Found it, 1979. It's 16 Mb, so might have to be dropbox. If you want a copy send me your email via pm

You really only need a governor if the load on the engine is changing. I most cases they just get run for display in which case a low VOLUME of air/steam will slow the engine. Speed like on full size is controlled by regulating the flow not the pressure.

But if built well with no tight spots then you don't need much pressure for display, it's only when the engine needs to work that you need to use higher pressures 5psi should be enough for display and the push fit pneumatic flow valves work well to adjust engine speed.

Running the governor faster will increase it's effectiveness but there are still a lot of losses due to friction in the linkages to overcome and the sprung belts are not the best for transmitting an even drive so best treat the governor as eye candy unless you intend to have varying loads on a working engine.

Also bear in mind that this is a model of a small beam engine not a massive great pumping engine so it would have run faster than what most people think of as a beam engine though you do still get people thrashing them.

Edited By JasonB on 29/01/2023 07:59:52

Which raises the question: How does time and speed scale on a model? If you build a 1:12 model of a beam engine, should the RPM be 1/12th of the original's RPM? Or should it be 12 times the original RPM?

360 degrees is the same however you scale a subject as it 60seconds so rpm should the the same. In practice the smaller the engine the faster they need to run if doing work.

It's only if the model is moving that distance may want to be scaled that things get complicated.

Regarding the pressure /volume issue, this engine is running on 5psi or less as that is as low as my compressors pressure regulator reads but I'm not altering that to get speeds from 2250rpm down to a tick over, it's the volume of air that I'm adjusting. You don't see a full size or model loco or traction engine letting the boiler pressure drop to almost nothing when they want to run slowly.

Edited By JasonB on 29/01/2023 13:37:53

Yes, as LBSC said, you can't scale nature, which would include time. Thinking about it some more, if a full sized engine doing 30rpm is viewed from a far distance so it looks the same size as a model viewed close up, it is still doing 30rpm. So model speed equals full size speed when it comes to rpm.

But linear speed not so much. The rim of the flywheel on the full sized engine will be doing many times the speed in feet per minute than the small model's flywheel rim at the same rpm. And I can't imagine a 5 or 7-1/2" loco doing 60mph and upwards around a typical club track. Its linear speed would seem to be reduced proportionately.

So presumeably, the model loco's axles and wheels could rotate at the same RPM as the full sized prototype, but the wheels being smaller in circumfrence transfer that same RPM into much less linear distance travelled, in the same amount of time. Time being not scalable as per LBSC..

So most videos I have seen of model stationary steam engines whizzing away like crazy on compressed air are in fact way over-revving. They should tick over slowly like the original big 'uns. But, who can resist the temptation to "see how fast she'll go"?

Edited By Hopper on 30/01/2023 04:11:59

Hello Leon,

In a full size situation the governor is mainly there to keep a constant set RPM – ie the working speed. If the engine for what ever reason speeds up the throttle closes and if a load comes on slowing the engine then the throttle opens up to bring it back to the set RPM

From a model perspective it's difficult – though not impossible – to achieve that but if a model engine is just for display then it's probably best to just ignore the throttle and let the governor follow whatever speed the engine is run at.

Increasing the governor pulley diameter relative to the drive will slow things down but even with a perfect throttle is very unlikely to achieve the result you are after.

I have made three engines with governors – the first, a twin Victoria had a throttles of my own design rather than the butterfly type recommended. These were on each steam chest connected by a common shaft. These were a barrel type similar to an RC carb. The second was on a scaled up Waller engine, again a barrel type and the third on a Corliss engine that controlled the timing of the valve opening.

All worked to a degree, the TwinVic the best of them – if a load was applied to the flywheel the governor would operate the throttles or valve gear but not enough on any to call a 'successful' governor.

The key from a model point of view is 'Throttle' – I'm my view its difficult to make a really effective and efficient throttle – especially the butterfly type – that works smoothly and efficiently relative to the governor speed

It's each to his own of course but a lot of time could be spent trying to make an effective governor set up to run the engine at a constant speed when for the most part it's visual effect that's required. In that case a governor that just goes round at a speed relative to the engine speed is all that's really required.

Regards – Tug

PS For a second engine that looks to be some very nice workmanship – good luck with the rest of the build 

Edited By Ramon Wilson on 30/01/2023 16:50:49

Edited By Ramon Wilson on 30/01/2023 16:53:14

Having picked up a few engines while running on air and accidently .put my finger on the exhaust it is a way to control the speed when running on air.

As Hopper says steam engines regulate the flow going into the cylinder due to the way the steam gives up it's energy as it cools and expands, by restricting the exhaust you will restrict the steams ability to expand to atmospheric pressure.

As you now say it will only be used for display I would set the compressor's pressure regulator quite low say 10psi to start with and reduce further if the engine is free enough. Then control the speed by having a flow valve in the air line which is the most effective way to adjust the speed.

If it were an engine with reversing gear then with those you do have the option of notching up or down which alters the valve opening again changing the VOLUME of air/steam entering the cylinder each stroke.

Here is an example of a simple oscillator of mine, up to 1min10 I am altering the speed by use of the reverser to cut off the air getting to the cylinder, after that I'm using a flow regulator. at about 3min50 you can see the flow regulator and then the compressor's pressure regulator that remained set to about 10psi for the whole video.

Your engine is looking great. Regarding the governor, mine begins to do its job at approximately 200 rpm. I used the Stuart ratio which is if I remember correctly, approximately 1.75:1. My governor’s balls are scaled down 20% and I substituted a weight for the spring and made other changes to improve efficiency and hopefully improve the appearance. I prefer to run mine at about 60 rpm, so the governor is not doing anything more than revolving.

One additional note about the Stuart governor. The drawing has you making an eccentric with a grub screw in the center and a separate pulley to drive the governor. This makes valve adjustment a problem because you have to dismantle the eccentric strap to adjust the timing. I simply bored the pulley out large enough to mount it over the cylindrical portion of the eccentric and use a single grub screw that is in the center of the pulley.