A small marine engine is not ambitious. Have a look at the engines in Stuart Models for some ideas. They sell kits, castings and drawings. A STUART 10V or D10 maybe what you are looking for.

https://www.stuartmodels.com/

I worked as a mechanical design engineer/draftsman for most of my life but had little practical experience using a mill and lathe when I started to build my 6″ traction engine. You have to start somewhere. (only took 1,500 hours to build over 7 1/2 years). 

Yes the Paddle ducks piston valve engine would be more in the “wilesco” sort of size range and being bar stock a lot less expensive than castings particularly if you much a piece up and have to buy even more expensive replacement castings.

If you do particularly want castings then Reeves do the borderer which is a twin and also a bit smaller than the Stuart as is Warrior

The 10v and paddleduck engine are quite big. A good starting point for learning but not the best for an actual boat because the appropriate size boat is 5-6 ft long. Yes they will fit in a smaller one but look bloated.
Anyway welcome to the forum. Learn how to search this site, find the posts about recommended books and gradually learn to use the machines expecting to mess up a few times initially.
Find your local ME club.

The 10v and paddleduck engine are quite big

Not sure about big and bloated, the Double 10 looks a bit lost in this 52″ hull, the paddle ducks engine at 10mm bore is about half the size and as I said more in the “wilesco” size range that the OP wants and would fit a 24-30″ hull quite comfortably. I think the double acting Wilesco engines are 12 or 13mm bore but as a we are talking about a twin slightly smaller may work better if being run of a Wilesco boiler.

Don’t be put off by a barstock engine looking what it is, with a bit of thought they can be made to look just like a casting kit engine and as Clive mentions you can take the basic mechanics and adjust the size to whatever you want.

I don’t think size has anything to do with a beginner’s engine.  What is more significant is choosing something that is within the capabilities of your machine tools and your experience.  Size is particularly important as regards the boat you want to power with it.

By saying that you are not interested in an oscillator is reducing your options quite significantly as they tend to be by far the engine of choice for smaller hulls.  They are also the best type of engine for someone new to the hobby to have a go at.

One of the best sources of small engine plans is the Paddleducks site but again, many of the smaller ones are oscillators.  I think one of the best engines you should consider is the Stuart Models Ninety, which is a ‘V’ twin marine engine but a valve operated engine and can be purchased as a set of castings.  Check here:

Stuart Ninety

There is also the larger 7V but that is probably bigger than you need to start with.  I would also seriously reconsider the idea of an oscillator for your first project.  It will enable you to get to know your machine tools doing tasks that are not as demanding as you will find with a valve operated engine and provide you with very useful training.  Again the Stuart Models twin oscillator is a superb little engine and comes available as a set of castings.  With a built in control valve the twin cylinder double acting engine is an excellent way to get into building your own plant for your first model boat project.

Stuart Twin Oscillator

There is also the consideration that buying your first engine as a set of castings complete with a set of drawings, instructions and the required fittings means that there is little research required as all the thinking has been done for you.

One of the biggest challenges I have come across over the years of testing model boilers is helping someone relatively new to the hobby to get started with a suitable project.  The problem is that invariably a newcomer isn’t even sure of what questions to ask so tends to base those questions on things they have seen somewhere that they like the look of.  At that point no-one has actually explained what is involved in making a particular type of engine so even the initial questions might be based on an impractical ambition.

Added to that is the other main challenge of many experienced modellers not being able to understand that, what they might see as a relatively simple project, to a complete novice might well be too difficult as a starter and could well end up being over facing and off-putting.  I nearly always try to suggest that the first project should be the easiest possible way to obtain a satisfactory conclusion that will generate a degree of satisfaction and enthusiasm to take to the next level.  For a model boat I always recommend a kit, preferably an open hulled model for ease of build and operation, and for a home made engine I would always recommend an oscillator.

The trick is invariably asking the right questions to determine the original posters levels of experience and capabilities rather than make suggestions based on our own idea of what is simple.  Perhaps Andy can let us know just what turning and milling experience he has had so far and whether he has made anything in the past. Does he have a technical background, does he have any experience with operating steam plant either statically or in a model boat.  As Jason has suggested, what is the intended use of this engine and, if in a model boat what type of boat would he be considering.  If it is for a boat then there is also the consideration that I would usually suggest that a newcomer identifies the boat they would like to make, which will then determine the propeller to be turned and then the size of the engine needed to turn it.  From that a suitable size boiler can be identified etc.

So Andy, can you help to fill in some of the gaps to help the knowledgeable chaps here to make appropriate suggestions.

Just to help get things into perspective, when I first went to sea my Dad dabbled in buying and selling antiques at fairs etc.  One day I arrived home from a trip and he showed me a steam powered model boat.  I didn’t have a clue what it was but I now know it was probably something like a Basset Lowke.  I fancied it so asked him if I could buy it.  He said sure, for 20 quid. We are talking late 70s here and I was still an apprentice.  I asked what he paid for it and he told me 50p.  I returned to the ship determined to prove to myself and him that I could make my own engine.  All I had to go on was what I had seen of this boat, I didn’t even know what ‘oscillator’ meant then.  When I got back to the ship I made a sketch on a piece of paper and took it down the workshop.  I made the engine below.  The main body is obviously a couple of brass pipe fittings and the cylinder and piston are both made from a scrap brass fuel tank sounding tape weight.  The only point being I would suggest that any newcomer starts with something very simple and achievable.

The kit referred to the model boat.  And as I suggested earlier, knowing a bit more about the experience and requirements of the original poster would be very helpful.

The cost comment is interesting. On numerous occasions when building my “barstock” versions of an engine I have done the sums and compared them to what the same or a comperable casting set would cost. In all cases I have come out at 1-3rd to a half the cost of the castings.

I cost everything so no scrap box diving. Smaller section I cost at a full 300mm length and larger section by the 25mm length so as I said earlier the builder will often end up with material to spare which can either be put towards the next engine or should a part not turn out right you have material to hand for another go. The added bonus is you have a decent length to get hold of rather than short sawn lengths that come with kits.

An example is this vertical the same size as the original Stuart No 7 before it became the A framed 7A. Current cost of a kit is £446.00. Materials including some packs of nuts just under £150. Muck up a 7A cylinder and you are looking at  £77.00 compared to £31.00 for the fabricated. Infact nearer £21 as I included a 300mm length of material for the end flanges in the total price so you would have had that to spare.

All materials could be got with one orfer from M-machine and one other order for fixings.

Yes I know some people want to make an engine from castings in which case Stuarts, Reeves or blackgates all have something suitable but when no preference is given barstock can be a viable option. The 10V was my first casting set but I had built barstock steam engines before that but a 10 V does not fall within the OPs requirements of a twin of Wilesco size.

Borderer frome Reeves doe sfit th esize and type requirement if a casting kit were wanted, costs £355. I’ve just priced the barstock required for the castings and it comes out at £167, just under half. If you were to substitute cast iron inplace of bronze for the cylinders, covers etc then you would be at about £100 so I can’t see that buying barstock is costly.

Clive has always been a little unconvinced as to the suitability of a “simple” oscillating engine for the very first, ab initio, project of a beginner with no previous machining experience. Especially one working alone without a mentor for physical in shop guidance and support.

Jasons little V twin oscillator is a most attractive design.

But accurately generating the flat surfaces the cylinders run against and arranging for accurate in-line assembly of the crankshaft/drive shaft and bearings may be more than a little challenging for the (probably) under-resourced and (inevitably) under skilled beginner. Accurately creating the slots in his equally attractive trunk guide engine shown further up may also prove difficult for the rank beginner.

A useful listing of the fundamental skills that need to be mastered to within functional tolerances in order of difficulty is :-

1) Accurately placing holes of the correct size in the right position

2) Making cylindrical shafts of the right size

3) Producing adequately flat and smoothly aligned working surfaces of sufficient area

4) Making several parts that can be properly aligned on assembly.

Once those are modestly mastered a beginner’s model engineering career will be safely off the runway and settled into a steady climb towards cruising height or at least be imitating an Ekranoplane skimming noisily (all those swear words!) over the Caspian sea at wave top plus a bit height.

Unless grossly over-ambitious project choices are made the usual “3 rd times the charm” rule will apply. After building skills on 3 judiciously chosen simpler projects you will be ready to either make your 4 th project what you really wanted in the first place or decide to make really good job of something intermediate first.

What I liked about the Popular Mechanics rotary valve twin design is that, if the crankshaft were re-worked to built up design so full circle big end can be used, its almost simple enough to build with a drill press and hand tools. A good ab initio complexity level. OK the fits may end up rattling good and running less than quiet but quite quickly making something where the wheels go round is a vastly greater lift than the usual apprentice course derived starter plans. Over half of which are tooling things not only outdated by modern costs but fundamentally boring.

The “Look I made this height gauge.” (or whatever). “Oh. So.” conversation tends to be deflating.

After re-calibrating from half my first years salary to two weeks pension I still reckon anyone suggesting its appropriate to start with £350 (ish) worth of casting kit that could be wrecked by completely understandable beginner error is out of their little pink mind. Even in today’s world that is still serious money to carve out of the family budget for a purely personal thing. Jasons bar stock Stuart No 7 “look-a-like” at £150 is a much better proposition.

But I still think the first 3 projects should be simple, low expenditure, skill builders aimed at learning to get the important innards and alignments right, hopefully first time, and hang the cosmetics.

The important thing with number 3 is that it turns smoothly, the valve events are right and none of the holes needed elongation to fit. Who cares that the supposed to be square base has a chunk out of the corner ‘cos the bit of steel you found in the road wasn’t quite big enough and one upright is all thread ‘cos you had a bit long enough about the place but no rod left.

What matters is that smooth spinning number 3 proves that the innards are right so you are ready to roll up your sleeves and go for a really nice job on what you really want to make.

Looking back over more than 5 decades Clive now knows he has wasted significantly more time and money by over-ambitious diving in than settling in to nail basics first would have cost. OK he is 12 inch to the foot Home Workshop Guy not modeller but the principle still applies. The mistakes just needed a bigger bin.

Clive

Many thanks for the additional information Andy, as I suspected it makes it significantly simpler to offer suggestions when we have a better idea of your levels of experience and the requirements for the engine.  It also allows us to cut through the clutter of suggestions not best suited to you.  As I strongly suspected an oscillator is almost certainly going to be a better option for you.  This is based on the initial ease of manufacture, as Jason mentioned there are far less moving parts to make, and from the point of view of operation.

Most valve operated engines, be they piston valve or slide valve, frequently require two channels to control, one for reversing and one for throttle.  There are some valve engines that can be operated by a single channel such as the Hemmens Caton but usually you require two.  There is also an electronic device by Denes Designs which automatically mixes the two functions into a single channel but, again, adding complexity.  A twin cylinder, double acting oscillator with a built in control valve will allow you full control from a single stick on the transmitter.  We usually set this up to be the left hand stick up and down, so the operation remains exactly the same as it would be for most electrically powered models.

With that in mind one of the best sources for plans at the moment is still the Paddleducks site.  They are paddlewheel orientated but they have a comprehensive plans and articles download section where you should be able to find a suitable double acting, twin cylinder oscillator plan.  Have a look through here:

https://www.paddleducks.co.uk/smf/index.php?action=downloads;cat=9

One of the more active members there in the sites heyday was a very good friend of mine who used the ID Bogstandard and who built this engine, sadly now passed away:

The engine is a bar-stock engine so possibly one of the simpler engines to consider building as a first attempt.  Having said that a small oscillator such as that is more than capable of powering a model boat of the 3 to 4 foot size with complete control through a single channel.

If you haven’t operated a steam model before just one or two other things that you might want to bear in mind.

1) Plan the internal layout carefully for accessibility.  An open hull is much easier for a first model but, if enclosed the access needs to be quick and easy.

2) A boiler without a feed system is easier to operate for a first time operator.  You should aim for a boiler that has a capacity to give you around 15 to 20 minutes running before you will have to bring it in for filling the boiler, emptying the separator and topping up the lubricator.

3) Probably one complexity that is well worth considering is controlling the burner to prevent over pressuring, lifting the safety valve and wasting energy.  The easiest is a mechanical valve called an attenuator valve or there are electronically controlled ones as well.

4) Try to arrange the plant to enable the boiler and the gas tank to be sat on a common base.  This will enable a bit of waste heat to transmit to the gas tank to offset the gas cooling effects.

5) Mounting the boiler, separator and engine all on a single base and using a simple pin type coupling makes for quick and easy removal of the plant for maintenance.

6) Disposable gas tanks enable dealing with the gas cooling effects but the tanks need a bit more space and are a lot more expensive to run than a refillable tank.  Disposable tanks do not need any form of certification.

7) If you are considering building your own boiler discus with a club’s boiler inspector first.  He will give you ideas on how to progress to ensure certification is easy.

As I suggested above I think a first steam model has more chance of being built and operated successfully if it is kept simple.  Large, imposing, impressive models such as the Wide-A-Wake certainly generate interest and look wonderful on the water but they can be complicated to build and need a degree of experience to operate.  I have come across a good number of modellers in the past who have admitted they have half built Stuart Turner engines or not completed models sat on a shelf because they have found them too difficult to build, too time consuming or, frequently, too expensive.  An engine of the Bogstandard type above I’m sure would be very rewarding to build and install in a model and be within the capabilities of a relative beginner with a technical background.