3CP Curve Plotting Tool for Model Railways

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1 1 3CP Curve Plotting Tool for Model Railways Introduction - What is 3CP 3CP (3-point Curve Plotter) is a precise and unique mechanical curve plotting tool used for plotting and forming realistic looking track curvature for OO scale model railways. 3CP is quick and easy to use, forming accurate alignment along the planned route without relying on the use of any other measuring tools. It has the ability to plot within structures and boundaries before any track is laid, and so eliminates the need to fix the track and avoids any subsequent re-alignment which may result in track damage or wastage. 3CP can be used to plot straight sections of track route, spiral and constant curvature. This enables the user to plot realistic transition curves achieving a smooth running appearance for trains and lessening the chance of derailments. How 3CP works 3CP has three main functions and these are:- 1) Forming - to form curved routes by holding flexible track in position. 2) Plotting - to plot simple and complex geometric track routes. 3) ening - to straighten flexible track for reuse, and to pre-curve track provided that the materials have not exceeded their elastic limits. The list of set radii are as follows:- 457mm (18") 533mm (21") 610mm (24") 762mm (30") 860mm (33.8") 915mm (36") 1067mm (42") 1219mm (48") 1524mm (60") 1828mm (72")

2 2 Figure 1 shows the method of use. The tool relies on three points on a curve to form the route. These points or route markers are always at the same direct or shortest distance apart from the next marker. The general operating principle of the tool is to forward predict to find the next route marker point based on the two previously plotted route marker points. In Figure 1, consider route markers 1, 2 & 3, where route markers 1 & 2 are any initial points on a line or curve. The location of marker 3 is defined by the setting of the tool, which would be on a straight line or a known set radius. Marker 3 becomes the forward predicted point on the curve. Usually, marker 3 would lie on a large radius forming the first transition curve, and all three marker locations would require some form of temporary marking (e.g. by pencil). To identify route marker 4, the tool radius setting could be reduced slightly and then the tool would be incremented to the next location, i.e. by moving the tool, marker 1 becomes 2 for the tool to locate, 2 becomes 3, and 3 creates the new marker 4. This now forms the second transition curve. This process can be repeated to continue a spiral or constant radius route, and can be reversed to blend onto a straight section of track. Figure 1 - method of forming a route

3 3 How to use 3CP 3CP can be used for preliminary plotting of the route with or without track. Without track, the tool can be used to quickly plot a very close approximated route. It will probably take a few attempts to achieve the best route, hence the need to use a pencil or any other form of temporary route marking. An example is shown in Figure 2 where marking by inverted-t's at the outer rail radius edge of the gauge ends and centre pivot defines the plotted route. This is recommended as a convenient place to mark, but if preferred route marking can be made along the track radius at the centre of the track. The track can then be aligned along the outer rail to the inverted-t markers, with the aid of 3CP to control the track curves. Figure 2 - Preliminary route plotting without track Track radius setting, mm and inches R = 1524mm Inverted "T" for route marking R = 1067mm Track gauge Tool aligning notch Track radius The 3CP tool is designed to fit into the track gauge to form the track radius (see example in Figure 3). The route can be plotted with the track, and Figure 3 shows how the track curvature is developed by marking the position at the ends of sleepers with an inverted "T". Also, note the plotted curve radius setting for the section written in pencil. If using this method, it is helpful to lightly pin the track in-place during development of the route. Once satisfied with the plotted route the track can be firmly fixed. This eliminates any permanent fixing of the track ensuring the route is correctly formed, and avoids any corrective reworking. Note written in pencil the plotted curve radius setting for that section. This is a very useful tip to ensure the curves are being developed correctly throughout the route.

4 4 Figure 3 - example of locating the track to the plotted route section R = 1524mm Inverted "T" for route marking R = 1067mm Plotting the route can take a few attempts to achieve the overall desired result as there are ultimately many options. This may be due to plotting the appropriate transition curves and to fit the route within boundaries or fixed objects e.g. stations, tunnels other railway routes, but generally it is quick and easy to plot improvements to achieve the best route fitting solution. When the best route solution is achieved, the tool can be used to hold the curved track in the position according to the marked route. The elongated holes along the tool allows access for nails or pins to fix the track to the base boards. There are some general rules to follow when route plotting due to the precision of the mathematical design of the tool:- a) Always plot the route from one end and plot one point at a time in sequence. b) Do not change the radius setting by more than two settings for one section or predicted route marker. Note, one radius step change per section achieves the smoothest transition curves. c) Mark the route accurately and consistently. d) Ensure the screw is securely located for the radius setting, but do not over-tighten the screw.

5 5 The curve plotting tool can be used to straighten flexible track providing the track rails have not been excessively curved (i.e. not exceeded the material's elastic limits). This is quickly done by setting the tool to the straight position and sliding it to and fro within the flexible track gauge. The track can then be reused, and can be used to form curved track again. Also with straight track, the tool can be adjusted to a radius setting for pre-curving by choosing a radius setting, and then by sliding the tool to and fro within the flexible track. This will form a near constant general curve. Further general information. The 3CP tool was originally developed to help solve the difficulty of accurate track planning and alignment of a 5 inch gauge miniature railway. A large scale example of the tool was constructed for designing the railway, resulting in superb track alignment (see photos below). In due course, it is planned to expand the range of the 3CP tool for other model railway track gauges. Intellectual Property 3CP tool is protected by the following:- Patent pending status, Application no , Publication no. GB European Community Registered Design, no Trademark, Application no. UK Contact: info@3cp-tools.co.uk Mobile phone: