Cylinder Boring Techniques for Steam Engines

[Clive HartlandParticipant @clivehartland94829]

Hi Will, The Ifanger Boring tool system is in a size system from about 3mm upwards to a quite large set suitable for boring very large cylinders.

Sharpening is easy, touch up with a diamond stick or a light touch on a white wheel, they are very tough and are Cobalt tooling and last a long time .

The head shapes are specific for 60Deg and 55Deg, with angle heavy duty and corner types. There is a set for cutting internal Cannelures.

i bought the cutters as certain types of work came up and the smaller ones were for a job doing Fibre Optic receptacles, a long complicated job that was.

The bigger ones I used on the Mill for boring bigger internal diameters rather than use the lathe as the job could stay on the rotary table.

Clive

[Will RobertsonParticipant @willrobertson16447]

Hi Clive,

It's good that Cobalt actually refers to the composition of the steel in this case.

Thanks for your advice about sharpening – am I right in thinking that tools like this should never be allowed anywhere near the dark grey carborundum grinding wheels used to shape HSS tools? Are white grinding wheels always a finer grain?

When you say 'diamond stick' what should I look for in buying one? I've a set of diamond stones but the manufacturer didn't specify the grain and they don't seem to hone to a very fine finish.

The fiberoptic job sounds difficult – small and fine alignment!

I was having a look at some of the suppliers AES had mentioned and trying to work out where to get materials to make the piston and valve spools. Looking through the 40 page catalogue of one at the moment – wish they'd state composition as well as code numbers for the steels.

Will

[Clive HartlandParticipant @clivehartland94829]

Will, Arc Eurotrade do diamond stones, a set of 4 at £12.60 . these are what I use. They are on a plastic handle and weigh nothing, so post will be cheap.

I use both types of grinding wheel, it all depends where I am at the time I need to sharpen tools as I work in two different places.

materiel, I would ask for S/steel in 304 grade for the spool and a bit of bronze for the piston if its used in a Cast iron cylinder. If its a Bronze cylinder then a bit of S/steel will do. As long as they are different no problem. You only need small quantities, unless you want to hold stock for other jobs. Remember to order enough to hold in the lathe so that you can get the job out of it !

Aluminium bronze is much harder than ordinary bronze so avoid it. Leaded bronze is good.

The bees were flying well today and I have another sale for a Nucleus as the chaps hives have all lost their Queens. I may visit to have a look myself to make sure. This chap is always in the hives and I think it upsets the bees.

I may take some honey next week, i hope the weather holds out, it was 23C at 3pm today.

Clive

[Will RobertsonParticipant @willrobertson16447]

Hi Clive,

Good to hear that the bees are doing well with the better weather.

We have wonderful creatures in France and Switzerland that oscillate their wings like a bees but look more like a giant moth. They don't land on flowers but hover in front of them to suck the nectar out – like a miniature humming bird. Probably very different from bees in their lifecycle but amazingly beautiful so I thought they merited a mention. Wish they lived in Scotland.

I hate paperwork so I'll try to get enough stock that I don't have to order again soon. I'm also expecting to have to make two or three attempts at many of the components (more for some) as I refine design and technique. Then there's the next engine to think about…

The diamond stones will go on my first order to Arc Eurotrade

One odd question came into my mind. How close should the piston come to the end of the cylinder? Trying to work it out from first principles I reckoned that the piston should come as close as possible to the ends of the cylinder but many designs seem to leave a fairly large clearance.

How should I work out the sise of flywheel to use? I vaguely remember the calculus to work out the moment of inertia of a a flywheel but I've no idea how to relate this to a steam engine so I thought I'd guess the sise of flywheel based on roughly the the relative sises of flywheels and cylinders used in horizontal mill engines.

Will

[Clive HartlandParticipant @clivehartland94829]

Hello Will, Your hovering Moth is a 'Hawk Moth' which mimics a humming bird, we get them here as well.

This evening I transferred the bees into a travel box for delivery on Sun. morning. I will go down tomorrow night at dusk and close the entrance and bring the up home and they go first thing in the morning.

I think most flywheels I have seen on models seem to be relatively heavy, they must add inertia to the motion. Working out what size and weight I have no idea. If it looks right it will work !

As most steam engines have the cylinder head flush with the head of the bore some relief is needed to clear the steam inlet ports. On the little 2 Cyl. model the cylinder head goes into the bore about 1mm as the inlet port is machined in the cyl. head, but on the Evening Star the piston stops about 3 or 4mm short of the end of the cylinder. This to keep the steam inlets clear which are drilled through the sides of the cylinder at an angle. It all depends on the design and method of steam transfer used.

I suggest that you draw it up and use cardboard shapes of the components in the flat with fulcrums pinned down and see what happens as you turn the parts. It will give you a good idea if your design is feasable.

Clive

Edited By Clive Hartland on 10/08/2012 22:08:03

[NJHParticipant @njh]

Sorry – nothing to do with cylinders but, seeing your discourse on the Humming Bird Hawk Moth, I thought you might like this pic of an Elephant Hawk Moth which visited the other day.

Norman

 

Edited By NJH on 10/08/2012 23:01:53

[Will RobertsonParticipant @willrobertson16447]

Hi Clive and NJH,

Thanks for the information about and photo of the hawk Moth – it must be too cold for them in the Northern half of Scotland. Did some background reading and interesting that some types of hawk moth pollinate orchids – interesting that such a beautiful pollinator works with such beautiful plants. (I've a collection of less specialised orchids – just simple Phalenopsis but still beautiful.)

Hope the Bees' move goes well.

I was thinking about bringing the steam in via the cylinder heads so that clearance coul.d be minimised – I was trying to work out how it would affect performance – theoretically I think it should give an improvement.

Cardboard prototype is probably a good idea to make sure that everything fits together.

Will

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Will ,

Re: End clearance in cylinders .

The cylinder end clearance and the passageways from the valve face all contribute to 'dead space' . This is a volume that has to be filled with steam every cycle before any useful steam can fill the cylinder and provide the power stroke . This steam contrbutes (almost) nothing to the power output and is a dead loss in efficiency terms . The actual calculation of the effect of dead volume on efficiency is complex in extreme for a full size engine but for a small simple engine running on cold wet steam the ratio of efficiency of a cylinder with dead space compared to a cylinder with (ideal case) no dead space is :

ie: (Swept volume of cylinder alone)/(swept volume of cylinder plus volume of dead space)

So for a cylinder with 1 cubic inch swept volume and say 0.1 cubic inch dead space you get a fraction of 1/ ( 1 + 0.1) = .91 . For a cylinder that is very inefficient anyway multiplying what you might achieve at best by 0.91 is not good !!

Like everything in engineering though the situation is not quite cut and dried – Just a couple of mentions on this :

(a) When an engine is working at very short cut offs the dead space can , in some cases , provide a little reservoir of steam which keeps the MEP up .

(b) Presence or absence of dead volume has an influence on whether the running of the engine is 'hard' or 'soft' . This is due to different deceleration and cushioning effects .

Re: Flywheels .

Calculations for a flywheel are perfectly possible but unless a lot of different factors are taken into account the result can be meaningless .

Most flywheels are designed by copying what has gone before on other successful engines .

Just a few thoughts though :

(1) There is no one unique solution for design of flywheel for a particular engine – there are thousands of viable alternatives .

(2) Purpose of of flywheel , apart from carrying an engine past any dead spots , is to provide regulation in respect of cyclic speed variations caused by non ideal running characteristics of engine and load – basically to control what is usually called 'hunting' – and to control (with other factors) the smoothness of acceleration or de-acceleration of planned speed changes .

Regards ,

Michael Williams .

Edited By MICHAEL WILLIAMS on 12/08/2012 10:17:08

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

I forgot to mention one purely practical consideration regarding end clearance of cylinders . An end clearance which is really small and a poor arrangement of inlet passages can trap droplets of condensed or primed over water . As piston nears cylinder head these water droplets can have nowhere to go and very high pressures can be generated – sometimes in full size enough to blow the cylinder cover off . Many engines do have small end clearances but are fitted with special blow off valves to avoid problems .

Not much problem in little engines though – the sllde valve will usually act as a relief valve and there are usually enough random leakage paths anyway .

[Clive HartlandParticipant @clivehartland94829]

Michael, Thanks for clarifyng some of the 'Dark details' of the steam engine. As you say a lot of designs just follow successful previous designs and whether they work well is another thing altogether.

Normal saturated steam and super heated steam, does cladding help in the first instance? I would assume that the less thermal transfer the better.

The reason I ask is that the boiler on my Evening Star is shown as bare and with no cladding, which is the best way to deal with this?

Clive

[Will RobertsonParticipant @willrobertson16447]

Hi Michael and Clive,

Thank you very much for such a detailed explanation. I think Corliss would definitely have agreed with you – he tried to keep the volume between valve and cylinder to a minimum. (He also had separate passageways for incoming and outgoing steam to minimise heat transfer from hot incoming to cooler outgoing steam). I think André Chapelon also put emphasis on the design of the steam passages.

Lentz certainly seemed to feel that cladding the cylinder was important – photographs of Lentz Paxman engines show thick insulation round the cylinder

**LINK**

Will

[Will RobertsonParticipant @willrobertson16447]

Hi Clive (any anyone else who's watching this thread),

Here's my first attempt to specify what metals to use for the bore, piston, etc. I'm probably wrong in several places so please correct me:

Metals bought locally from http://www.ateliermb.com to avoid high shipping costs from the UK.

First I need to rebuild the mangled-remains-of-a-Suart-S50 I bought on Ebay – a new piston will be needed so I'll try this brass

Messingrundstangen Ms 58 Bohr- und Drehqualität, Festigkeit: F45 – 50, sehr gut zerpanbar
Which I think means:
Brass Ms 58 Drilling and machining quality, strength: F45 – 50, very good machining properties

(I'm guessing that it's right to use brass rather than bronze in a cast iron bore? The oroginal Stuart parts list said brass.)

I'll make a new eccentric strap from the same stock (going to have to hunt for a tap for the BA threads Stewart use).

All the gaskets and gland packing mentioned in the Stuart parts list are missing – I'll phone Stuart and ask for replacements. (The poor engine is in a terrible mess – it looks like an encyclopaedia of bad machine technique.)

The eccentric like it may have to be re-made – for this and for the valve spools of my own engine a steel with good machining properties – I think I've 3 choices:

Edelstahlrundstangen 1.4305 Blankgezogen, Automatenqualität, Festigkeit: 60, gut zerspanbar
1.4305 stainless steel round bars Drawn Blank, machine quality, strength: 60, good machinability

Stahlrundstangen 9SMn 28 K Blankgezogen, Automatenstahl, (teilweise auch 9SMnPb 28K), sehr gut zerspanbar
Steel rods 9SMn 28 K Drawn Blank, mild steel, (partially 9SMnPb 28K), very good machining properties

Stahlrundstangen St 37k Blankgezogen, Festigkeit: F40 – 45, gut zerspanbar, gut schweißbar
Steel rods St 37k Drawn Blank, strength: F40 – 45, good machinability, good weldability

Which one should I go for? The second one would maybe make my life easiest (a nice free-cutting leaded steel) but first might give best corrosion resistance.

Now for my own engine:

For the piston:

Graugußrundstangen GG 25 Gußeisen mit Lamellengraphit, geschält
Cast iron rods GG 25 cast iron with lamellar graphite, peeled

Sphärogußrundstangen GGG 60 Stranggegosen, Gußeisen mit Kugelgraphit
GGG 60 ductile iron rods contunuously case, ductile iron

Not sure which of the above I should use.

Cylinder: Random lump of scrap brass supplied by a friend.

For the base plate a cast iron cooking plate from scrap catering equipment – hacked into shape with a circular saw then milling machine to tidy the edges.

Flywheel: bought as casting.

All other parts from the metals listed above if precision is required, otherwise from random scrap.

Can you suggest flexible piping that's safe for use with steam while I experiment with different valve designs, etc.?
(I want to experiment a little with rotating valves (similar to Corliss valves) and piston valves before deciding what type of valve to use.)

Will

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Clive ,

Difficult to come to any definate conclusion as to whether lagging the boiler of a small locomotive actually makes any difference to performance and efficiency . Both theory and common sense suggest that conserving heat should be beneficial but in reality the effect must be minute .

There are however practical advantages in lagging the boiler which are certainly worth having :

Makes outside of boiler a little less hot to touch – this gives handling and safety benifits .

Provides a good smooth base for paintwork .

Regards ,

Michael Williams .

PS: I did a lot of work on the late Neville Evans prototype engines . I lagged two boilers – one with brass sheet over industrial lagging sheet and one with tinplate over wood strips . Both were ok but the tinplate was the nicer to work and gave better finish . One noticable difference was that the tinplate/wood version was a lot cooler to touch than the brass/sheet version under similar steaming condition and for about the same total thickness of lagging in each case .

[Will RobertsonParticipant @willrobertson16447]

Hi Clive and Michael,

I rattled through some equations and the result came out that the smaller a boiler is, the more important it is to insulate it. I'll try to post them on here so that you can check for errors in my working (not sure the best way to typeset equations in HTML). Lentz put a lot of insulation round the cylinders of his engines but I know nothing about boilers so I'm only guessing that they would have been well insulated as well. The heat loss from an uninsulated metal vessel filled with water is substantial – great for domestic central heating systems but a problem when trying to keep metal vessels filled with water or steam hot (I found this out the hard way on dairy equipment but a little insulation made an enormous difference).

What did you think of the choices I had to make re. what stock to buy to repair the Stuart S50 and build my own engine? I'm particularly confused by the different sorts of cast iron.

[Clive HartlandParticipant @clivehartland94829]

Hello Will, Tardy of me not getting back to the forum quickly, lots going on with the bees and I had to go to a bee keepers apiary to sort out what was happening. He had united four hives into two and it was all wrong and he wanted another Nucleus as well. Alls well now and I onkly hope he stops manipulating the bees so they can get on with what they do best !

Looking at the choices of metal, first go for the Mehanite Spheroidal. the choice of metal for the spool as you call it, is of course the s/steel and then the free cutting mild steel, equivelent to our EN1 I think.

Buy a length of each and even if you dont use all of it, it is still useful.

The flexible steam pipe I dont know but hopefully someone will read this and have an idea, I have not seen flexible pipe in small dia. that we might use.

I am going to clad the boiler with some thin insulation blanket which I have now found and then cover it wih a metal covering. Lots of work involved and fine detail.

I am afraid bee keeping has raised its head again as I have an order for some more bee boxes to make, so everything goes on the back burner while I do them.

Shortly I will be taking honey from the bees and having to spin it out and filter it, too hot at the moment as we are sweltering with 29C here at the moment at 2030hrs. We are not used to it at all.

Clive

[Sub MandrelParticipant @submandrel]

> Shortly I will be taking honey from the bees and having to spin it out and filter it, too hot at the moment as we are sweltering with 29C here at the moment at 2030hrs.

Hi Clive,

My wife says "Lucky you!"

Hi Will,

I'm not sure your choices are as critical as you fear. Ductile cast iron is abit posh for pistons, in theory that with plenty of graphite should be more tolerant of poor lubrication and may be more likely to form a hard, black glaze that resists further corrosion.

I'd go for stainless for piston/valve rods, just as a matter of habit, but meake sure teh surface finish is very good or they will tear up O-rings or other gland packing.

Neil

[VersabossParticipant @versaboss]

So you are somewhere in Switzerland, buying from Mr. Burkhard?

Regarding your list of materials: stay away from St37 when you can. It's usually called 'garden fence iron' here and difficult to get a good surface finish

Also for a piston I think GG25 is possibly better suited than GGG60. The latter would be good for highly stressed machine parts (wheels, gears). It is much stronger; I think the number gives the tensile strength in kg/mm2.

Greetings, Hansrudolf

[Will RobertsonParticipant @willrobertson16447]

Hi Clive and Neil,

Thank you very much. I don't fully understand Mehanite Spheroidal (Sphärogußrundstangen Kugelgraphit I think) – does this referr to the way the iron is cast and the resulting crystal structure of the graphite?

Will reply properly ASAP.

Will

[Will RobertsonParticipant @willrobertson16447]

Hi Hansrudolf,

>So you are somewhere in Switzerland, buying from Mr. Burkhard?

I think so – I get the impression that he supplies the kind of metal stock I'm after and that he doesn't mind handling relaitvely low-value orders. I've still got a lot to learn though. Thanks for the advice about avoiding St37.

Hi Neil and Clive,

Great to hear you've got some good weather. The weather has improved here as well, 27 degrees all night last night. In Scotland I reckoned that it was impossible to sleep above 20 degrees but the Alps forced me to change my views on that. I remember my great uncle's equipment for spinning honey – miss that a lot.

Thanks for the advice about surface finish – I'll give a lot of attention to that – I think it will take me a few attempts to get it right – any suggestions?

It sounds like a lot of work sorting out the wrongly united hives – hope the owner does leave them alone now – some people have a terrible urge to interfere with nature until they mess it up.

I might have a try with silicone hose for dairy systems – fairly resilient stuff to withstand sterilisation by hot water and aggressive chemicals – small diameters were used for the vacuum lines.

Will

[Sub MandrelParticipant @submandrel]

Meehanite is a cast iron with (i think) a little nickel added and heat-treated for several days after casting to give a fine, easy machining, ductile end product. It is a pleasure to machine.

Neil

[VersabossParticipant @versaboss]

Posted by Will Robertson on 19/08/2012 17:51:28:

Hi Hansrudolf,

>So you are somewhere in Switzerland, buying from Mr. Burkhard?

I think so –

Well I really hope you know where you hang your hat…

Yes I know my question was a bit awkwardly formulated. We foreigners don't know every trick, sorry…

How do you like:

According to the fact that you buy from Me. B, I suppose you live somewhere in Switzerland, is it a secret whereabouts?

Greetings, Hansrudolf

[Will RobertsonParticipant @willrobertson16447]

Hi Neil,

Thank you very much. That definitely sounds like what I'm after. Am I right in thinking that Meehanite Spheroidal would translate to "Sphärogußrundstangen GGG 60 Stranggegosen, Gußeisen mit Kugelgraphit" not "Graugußrundstangen GG 25 Gußeisen mit Lamellengraphit, geschält"? I really struggle to understand the German descriptions of metals.

One component I forgot – the lubricating oil. Can I use the 10w-30 part synthetic engine oil I use for my turbo diesel or would another oil be more appropriate?

Will

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Will ,

Meehanite is strictly speaking a trade name for a group of types of iron made by a (once) patented process .

There are many grades of Meehanite iron ranging from butter soft to rock hard . You ideally want Meehanite grade 200 or 250 for steam engine parts . Meehanite 250 is the most useful for general engineering purposes anyway and is widely available .

Regards ,

Michael Wiliams .

Lots of general information about Meehanite and full data sheets here :

http://www.unitedcastbar.com

 

Edited By MICHAEL WILLIAMS on 20/08/2012 23:22:01

[Clive HartlandParticipant @clivehartland94829]

Niel, just to let you know I took 63lb of honey from two hives and got two stings for it ! Very nice quality as well.

Hives and bees doing well. I have another three to do yet.

Clive

[Will RobertsonParticipant @willrobertson16447]

Hi Clive,

Congratulations on the honey and the health of the hives – a great outcome in such a poor summer!

You mentioned that you sharpened your Cobalt boring tools using diamond stones. After sharpening, do you finish honing the edge using the fine diamond stone or using an oil stone or water stone?

What were your thoughts about lubricating oil for a model engine? Can I use the 10w-30 I use for my turbo diesel or is another oil more appropriate?

Hi Michael,

Thanks for the link to United Cast Bar Limited – interrestign to find out more about cast iron. A lot I wasn't aware of.

Hi Hansrudolf,

I live at the North end of canton Schwytz – near kussnacht am Rigi and Luzern. I'm new to buying stock – when I was younger I just grabbed a lump of the right sort of metal from a box in the corner of the workshop – if it wasn't there I went to be grumbled at by the storeman and maybe get a lump of something which was hopefully suitable thrown at me. I never had to know how to specify exactly which alloy or where to buy it from.

Will

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