Complicated Software

[John Candy]

John,
The easiest question to answer is what "translate" does .... it simply shifts the object around in the 3D space by specifying co-ordinates.
The only item, so far, which involved plotting co-ordinates on graph paper is the coach roof end where a smooth curve had to be produced to the correct profile.
Most items can be plotted by specify dimensioned objects (cubes, spheres, cylinders, etc) and manipulating them into position (translate, rotate, and so on).
2D objects (circles, squares, polygons, etc. can be extruded into 3D objects, either as straight objects , using linear_extrude command, or as circular devices using the rotate_extrude command.
All I can say is, "give it a go", it is not as difficult as it looks but complicated shapes will take many hours to perfect.

Regards,
John.

[IanT]

Hello JohnB,

Have a look at the Open SCAD Tutorial at the bottom of this G1MRA '3D Circle' page....

http://www.cs.rhul.ac.uk/~adrian/GaugeOne3DCircle/index.html

It will download as a PDF. There is other material here that might be interesting too.

Regards,


IanT

[IanT]

I was curious John - so loaded the coach end into SCAD and then exported & saved it as a .STP file.

I then imported the .STP file into Solid Edge and saved it as a .PAR file in SE, which (I think) should let me use it as part of a Solid Edge 'Assembly'. SE works by constructing 'Parts' which can then be combined into 'Assemblies' - which in turn can be combined with other assemblies (ad infinitum - or until your memory hits the buffer I would guess).

I haven't played with it beyond this simple exercise and I'm sure there will be some "gotchas" in there somewhere (I don't know enough about these things - still a White Belt) but if not then this work will be useful beyond Open SCAD designs too.





Regards,

IanT

[John Candy]

The tables for the 3rd class two+two Open stock
The file provides the option of having a leg at both ends, rather than having one end fixed to the carriage wall (as on the real thing).

http://gauge3.info/openscad/LNER3rdclasstable.scad

John.

[John Candy]

Ian,

Glad to know that my work is being used if only for experimental purposes at this stage.

If there is an easier way than OpenSCAD, then perhaps more members will "give it a try".

Only wish I had "jumped in" a few years ago but then the quality of the equipment (certainly at the "hobby" price level) was nowhere near as good as it now is.

Regards,
John.

[John Candy]

These are the tables fitted in LNER Open coaches with the 2+1 seating arrangement.

http://gauge3.info/openscad/LNER1stclasstables.scad

Now giving my fingers and eyes a rest for a day or two!

John.

[IanT]

As you will know John, I've used TurboCAD 2D for many years but never managed to get to grips with the 3D version. I always struggled to know what 'plane' I was drawing on (sounds simple but really wasn't! ). TC isn't parametric either, which can make for a lot of work when making changes to more complicated designs.

Ralph suggested Open SCAD as an alternative for 3D printing and I found that I could script simple objects very quickly and learn step-by-step. But it wasn't a replacement for TC in terms of engineering drawing & design or for more complex parts (at least for me).  I think SCAD's main strength is it's portability and ability to fairly easily customise other folk's designs. Anyway, as previously stated, I've been learning Solid Edge 2020 to replace TC 2D - not SCAD, which I will still use for some designs.

I've found Solid Edge to be very powerful and generally intuitive - no issues with visualising 3D objects or knowing what 'plane' I'm drawing on. However, these high end 3D CAD systems do need some time invested to learn the basics well and some aspects of the SE2020 UI can be puzzling at times. There are usually good logical reasons why some things work (and others do not) but they are not always that obvious.

I'm on my fourth version of a loco bogie frame at the moment, not because the 2nd or 3rd weren't generally good enough but because I know I'm still not 'thinking' about the drawing process correctly. I still tend to 'sketch' as I would with (non-parametric) 2D CAD, where anything & everything can be changed in retrospect - whereas clever Solid Edge is keeping tabs and quietly making assumptions about my "design intent" - something I need to learn to work with, rather than fight against. So I'm trying to get some of this clever tech figured out before I draw too many more parts and find they don't meet my (future) drawing standards any more.

Of course, Open SCAD has it's own challenges, especially if you want to draw more complex parts, where the scripts become longer & larger. So I think the lesson is that all of these 3D CAD tools are potentially very powerful but do need time & effort to learn them well.

Regards,

IanT

[John Candy]

Ian,

There seem to be plenty of options....a case of "horses for courses", I guess.
Would it be more useful to have uploaded the .STL files, as opposed to .SCAD?
The G-Code files have been matched to the Snapmaker 2 A350, so I guess they would only be of use to someone with the same machine?

I have yet to investigate the laser and CNC milling heads of the Snapmaker (daren't use them in the house or I suspect the smell/smoke would set off the alarms....quite apart from objections from "the Boss") and that will involve learning different software.

Regards,
John.

[IanT]

No, not at all John, I much prefer the SCAD text files (the 'source' code if you wish).

They are not only compact but also readable and (assuming I can understand them) customisable. SCAD can create the .STL files very simply at the click of a button. So the SCAD scripts are ideal.

Regards,

IanT 

[cabbage]

John,
I own a reprap, a laser cutter and cnc router. Each of which has its own learning curve. The laser cutter is surprisingly easy to use. The main problem is with the % control... If my laser 4W is cutting at 100% then the smoke and flames obscure everything!!! I have found that 2% is superb! What you WILL need is a backing piece of ply covered with copper foil which will reflect and conduct the laser after penetration.

The router is a two year old with a bag of flour !!! The dust from it goes everwhere in the blast from the citterotor cooling fan.

Regards

Ralph

[John Candy]

From 1906, "sprung equaliser beam" bogies were fitted to many GWR passenger coaches and NPCS, either as original fitments on new stock or replacements on older stock. It was commonly known as the "American bogie" since it was of a type common in the USA and one of a number of foreign innovations brought to the GWR by George Jackson Churchward.

It was made in both 8ft and 9ft wheelbases but the 9ft seems to have been the more common on the GW.

The OpenSCAD file has apertures left to accept alternative patterns of axlebox. The box I have initially prepared is of the familiar, arched-top, "OK" pattern.

My plan is to use this bogie under autotrailers and Siphons.

I have a copy of John Lewis's definitive study, "Great Western Autotrailers, Part One", which covers the pre-group trailers, including the steam railmotor conversions.

I particularly like the gangwayed pairs and the matchboarded types, which are very different from those more usually modelled.

Be aware that the bogie sideframe file is potentially a "computer crippler" and can take several minutes to "render".

http://gauge3.info/openscad/GWRAmerican9ft.scad
http://gauge3.info/openscad/GWRaxleboxOK.scad

John.

[IanT]

Very impressive SCAD scripting John.

Regards,

IanT

[John Candy]

Very impressive SCAD scripting John.

Thanks Ian, I am really "getting the hang of it" now ...... am even considering the possibility (eventually) of a complete loco......the book with the LMS 10000 drawings is close-by!

Back to the present and the GWR sideframe took around 6 hours at 80 microns, while the axlebox took 45 mins.

Regards,
John.

[John Candy]

The main visual differences between the 8ft and 9ft "American" bogies (apart from the WB) are two (instead of three) elliptical leaf springs and the different taper at the ends : On 9ft the lower edge is horizontal, on 8ft the lower edge tapers upwards, with a less pronounced fall on the upper edge.

The dia. F14 "toplight" slip coaches ran on the 8ft bogie, which is one reason for my interest in them.

http://gauge3.info/openscad/GWRAmerican8ft.scad

Incidentally, for anyone who has already downloaded the 9ft file, I have uploaded an updated version with a couple of "tweaks" to the detailing.

Regards,
John.

[John Candy]

GWR Collett 7ft bogie.

This 7ft bogie was widely fitted to all types of passenger carriage as well as to the more modern Siphon J.

It is a large file and will take many minutes to render.
The axlebox is a different pattern to that for the "American" bogies and will follow soon.

http://gauge3.info/openscad/GWR7ftbogie.scad

John.