Metric Build

[danieldlonsdale@gmail.comParticipant @danieldlonsdalegmail-com]

Hi all,

I’m looking to start my first traction engine build and I’m hoping to find metric drawings for a 4”, 5”, or 6” scale engine. My grandad built a beautiful 3” engine, which I absolutely love—but I’d really like to take on something a bit bigger myself.

Ideally, I’m after something with a good amount of detail and solid documentation. I’m open to different makes and designs, so long as there’s enough information to support the build from start to finish.

If anyone has plans available, knows of a good source, or can offer any advice for choosing a good first large-scale project, I’d really appreciate the help!

[JasonBModerator @jasonb]

The vast majority of Traction Engine designs are imperial but LSM do also have some of theirs in metric.

Although Imperial have a look at the GMT and Devonshire which were previously done my Edward George and are now done by AN Engineering. The Little Samson is another of his which LSM are now doing castings for. These are good popular designs with plenty of build threads to give you an idea of what is required.

Also register with Traction Talk Forum then look at the Miniatures section as well as tracking down a copy of Edward Georges book “Scale Model Traction Engine Construction”

[parovozParticipant @parovoz]

So I suppose that will be 101.6mm to 300mm scale, 127mm to 300mm scale and 152.4mm to 300mm scale…..  🙂

Given the inch to foot scaling for TE models and most models etc. then most drawings will be in imperial. My advice….. just have your calculator to hand and convert it…. fairly easy. Then for threads etc, use the nearest metric equivalent where practical. Just be consistent in your substitute threads. And use BA sizes. Well…. BA is actually a metric thread….

In the end it is not too difficult to work with imperial drawings in a metric workshop, I have a range of metric and imperial tools so I do it all the time 🙂

All the best.

 

 

[JasonBModerator @jasonb]

If you are already setup for and used to working in metric then I feel it is more of a pain to just do a mathmatical conversion.

Typical example a bit of 1/8″ rod with a 5BA thread. You can call it 3.175mm and still use 5BA but why not go the whole hog and use 3mm rod and M3 threads. metric tools and materials also tend to be cheaper than imperial.

[Nigel Graham 2Participant @nigelgraham2]

Most of the material and fastenings stock sizes in binary-fraction of inches, and sheet thicknesses in SWG, have close metric equivalents, some to small fractions of a millimetre. So straight conversions by material, e.g. 3mm for 1/8″, or 10mm for 3/8″, should often work without noticeably impinging on scale proportions, except in very fine detailing.

Where you do need care is if working from Imperial-dimension drawings, that the change to mm materials will not give assembly problems such as affecting clearances.

 

Gears, such as on a traction-engine, may need particular care if metric (module-pitch) unless the drawings are all in metric anyway; due to much less equivalence by diameters with inch-based versions.

 

The standard ISO-M Coarse fastenings are readily available but their diameters and spanner sizes do not follow very regular series, the threads sometimes seem rather loose, and with their stamped heads might not always suit fine-detail work. There is the ISO-M Fine series but I don’t recall encountering any, let alone using them.

The button-headed ISO-M screws with Allen socket heads are quite good at pretending to be rivets, once painted so the sockets are largely filled.

 

Still use ME Standard threads for steam- and water- fittings up to 3/8″ diameter, and BSP for 1/8″ BSP upwards. (The o.d. of 1/8″ BSP is approximately 3/8″.) This is because the majority of fittings are still made in those, indeed BSP is still the industry standard though I think a.k.a. “G” to hide the fact!

Although the ME threads (32 and 40tpi) are also valuable where a fine thread is necessary for adjustment purposes, such as the cylinder valve-spindles, I would think the ISO-M Fine standards will work just as well

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