Author Topic: Use of Smaller Boilers in G3 Locos.  (Read 937 times)

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Offline John Candy

Use of Smaller Boilers in G3 Locos.
« on: Apr 14 2018 09:55 »
Use of Smaller Boilers in G3 Locos.

I hardly need tell you there has been long-standing controversy over the use of smaller (i.e. <3 Bar-litre)  boilers in gauge 3 locos. If you have been a member of this forum for several years, you will have seen the topic raise its head on a number of occasions.

The annual certification regime which the G3 Society introduced for such small boilers (as a requirement to be used at G3 Society functions) has been the cause of friction.
Whereas other organisations (including insurers) have exemptions in place, the G3S adopted a regime, endorsed by the Southern Federation, as applied by model engineering societies to passenger hauling locos.
 This requirement has been considered by some G3S members to be an unecessary burden and a deterrent for possible convertees from G1 and 16mm scales, where no such restriction applies.

It is now understood that a revised testing regime has been adopted by the Southern Federation which takes into account the minimal risks posed by <3 Bar-litre boilers and , consequently, the G3S will adopt the new testing regime.

Forum member "jamiepaige" has long been a campaigner for the lifting of small boiler annual certification and had the following to say on the use of small boilers. 

1. The 'new' Small Boiler code is welcome and can be used to help encourage growth of activity.
2. Within the Small Boiler world, simple proven G1 designs already exist and boilers can be made and certified by Society Inspectors, or purchased cheaply, fully certificated, from professional manufacturers.
3. These boilers can often fit well into G3 scale models of small prototypes.
4. Numerous prototypes could be fitted with <3 bar litre boilers and turn in adequately scale performance.
5. These same small models could also 'pick and mix' other off the shelf G1 items such as cylinder blocks etc
6. Published  designs for a large G1 loco can often be adapted to use for a small G3 loco. Certainly the important working bits.
7. 16mm designs, boilers, parts etc,  have to some extent evolved along different lines, which opens up another source of the necessaries.
8. Using these items could encourage new blood into G3. Once in, they may want to build bigger and enjoy the additional complexity of bigger boilers etc
9. It's not either/ or. If someone wants to start with a Pacific, then that's excellent as well. Find a set of drawings or use a large boiler design.
10. G3 needs to move on from its 'legacy' of ride on activity and focus on scenic railwaying.
« Last Edit: Apr 14 2018 12:54 by John Candy »
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline IanT

Re: Use of Smaller Boilers in G3 Locos.
« Reply #1 on: Apr 14 2018 11:06 »
The idea of using of live steam ‘components’ from other scales is not a new idea in G3 but has never managed the tricky passage from “good idea” to “general practice” somehow.

‘Ginger’ first published his ideas in this area in the G3 Newsletter having previously worked on a project called the ‘Victorian Locomotive’. This internal twin-cylinder design used a CNC machined block (funded by the G3S) as its core component. I don’t know how many engines were actually built but several cylinder blocks sat in G3S Shop stock for some years before being sold off at a small loss. This may have prompted Peter (Ginger) to think about using the single cylinder G1 Project block – which was readily available.

Whilst Gingers ‘G3 made simple’ loco build description is very good, it is still not exactly a beginners guide to building an engine. It certainly describes all the processes very well but it is deliberately vague in selecting an actual prototype (many are possible) and therefore no detailed drawings are provided. A more experienced model engineer (Jamie for instance) who has previously built engines would probably not find this an impediment. But anyone ‘new’ might prefer to look for a better documented design (in 16mm or G1 for instance). This is not a criticism of Gingers work, just an observation.

Thinking about this, there are several areas that seem useful to comment.

To succeed, any new design has to be a complete ‘package’ and it also has to be widely publicised. Complete in that everything required (build instructions, parts, drawings, suppliers) has to be well documented & easily obtainable – and for a specific end result (a particular engine). Widely publicised I believe means that it needs to appear in one of the mainstream specialist magazines.

What ‘components’ to use? Well (in simple terms) there are the G1MRA engine ‘parts’ and there are Roundhouse ‘kits’. The G1 designs are all inside cylinder but perhaps simpler to achieve a scale appearance with than RH (NG) outside cylinders. Other factors do then come into play – such as the need for a crank axle.

However, I think there is another factor. RH provide their overall ‘kit’ dimensions but they are otherwise proprietary designs. G1MRA ‘parts’ are available off-the-shelf but if someone does want to self-build then the original drawings are available to do so (by purchasing the G1MRA books). I think this would make use of G1 ‘parts’ more appealing to a wider audience (to both kit and scratch builders).

I could ‘go on’ but that’s probably enough for now and I’m sure others will be happy to enlarge the conversation. However, whatever the consensus is, nothing will happen unless someone (or a small group) decides to invest a not inconsiderable amount of time and energy to make it so. I’m afraid that won’t be me at this time.  I’d like to focus on my own (many unfinished) projects for a change but I do hope some of you will decide to do something in this area - as it could be an important step forward in making G3 live steam more accessible...


Nothing's ever Easy - At least the first time around.

Offline jamiepage

Re: Use of Smaller Boilers in G3 Locos.
« Reply #2 on: Apr 14 2018 12:34 »
Thanks for sidestepping the previous nonsense and getting to the point of it.

This was part of what I started with, so it might find a home here?

......... it could dissuade new blood from trying G3 scenic railwaying by leading them to believe that G3 norms are somehow entirely different to G1 and 16mm norms.
In other words, more expensive, more regulated, just plain harder work.

Whilst that might be to some extent true for a large Pacific, it is utterly untrue for what could be seen as an entry level first scenic steamer of a smaller prototype.
'Ginger' encouraged this approach a few years ago, and it is still entirely correct.
Much already exists off the shelf in the G1 and 16mm world which could be easily used on a G3 loco.

For instance, this new supplier recently advertised plans for a batch of both Dee and Project boilers, fully certified, for a price iro a couple of hundred quid each.

I don't know whether there are any spaces left on those batches, nor how long those prices might hold, but they are also open for one- off builds.

I have one from their Dee batch on order. Modded slightly with the dome bush shifted to suit the prototype, it will slide into my small G3 0-4-4T nicely.

Since the order, I can say communication has been first class, and photos show a very high quality product. Proof will be in the eating, so I will report further when it arrives next month.

With an off the shelf (relatively cheap) batch built certificated boiler, plus off the shelf batch built single or twin cylinder blocks machined to various G1 designs, it would be extremely straightforward to collect the various bits to assemble a G3 scale steamer based on any number of smaller prototypes, without any boilermaking or much machining skills. And all with a bit more space (wriggle room)  between the frames than in G1.

 Such machined cylinders etc are already available from eg

I have used one of their ready assembled twin cylinder assemblies before, and was pleased with the standard of machining.

The 16mm world is also generating many items suitable for small G3 steamers. Whether Roundhouse boilers and gas systems etc, or 'after market' regulator assemblies etc, there is a great deal that could be used.

An ebay supplier occasionally offers G1 items such as 'Project' type water pumps.

MEL would almost certainly produce G3 scaled laser cut items to any design.

It is probably a slight stretch to say a G3 loco could currently be built with a screwdriver alone, but  people shouldn't be unnecessarily misled or discouraged. It should be no less accessible than  the other 'garden scales'.

If someone is looking for an entry level, or relatively cheap, live steamer for scenic railwaying, then G3 can be just as straightforward as G1 and 16mm. It's just a question of choosing the prototype.

I don't pretend there is any original thinking here, but there is an opportunity to send a message that G3 needn't have any more barriers to entry than the other live steam garden gauges.

IanTs point about a construction series is well taken, but it's also possible to scavenge from what is already available. A full construction book (plus many years of accumulated knowledge) exist around the G1 project. Someone wanting to build a first steamer could easily adapt the plans for G3. I don't mean everything should be multiplied by 1.35 to generate a larger 3F, but rather take the given dimensions for the working bits, hang them on appropriate frames and decorate with platework.
Money where mouth is, here's an example, slowly (too slowly but that's no fault of the concept) being put together.

The boiler design is basically a Project, lengthened to 8in. overall. It will locate in a smokebox which itself has a  lengthened rear annular locating ring to 'bridge the gap'.
The additional length could have been taken up with another 1/2in or so of boiler length, but boiler capacity is already 33% up on a standard Project and it's nice not to be squeezing everything to fit.

(Some photos show a 4-4-4T G3 loco also being slowly built. That loco uses another published G1 design of boiler this one 9in. long, bought off the shelf, and which fits perfectly) 

True, this might be a more appropriate approach  for someone who does specifically want to do some model engineering, but it is SIMPLE engineering, and cheap as well.
Anyway, with some imagination an awful lot of bits can already be purchased off the shelf and assembled.

Now, this approach simply raids what is currently available elsewhere, and adapts.
If my simple maths are correct though, a 8in x 2in dia boiler sits easily within the <3bar litre limit, (<1.7)so it would be easy enough to exploit the capacity to produce a simple design with say a 2 1/4 - 2 1/2in diameter for slightly larger prototypes.
I would though envisage G1 type construction principles with spirit or gas burner, rather than scaling down full multitube, wet firebox, coal fired principles.

(There is a circular argument that as the boiler gets bigger, the easier it is to use coal and all that entails for design. True enough, but this is about simplifying entry into the scale in the first place)

ps On a practical level, I received my boiler from Castle instruments today (see above).
It is superb, and complete with the Dee-type regulator/ blower set up so will save a lot of time. I can thoroughly recommend them as a supplier. And they do larger boilers as well!
For the sake of accuracy though, the boiler that arrived today was actually for a G1 loco I am (also slowly) building. The larger 'lengthened Project' one for this 0-4-4T is still in the queue. Doh. My mistake.

Offline MikeWilliams

Re: Use of Smaller Boilers in G3 Locos.
« Reply #3 on: Apr 15 2018 18:14 »
When I started “Venture” it was conceived as a Gauge 3 version of Project, and I hoped it would result in a set of standard components to help the builder of live steam in our scale, with major lumps being available from the trade.  It was also intended to be a group project, but somehow I ended up doing most of it or, to be exact, finding experts to do most of it for us!

To that end the cylinders were commissioned from Barrett Engineering as an enlargement of their proven Gauge 1 design.  I still have a few available.  The boiler I also hoped would be a standard so that builders could approach the trade and order a “Venture” boiler and everyone would know what it was.  Unfortunately the major boiler manufacturers had such a long lead time (years) that this has not happened yet.  The valvegear will also be available as a set proved to work.

In reality and to my disappointment, there has been little interest in the live steam parts, but quite a lot of interest in complete engines.  I conclude that live steam builders either want to buy ready to run, or enjoy the challenge of making it all themselves.  Very few seem to want to buy commercial components for the difficult bits and scratch build the rest.


Offline IanT

Re: Use of Smaller Boilers in G3 Locos.
« Reply #4 on: Apr 15 2018 18:39 »
There are probably a few factors at work here Mike.

As you say - for some it's all about the building, for others just about the running. Then there is the matter of money versus time. A large RTR G3 live steam engine can cost many thousands to buy new or many years to build - unless of course you are talented a' la Pavie, Marsh or Allen (which unfortunately I am not!).

But I suspect that the biggest problem is that everyone has their own favourite engine (from of course their own favoured Railway). I seem to recall this question being asked a few years back (favourite engine) and we didn't get anything with more than two votes. It's one reason why an inside cylindered engine is a (slightly more complex) better choice for a 'flexible' design - because it's generally simpler to adapt it across different engine types.

So you throw all these factors into the mix and basically everyone wants something different. It's not a problem unique to G3 but dogs us just the same.


Nothing's ever Easy - At least the first time around.

Offline MikeWilliams

Re: Use of Smaller Boilers in G3 Locos.
« Reply #5 on: Apr 15 2018 23:17 »
I agree and understand that Ian, but I would have thought that a twin cylinder block complete and ready to use, with valve above, would be fairly generic and at least as adaptable as the "Project" parts in Gauge 1.

Maybe I just need to get a few Ventures out there and running, so people can see how they work.


Offline IanT

Re: Use of Smaller Boilers in G3 Locos.
« Reply #6 on: Apr 16 2018 10:28 »
I don't disagree Mike - but I think it goes back to the completeness of the 'package' and how visible it is to the outside world. If very few people know of somethings existence, then the potential customer base for that particular item remains small.

And I very much look forward to seeing (more than) a few 'Ventures' up in steam too.


Nothing's ever Easy - At least the first time around.