Recycled Plastic Garden Railway Information
Garden Railway products
A customer of ours shares his experience developing a recycled plastic trackbed system. We hope to develop a kit on the basis of this and a prefabricated set track system:
I had been planning a garden railway for a number of years and decided that it should be a raised line to make operation easier. I also wanted to build up the ground level of much of the line so that it had the scenic advantages of a ground level line. A further constraint was that I wanted the line to run through established shrub borders without disturbing them.
The method designed by Bill Logan appeared to solve many of the problems I was attempting to solve – it offers a single method of construction for a recycled plastic ladder frame which is suitable for use above ground, on the ground, or set into the ground. The HDPE plastic will not rot and bends easily to form the curves for the railway. However, the specific HDPE material used is not available in the UK, and the ladder frame described is for G Scale/ Gauge 1 track. The line I was designing uses SM32 (“O” Gauge) track, which is common in UK. It needs a narrower ladder than the 45mm G scale, so the detailed construction method needs to be adapted.
The ladder frame construction consists of two stringers separated by spacers (rungs). The frame is supported on posts inserted through the ladder. For the frame to work, the track sleepers must rest on the stringers and the spacers must be the same length as the cross section of the posts (i.e. the posts should touch both stringers when pushed through the frame). The material for the stringers and spacers needs to be thick enough to make a strong framework when joined together, but thin enough to bend to shape in situ. Bill Logan’s work suggested that ¾” was about the right thickness.
After much searching on the internet, I found the recycled HDPE available from Filcris. The 18mm thick planks are ideal for making the stringers and spacers. The 38mm * 38mm solid posts are also ideal for the supports. This gives a ladder frame width of 18mm + 18mm + 38mm = 74mm. The SM32 track has sleepers that are 70mm wide, so they are properly supported on the stringers, with 2mm extra on either side. This gives good support and looks neat.
The construction method is to rip the 140mm deep planks lengthwise into three equal parts, approximately 42mm deep after cutting. One of these planks is then cut into spacers 38mm long – use a post as cutting guide. Next cut some spacers from post material into lengths of 40mm – 50mm for joining stringers together. Not too many are needed, as off cuts from the support posts will be used once some track bed has been installed.
The preparation of the ladders can now be started. One side of the ladder is prefabricated in the workshop/garage. This is done by attaching spacers at 6inch intervals along one stringer only. At one end of the stringer and half way along the stringer, attach a joining spacer made from the post material, the one at the end should overhang the stringer by half its length, ready to join to the next stringer. If possible, set the joining spacer level with the top edge of the stringer to give a good point for fixing track later, although this is not critical.
Once enough stringers have been finished to complete the first section of track bed, they can be installed in the garden. I found it helpful to mark the path of the track bed using a hose pipe. This is good for getting a visual impression of the layout and checking access and curve radius. The following assumes that a simple loop will be the first section of track bed to be laid.
At least five clamps will be needed for bending the ladder to shape, also garden canes, tent pegs and posts are helpful too if working solo. The prefabricated side of the ladder is laid in situ and pegged at one end to prevent it moving, join another prefabricated stringer to it. It is easiest to have the prefabricated side on the outside of the curve, but this cannot always be arranged, e.g. with reverse curves. Shape the stringers along the path of the hose pipe, using canes/tent pegs pushed into to the ground to hold it to the rough shape required. Clamp a plain stringer to the open side of the ladder, starting at the joining spacer in the middle of the first section laid, i.e. overlap the sides by half a stringer length. Fine shaping of the ladder is now performed by bending and clamping the ladder, progressing from the starting point and clamping tightly once the shape is correct. The plain stringer is now screwed into the spacers. Once the ladder is screwed together the clamps can be moved further along. If the shape is not right, clamp again, undo the screws, adjust the curve and re-screw. If tight curves are being made, then the joining spacers may need to be moved along the stringer if the prefabricated side is on the inside of a curve. After fixing , the end of the inside stringer should be half way along the joining spacer. If it is too long then trim the stringer to length, if it is too short then move the spacer.
Continue adding a prefabricated side and bending, then fixing a plain side until the loop is complete. As described, the method of bending forms natural transition or spline curves. If set track (fixed radius curve) is to be used then a bending jig will be needed to ensure that the curve is true.
For double track, two ladders are required running side by side. Spacers between the two lines can be used to keep the gaps constant. It is easier to fasten these onto the first ladder before the sides are fixed in place. For points, two ladders are merged by cutting the stringers of one ladder at an acute angle and screwing to the other ladder. Use of at least three screws per stringer is recommended where the ladders merge, with extra spacers inserted as needed to provide enough grip for the screws.
Once a section of track bed is finished it needs to be levelled and pegged to the ground with posts, or raised on the posts depending on whether it is ground level or raised. This is done by driving the posts into ground through the ladder frame every 18 to 24 inches. Pay particular attention to the posts being vertical “across” the ladder as this controls the lateral level of the track. They can be inclined inwards by 2 – 3 degrees on bends to provide super-elevation for the curve if required. To level the track along the bed simply raise it up the posts where it is low until the desired level is achieved then clamp and screw. When the whole loop (or section) is level both laterally and longitudinally then saw off the post tops level with the ladder. The off cuts are used as joining spacers for more track bed. Because the loop is joined on the ground before levelling there is no possibility of there being a height difference at the start/finish point of construction unlike some more traditional construction methods!
In Bill Logan’s method he advises that the posts should not be more than two feet high. Although I have not tried this I think the moulded solid posts from Filcris are less flexible than the sawn sections he uses as posts, so raising the track to a height of three feet should be possible.
When track is laid, the ladder provides a ready made template for rail bending. Remove the rail from the sleepers (WD40 helps), and bend each rail to fit its side of the ladder (at the join of the spacer to the stringer). When the shape is right, thread the rail back into the sleepers and screw to the ladder. Note that the HDPE ladder will expand and contract more than the rail does. Because of this, gaps should be set very small if track laying in cold weather and set large if laying in hot weather contrary to normal track laying practice. Using SM45 joiners gives more expansion room than SM32 ones, and if the gaps get too large offcuts of rail trimmed during installation can be inserted in the joiner during the summer and removed in winter.
- All screws used are stainless steel self tapping screws, mostly 4*40 with 5*40 for high stress areas.
- Always drill pilot holes.
- Countersunk screws have been used because they are readily available. If they show signs of pulling through the stringers then cup washers will be inserted. None have been needed yet.
- Good quality clamps are needed, cheap plastic ones will not last long.
- When fixing to joining spacers the screw will usually need to be removed after screwing in half way so that swarf can be cut off the spacer before fully inserting the screw.
- A 3m length of stringer can be cut into 72 to 75 spacers (depending on saw blade width). This is sufficient for about 12m of track bed.
- Don’t be afraid to experiment, it is easy to undo and relay without wasting material. It does not harm the garden – there is no concrete in the ground.