Encouraging my little entrepreneurs, or a saga of a vacuum cleaner and a hot air gun
Entry posted by whart57
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One perennial problem for layout builders is how to fill the foreground of layouts. It's not always a good idea to lay tracks right by the baseboard edge but if not then something has to fill the space. Obviously that something has to be low in height so as not to obscure the view of the trains, which limits the possibilities. For layouts set out in the countryside it's not difficult to get out the grass machine and scale cows and create a meadow or two but you can't do that in an urban environment. I have a number of ideas, a parallel road, a car park, hard standing next to a siding, and I will use all of those, but with some three metres of baseboard edge to fill I still needed another idea.
Inspiration came from an unlikely source - the Guardian newspaper. The Guardian normally has a big centre page photo feature in its weekday print editions, and on Tuesday 5 September the subject was a single - double page - image of the Ratchada night market in Bangkok, taken either from a tall overlooking building or possibly from a drone given that it was an aerial view but not from too great a height. I had considered a market scene but the examples I had in mind were in large shed like buildings and thus too tall for the site to be filled. The Ratchada night market on the other hand was made up of rows and rows of small gazebo like canopies, presumably of the standard 3m x 3m dimension, and from the open sites where the stall holder hadn't bothered with the canvas cover it was clear that the canopies were on standard collapsible frames too. A night market made up of lots of these portable stalls looked an interesting idea, particularly as the canvas was of bright, but different, colours. When I suggested this to my wife - who is my arbiter of whether a feature might be of interest to the majority non-ferroviarophilic population - she was enthusiastic about it.
The Bangkok night markets have an interesting history. Of course there have been street vendors in Bangkok and other cities for as long as anyone can tell, and my first experience of such a market was on my first visit to Bangkok when my company put us up in a hotel on the Sukhumvit Road. At that time the pavement between the Asok interchange and the railway crossing at Ploenchit was a solid ribbon of small stalls selling clothes, designer knock-offs, tourist tat, and - after 9 pm - some extremely dodgy videos and some nasty looking weaponry. How you are supposed to get one of those spinning knife jobs past customs is a mystery I never tried to solve.
Recently I have read that the Bangkok city authorities propose to clear the Sukhumvit Road stalls. I can understand that. Apart from reducing the pedestrian traffic on one of Bangkok's major thoroughfares to single file - and if you get stuck behind a Middle Eastern type and his multiple wives all browsing the stalls then progress can be very slow - it is also rumoured that there is a strong underworld element demanding protection money from the stall holders. The city will lose something though.
However Thais are entrepreneurial so the demand for low entry cost retail facilities is high. The night markets provide that and by creating a critical mass in one place also attract custom. The first was apparently the Rot Fai market held in the north of the city next to the more famous Chatuchak weekend market. "Rot Fai" means "railway" and it was so called because it was on land that was once part of the Bang Sue railway yard. After a few years though the land was required for development so the market moved to On Nut in the south eastern suburbs. Since the market catered mainly for local Thais the fact it was way off the tourist track didn't matter much. Interestingly it retained the Rot Fai name even though there was now no railway connection. However even though it was out in the sticks of On Nut, Rot Fai market proved popular among young and youngish Thais as a place to go, meet, eat and shop. The people behind it then thought of expanding and a couple of years ago opened up a second site at Ratchada. This site is closer to the city centre and is more accessible using public transport. This Ratchada market is the inspiration for mine.
I had to solve one technical problem though - how to make fifty odd gazebo like canopies. Or maybe more. The space to be filled is some 40cm x 20cm and as each canopy is 3cm square that means some four or five rows of thirteen stalls. Additionally the canopies needed to be of uniform size but not perfectly uniform. I think I have a solution - vacuum formed plastic.
This technique is not entirely new to me. Like many others of my generation I struggled with the vacuum formed plastic sails of those Airfix ship kits like the Endeavour and Revenge. Unlike most though I have played with a vacuum forming machine. This was some forty years ago when I had a job as a lab technician. From that experience I had a rough idea of what I needed to do. I knew it would be possible to mould plastikard round a former of wood or plaster of Paris if I could get the plastic warmed up to around 100℃ and provide some decent suction. A hot air gun of the sort used for paint stripping would probably achieve the former, and the household Miele vacuum cleaner would have enough suck for the latter. The machine I used all those years ago heated the plastic with a couple of electric heating bars mounted in the lid and had a lever operated suction mechanism, and that did sheets of 18" x 12". I was going to be far less ambitious, something of the order of 4" x 3".
I then set out to make a small vacuum forming tool using off cuts of MDF and 9mm ply, which I had from building the baseboards. The drawing below shows the schematic layout
In the actual implementation, the vacuum chamber is extended sideways so that I can fit the vacuum cleaner hose from the top rather than from underneath. A couple of waste pipe fittings left over from a plumbing job made a nice connector which could be Araldited in place. A stack of MDF and ply pieces drilled through and with the centres cut out form the business section. Four M8 bolts with butterfly nuts are used to screw them down and thus clamp the Plastikard sheet. At this early stage a test was done using a metal bottle cap as a former, and some 10 thou sheet was successfully formed around it, picking up detail like the screw thread and the serrations quite well. After that I moved on to making formers for the gazebo canopies.
The first canopies I tried were simple pyramids, though I did put a bit of a bow in the vertical formers to simulate how canvas sags. I then cast Plaster of Paris around them and the idea was that this would form a depression into which the hot plastic sheet would be sucked. It didn't work very well. One of the problems was that air was sucked from the sides the mould and this pulled the hot plastic sheet too far and it popped.
I then made the canopy in reverse using plastikard, and cast little pyramids using plaster. When I had four of them I stuck them to a small piece of ply and drilled small holes around them for the suction. To seal the bottom of the support I cut up a cheap mouse mat bought for £1 from - well, where else? Strips of the thin rubber made a more airtight seal.
Now I can get reasonable results, occasionally quite good ones. Ten thou Plastikard gives a nice result but it can stretch too thin and pop before it has fully taken on the desired shape. Fifteen thou gives a better result. The most effective technique so far is to play the hot air gun over the Plastikard sheet, watch it bubble up, settle flat and then start collapsing around the formers. Then, and only then, switch on the vacuum cleaner to suck the softened sheet down and around the formers.
That is where I am now. In a week or two I'll come back and report on whether this potential solution becomes a real one.
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