Model Subjects that Inspire, and to Aspire to..

[DiogenesParticipant @diogenes]

Following on from the ”Traditional Model Engineering” thread and the subject of the same old designs being made I thought I’d start this thread both for those looking for modelling inspiration and those with something new to share that might provide inspiration to others.

Any contributions and ideas welcome, from discussions of the nature of suitable subjects, design, and methods of construction, right through to drawings & plans, or even just ‘mood board’ shots of things that might make an interesting subject.

[DiogenesParticipant @diogenes]

I guess it should fall to me to get the ball rolling with a couple of ideas to start things off, so, first-up..

An idea which has always had some attraction as a modelling ‘experiment’ is to investigate the possibilities that might be offered by the small petrol engines that power garden ‘strimmers’/ brushcutters.

These engines might have the potential to yield up a useful ‘bottom-end’ upon which to base an interesting model – a main point of interest (to me) being that they invariably come with their own self-generating ignition system.

The common models are generally three-port loop scavenged two strokes, with a vertically-split crankcase containing a pressed-up crank, usually with a flywheel magneto affixed to one end; the defunct Stihl FS86 under my bench has a 28mm stroke, 32-ish bore, and a flywheel magneto 90mm in diameter.

The transfer arrangements are usually simple  – anyone familiar with the inside of a two-stroke single from ‘mid-last-century’ is unlikely to find anything to greatly vex them inside one of these..

I am tempted to try a new top-end on (either) the ‘cleaned-up’ lower (or a set of new cases) to see what can be done to create a useable, but period-looking, powerplant.

If anyone else has ‘ever wondered’ and is interested in a dissection, I could be persuaded to record it.

 

[DiogenesParticipant @diogenes]

I have another subject to cover on a completely different branch of the modelling tree, illustrating a couple of points, but not unfortunately, time to post this morning (or permission to use someone else’s picture’s)..

[BazyleParticipant @bazyle]

Moved as best I can to the What is Model Engineering thread as it seems to be more related to that.

[JasonBModerator @jasonb]

A strimmer engine would be a reasonable source of parts and is certainly not a new approach. The likes of Graham Corry would use various parts from readily available (at the time) engines like Jap or Villers cranks and pistons and design his engines around those.

The strimmer crankcases being ali could quite easily be chopped about and additional parts bonded on. As you say the top end could be swapped to a more period looking aircooled design or you could even go with a jacket and inserted liner to make a water cooled engine. Flywheel again easily changed to remove the centrifugal fan blades and the ignition parts built into the new flywheel which would not have to be spoked so just a turning job would give you something that would not look out of place on a tether boat or car.

Add a couple of gears and you could even get a 4-stroke out of it, just needs a cam to work the exhaust valve, inlet can be atmospheric.

[JasonBModerator @jasonb]

Some of the old inboard single cylinder marine engines would be a good candidate for the water cooled option

Old tether engines for air cooled

[noel shelleyParticipant @noelshelley55608]

The one thing I have always wanted to do is make/ have is a steam powered vehicle, on rails though The need for a railway to run it on would not be ideal, or an adaptation of boiler, engine and some form of transmission that would enable said vehicle to carry me down to the pub, and back. I lack the money to buy a ready made machine and the time to build from scratch ! The current plan is to use a Stuart No1 and a 6″ vertical boiler, and possibly Myford change wheels for the transmission. Inspiration? The Burrell tractor, Trevethicks first creation Etc.

The very rapidly changing world we live in, with some with the money but not the knowledge or skill to use the tools they can buy and also  the number of companies producing ready made vehicles, along with the slow loss of skilled men able to teach/ help, make our hobby an interesting place to be.

Can I have a crystal ball please ? Noel.

[JasonBModerator @jasonb]

You just need to find a scrap ride on lawn mower or mobility scooter and graft the steamy bit onto that.

[noel shelleyParticipant @noelshelley55608]

That had been thought of Jason but the rolling resistance I considered to be rather high and whilst the No1 has the power I fancy the boiler may struggle.

In the context of small 2 strokes, some only have an overhung crank and one main bearing, the give away being the starter cord is on the drive side, as opposed to those that have 2 mains and the starter cord on the outer end. The latter would in my opinion be the best candidate, though that does depend on what your making. Noel.

[SillyOldDufferModerator @sillyoldduffer]

I mentioned the need for a wow-factor project in the “Traditional Model Engineering” topic, so Diogenes starting this thread is helpful!

Here’s one I’ve put a little effort into.   Not got far because I’ve already got a long to-do list, and am poorly in a way that intermittently destroys my concentration.   Not allowed to operate machinery whilst ill, and even armchair engineering is takes forever because I can only work in short bursts.  Been a bit better recently, but being unwell has left me even less productive than normal.   Hats off to everyone on the forum who has to cope with illness – it’s hard!

Done some work in Solid Edge, but no developed plans yet, so this calls for original design work.   To speed production, I  intend to 3D-print most of the machine, only making  metal parts as necessary to stiffen it up or reduce friction etc.  I also expect it to be driven by electric motors and solenoids controlled by a microcontroller.   None of this is required:  a purely mechanical system worked by cams and made in metal is fine.   As this for public display, lots of shiny brass and polished steel would be good, even better if the device is powered by steam rather than electricity!

Anyway, here’s the requirement.

• A table top machine that loads and unloads marbles from matchboxes.
• The machine should rotate a small number of matchboxes, say 5, through the following cycle:
  1. Empty closed box arrives at station 1 and is pushed open.
  2. Open box moves to station 2 where a marble is dropped in.
  3. Open box with marble moves to station 3 where the box is closed.
  4. Closed box is moved to the station 4, where it is opened and the marble removed.
  5. Empty, but open box is moved to the 5 station where it is closed.
  6. Next move is to station 1, and the cycle restarts.
• When a marble is removed, the machine should return it to a magazine for re-use.   Moving the marble is an opportunity for bling, perhaps lifting the marble out and high with a rotating helix and running it back to the magazine via a Heath Robinson arrangement.
• Desirable to extract marbles from the magazine and deliver them to Station 2 with another Heath Robinson affair.   I think it’s harder to add bling to this than lifting marbles into the magazine.

This type of matchbox, home-made allowed:

My first attempt in Solid Edge carries the matchboxes on a rotating carousel, with the marble magazine and lift in the centre, main motor underneath.  The matchboxes are opened and closed by solenoids, and CAD suggests the geometry requires them to move levers rather than push/pull on the boxes directly.  The question is still open.

As the design got more complicated, especially planning the way marbles are removed, which requires boxes to be lifted and turned vertically, I started to favour a conveyor belt, in which Stations 4 and 5 receive the matchboxes held upside down.  Gravity drops the marble out at station 4, very simple, but hidden and not exciting.   To maintain symmetry a conveyor belt using top and bottom would need 6 stations, where one does nothing.   Other configurations are allowed.

Any takers?  Be warned, could be a lot of work.   Though CAD breaks the back of the design by ensuring parts fit together and will move without interfering, CAD won’t spot all the practical gotchas.  Like as not, the prototype won’t work first time and it will be necessary to fettle and adapt.   Not much to do if the design is well thought through, but start again from scratch if something major is missed!

Dave

 

[JasonBModerator @jasonb]

Single sides crankshaft is no problem, although a 4-stroke this is one that is in my Future Projects folder and could be done as a 2 stroke if the builder wanted.

They also did a simpler to model one with horizontal cooling fins

I’ve started so may someday finish.

[JasonBModerator @jasonb]

Keeping it to the “Models that I might aspire to”, these are a few that are closer to the top of my “Future Projects” folder. In no particular order except the first two have the majority of the CAD work done and the first I have the metal for.

The one on the left

Had better stop there but hopefully if I post one or two of these builds it may inspire others to have a go at something a bit different. Even old and rarely visited designs can be made with a modern twist or just as originally designed rather then the same old.

 

[DiogenesParticipant @diogenes]

Thanks all for your support and comments – and good to see such a broad range of interesting projects proposed, just what I was hoping for, there are a couple in there that I do like the look of.. ..the elegant table engine is a really attractive thing, and being a ‘steam’ model brings me neatly to another that has appealed to me since I first saw it – not because it elegant or intricate, but rather because it’s compact & workmanlike, and to me, there’s a certain attraction in making something based on a real prototype.

The engine in question is a small, black, single column ‘Doktor’ beam pumping engine that Preston Services had in a few years ago – the photo’s that they produced are clear, ‘scaleable’, and show enough detail to make having a stab at a model a realistic proposition (- they are discoverable on an image search, but I can no longer find them on Preston’s site).

Why do I like it? -there are some interesting aspects to the construction – it’s very compact and economically produced – there’s enough going on in a small space to ‘fill it’, but no clutter – bits of it would be interesting to produce without feeling like it will take forever to complete; sometimes having a good balance of ‘difficult’ and ‘easy’ parts in a model helps with the enjoyment.

As they are easily found, I’ll post one here (- if a moderator feels it is likely to cause ‘issues’ please feel free to delete it – if anyone is very curious/can’t find them, pm me)..

 

 

 

[JasonBModerator @jasonb]

Looks like it was almost designed with the model engineer in mind.

Nothing there that would be too hard to fabricate – parallel column, plain twin beams, simple flywheel, no Watt fiddly linkage, etc.

Cylinder is an easy fabrication and the round valve chest is a bit different but should present no problems.

Nice to have the two ram pumps and their four non return valves working. There is some hidden plumbing within the base and I assume that one has the water inlet on the far side, the outlet is the flange on the bottom of the column. This one has them both on the same side so you have the option to model it either way.

So what is the biggest flywheel you can turn?

[DiogenesParticipant @diogenes]

About 280.. ..as a straight turning job..

[DiogenesParticipant @diogenes]

connections.. ..there’s now a gallery in my profile..

[JasonBModerator @jasonb]

I suppose a 200-225mm flywheel would keep the other parts a managable size.

Thanks for the other images, surprised the beams are so thin and that top support for the cross head guides looks a very light construction but expect it did it’s job.

Looks like there was an option to use either side as the outlet or even both. Shame they could not manage a photo from below but the pipework should be quite simple and is probably just a tee to take the feed to both sides and similar to bring them back down to one at the base of the column. I wonder whether it was all cored and cast into the base or just pipework, the later would be the easiest option on a model.

[DiogenesParticipant @diogenes]

Yes, they didn’t waste much metal – one of those when you are glad to have kindly Preston Services’ pictures of the real one, it’ll probably look even more flimsy as a model..

I’m guessing it was clearer to you, much quicker than it was to me, that the bits you can’t see are going to be far more tricky than the bits you can – going to end up with quite a lot of pipe to fit in there..

I wonder if it’d be possible to mill the galleries and passages between the pumps and valves in the upper face of blocks and secure to the bottom of the tub from underneath – even have the valves/seats in there..

..or sit it on top of one of those suspiciously box-like plinths you occasionally see 😁

It’ll give me something to think about at the weekend..

 

 

 

 

[JasonBModerator @jasonb]

I was thinking along similar lines, there are a few options particularly if you assume nobody will get to look at the underside.

1. a lot of pipes and joints

2. a block which could be drilled horizontally to get to the pump and valves and vertical hole sup to them. Th eends of the horizontal passages could be plugged.

3. Top of the block milled out as you say and closed by the upturned “bathtube” engine base.

On the Camron pump I went with the tube option though most of the passages were within the upper casting not the base

 

 

 

[KEITH BEAUMONTParticipant @keithbeaumont45476]

When I look through all the engines that get shown on here, I notice  that the Atkinson Cycle engine is not one that shows up,or gets discussed. Though perhaps Jason has one in his “to do” folder. Before anyone suggests that I start the ball rolling and make one.I think it will take me too long. At my age I like to keep my projects reasonably short.

Keith.

[Nigel Graham 2Participant @nigelgraham2]

This idea was inspired by a reference-book I’d inherited from my father, a Chartered Electrical Engineer.

For anyone wanting pure engineering puzzles, in a sort of half-way between ornamental-turning and replicating antique prime-movers, the huge range of mechanical-transmission mechanisms invented over the last couple of centuries might be interesting to explore.

Replicas of them might not strictly be “models”, and the full-scale ones were made in many different sizes anyway, but would demonstrate how machine designers solved such problems as varying shaft speeds in a set manner throughout an operating cycle, when things like stepper-motors were far into the future. I wonder if some were intended to circumvent (or “improve” on!) others’ patents, as patent-lawyers appear to have been as lawyerly then as now!

I exclude ordinary cams. Anyone can make a cam (though they can be difficult, so a challenge, to design).

I include all manner of link motions, non-circular gears, variable-speed controllers, etc. How, for example, do you cut correctly, a pair of square or elliptical gears so they operate as intended?

……..

Having been rude about poor cams, actually a cam-driven device was among my earliest inspirations of a general interest in engineering. When very young I was fascinated by the then-mysterious bobbin-winder on Mum’s ‘Singer’ manual sewing-machine.

A heart-shaped cam drives a rocking-lever thread-guide so the bobbin winds each layer evenly, needing constant velocity for the bobbin’s full length with near-instant reversals. Not long ago it occurred to me to wonder if the cam curve is based on (A, Sin A] on a polar axis, where A is the cam’s angle of rotation – but I have yet to experiment, probably by spreadsheet. I found some years ago that the polar [A, Sin A] graph does look cardiac.

In recent years I saw a much bigger solution to a similar problem, on a special winch. The follower is a roller or a lozenge-shaped block on a pin, in a pair of helical “threads” of opposing hands, like a giant knurl, linked by a rapid transition point at each end of the travel. The thread pitch is the diameter of the hose wound onto the drum, via a fairlead connected to the follower.

[JasonBModerator @jasonb]

The Atkinson is not really on the list but I did look into them a few months ago when someody asked me to identify some castings. I have seen a couple made on US sites.

Nigel here is your starter for 10

Here is another nice model that may appeal to those who don’ build engines which I came across while looking at the Doctor type beam engines. Not only did the original have nice lines but the model is very nicely done and the patina just right. Anyone up for it?

[DiogenesParticipant @diogenes]

Thanks Jason – the base will be the starting point, then.. ..don’t expect much progress before lunchtime..

Keith, you are right, there haven’t been too many Atkinson’s crowding the forum – I like the appearance & motion of the Differential Engine especially and it is one of those engines that seems to have a visual appeal and interest to ‘non-model-engineers’.

If anyone has pictures, especially if they have built one, please do post.

Nigel, yes, modelling ‘mechanisms’ is often overlooked, but as you say could probably be made an avenue of modelling to occupy a lifetime – I have seen cased ‘exhibition/demonstration’ models of ‘mechanisms’, I can definitely see the appeal of producing a couple of those, or even a series illustrating variations, or the ‘evolution of an idea’..

..also ‘the interesting parts’ of larger structures, such as engines and transmissions as standalone models – Monitor and paddle-steamer engines are a popular choice, but I’m sure there are many other candidates – I did look with passing interest at the ‘Shay’ drivetrain in a recent thread.. ..I’m pretty sure there are locomotive valve gears etc., that are complex and interesting enough to make a good model in isolation, let alone a whole world full of more modern subjects..

 

[DiogenesParticipant @diogenes]

Nice gun – the finish is spot-on indeed – is it a bronze ‘spine’ to the carriage?

..be a nice one to ‘do’ for relief in / to break up a larger project.

Do you have a link?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi JasonB, I really like the look of this one, just as it is, as the characteristic look reminds me of some of the background machinery that I’ve worked on, that have been in place for many years, that VIP visitors don’t get to see, which don’t have to look all shiny and new, but keep on working, not that I’ ever worked on any steam engines though. But I’m sure it will look good as a model all painted up.

Regards Nick.

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