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Member postings for Nigel Graham 2

Here is a list of all the postings Nigel Graham 2 has made in our forums. Click on a thread name to jump to the thread.

Thread: Is a 3" Cornish coal fire possible?
23/05/2022 22:06:03

Nicke gives a fair assessment of proportions: the flue is about or slightly above 1/3 the shell diameter, and is placed so its highest point is on a bit below the shell's centre-line.

The furnace section seems typically about 1/3 total length, and the flue is of constant diameter for its full length to the smokebox. That was always given an access hatch for cleaning.

The grate is slightly narrower than the flue's inner diameter so it rests below the flue axis, and the "ash-pit" segment is closed by a door containing a damper.

The firebox, as such, is therefore rather like the "marine" type used on some narrow-gauge locos - I think the 'Polly' range exemplifies them although those boilers have firetubes, not a single flue.

Taking up Nick's point about coal-fired O-gauge locomotives, I would endeavour to find how their boilers are arranged, since on the face of it your proposal is for a boiler somewhat larger than those. They evidently work, but I don't know their secret!

If you use a hidden fan as Mark suggests, I would think it better to make it induce the draught in the chimney by driving air through a simple ejector in the chimney base, rather than pulling the hot gases through the fan.

Cornish boiler-houses generally had the chimney right up against the house wall, and the chimneys I've seen didn't seem to have the pedestal common to many factory chimneys. The fan etc, could be concealed in an adjoining coal store, with a discreet tube within the model's base to feed the ejector.

'

An interesting challenge! Do keep us posted!

.

As an aside, some may recollect Ron Jarvis' magnificent models of particularly significant, early steam-engines, including Newcomen's Atmospheric Engine. This, complete with all-correct lead pipes and square nuts, works as it should (I wonder where his models are now - Ron died quite some years ago), but for the boiler. About the shape and size of an orange, and with an orange-peel finish to simulate the original's hand-forged wrought-iron plates, it uses an electric heater to produce steam at the prototype's not-so-strong 2psi. Ron used to joke to us, his fellow society members, that the heater's electronic controller made this the only 18C engine with 20C microprocessor control!

Thread: Looks a lot like plastic
23/05/2022 21:40:50

More likely a machineable ceramic, surely.

Thread: Removing a retaining washer
23/05/2022 17:59:47

never let it be said....

I followed up my own post.

Yes, they or equivalents do exist.

"Starlock" is one make, according to Intafast.com who also show a simpler, more generic "push-on fastener" with no trade-mark name.

You might find them stocked by motor-factors (probably in a snazzy compartment-box of oodles of several sizes!), or you could try a domestic-appliance repairer happy to sell you just a few of suitable size.

Model-Fixings might stock them too: worth asking. Among "our" suppliers, and I have used them a few times for small metric screws and nuts.

'

For more specialist parts like the pump leather and valves, you could try BaseCamp, in Brighton. They specialise in spares for oil-lamps and the like.

23/05/2022 17:49:03

I'm pretty sure replacement washers of that type are still made. They are commonly used for retaining revolving parts on light-loaded, often cheaply-made (if not cheaply sold!), products.

They are probably sacrificial, normally replaced after a repair.

Using side-cutters on them might work but is likely to spoil your cutters with it.

Thread: Is a 3" Cornish coal fire possible?
23/05/2022 17:42:32

Corrugating the flues did increase the heating area slightly but that was not the main reason.

It was for strength!

Some manufacturers relied on single, circular embossings, especially at radial joints, for the same reason. I believe this was sometimes called a Bowling Ring, but my memory may be shaky on that detail and it might have been one builder's name for it.

It also eased the expansion / contraction strains: some 19C Cornish and Lancashire boilers burst because ironically they were structurally too stiff.

The main problem with a flue several times longer than its diameter is that it will fail at far lower external pressure than the same tube under internal pressure, and in very complicated ways with many variables at play; although if the boiler is supplying a model Cornish mine pumping-engine it won't need work at a very high pressure at all. Scaled-down strong steam!

The corrugated pipe sold for plumbing is to allow easy bending from rigid pipe to (usually) the tap tail; and I would not like to guess how it would cope with being used in a boiler. From my catalogues, it would not be suitable at all. Such pipes are too small for a start, at 15mm and 22mm bore; and are short lengths of corrugated stainless-steel with both ends terminated by copper end-pieces to allow easy jointing with conventional plumbing methods.

Marshalls patented a stayless firebox for their portable-engines, in which strength was given by profiles pressed in the crown-plate. The principle is of course common throughout engineering: think of all the wiggly bits in the thin steel of your car.

.

As for efficiency, they were probably not ever so efficient; but the engine was not much better, even after James Watt's major improvements to the operating principles. Cornwall is not all that far from the nearest coal-fields in Somerset and South Wales, especially after the railways arrived. The metals' main buyers were probably much further away.

Thread: Between centres boring bar bit grinding
23/05/2022 10:41:39

Useful information in that Eurocode site, though its other tabs suggest it is aimed mainly at structural engineers so some of the calculations may not be strictly relevant or useful for machine design.

It almost certainly won't work for fine-scale model-building where edge distances and pitch or centres, (which it clumsily calls "center [sic]-to-center distance" )  are dictated by the prototype's practice, and sometimes by accessibility. On the original, that was matched to the available fasteners and spanners; so may fail in some scale applications.

It explains those numbers, such as 8.8, embossed on bolt-heads; encoding the bolt's strength, but the effects of scale on strength have long been a topic discussed in model-engineering, with the point emerging that if anything the scale components are proportionately stronger than their full-size originals in similar metals.

The caveat being that our strength is not a scale version of the Victorian or Edwardian fitter's; when spanner proportions were established that related them to both fastener strength and male arm strength. They had no torque-spanners but were 'ard, in them days!

I am not sure taking things to the Euronorm depth need worry us as model-engineers too much, though it could help anyone designing to metric dimensions, critical parts like cylinder cover studs and more so, boilers held together with bolted flanges (e.g., Hindley, Merryweather, Sentinel). Their originals would have used BSW bolts and nuts.

You do though need know the actual material you are using, and for some applications including studs, that is not necessarily a grade listed in those tables made for engineers designing big, heavily-stressed steelwork to surprisingly low factors of safety. And of course the document does not cover non-ferrous metals, such as bronze, at all.

The upshot really is that we need consider what is fit for purpose, and provided it is reasonably stiff for its working range, there is nothing especially critical about a mild-steel boring-bar with a small HSS bit gripped and adjusted by ordinary commercial screws. After all, if use a single-point boring-tool from the tool-post, we know that even a high-quality item from an industrial-rated manufacturer may flex slightly, so we often need take a careful spring cut at intervals.

.

Odd that despite the American spellings and apparently being a commercial site (it asks for donations) it shows the EU flag as if some sort of EU-published document.

Edited By Nigel Graham 2 on 23/05/2022 10:50:35

22/05/2022 22:03:35

Having made but yet to use a Hemingway Kits between-centres boring-bar set this thread is of particular interest to me.

These bars have radial cutters set using a simple micrometer which also forms part of the kit. The instructions tell you to mark the head of the micrometer screw but since the graduations have no fixed reference-point with which to align, I am not sure how helpful that is.

To answer Fowler's Fury point about a "smooth plug", I assume as plug-gauge.

I'd pondered that and suggest not a solid plug but a ring-gauge, bored out to an easy fit on the bar. Hold this at one end of the bar using a rubber band, close-fitting O-ring or something of the sort, while actually cutting metal.

Thread: This trolley/cart could be useful
21/05/2022 22:37:18

Most trolley would struggle - or their users would - when faced with such inconveniences as the beautifully-manicured lawn (or my patch of grass).

Obtain some reasonably large sheets of shuttering-ply, Stirling-board or similar to use as temporary runways over such surfaces. Even just two would do it, a bit laboriously.

Thread: CHRIS DEITH
21/05/2022 22:31:00

An important person - for very valuable contributions to the hobby.

Thread: Any idea what these are for?
21/05/2022 22:28:42

If they work well as gravers... fine!

I wonder if they were actually for cutting ceramics in some way. Perhaps to score a groove along which a tile would snap? Just a thought.....

Thread: Reinventing The Real
21/05/2022 21:51:37

A very elegant machine!

It is an unusual layout - a true vertical. (The more common ones with the crankshaft at the bottom, marine-engine style, as more properly of "inverted-vertical" layout.)

As finishing touches the pulley (not flywheel) would have been very slightly crowned - though that is probably barely noticeable at that scale - and it may be worth examining your source engraving to see if it had square or hexagonal nuts, especially in the larger diameters.

Curved spokes were common practice on cast-iron pulleys etc, not for looks but to absorb the contraction stresses in cooling.

Thread: Fkesxispeed...what is the back gear for and how to use it
21/05/2022 21:29:14

NDIY

As I said... yes... to a point.

I also said I use the pulley steps and back-gear, not only for torque but also to keep the motor running fast. The speed controls have amber and red sectors warning you the setting is too slow there. All right for a few moments perhaps but not long duty.

I did and still do not advocate never using the mechanical reductions, but instead using them in conjunction with the electronics!

The cabinet was noisy at all spindle speeds, because the motor was still running at its single speed.

You are right though. The question was about the back-gear on a Flexispeed lathe - but - not because the lathe is a Flexispeed. It was about the purpose of the gear.

Thread: New To CAD? No, but....
20/05/2022 22:56:14

Dave -

A challenge, eh?

Draw a cotton-reel in 3D, using TurboCAD.

Obviously that is dead easy for TC, but for me?

I didn't try to copy the original but invented one in the same spirit. The two black lines are the original X and Y axes markers I had to make, and left in place after I had deleted the other construction lines.

How I created this, I describe below.... Along with why I had to omit the recesses in the ends.

cotton reel.jpg

First was open a "Normal Metric" template. That worked. And to turn on the Grid. That would not work - I think IMSI must have set the template grid-free, for whatever reason.

First mistake but not realised then. Oh well, nothing ventured...

Draw two (X, Y) axis lines (those shown) and various construction / outline rectangles. All in one Layer, Layer 0 allegedly we are not suppose to use. Why is it available then?

Intersection snap on, four circles to give the rims each a nice neat radius.

Tangent-tool: the sloping lines to generate the two conical frustra.

Lots of Trimming and deleting, join what's left as a Polyline.

Revolve that about the X-axis. Smooth the surface (TC develops cylinders as 14-sided prisms and leaves you to edit their appearance). Delete the generating polyline.

I'd needlessly drawn both "sides" of the generating elevation. I'd not thought of that until I was deleting all the temporary constructions. Oh well, no harm done.

Lo and behold, the basic reel with a 6mm dia axial hole through it. That disappears in rendering more deeply than the hidden-lines level shown there.

The end recesses?. . .

Errrr...

The original had 6 radial recesses in the ends, I believe. Certainly most moulded plastic real reels do, though not wooden ones. So mine is wooden - painted blue if rendered.

I had worked out how to create these recesses, 6 per end, from 12 extruded pie-portion plugs. That itself is not too hard, IF the grid and snaps work as they should. They didn't, I think because I was using a template rather than a "New" file with raw "Model Space".

I would have had to create the two plug sets concentrically to the reel (on the invisible X-axis), sink them the required depth then Subtract them to leave the cavities.

Now, the so-called "Inspector Bar" was all active, showing the sizes and co-ordinates of any selected entity, and allowing its move in any (X, Y, Z) direction - and angular rotation in those planes if you want - by your entered values.

The plugs would have had mid-length Reference Points. So if each was 20mm long and shown as 20mm from the end of the reel, moving it 10mm would make it touch the reel; 15mm would sink it 5mm. The reel's mid-point of known length is at (X=0), so I know where the reel face lies. Fine so far.... provided the rose pattern of "negative recesses" is concentric to the reel. Might not be the "official" method but it will work.

So: draw 2 plug sets, identify each plug X-co-ordinate and move it in X to sink the few mm into the reel end. Then subtract it to leave the recess. TurboCAD does not have "negative" extrusions, only negative co-ordinates and distances. All its extrusions are solids; hence needing subtracting to make a hole.

Only, with no grid as a guide, at this stage in the drawing the grid-snap fails so you cannot create those extrusions. Or if you can, I don't know how. Besides, despite the values displayed, trying to visualise where things are in that open space would have taxed Escher!

I should have made the plugs' base figures at the same stage as the Revolve figure. Even then I might have run into co-ordinate and entity-type difficulties.

Clearly I go no further with that drawing, so I show what I had produced. It's a cotton reel but with a solid body apart from the spindle hole!

At least I rose to the challenge even if it partially defeated me.

Thread: Advice on DROs for a mill
20/05/2022 15:22:45

I fitted a 3-axis "Machine-DRO" set specified for my mill, a Myford VMC, and although I indulged in a heck of a lot of elaborate bracketry to both support and protect the sensors and magnetic strips on a machine not designed for DRO scales, I have never regretted it.

The instruction advise protecting the armoured sensor cables from coolant. I don't use flood-coolants, nevertheless I ran them through flexible conduit, actually spiral-wound polythene sink-waste hose from a camping & caravanning shop. (You'd be surprised where you can find engineering materials!) The standard electrical flexible conduit is too small to allow the sensors or connectors, passage.

One thing I did do, when setting the specified gap between sensor and strip, was use a plastic (soft and non-magnetic) feeler-gauge. I measured a few old plastic bank and club cards, which make very good shim material, and cut a strip from the appropriate one.

'

It was joy on first use to drill several holes in two bits of metal to be screwed together, and find all the screws fitted through all of them first time!

The one drawback is that fitting the long axis strip and sensor lost the use of the table-stops. Some would argue that a DRO avoids their need, but as with the 3-phase conversion sets I put on this and other machine-tools, I prefer to enhance the machine as it exists, not simply replace bits. Also, once a positive stop has been set by the numbers, you don't need keep sidling up to digits or dials.

So from time to time I look at the mill to work out how to make and fit new table-stops. In any case, sometimes I do use the handwheel dials alone, on short, simple tasks. If nothing else it keeps my hand in!

'

The fitting and operating instructions are nice and clear, and though I have not so far used the more advanced features like generating radii and pitch-circles, I have no qualms about doing so. Though I might practice on a bit of scrap material first!

Incidentally, I don't keep this or any of my machine-tool manuals in the workshop. To protect them, they normally stay in the house where I write the salient details from them on a notepad. If I do need the document in the shed, I put it open at the relevant page in a polythene bag or a walker's map-case.

Edited By Nigel Graham 2 on 20/05/2022 15:35:53

Thread: New To CAD? No, but....
20/05/2022 15:02:02

I'm sorry if you felt that, Martin, but that was not my intention at all.

I wanted something of a view of several different makes, because I was becoming bogged down; and that is what happened.

I stuck with TurboCAD for a long time because having bought it and advanced so far with it, it seemed silly to switch to a completely new one like Alibre or Fusion - though I did give them a brief go.

I had however hit something of a brick wall with TurboCAD because the more you advance in it the harder it does become to make each step further. Even some of its basic functions like printing the image is a minefield. Also, finding help with it is not easy.

Gordon has given me an introduction to Solid Edge _ I printed the instructions he sent me - and though it looks very different from TC it does seem a more logical programme to use, and it is easy to seek advice. Gordon's introductory exercises also didn't assume prior CAD experience, as the Siemens web-site seems to do; though Siems do seem to have put a lot explanatory material on it as well.

Plus, plenty of users! Indeed I think it was one of the "Solid"-stable that one my own club fellow-members used to teach, in a school. Possibly a "student edition" of SolidWorks: a crafty piece of salesmanship by the makers!

I will try SE further, and may well switch to it. From what I have seen of it so far, it does have some very good features reasonably easy to grasp.. It also appears to have a relatively much more straightforward approach to representing solids than TC's two or three methods. Though those are the programme's' internal functions they affect how you use it, and in TC they can present a lot of hidden traps for the unwary..

So "waste of time" no - I was trying to find something within my ability to learn to sufficient level to use practically.

I may well never find or use every last bell and whistle, but who uses all those in Microsoft's 'Office' programmes? Instead, what I want, is to learn a CAD programme that will help and support my model-engineering.

20/05/2022 12:55:20

I don't know if that's meant as a sneer, as it reads, but like the Spice Girls, I know what I want.

And that is to use the system I have effectively, be it TurboCAD or SolidEdge, not keep starting yet another! (I'd not even heard of MOI until someone mentioned it here.)

20/05/2022 09:47:00

The last few posts have identified one of the possible difficulties in learning to use CAD is the sheer flood of tools and commands, daunting even before you recognise by their names and squiggles, what they do, which ones to use and how to use them.

In that regard being able switch menus on and off easily is an advantage.

I see SolidEdge appears to do that by a tab system, but that does obscure common application basics like File - Open / Save / Copy / Print. That is one I think should stay like a Victorian child, seen but not heard until needed, in its usual spot top-left. I know "Print" might be a bit more demanding in CAD, so may need its own route.

TurboCAD uses a master tool-bar menu that is simple to use, but use it without care to close short-term selections after use and you can create very cluttered borders hard to search. (I think MS 'Word' is slightly similar in that respect, though without the index.) Bit like my workshop then....

Thread: This trolley/cart could be useful
20/05/2022 09:24:55

Advertisers outside of the specialist fields are not noted for literacy!

Looking at the link we find -

The wheels are "new and improved"... Errr... Pardon?

The wheels can also cope with a wide range of "terranes". I think they mean "terrain", which is also singular. I forget the accurate definition but "terrane" is a specific geological / geomorphological term.

That aside, yes the trolley does look useful!

Thread: Oil can (again)
20/05/2022 09:18:20

Not oil-cans as such but I have found the pumps from liquid-soap dispensers useful for decanting lubricating-oils, wood-preservatives and the like from full 5l cans.

They are also a source of springs, some in stainless-steel - safety-valve candidates?

Thread: New To CAD? No, but....
20/05/2022 00:34:29

Lee -

Thank you.

Err, Oh No, no not another make of CAD! Oh for a simple life. I want to be able to get to grips with what I have, not act as a sort of reviewer of relative difficulty by trying one wretched programme after another.

I wonder if I can put my drawing-board back together?

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