k206/Gugger_2006/Corliss/
You mentioned ''Slump'' when referring to your casting, is this applicable to only aluminum?... Point taken about the ''angle grinder''
                                                                                    John.

[Stuart]

That's a good looking project, Jo, and I really like the color.  I hope to see it run. Which leads to my question.  In estimating the steam requirement of a compound engine, is the swept volume of the LP cylinder considered in the same way as the swept volume of the HP cylinder?

Jerry

Jerry

You only calculate for the HP piston , that is the one the boiler sees the rest is considered as exhaust gas ( steam ) and therfore as no impact on the steam needs



Good build you have going on there Jo   I have a triple expansion engine on the go as a side project ( to get over a stalled BR class 4 project I cannot get a start on the plate work at the moment )


Stuart

[Jo]

Hi guys,

Just back from the workshop, but sorry you will have to wait for the morning for tonight's update (my photo upload rate is <20Kbit/s at home  ) when I am back on full speed internet access.

Dave: the flywheel is a massive lump of cast iron, I have already added rope grooves in the outside. I like the idea of wood cladding, but I hate working in wood.  (As I tell my friend in my club: "Wood" is a four letter anglo-saxon word like all those others that come so naturally when things are going wrong in the workshop.) I found a good source of wooden ice cream sticks that might be a suitable donor but I only have half the number I need . I have an interesting photo of a Hick, Hargreves  & Co engine (Stationary Steam Engines of GB, Vol3.1 Lancashire, page 61) which has a very sexy wooden fan pattern in each quarter of the wheel which looks like it could be made from my favorite coffee stirrers .

Jerry: The colour is growing on me, but it may be a function of being under artificial lighting this evening.

Gugger's engine is wonderful but I did find the checker board floor a little over whelming, a bit too bling for me, I am sure Bog's would love it  .

Jo

[zeeprogrammer]

I've never heard of, and wouldn't know if I'd seen, cladding a flywheel.
I'd appreciate a pic.

Oo...we need a pretty please emoticon.

[Jo]

Having painted up the trunk support stands and the outer bearing stand I thought that I would move up the engine (having remembered that I have to assemble her as a single piece before bolting down ) so last night I moved to the crosshead guide and the connecting rods.

The cross head guide is a long and thin machining job and must be made before you start on the cross head as the cross head must be made as a good fit in the cross head guide bore. I used my fixed steady when boring the guide and tailstock support when I turned the outside. The window in the side of the guide was a simple milling job. The cross head is a simple BMS turning which has had flats milled on either side to take the end of the connecting rod. I made the width of the flat the same as the width of the slot in the cross head guide because it looked better and added a bronze pivot bush.



The coupling rod is made up of three pieces of BMS silver soldered together, 1, a U section to fit around the cross head, the central parallel rod and the rectangular end that forms part of the small end. The strap was milled from 3/8? stock and then the end of the coupling rod brought down to the correct width to fit within the strap.

I love engines with cotters and wedges  , on this engine they are nice and chunky being 3/32? thick. This means cutting slots in both the end of the connecting rod and the strap, but not before making up the bearings! The bearings are simply made from two pieces of GM soft soldered together, milled to size, drilled and reamed for the crankpin and then the slots are cut in the bearing sides to allow them to fit the strap. Having made the bearings it is now possible to fit them into the strap to check the location for the slots. I originally did mine with a mixture of drilling, milling and use of a needle file using a piece of 3/32? as a gauge, today I might use my hand shaper. Once the strap slot is finished we now put the bearings back into place and mark out where the slot needs to go on the end of the rod and using the same technique as on the strap cut the slot. Sounds easy but remember the slot in the strap and the end of the rod must not line up we need an overlap that the cotter and wedge can push against to take up wear in the crank bearings.



The Cotter and wedge being 3/32? are nice and easy to handle (the ones on previous engines I have made were as thin as 40 thou ). To make sure all have the same angle the trick is to first make up a suitable ?non-parallel? to go under the work in the vice and then the embryo cotters and wedge?s put on it to cut the tapers.

It had been my intention not to fiddle with this engine but to put her together ASAP but doctor meticulous has been in the workshop  and both the crosshead pin and the crank pin have been rejected and are about to be redesigned and remade .

This is a view of the cross head guides now mounted onto the trunk support stands. You may notice that there are a lot of studs holding it on, this is nothing what until you see the cylinder mountings. I fear I will be running out of washers before long.



Jo

[steamer]

".....I have an interesting photo of a Hick, Hargreves  & Co engine (Stationary Steam Engines of GB, Vol3.1 Lancashire, page 61) which has a very sexy wooden fan pattern in each quarter of the wheel which looks like it could be made from my favorite coffee stirrers . ....."

If you can, do publish that....would love to see it!

Dave