PART 5 SITE SURVEY & PLANNING
Whilst it is essential to plan your garden layout in sufficient detail, having due regard to the natural landscape and potential hazards, it is also important that you avoid the loss of inertia which easily occur if planning becomes too meticulous and starts to become an obstacle to actually getting your trains up and running.
It is certainly important to avoid any costly pitfalls that could arise from inadequate preparation but you will probably want to modify your layout at some stage in the future so in practice most mistakes can eventually be rectified.
Every location will be slightly different and present its own challenges. See if the natural landscape can be used to enhance your layout ambitions rather than be a constraint. For example if you have a steep rock outcrop consider a mountain line hugging the sides of the rock-face along narrow ledges; perhaps with switchbacks or loops to enable your trains to gain height.
Surveying the terrain is a vital pre-requisite to be completed before you even contemplate laying track. Unless your site is completely flat you need to plan how you will either follow the contours of your garden or undertake earthworks to reduce the high levels and build up lower sections, dips and troughs so as to ensure that your locomotives can navigate the line. In determining the best way to utilises the terrain make sure that any ground-works (especially moving earth from one location to another) are kept to a minimum as this work can often involve moving tons of heavy soil which is hard work (particularly if you suffer from a bad back)!
Avoid boggy areas and land subject to possible flooding for tunnels and excavated cuttings, sighting ponds under tree-cover where leaves and assorted debris might prove a problem.
When deciding where to locate tunnels, cuttings, embankments, bridges and viaducts, etc. use common sense to avoid impediments which cannot easily be re-positioned. Try to steer clear of obstructions and potential hazards such as overhanging trees, washing lines, concrete paths, etc.
If in doubt the old adage "keep it simple" is definitely the most appropriate course.
Surveying the Site
There are various tried and tested methods from the very basic techniques to the latest high-tech solution employing sophisticated modern lasers. Each approach has its adherents.
Start with a rough sketch showing the overall dimensions, physical features and approximate elevations (See Diagram A). This will help you to visualise what you have to work with and plan accordingly
Measurements are probably best taken using a simple 'grid system' where the site is divided up into uniform squares (1m or 3' is about right). You may need to use string to map out the grid pattern and hammer small marker posts ( approx. 2"x2"x30") in the ground at intersections (See Diagram B).
Then, starting at the lowest point marker use a builders level (at least 4' or more in length) to establish the height of each adjacent marker. Alternative the laser would help speed things up once you have mastered the technology.
Transpose these to a large sheet of graph paper using a suitable scale e.g. 10mm to 500mm, to make a more accurate site drawing.
INSERT
: DIAGRAM A
Grades
Then overlay the proposed line and establish where the adjustments to the surface have to be made. Do not make the mistake of making your grades too steep as this may severely limit the length of train that can negotiate the line. Tracks don't have to be perfectly level but bear in mind that on inclines a steady grade of 1% is desirable i.e. 1' in a 100'; 1cm in 100 cms so that your locomotive can pull a reasonably number of cars or wagons without undue exertion. You can increase this to 2% - 3% if you have to (or even 4% if you are prepared to "double-head" your trains or use a more powerful locomotive for that stretch of line) but bear in mind that, as a general rule, for each 1% increase in the steepness of the gradient the potential length of train reduces by a massive 50% so for a train comprising a loco and 8 wagons on the level you could only run the same loco and 4 wagons on a grade of 1% and as few as 2 wagons on a 2% grade.
Designing the Track Plan
To be added at a later date.