laurie

Having experimented with all plastic construction I realised it was far to convoluted and I wasn't enjoying the process. I decided to stick with the plastic posts and use suitably treated timber as the road bed, this has meant I have made some progress in the garden marking out the route with posts and building some of the route. Last week I put a couple of yards of flexi-track down and staged a train. This gave me a huge boost in enthusiasm and I am raring to go, of course it immediately started raining.

That is cool, love the 45 with mk1s!

Hi, I still haven't worked out how to accommodate the longitudinal expansion of the track base. If I limit road bed sections to 50 cm then the expansion range would be 3mm and I'd probably want to leave that sort of gap at mid range temperatures (as I expect the upper end of the range to be higher when it bakes in the sun). With normal track joints I think I would want to spread that over at least 3 joints (1mm each) which implies 3 pieces of track on each 50cm board. an 18yd panel would be 216mm so each of my pieces would be shorter even than this! Thats alot of joints over even the relatively short length of line I am building. If I want to have fewer track joints and also longer base sections I would have to make prototypical expansion joints! These might be tricky to make as it would involve filing rails exactly down the middle so that two halves could overlap and fit within a rail joiner.

I'm going to mock up a couple of sections at different heights so all the stakeholders can attend an "optioneering workshop"., now thinking of 60cm and 30cm high as potential options. I'd prefer the higher one as at the lower height the railway would disapear for a long stretch behind the tomato jungle every summer. Yes, I didn't plan on operating at the extreme ends of the temperature range! So as long as I can work out how to attach the track to the road bed so that the expansion of the latter doesn't cause buckling or disconnection at likely temperature extremes I'll be delighted. We are more likely to get to the top end of the range especially as the plastic is dark and I expect it to be hotter than the air temperature when there is lots of sun. Has your line side fencing been used in anger yet? My recollection of the Hornby fencing was that it was quite brittle, mind you that was 80s vintage stuff so it could be better now. thanks Laurie

Having committed myself it would be a shame at least not to have a go with the stuff, if it doesn't work out there are other methods and it all sounds like fun. I think I may be able to manage the expansion on straights and easy curves, not sure about the necessary tight ~3ft, 90 degree curve I need to make at one end though, the plastic will expand in all directions so it is not so easy to envisage. thanks Laurie

Hi Riddles, You are quite correct! The actual coefficient should be 0.15mm/m/C. Unfortunately it is still a 6mm expansion over 40C At least it is not a 60mm expansion, I think it would definitely be unusable then thanks for spotting that. Laurie

Contacted Filcris today to find out what the coefficient of expansion for the plastic is and it is 1.5mm / m / degree C. This is 10x that of nickel silver rail (0.016mm/m/deg C - source 'Theq'). So whilst, over a -10C to 30C worst case operating range, a metre of track would change by 0.6mm an equivalent length of the plastic base will expand by 6mm/m. It occurs to me though that the worst case temperature operating range is air temperature and that after baking in the summer sun for a few hours the dark plastic could well be hotter than 30C. I will have to investigate once the plastic arrives. It seems there are two problems to solve: 1. Constructing the base to account for its own expansion and contraction. As suggested elsewhere on the forum this will mean limiting the length of any piece of plastic used in the road bed to as short as reasonably practical. 2. Fixing the track to the road bed in such a way that it has one fixed point only with other points held down but allowed to slide longitudinally.

Hi Peter, Thanks for your encouragement, but after reading the thread on your layout, which looks lovely by the way, I am now expecting the dark brown plastic I've bought to be a complete disaster! It all depends on whether it distorts when it heats up or just expands. Oh well, you live and learn and if it doesn't work it will teach me to do my research first! thanks Laurie

Aargh! I had already committed my self and bought some which arrives tomorrow! Thanks for the warning anyway, forewarned is forearmed. I'm keen on the maintenance free appeal of plastic, hopefully with some thought before construction I can overcome any expansion problem. Is it longitudinal expansion that is the problem? If so then presumably limiting the the length of these members should help, it means more joints in the sub-structure, but that is better than buckled track. I'm going to have to deviate from Filcris's prescribed construction method anyway as i am not working in an empty space so its all a big experiment. thanks Laurie

Salutations one and all, The planets have finally aligned to allow a first foray into outdoor railways so I'd like to introduce myself. I have been into trains and model railways since the mid 1980's however I have never progressed far beyond ovals of track on the floor . in adult hood the intersection of money, time and motivation was rarely achieved although I got as far as part building a small station layout with copper clad points. Finally with the children mostly raised and with my sons infectious enthusiasm helping I am finally getting off my behind. The overall scheme will be a single track line through a flower bed with a small station at each end, whilst a line circling the garden would be nice, the railway has to fit in with the other uses of the space, e.g. drying washing, greyhound zoomies, storage for bicycles and the annual potted plant plant explosion. Having said that I have couple of ideas for extensions. The railway will be approximately 75 cm off the ground, to clear the raised bed, and In lieu of timber I plan to use the recycled plastic members from Filcris, although this is more expensive than wood, the idea of not having to worry about rot is very appealing. Control will be analogue DC initially but I am fascinated with radio remote control although that will come with a steep learning curve. I have realised just how much I don't know about running out doors and I was delighted to find some fellow travellers, oo outdoors is definitely a niche within niche so it will be nice to have somewhere to ask scale specific questions. all the best Laurie