What is the advantage of more than 2 cylinders

[joanlluch]

Hi, I am new to this hobby and I am starting to arrange things to build a freelance 5" live steam loco.

I have a question regarding the number of cylinders on steam locomotives.

A loco with internal cylinders will be harder to build due to more parts involved and so on. I wonder if having internal cylinders really pay the extra building effort?

Considering a locomotive with 2 sideway external cylinders, and another one with 3 cylinders, can both be expected to perform the same provided that the total volume displacement is the same (i.e cylinders on the first loco are 50% bigger to compensate for the lack of one more (internal) cylinder)?.

So, what is the ultimate reason why locos would have more than 2 cylinders. Is it a mater of compactness (constraints on total width on full scale locomotives) or is there a more subtle reasons, such as smother running? Is there any significant difference between 3 cylinders or 2 bigger cylinders for a model locomotive?

Thanks.

John

[digger]

A three or four cylinder locomotive, delivers power more smoothly, two outside cylinders can induce a rocking effect known as shouldering I believe, for the same cylinder capacity, a multi cylindered ( three or more) locomotive should be more powerful, due to the additional adheshive weight.

Digger

[Roger]

I have no idea about the benefits of many cylinders in model locomotives but the complexity means that the design and build time is going to become much longer. Don't underestimate the amount of time this is all going to take. I see so many part built locomotives for sale where builders have bitten off more than they can chew and started too late on their projects. I don't know the ratio of locomotives started to locomotives completed but I'd wager that more don't get finished than do. If you really want to complete this locomotive then I'd suggest keeping it as simple as reasonably possible.

[Deleted]

I would to a point disagree with certain parts of that Roger, personally when I was embarking on my journey I considered primarily 2 designs, both 3 cylinder, the reason being I have no idea how much time I will be able to commit to the project and I decided that I wanted to get one engine finished so best make it a good one in case I don't have time for a second.

(By that I mean a larger main line prototype of express pass/goods type, which is my preference, I am not insinuating that any other type of engine or anyone else's engine/decision is the wrong one)

The 2 choices were Michael Breezes V2 and Neville Evans Schools Class, now this is where Rogers other comments ring true, I decided on the V2 as it saved 1 set of walschaerts valve gear from being made and Schools are more likely to be "slippery" being 4-4-0s so the V2 it seems to me to be more practical (yes you did hear that from a southern man!)

It's horses for courses, you have to do what's right for you as the builder

Cheers
Ben

[digger]

If the interest is truly there, you can achieve what you set out to do, My first locomotive a GWR Manor took me six years to complete, I remade several parts I was not happy with.
My second locomotive that I built took three years to complete a three cylinder re-built Royal Scot, far more complicated than the Manor, but very few parts remade this time, once you have completed your first locomotive, the second one is easier, by virtue of the 'learning curve in both machining techniques and not repeating previous mistakes'

Digger

[austerity]

Sept 27, 2014 20:29:00 GMT Roger said:

I have no idea about the benefits of many cylinders in model locomotives but the complexity means that the design and build time is going to become much longer. Don't underestimate the amount of time this is all going to take. I see so many part built locomotives for sale where builders have bitten off more than they can chew and started too late on their projects. I don't know the ratio of locomotives started to locomotives completed but I'd wager that more don't get finished than do. If you really want to complete this locomotive then I'd suggest keeping it as simple as reasonably possible.

Many years ago,in the early 1970`s,i joined a model engineering evening class run buy the ILEA in N.London,this was where i built a lot of the parts for My Simplex,now sold i`m afraid.However we used to get quite a few people who wanted to build a live steam loco.We used to explain to them that it was a long job,focus on the finished loco but you had to be interested in using hand tools & m/c tools,a lot of these folk used to go away & we never saw them again.



Ray.

[austerity]

The chassis & castings for my 2-10-0 Austerity have been lurking about in my garage since about 1983.My wife told me to get on with it as i`m not getting any younger which led to the purchase of the new milling m/c.Milling coupling rods out of steel bar is very time consuming.I remember an article in ME some years ago by Keith Wilson who described making the bosses & welding them to steel bar,if they were too long,he heated them & bumped them up to shorten them or stretch them a bit to make them longer.I never learn t to weld but it seemed a good idea.


Ray.

[Shawki Shlemon]

I read all of the above , everything said is relevant to loco building , however I believe one must build what he/she like and think it is within his/her capability to do so , most models are of two cylinder design ( I have built both two and four cylinder engines) , two cylinder engines perform very well each for their size and power . I must agree with Roger that a lot of engines do get started and not completed , I personally have bought castings from persons who bought the castings but gave up the project . Now this is my opinion , study the plans carefully , acquire castings and materials , break the project into small sub projects , achieve each one and celebrate success , join a club , ask people with experience , it is not a shame if one does not know something , there are more people to help that one thinks . I would build a two cylinder engine for starter then whatever I fancy , that is not to say that one can't build a 3 or 4 cylinder engine first , it will take longer time to finish it .

[isc]

As far as extra power from a four cylinder engine, at this size it would probably be cancelled out by the extra friction of the multitude of extra moving parts, yes the multi cylinder engine will be smoother, and may be easier to start off, but I think a two cylinder engine will out do the four at normal running speed. isc

[Deleted]

Hello there--------welcome and thanks for seeking help from the members.......I would appreciate some of your background info. such that we can gauge to what depth of instruction we need to go............Are you UK based or elsewhere in the world --------------------what, if any engineering skills / tools do you posses-------------what do YOU think this freelance loco is going to cost you to build overall ??------------

[Roger]

I'd be curious to know if at model scale you can ever put down the extra power onto the tracks.

[cotswold]

At your stage in the game, surely the best advice is to "Keep It Simple"!

And no, as normally designed and built, a four cylinder loco does not deliver power more smoothly. The most well known exception to that rule is the "Lord Nelson" class of 4-6-0 on the Southern Railway. They had their cranks set at 135 degrees rather than the normal 90.

[uuu]

Once you've figured out how many cylinders you want, or even before you've resolved that, you can start to think about valve gear. Walschaerts? Stevenson? Baker, Joy, Hackworth? Holcroft or Gresley conjugated? Oh, and piston or slide valve (or poppet)? So many choices.

Wilf

[donashton]

John,

Welcome to a great hobby. A crucial point to success is your enthusiasm, especially if you hit a difficulty. A freelance engine will require a good deal of design knowledge - are you sure that you can cope with this? There are plenty of fully drawn locos in the 'fairly straightforward' category with a proven record and the helpful guys on this forum can advise because it has all been done before. That help is less easy for a freelance.

Don.

[Deleted]

I've just re-read your post.....Is it that you actually want to ...a) DESIGN and then BUILD your own loco ( "Freelance" in that sense ) or do you want to....b) BUILD an existing loco that is of a "Freelance" design and not based on a full-sized prototype eg}--SIMPLEX ??............. If you have absolutely no experience at all then (a) is going to be a long, torturous, drawn-out affair and probably won't get finished and it will all end in tears !!................Listen to DON's advice.....and as COTSWOLD says}--- Keep it simple..

[joanlluch]

Hi all, thanks for all your comments


Roger, What I want to do is (a) : "DESIGN and then BUILD my own loco". And I fully understand your point. It is true that I have no previous experience on steam locomotive design but I worked on the chemical industry for more than 20 years implementing gas-liquid chemical reactors, industrial dryers, industrial furnaces and head exchangers. The job involved designing, building and commissioning of said industrial equipment. I own an Industrial Engineering degree.

My intention is to base the locomotive on one or more existing designs, particularly for dimensions of parts. I am looking for example to the 5" Britannia. What I have done so far is to design the geometry of a Baker valve based on a loco with a wheel diameter similar to a Britannia. Please, see this video I posted some days ago to YouTube: youtu.be/hzJr6GkfezY. I am using mm in all dimensions. I chose the Baker valve gear because It has no sliding parts and thus it should be possible to use lubricant free polymer based bearings. My question was whether it is worth to bother with implementing internal cylinders (like the Britannia) or not. I am happy the consensus has been "2 cylinders is perfectly fine" because, as you (and others) recommended, It is best to keep things as simple as possible.

I do not want to just build a kit because my stronger motivation is on design, because this is what I have done in the past.

Wilf, I chose Baker with piston valve. Please see my video of my progress so far to define the valve gear geometry (see link above). I understand that valve time events obtained using the Backer are not as perfect as Stephensons or Walschaerts, but as said, I chose Baker because it has no sliding parts and thus it brings the potential to chose (and test) several kinds of bearings. In any case I would appreciate any comments on your experiences with valve gears.

@4930hagley, I am based and born in Catalonia but I traveled reasonably around mainland Europe and the UK, so not based in the UK currently. (Before anybody gets it wrong, please do not call or consider me a "Spaniard", that would be on the edge of being offensive, and hopefully Catalans will get rid of that heavy load really soon, you know :-)). I am aware that the costs involved on building a loco are not low, but to be honest I can not tell exactly how much that could be. I understand that cost could be at or above 5000 EUR. Any hints would be appreciated.


Last but not least: Of course, I can't completely be sure at this time whether I will succeed at it, or whether difficulties will set me back at some time, or if my motivation will fade away. But so far I can tell that I am very determined and I hope that with all the online (and off-line) resources available and your help, I have some chances of ending doing a reasonably good job. Or at least this is what I hope.

Thanks !!!

John

[Roger]

I think you might be under a false impression about what's involved in making a published design because you use the work 'kit'. Things really couldn't be further from that. In reality, there are castings for those and some laser cut frames, but after that you're on your own. Take a look as my SPEEDY thread and you'll see how much redesign and re-engineering sometimes goes on even though my plans go back to the early 50s and ought to be right.
If you're going to go ahead with your project, I'd strongly advise you to build the whole locomotive as a 3D solid model, it will save you endless hours and heartache. Don't forget too that you'll need to work with a Boiler Inspector to get any new or modified boiler design approved before you even start that part. I don't think you'll be short of challenges even if you decide to build an established design. Mine won't have much of the original left once it's finished but at least the overall proportions and look will be more like the real thing. What I'm saying really is that you don't need to go to the extremes you're proposing to get a real challenge with plenty of design involvement.

[Deleted]

Hello JOHN--------- A lot of folk who want to build a steam loco/traction engine/boat etc. and come on here for help and advice literally have absolutely no engineering experiences whatsoever----------With your Industrial Engineering degree, the computer drawing skills ( say "hello" to ROGER ) and the type of work that you do then I don't see any major problems ahead in those departments.......I'm guessing that your Bench fitting and machine tool skills might not be up to what's needed ??---- but that will come with time spent on the job as we make progress...................So, welcome aboard and let's get started !!....I'm particularly interested in this as I've not long ago finished the design stage of my 5" GWR 4-6-2 The Great Bear....But this by comparison was fairly easy as it consisted mainly of modifications and alterations to existing designs AND a whole HEAP of research work................... Of course it WILL succeed because your motivation WON'T fail because we WON'T let it !!...There --- how's that for starters then ??............................Have you access to, or do you own}---- a machine workshop that has at least a decent size lathe and/or a vertical miller ?? ( Plus the usual bench, vice, hand tools etc) -----------------------and looking slightly ahead, equipment to form and assemble the boiler ??.........................We have on this forum people who can do small quantity castings if required,------ laser cutting is also available ( will save you lots of time and seat !!)............... EDIT}---- oops, just missed that one...YES, as per ROGER's post as well------especially the Boiler Inspector bit...That's what I had to do with mine ( It also helps that he's building it as well !!)--------------

[joanlluch]

Hi Roger, thank you very much for your highly involved replies. This is really appreciated. I am aware (or at least I believe so) of what is involved, including the need to machine castings and to silver solder things. I may have used the work 'kit' suggesting a wrong meaning possibly because English is not my first language, but nonetheless I think I understand fairly well what's involved.

Indeed, I intend to draw the loco or parts of it, on Solid Edge before starting building it. If you looked at the youTube link I posted above you'll see I started at it already. I have taught Solid Edge myself very recently because on my past job in the chemical industry I had some staff working for me (younger people) that were at the actual drawing. So yes 3D drawing of parts and mechanical simulation of the locomotive assembly is a must have to get some chances of success.

About the boiler, this is something I have not looked in detail so far. However I have been asking around and apparently in my country, and also in France I think, constraints and regulations for model boilers are not as stringent as in the UK. In particular I have been told that there is no specific regulation for model steam boilers and thus the existing rules apply to pressurised recipients in general. These rules would apply starting from a particular pressure and recipient volume. I definitely need to look at that carefully before starting with the boiler design. Of course, if I sometime would have to bring the (finished) loco to the UK to run in public, I am aware that I would have to ask for a proper boiler inspection and certificate following UK rules. Ultimately, in order to minimise headaches, for the boiler I can look at one of the commercially available ones.

Thanks

[jma1009]

hi john,

and welcome to this forum!

john has already raised these matters on the ME forum over the past few weeks.

i firmly believe that very little can be done in miniature to 'improve' upon the best of the well known 5"g ME and LLAS locomotive designs by the likes of martin evans and don young. and dear old LBSC designed some extremely good 2.5"g and 3.5"g locos.

(the bad designs can require a considerable amount of work as roger and others have found out with SPEEDY etc)

even the really good designs can be indifferent performers if some of the basics are not adhered to and the valves incorrectly set and draughting, and springing not done carefully, or simply driven and fired badly!

in fullsize there have been some notable 'improvements' to fullsize locos with perhaps the Bure Valley, RHDR, and Ffestiniog locos being the best examples in the UK. however to 'improve' something you have to have a knowledge of what the problems are that you want to overcome, and on a steam locomotive there are many factors that cause a purely theoretical approach to be constrained.

if you dont have any experience or knowledge of what makes a 'good' loco different from a 'bad' loco then i would strongly suggest building one of the well known 'good' designs. even then you could still end up with an indifferent performer as an awful lot is left in the hands of the builder to sort out such as valve setting, springing, correct fit of parts etc

one of the best type of boilers for producing steam efficiently is the type of boiler fitted to the old GWR Broad Gauge locos with raised firebox, and the short but wide and raised firebox of many narrow gauge locos is also very efficient. one year at IMLEC, much to everyone's surprise, a 5"g GNR single won the cup!

cheers,
julian