General Notes

A Few Words …

These advices, taken, several moons since, from John Lythgoe's instructions for his Formil Model Engineering Dyna-drive kits, have proved to be useful and enduring tenets:


Our kits are intended to be assembled by adult modellers, with some workshop experience and awareness, who are able to exercise due care and attention when handling the materials and carrying out the various operations involved. Many of the metal components have sharp edges. Chemical products used in assembly can be injurious through contact with skin or eyes, ingestion or inhalation. Some processes involve high temperatures. The user should be aware of and follow the manufacturers' or suppliers' safety data and instructions for all tools, materials and products.

The Instructions


We've divided up the instructions into "narrative" paragraphs, like this one, which indicate what is being accomplished by a particular stage,

"instruction" paragraphs, like this one, with the tick-box; "box-ticking" not our favourite activity perhaps but nonetheless can be useful, on a printed copy, for recording progress and making sure nothing is forgotten,

and "advisory" paragraphs, like this one, which pass on techniques that we found useful but aren't necessarily the best way, or the only way, of achieving a result.


We have introduced a "Check List" for each kit, which contains the texts of all the instruction paragraphs for the kit. This is a great deal more compact for printing than the full instructions, and perhaps more suitable for the workshop. The Check Lists are available only from the on-line copy of the instructions, from this Index Page.

We intend the Full Instructions to be viewed 'on-screen'. If you did need any of the diagrams or pictures in the workshop, you could download and print them individually to complement the Check List.

If you wish to print out sections of the instructions, they are formatted in standard HTML/CSS but, even so, the print function in some browsers does a better job of rendering them than others. We find that 'Print' function of the Google Chrome browser produces a good printed result: it also gives the option of 'Save as PDF', which is a convenient way of creating a single portable file, including all the illustrations, which you can view or print on any device.

If your printer can produce half-size A5 prints (two per A4 sheet) or, better still, double-sided A5 booklet printing, using those options can save a great deal of paper.

The Etches


Tag cutting knife Components are attached to the fret by small half-etched tags. These can be cut through using a heavy craft knife with an old, stubby, blade (avoid the thin, pointed, 'scalpel' types, as they will break), against a hard surface. We keep a rigid Stanley knife expressly for this purpose, with an old carpet trimming blade ground to shape as shown.

Any remnants of the tag may be cleaned up using a flat file. We have tried to avoid putting tags on mating faces, but there are some instances where they need to be removed thoroughly.


Checking slot width Some of the parts of our kits are designed to fit, perpendicularly, either into or through slots in other parts. The slots are intended to provide a loose sliding fit for the other part. Because of variations in the degree of etching (q.v., below), it is possible that the fit will be looser or tighter than ideal.

Check the width of each slot with a piece of scrap etch before assembly, preferably before folding the slotted part. If the scrap will not pass through, hold it in pliers or a hand vice, as shown (though make sure the part is well supported), and work it through the slot until the loose sliding fit is achieved. In tight spots, it is possible to use a small drill held in a pin chuck as a file.

Degree of Etching

The etch is created for us by a third party industrial manufacturer using a process of chemical erosion. The 'Degree of Etching', i.e. how long the metal sheet is left in the chemical bath, is a variable which is set by the skill and judgement of the operator as each batch of sheets is produced. That dictates that the sizes of the etched parts on different sheets can vary, within a certain tolerance, around the nominally designed values. The variation is more significant with the relatively thick materials, that we use in the main structural parts of our kits, than it is with the thinner materials typically used for detail parts.

The ideal degree of etching is indicated by the slots (see above), as manufactured, being just slightly on the tight side of the easy sliding fit required. The range of degree of etching which we deem to be acceptable is from a 'lighter' etch, in which the scrap material has to be pushed through the slot quite firmly to achieve the clearance, to a 'heavier' etch, where the fit is a little loose. We have test built our kits from etches across this range to confirm that they may be assembled successfully.


Cusp on edge of etch The chemical erosion process works equally from each side of the metal, resulting in the edges of the etch having shaped 'cusps' as in the diagram here. On edges which will be visible on the finished model, it is good practice to file the edges of the metal flat. Many of the edges on our kits are hidden from view.

Where edges form joints with other components, on a 'lighter' etch the edges may need to be filed to a flat surface to achieve a fit, whereas with a 'heavier' etch one might leave more of the cusps in place. In places which can't be reached by a file, e.g. in acute corners of the etch, the cusp may be pared away with a sharp knife.


Etched fold anatomy Folds are indicated on the etches by half-etched lines. Unless stated otherwise, all folds are made at 90° with the half-etched line on the inside of the fold. Most folds may be made by holding the larger part of the workpiece in the fingers or, for smaller items, a hand vice or similar clamp, and then driving the fold from the smaller part either by using smooth-jawed pliers or by turning it over against a smooth, flat, hard block of material such as hardwood, metal or tufnol. For longer folds the workpiece may be clamped between two flat, straight edged pieces of similar material. Special folding tools or bending bars are not necessary, though of course you may find them useful if you have them.

Whichever way you make a fold, try not to force its location or direction, but let the brass bend at its weakest point as determined by the centre of the etched fold line. This should result in a correctly positioned and symmetric fold as shown in the diagram.

The act of making the fold will work-harden the metal along the line of the fold and may even, especially with a lighter etch, cause it to yield on the outer corner of the fold. Try, therefore, not to work a fold unnecessarily once made, as it will become increasingly brittle and prone to breakage. In general, folds are reinforced with a fillet of solder but this is explicitly dealt with in the instructions for each component.


We use Carrs 145° wire solder with Carrs Green Label liquid flux, except where stated otherwise.

Flux can be applied to the workpiece using either a brush or a pointed cocktail stick. It may help to reduce the surface tension of liquid flux, for example by adding a drop of washing up liquid or ox-gall. The soldering iron bit is wiped on a damp sponge, and then momentarily dipped in flux, before each use. A small amount of solder is picked up on the bit and the bit applied to the workpiece, holding it there until the solder 'flashes' into the joint; we are using relatively thick material so can afford to linger with the iron and get plenty of heat to the job.

Flux residues should be neutralized and/or cleaned off after each working session. Green Label flux may be rinsed away with water; a little added citric acid will neutralize it. Liquid or paste fluxes can be washed away either with a proprietary flux cleaner or a 50/50 mix of methylated spirits and water.


The procedures described in our instructions require the proprietary locomotive to be dismantled and some of its components to be modified. The manufacturer's warranty will almost certainly be rendered void by carrying out the modifications. The user should ensure that the locomotive is free running and has no warranty issues before commencing work.

Please follow the manufacturer's instructions for the dismantling of the locomotive.

Our instructions guide you in making modifications to components of the locomotive and fitting the kit. The modifications, the kit and the instructions have been tested by the kit designer and others to confirm that they are practical, serviceable and, when used as intended, produce a working locomotive whose performance will bring much pleasure. However, as the fitting of the kit by the user is out of our direct control, we can make no warranty, expressed or implied, as to the performance and continued serviceability of the locomotive following modification.