Always think that if you know the old school ways it makes CAD easier, my swirls at 45 deg as I could not be bothered to hunt down the adjustable set square

Good grief, SoD must be really bored!

Andrew

Sorry you both fail on the railway lines one – no transition curves

Both F360 and Alibre start any item with a two dimensional "sketch" eg you draw one elevation, then the extrusion is really nothing more than adding another elevation to give the part depth just as a drawing side elevation would give depth to the front view.

Dave's part I showed above was just a series of three arcs on a two dimensional plane for each area which I chose to give different heights to.

Areas are all the same.

.

If I try really hard … I can just about believe that there may be some underlying logic in that abuse of the English language : If a thing is considered ‘uni-axial‘ then changing it has no effect upon things that are orthogonal to it.

[or something like that]

MichaelG.

If you can solve it using a magnetic thing, surely that deserves considerably more than double.

If you can solve it using a pair of compasses, that also deserves more than double as drawing the straight lines that form the angle bisectors and whose intersection defines the inscribed circle centre is quite challenging using an instrument for drawing circles.

Referring back to the original challenge, I am dubious that any railway would be constructed from simple circular arcs tangent to straight lines. AIUI, transition curves are always necessary (and drawing those, whether manually or on a computer, is somewhat tricky).

70mph round a 100 metre curve? I'd guess you're tilting it 90 degrees and fitting ejector seats…

pgk

My wretched typing! I'd about finished this when yet again I hit an unknown key-combination and deleted it.

Orthographic! Yes of course! Thank you gentlemen for the correction! Same root though.

Of course I am aware that CAD calls the 3D images "models", but TurboCAD's view-changing tool offers two types of view and calls one isometric. I forget the other.

I am also well aware of the industrial practice now being taken up in some ways by model-engineers, of drawing-files translated straight to CNC-machine drivers.

'

Really, for us amateur engineers the choice of whether to use CAD, and to what extent, is by budget, time, preference, learning-ability and indeed interest.

First we are assuming designing our own projects, rather than sticking to published ones; and considering their complexity. This was my starting-point, as my main project's source is merely a few scrappy old trade photographs from 1908; and I bought a copy of TurboCAD 19 Pro.

Next, unless you have a particular gift for learning extremely difficult and unintuitive software, which I do not, it can take a formidable time to grasp sufficient CAD experience just for simple orthographic drawings adequate for your own purposes.

3D-model drawing adds greatly to the complexity; and when designing for yourself, you need ask why lumber yourself when you actually make the parts from 2D drawings. The one advantage I see, was that CAD enables 3D models to help determine complete assemblies. This too, helped sway my decision.

However, as engineers we should be able to visualise a 3D assembly from 3 orthographic views – depending on its nature.

So why 3D CAD for own drawings for own projects in own workshops…?

The only answers I can see are that either you have the desire, time and ability to learn it, or you've bought a CAD package that gives you no choice!

If we buy CAD because we want to design our projects, presumably we can already create engineering-drawings of appropriate standard. The trap is that of trying to learn the CAD package taking much longer than we would have spent drawing the project manually.

I bought TurboCAD but really, that it lets me draw a 3D image of, say, my engine's crankshaft does not mean I have to do so. I want to make a real crankshaft, not a pretty picture of one, and after untold hours of struggle better spent actually designing and making the engine, I was just about capable of a pretty picture of the shaft. By then I had made it, to a CAD drawing but orthographic, dimensioned and set out from the orthographic GA.

I did try other CAD packages.

I have a copy of AutoCAD 2000, which is 2D only I think, but no manual for it.

I found Fusion 360's brashness off-putting, and it assumes prior CAD-principles knowledge – to be fair, they all do.

I tried Alibre but I missed two episodes of the MEW serial. Why buy and learn a complete new package when I'd already bought TurboCAD? I thought the magazine series would make it easier to learn, than trying to teach myself what I already had. So I abandoned Alibre too – which took its publishers months to understand. Luckily, I already have a scribing-block.

Both Fusion and Alibre are based on 3D- model first – I do not use a 3D CAD/CAM system at home, so regard 3D as nice-to-have, but of limited use, extremely difficult and time-consuming to learn and frankly, not really necessary. It is for brochure artwork, not workshop drawings.

The only useful 3D images I have drawn were two geological diagrams for a caving-club magazine article.

'

Training materials?

TurboCAD's own on-line 'Help' manual is not much 'Help'; and I can't learn from videos. Far better than these is Paul Tracy's CD manual for TurboCAD, a step-by-step pdf primer.

D.A.G. Brown's general CAD primer has a very dated cover photograph, but does outline the principles of CAD engineering-drawing. Neill Hughes' more modern alternative, which I also own, is sketchier and more for the 3D-artwork people – and despite a British author and publisher, neighbours to France, it insists on calling "metres", "meters".

'

So to sum up, CAD can help us but it is not the be-all-&-end-all of model-engineering. Unless you also intend using CNC machine-tools as well, or buying a lot of profiled work-pieces, CAD is only worth buying if –

you design most of your own projects,

you need draw them accurately,

manually drawing them would take much longer than learning the CAD package sufficiently.

For me the ability to assemble and move all the part on the screen to check for fits and clearances is a big bonus before I cut metal, can't do that with 2D. Once modelled then 2D drawings can be produced to take to workshop.

Anyone with CNC will also want to take advantage of its 3 (or more) axis of movement so having the part drawn in 3D is needed. Same applies to those with 3D printers either for printing finished items or maybe printing test items before cutting from metal. No paper drawings would be used in this case as straight from screen to memory stick and into machine.

It can also be handy if you want to know weight or volume of an item which is just a click away even for complex shapes