Member postings for Nigel Graham 2

Examined my Myford VMC mill to see how best to fit the Allendale DRO magnetic-strip profile. Not easy to find anywhere suitable, really!

If I put it directly along the front edge of the bed I will need either to make little dovetail nuts or drill and tap the back wall of the slot in which the bed stops work. Only they won't be there any more.

A fraction too high and the profile and its cover are above the bed surface. A fraction low and it fouls the oil-nipples. Also if for any reason I had to remove it from the bed, I'd have to destroy the strip itself as that is stuck on, and hides the mounting-screws.

So thinks on.... Machine a set of cross-pieces to be screwed into the bed face, outside the profile which would be screwed to them? Not much room available, but it might be possible. I'd still lose the bed-stops, probably also the locks, and risk the oilers being inaccessible.

And that's even before I think about trying to fit the cross and vertical travel encoder profiles on a machine not designed for such luxuries!

By now my stomach was telling me to forage for food, and my brain was fading from all that thinking! So I locked up and retreated to the house for the evening.

I would advise you build the track to 7-1/4"g for the passenger-trucks, with a third rail for the 5"g loco. To my knowledge no-on has had problems with the resulting, off-centre draw. You will need to ensure a raised portable-track is built up and stabilised more carefully than may be sufficient for a ground-level equivalent on the same ground.

Regarding replacing the old HSE Guidance, it was drawn up partly to avoid our miniature-railways being treated as "fairground rides", because meetings between the hobby's representative and the HSE soon established that would have mde us safe by simply rendering it basically impossible to operate at all.

I attended one such meeting, with Her Majesty's Principal Inspector of Fairgrounds (from HSE) as the speaker, and hosted by the Southampton model-engineering society. He understood our needs, and emphasised and explained the "duty of care". He told us to safety seriously, and be able to show we do, but not so we stifle our own activities. I remember him saying, "You are not building nuclear power-stations!"

I am not a lawyer and we all know the allegation that an insurance company's aim is to avoid settling claims in a logical and common-sense way; but the law's main message is, do all you sensibly can to minimise the risks, and show you are doing that.

It's also worth remembering that some people will try it on, and most such claims are indeed thrown out by insurers and solicitors as invalid - the incident was the claimant's fault or occasionally, proven to be a downright lie. I recall learning of one claim for spark damage being proven fraudulent by the club's own log-book showing the event was a battery and i.c. loco day, with no steam locos.

If you can show you "taken all reasonable care" - and I would include anti-tipping rails on raised tracks, and side-sheets to keep legs and feet outside of trucks - you will have a far better chance of withstanding claims.

If a local-authority or other body tries the "fairground" route, it should be possible to show you are following genuine legal, insurance and good-practice routes designed by people who understand the matter, and the HSE and our insurers separate our railways (and rides behind miniature traction-engines) from commercial fairgrounds.

Yes - the tidy-minded mouse was mentioned on the radio too.

A friend used to keep his 7-1/4"g, NG loco in a un-heated wooden shed so to keep corrosion at bay kept a garage inspection lamp in the firebox, while an old blanket over the whole lot kept it clean.

Centrally-heated luxury accommodation for for the mouse who found it, and made a nest on the running-plate with threads from the blanket!

As to why a mouse might behave like that though, collecting small but inedible objects in a convenient pot, is a mystery perhaps any zoologist here might be able to explain!

Was supposed to have had a visitor but he'd fallen ill.

My model-engineering society was to have had a Magic Lantern demonstration this evening but the speaker (himself a society member) had fallen ill.

Spent some hours trying to progress my Hindley wagon-engine's design.... I'm not sure which is harder, designing an enclosed, inverted-vertical compound engine with Stephenson's Link Motion, or learning to draw it by CAD!

Yes, to a point. For a start, engineering standards don't change so often that they worry us as amateur engineers.

Also, the new standards do not mean we cannot find new owners for our equipment, because rather than rapid replacement they tend to add to the range.

We can use Morse or R8 tooling for example, because although industry now generally uses the INT series, there are still plenty of users and buyers of older machine-tools and fittings still serviceable decades after manufacture - and there are plenty of the smaller machine-tools and tooling using the Morse, possibly also R8, tapers still being made.

I know some tooling standards have fallen by the wayside (I never identified my IXL/ Erhlich lathe's spindle taper!), and BS / BA fastenings are disappearing, with the American inch-based UN series possibly following suit - but these are gradual, evolutionary rather than revolutionary, changes.

The IT trade's model is to make sweeping changes every few years and render anything in its older forms as unusable as rapidly as possible. Some reflects genuine electronics development but a lot of changes are just tinkering for nakedly commercial reasons.

People like Whitworth introduced standards to help engineering, not hinder it, by ensuring both interchangeability and long-term continuity.

MS and its ilk manipulate standards to obstruct while maximising profits, by technically-needless changes that stifle interchanging and prevent continuity.

A good point, Michael, but I don't think that's the problem. As engineers we are all used to the principles established by Sir Joseph Whitworth.

The difficulty is not industry-standards: we all benefit from them. Rather, it is the underhand actions of the computer and telecommunications trade, including its wilful attempts to render working systems and files obsolete or difficult within spans of years well within physical reality.

You buy a machine-tool and its tooling as one-off purchases, knowing whether they are brand-new or fifty years old (as long as they have not been abused or simply worn out), they will fit together and work properly.

You might buy by hire-purchase (credit-card or bank loan), but you do not hire the equipment on open-ended contracts - and once you've paid the debt off, that equipment is yours and fully-useable indefinitely.

You might hire rather than buy a concrete-mixer to lay your workshop foundations, but that again is a clear, transparent and honest transaction.

You subscribe to ME, MEW or any other magazine, or to particular TV channels, but whilst prices do rise over time, these too are transparent contracts. Also, you know you can keep printed literature and re-read it easily years hence.

Each model of machine-tool has a production life like any other large manufactured item, so spares are eventually no longer made new even if the maker is still trading. However, you do not expect the manufacturer to try to force you to buy new by rendering the existing machine and tooling unusable.

Nor will the maker or dealer demand you hire the machine at rates that over, say, 10 years, will total far more than the original single-sale value; and unlike software run by a remote monopoly, the machine will not stop working because you have not installed unsolicited "up-grades". (Unless it's a CAD/CAM machine, perhaps!)

So whilst I agree we do not object to engineering standards, and might not object to software standards, they are not the problem. It is how they are exploited, that is.

I was first aware of docx. and xlsx. a couple of years ago when I wanted to send pensions-related documents home from my work computer, in preparation for my retirement; and discovered they had been automatically converted to this locked form, like a pdf image-file. Luckily I found saving documents and spread-sheets in early formats seemed to bypass this little racket.

(The spread-sheets did include some lunch-break work, as change-wheel tables for the EW lathe, and one of somewhere-useful equivalents for my small Denbigh horizontal mill with its one 8tpi and two 6tpi, lead-screws!)

Also, I had a frustrating time as a society committee-member, when fellow officers circulated reports in all sorts of different appearance formats and file types, including those "x" ones. The latter were impossible to edit so I could not compile them all neatly into single meeting handbooks.

I noticed the docx. files invoked a pop-up from Adobe, with a big blue "Convert" button under a file-type menu. It was, how shall I put this politely, disingenuous! The Convert button actually opened a sales page making clear you do not buy Adobe Acrobat outright but subscribe to it at tens of ££/month. OK perhaps for a company but not for a private user needing such software only ad-hoc and occasionally.

WinZip has gone the same way, at about £30 - £40 / month, according to its own pop-up ads saying my "software is out of date".

Sharks!

Continued putting my Harrison L5 Lathe back into use.

By today I'd already given it a 3ph conversion courtesy of Newton-Tesla (I told them the machine and they chose the appropriate conversion set.)

The new motor is on an adjustable bracket arrangement on the steelwork for what will be an overhead hoist arrangement, and above the headstock. This puts the motor up into cleaner conditions and allows the lathe to go back close to the wall. I made the adjustable tie-bars involved, from bits of scrap miniature-railway track. The original, large, 1-ph motor was on a massive steel box welded to the back of the cabinet, too greedy of space in a cramped workshop so now very un-welded. I'll also need to chop the original change-wheel guard, or make a custom one..

The inverter and "pendant" control-box live on the wall above the tailstock.

Today's task was adding oil to the headstock and replacing the cover, with a new greaseproof paper gasket cut from the bag inside a cornflakes box. Then oiling round, and carefully testing the machine.

Finally, sorted out the "pre-owned" QC tool-post I'd acquired for it. It needs appropriate stud bushes but they are no problem. However, I discovered the three blocks with it, all have the same clamping and guide grooves but slightly different tool channels and screw-threads! For consistency so I need just the one key I have, I will have to make the replacements for missing locking and clamping screws, with square heads are equal across the set.

So that's the next shopping-list: more QC blocks (2 or 3 more will probably be sufficient), and replacing missing change-wheels.

Ummmm, how can anything be "pre-owned (pre- booked / ordered / existing)? Unless you are Doctor Who?

Re Nicholas Wheeler.

It's interesting how different people have very different perspectives (!) on CAD depending on previous experience. I think all draughting skill depends on how easy you find it to visualise a real object from a drawing, and vice-versa.

Mine's the opposite way round, nearly. My only school-leaving GCE A-Level was in Technical Drawing, long pre-CAD; and not that many years after The Eagle comic published those superb, manually-drawn, pictorial cut-away views to explain ocean-liners and such-like. I worked at low levels in various engineering-related trades for many years. So I am used to orthographic drawings, which anyway you still need for workshop use, and isometric part- and assembly- drawings.

And I've been a model-engineer, sort of, since my teens, so over half a century ago.

I took a GCE A-Level course in Geology some years ago, and that can make your head spin sometimes, trying to read a geology map and visualise what's what below the land surface from the plan of the outcrops and the angles of dip (the slope of the strata). Nature does not build hills to neat regular geometry! Recently, I prepared a geological section projected from the map for a particular project in which I'm involved, and that is only possible manually, on the parallel-motion drawing-board.

Trying to learn therefore, to create a 3D model then take off the elevations for actually making the thing - reverses my thinking. And baffles me, mainly due to the software's complexity but also because I cannot visualise co-ordinate sets and work-planes floating in an abstract infinity.

Manually, I might start from a rough pictorial sketch but draw in orthographic-only. You can in TurboCAD, but I don't know if Alibre and Fusion offer that choice.

My last 3D attempt was of one of the two cross-heads for my steam-wagon engine, having measured the "adopted" pair of raw castings. I have to accept my rough drawing quality; but more importantly, what then? It's merely a non-dimensioned picture of one disembodied cross-head lying on its side, in free space.

So I suppose in the end what matters is what and for whom you want CAD drawings for, to what complexity and quality - and whether their help in your making physical items, sufficiently repays hundreds of hours trying to learn to draw them!

Mechman48:

I would not recommend using sintered bar if you need to machine what will be the bearing surface, as the cutting action is likely to burnish the grain closed, so rather defeating the object. It is however possible to buy sintered-bronze bushes, and there may be a size available to suit (or so close you can modify the diameters without compromising the engine as a whole)..

In full-size, the eccentric sheaves and straps were usually both of cast-iron. Mild-steel and cast-iron and happy together too, with good lubrication: my old IXL lathe countershaft used this pairing, as does my little EW lathe headstock.

I've an idea mild-steel and phosphor-bronze are not so, with the steel wearing more.

Re original: "what other" bronzes to avoid!

Beware of Aluminium Bronze, widely used for marine equipment thanks to its very high corrosion resistance. Drills bind it for a pastime, but more pertinently here, it will not take conventional lead/tin and silver solders.

Polished, it has a rather paler than normal brass colour, which helps to differentiate it from other cuprous alloys.

How do I know? Guess! One of the hazards of the Pre-loved Metals bin...

I am sorry - I had no wish to be offend anyone though I don't understand where I was "condescending".

I wrote as I had found by a lot of shopping around and trying a lot of free or low-cost CAD packages. I wanted to know: their value for engineering designs, their relative ease of learning, and obviously, price.

I was disappointed to find most virtually useless for mechanical engineering. They were probably good for their intended purposes, mainly landscaping and kitchen design. The nearest to engineering in these packages were electrical circuit-diagrams and process flow-charts.

Others were potentially more useful for mechanical engineering, but peddled as "free", "student" or "trial" versions. These proves just introductory, with useful features labelled but switched off. The real versions were costly, as they were aimed at commercial companies and educational establishments.

I did find one giving engineering-drawing features, apparently free and reasonably simple to start using, but I think that too was a limited form of its real editions.

SolidWorks & SolidEdge are used extensively in industry, including by my employer, and by the college that is home to my model-engineering society; so it gave me an insight into CAD. However, is not available for private users, as far as I could determine from its own web-site which does not even give the price. If you have to ask...

So having rejected quite a number for failing my tests, I looked at two, and now three, professional-quality ones available to the amateur.

In chronological order of experience:

TurboCAD was not free but readily-available, a one-payment purchase, very reasonable price, complete and with a sizeable Users' Forum that compensates for its own on-line "manual" being poorly-arranged and only really an aide-memoire for experienced users.

I had a bad start though as the training CD supplied with it, proved faulty. It walked me through drawing a rectangle, putting two "holes" in it, slotting one to the edge... It said "press Escape" to complete each step, but at some point Escape turned itself to Delete and erased the whole drawing!

I am still trying to learn TurboCAD and can now draw fairly-adequate 2D views but have more or less given up on 3D modelling with it, as I find it almost incomprehensible. Its Users' Forum Gallery shows exquisite engineering and architectural renderings but such work is all beyond me.

Fusion 360 is the only CAD package available genuinely free to private users, and in full version. I found its presentation and look-what-we-can-do approach off-putting though; as was its lack of instructions. After a hopeful start I was rapidly baffled.

My first attempt was encouraging. I soon drew a simple square plate with a large central hole and "bolt-holes" in the corners (e.g. a pipe-flange), dimensions too, and saved the drawing. On my next session I discovered the "pipe-flange" still existed but as an isometric rendering with the dimensions deleted, and nothing to help me understand why.

TurboCAD's gallery is at least by users. Fusion's web-site "look-at-me" pictures, by its staff professionals, and its over-enthusiastic approach, very disheartening. If I can't draw a dimensioned flat plate with five holes and save it from one session to the next as I'd left it, fancy pictures will be beyond me.

Allibre is the new-comer. I tried it, to see if it is easier to learn than TurboCAD and Fusion whilst still letting me produce what I want from a draughting programme: engineering-drawings!

It's certainly friendlier and more welcoming than Fusion, and seemed easier than TC. I managed the first instalment in MEW but that's all, and now know it will be quite expensive. I began to feel I was not learning Alibre, just following instructions to draw a scribing-block, using Alibre. It showed me what Alibre does, but greatly widened the gap I felt between exercise and own drawings.

Anyway, it's not really logical to make some progress with one package then start from scratch with another that will cost more than TC and cannot read my accumulated TC drawings.

I appreciate advanced software is very expensive to produce and the publishers need to recover their costs and make a profit. I don't expect anything genuinely free and I was surprised that Fusion360 is, for private use. In fact I tried F36o twice, and noticed that on the second go this service was far less explicit on the Fusion site.

I do not mind subscribing to a magazine - that's no different from buying it an edition at a time in a shop, in fact it can be cheaper. However, I would far rather buy software outright than subscribe via an open-ended arrangement at prices that are small change for a large company using it intensively, but prohibitive for an individual.

To sum up, my best course is to stay with TurboCAD. I have it, it's paid for, I will never be very good at CAD; but at least I can use what I have so far, to make simple orthographic drawings adequate for my own workshop use.

A note regarding Fusion's use of the "cloud" (i.e. the Internet) for storing your data...

It is the default setting but when I tried Fusion, you could choose otherwise. That was several months ago but I'd be surprised if they've changed that.

Actually it's amusing that we amateur engineers might worry about our drawings being in an Internet server. Although companies handling very sensitive designs would not risk it, I am sure Fusion takes extremely good care of its users' security - to be negligent would be commercial suicide - but I doubt Mr. Putin or Kim Whatsisname would be after our drawings!

Regarding future pricing, much of the IT trade is moving to a subscription-only business model that must make far more money for no more work by the publishers. WinZip for example, is available now only by costly monthly rental, according to its own pop-up ads. So it may be that in a decade, perhaps less, we won't be able to buy any professionally- made software, not just CAD, outright, but will be forced into either low-quality free-ware, or open-ended contracts at prohibitive costs.

Incidentally, what happened to TurboCAD? It was being sold through the model-engineering trade, and at a very reasonable one-off price, but seems to have disappeared more thoroughly than a parted-off 12BA stud in swarf.

TurboCAD seems to have been the first industrial-quality CAD available to amateur users, affordably, in full rather than "trial" form; but is no longer advertised in ME or MEW. TC is very much mechanical-engineering focussed but also has a strong architectural section, as its Users' Forum gallery shows.

TurboCAD orthographic and parallel dimension problem: where am I going wrong?

I cannot properly dimension anything from a datum end.

This was highlighted on the side elevation of a two-throw crankshaft nearly a foot long, with various intermediate and end diameters as well as the webs. Geometrically it is a chain of joined rectangles of various sizes.

I thought I had to Snap the dimensions to the Vertex and Intersection points, but an error message tells me "No snap points in snap aperture", and the cursor won't release the dimension.

I find I have to turn the Snaps off to set the dimension down, but that leads to inaccurate lengths by having to place the cursor entirely by eye.

Circles and arcs are not a problem: the dimensions work on them, so it's specific to straight-line features.

Anyone know where I'm going wrong, please?

Is it because the rectangles are all joined but are of different heights? I can't seen it would be that, because that would dimension the resulting diagonals.

[Incidentally, I would have asked on TC's own Users' Forum but its log-in routine from my computer was always fragile, has now broken; and so far, IMSI has been unable to re-connect it for me.]

Thank you Neil.

I can answer that: I knew what I hoped (and still wish to) gain from CAD before I started, and I always knew the envelope-sketches still have a place.

The main points for me were and are:

Orthogonal drawing techniques whose advantages over manual drawing, include:

- copying repeated features or even large parts of the drawing, readily and accurately, to another area or even a new drawing.

- making changes or corrections more readily and less messily than on the drawing-board (I saw parallels with word-processing v. typewriters here),

- accurate dimensioning, as the computer does the sums,

- consistent lines etc, admittedly more aesthetically than functionally important.

Also, Isometrically-based assembly-drawings readable from different sides, to help ensuring Part B will rotate freely on Part A without hitting Part C; or to make building & servicing notes for future reference.

I was vaguely aware of brochure-style CAD pictures, from works drawings having small pictures to help the machinists and fitters visualise the task. This though, was and is of lesser importance to me, and worse, I now know adds only considerable difficulty.

Although not a time-served, professional machinist I do have a general, somewhat sketchy, semi-skilled background in electrical and mechanical engineering trades. So as well as my model-engineering hobby, I already understood engineering-drawings, in both manual and CAD days.

Also, I had some 20 years computer experience: MS 'Word' and 'Excel', and using laboratory instruments controlled by BASIC and 'Labview' programmes.

My encouragement was a perhaps too-ambitious project to build a 4"-scale steam-wagon from the scanty publicity photographs and Commercial Motor magazine trade-reviews remaining of the original, introduced in 1908. It was and is a matter of design a bit, make it, design the next bit, make it... then a few years later find Part B will not only hit Part C, but would obstruct Parts D to H.

So I saw CAD as potentially very useful.

I even hoped that one day I could reclaim the dining-room from its resident, A0-size, industrial-pattern drawing-board!

My reasons for wanting to take up CAD, was clear, and still stands. I knew it is a lot to learn but unfortunately, not how difficult and non-intuitive it all is to learn, nor the lack of useful supporting literature.

Thank you Neil. I would ask if I do convert to Alibre and need help.

I need decide whether to continue to attempt to learn CAD or give up; then choose whether to stay with TurboCAD or to convert to Alibre.

TurboCAD has a third way to generate solids: "Primitives", a few common solids like cuboids and cylinders you set to your own dimensions. These too, have their own characteristics.

I think the relative difficulty of Design and CAD is in favour of the design to start with but I understand your point.

I see using CAD or indeed manual drawing means acquiring a set of fixed skills, as tools to perform a project. Those tools change only in minor details; but the project is the real variable. In model-engineering, it can be anything from a simple machine-tool attachment to a showmen's road-locomotive or radial aero-engine.

However, I find CAD far harder to learn than I had envisaged, irrespective of what I design; and I can learn any difficult subject only to a random, unpredictable but rigid level. I abandoned CAD for about 6 months within a year of buying it; but having tried again I think I am near or even on my level for it.

My Drummond manual shaper's been busy lately!

I've just fitted a 3-ph motor set to my Harrison L5 lathe, and made the pair of tensioning arms holding the motor frame above the headstock* , from bits of old miniature-railway rail that our Mam would have said "looked as if they'd been dragged though a hedge backwards". They almost had been, left stacked among shrubs and dead leaves.

That shaper gave a pretty decent finish on the two shorter parts of the arms, more importantly with no rocking when tested on the table of my Meddings bench-drill. It did take a long time to cut below the worst of the rust pits, and I ended up with a sore shoulder, but it was otherwise rather relaxing and satisfying.

I chickened out and milled the mating faces on the longer arms, and the slots in the shorter ones!

As a point of model-building integrity, it occurred to me that a really good shaper finish would not only be functional but also right in looks for surfaces whose prototypes would indeed have been shaped or planed.

It's worth searching out older reference-books on shapers and shaper-tooling, and noting that the cutting edge should be under the clapper-box fulcrum to minimise digging-in. It was also common to use spring-tools, but this is less essential.

This means borrowing your lathe's tools may not be right. I recall seeing one poor shaper holding a lathe tool not only too deep itself, but packed out to push the edge even further forwards. I was too polite to query this with its operators, in a demonstration workshop at A Major Model-Engineering Exhibition!

I also file a small chamfer on the entry edge of the work-piece, slightly reducing the shock as the tool starts cutting.

For internal key-ways and splines, it is normal to draw-cut with the clapper-box locked. Some books show a locking bar screwed across the box. If you don't want to risk modifying the machine in a way that weakens the clapper-box holder, you can use a tool-holder with a jacking-screw in a top end that projects above the clapper-box.

For those who like making tools (to make more tools?) there exists an old design principle for a secondary table that allows a shaper to cut large-radii concavities such as smoke-box and motor saddles. This alternative to rather alarming fly-cutting, uses the geometry of rigid guides constraining the sub-table to move horizontally and vertically, simultaneously, so at each increment it forms a new tangent to a constant arc.

Most people motor-driving a manual shaper probably use these machines' usual crank and swinging-arm, but given that higher return-stroke speed is less important in amateur than production work, I have wondered if a self-reversing screw-drive would work here. It would be a challenge to thread-mill a full L+RH reversing-screw, but its main disadvantage is the fixed travel. I think my dear little Drummond will remain driven by an H.Sapiensis powered by tea!

*Lathe motor. The original Harrison L5 motor-mount was a massive steel box welded to the back of the cabinet, forcing the machine a long way out from the wall. To regain this lost space in a cramped workshop, I have cut the box off, and placed the new motor on a wall-frame over the headstock. It also raises the motor away from the dark and dusty depths.

Aluminium / steel, especially stainless-steel, couples are very unhappy partnerships, but it's the steel rather than the aluminium that corrodes.

I don't know what happens with aluminium/copper, but I think in some situations it will be the copper that is eaten.

This point is also pertinent to anyone building miniature railways with aluminium rail. It may seem best to use stainless-steel fastenings and I know some have done this. However, whilst they are good with mild-steel, the combination risks aluminium-alloy rail-ends corroding rapidly, leaving the stainless-steel screws all smugly bright and shiny.

I found this from experience at work, having spent some twenty years trying to tell my far more highly "edumificated" betters why their nice anodised-aluminium test-pieces emerged from a few days in a laboratory tank holding only tap-water containing ordinary swimming-pool treatments, with white "measles", especially around the stainless-steel screws!

I am not convinced by the fire risk. The high-Mg proportion aluminium alloys will burn in the right conditions, but the allow we are most likely to encounter is bog-standard HE30 (or whatever it's called now!), which is Al with a trace of copper. That doesn't so readily burn at all. In a simple model steam-boiler it's more likely just to melt if it runs dry.

YET... aluminium alloy IS used commercially for pressure-vessels, and for the heat-exchangers in modern domestic hot-water boilers (though a friend in the trade says they don't last long). If you read the dreaded Pressure Equipment Regulations - the original lawyers' version, more than the DTI guidance-books - you find its authors only ever knew of aluminium or stainless-steel alloys. I think the difference relevant here between commerce and we amateur engineers is that the trade has far greater resources of exotic alloys designed for the intended application classes, their relevant fabrication methods, and sophisticated testing facilities.

Andrew Johnston;

Re your, "For workshop use I create 2D drawings plus an isometric view of the part."

From what I saw at work (I retired a couple of years ago) it is common professional practice to put a coloured isometric picture alongside the annotated orthographic views to help the machinist see what he's making.

Having bought both their boring-bar and Worden tool-grinder kits, I see Hemingway Kits uses the same principle.

A rather unusual engine design there, Jason, with that long bifurcation on the connecting-rod and very wide angles in the crankshaft. What was it (the original)?

Two hours work so far... Ah, but such productivity with shapes like those is possible only with considerable operating skill; beyond my realistically achievable level whether I convert to Alibre or stay with TurboCAD. It would take me two hours to draw even one of the simpler components, and most are by no means straightforward.

I like your system for using colour to signify materials. In fact 19C designers sometimes used colour-wash for a similar purpose, and I think a certain standardising came into use. In some cases, civil-engineers at least also to tinted what might have been contract-negotiating drawings, to make them more eye-catching to the client.

My last attempt at a 3D drawing was of my steam-wagon's cross-head. These will use a siamesed casting pair I chanced upon in one of those boxes of lonely and forlorn castings that appear on model-engineering show trade-stands. A bit big for the scale of my steam-wagon engine but as it's all enclosed and their are no surviving drawings and prototypes, I don't think anyone will quibble!

It's similar to your engine's cross-head but with an internal small-end, and triangular cut-outs at the front and back. I think they were originally for a 7.25"g loco, and narrow-gauge at that. I measured the castings to establish possible machined sizes, then drew it as an extruded outline in thickness, with extruded cuboids subtracted to give the guide-bar channels.

As it happens an Alibre "magazine" has just appeared among my e-posts, containing a short (8 minute) video on common sketch errors. For some reason I couldn't get the separate amp and speakers to work so had to watch in silence (well, to the background of the concert on Radio Three!), but it clearly showed the effects of misclosures not apparent until you magnify the image.

That was one of the first things I learnt eventually on TurboCAD and probably common to any similar make of CAD - that closures have to be pixel-perfect (in fact I think their real definition is finer still; numerical not visual).

I think its point was that in Alibre an extrusion won't work and an un-closed or over-stepped joint is the likely cause. In TurboCAD it might extrude but as a thin-walled polygonal "tube".

I've also found in TC and I imagine you can equally unwittingly do this in Alibre: a lot of editing can leave tiny line fragments hidden under the visible lines; and these fragments play merry hell until you find and exorcise them.