Saturday, April 27, 2013

How I made some milk churns

OK. I'll admit this doesn't sound like the most exciting of topics - but actually, now I've done most of the heavy engineering on the railway, I'm beginning to get down to the finer details - and I believe it is details such as these which will ultimately bring the railway alive.

The motivation

As my railway is set in the Cheshire countryside in the early 1930s, noted for its dairy farming, one of the main sources of traffic would have been milk, and this product in those days would have been primarily transported in churns. The line therefore needs a healthy supply of milk churns.


 The prototype

A quick bit of research on the web revealed that until the mid 1930s, milk churns were mostly conical in shape and held a staggering 17 gallons!

Reproduced with permission from http://www.gwr.org.uk/nochurns.html
 For general information about milk traffic on railways, I found the Goods & Not so Goods website very useful. An excellent source for background information for the 17 gallon conical churn was found on the GWR Modelling website. An article by Russ Elliot was particularly helpful as it not only gave  background information, it also gave dimensions - though he does point out that sizes tended to vary with manufacturer. Armed with this information I now set about finding suitable models.

Off the shelf models

I found that appropriate models in 16mm scale can be purchased in either whitemetal from Garden Railway Specialists (GRS)

....... or as resin castings from Trenarren Models


and Modeltown

These provide reasonable representations of 17 gallon cans but they all seem to be too narrow at the base - even taking account of the variations between manufacturers.
Image Source: http://pilgrim.ceredigion.gov.uk/utilities/action/act_download.cfm?mediaid=1791&stname=large_image

Furthermore, although they are reasonably priced given the work which goes into producing them, I felt that, considering the quantity I would require for my railway, the cost of buying them from these sources would have been prohibitive, so I cast around for a source of materials to make my own.

Experimentation

I considered making churns from scratch, but felt that making consistent truncated cone shapes in weatherproof materials (eg plastic, wood or metal) would be beyond my capabilities. I have some experience of casting in resin (see How I made my third batch of open wagons) but this would still require a master to be made from which the mould could be cast.

My first effort involved using oven hardening polymer clay. Whilst this was reasonably successful, I found it difficult to make the model with sharp enough edges to represent the galvanised steel from which the originals were constructed.

Furthermore, I doubted I would be able to keep them consistent in size and shape. I then considered plastic. Where could I find a cheap source of suitably sized conical plastic shapes? A visit to my local 50p shop unearthed some party horns with conical mouthpieces.

A couple of churns were made from these, using brass plated metal cups for screw heads and plastic domed screw-cover-caps for the tops of the churns.

Whilst this approach worked, the base of the churn was even narrower than the off-the shelf models and so in reality would have had to be considerably taller to contain the requisite 17 gallons.

My next thought was to find suitably-sized cone-shaped tops from plastic bottles - but none I could find were the right size. However, whilst browsing around the party section of my local supermarket for some larger party horns I came across some fairly cheap basket-ball toys with conical bodies which looked about the right dimensions - and they were on special offer - buy two packs of four and get another pack free!

So, I splashed out £2.80 for a dozen toys and started experimenting. After a couple of attempts I found a reasonably reliable way of bashing the main component of each toy into something which more or less resembled the original 17 gallon churns in 15mm scale.


The process

The first job was to disassemble the toy to get at the conical plastic section. The protrusions for the ball-flipping mechanism were carefully removed with a razor-saw.

The next job was to find a way of marking off the cone to enable it to be trimmed to a suitable size. This I achieved by mounting a pencil 21mm above the table on a couple of wooden blocks and then rotating the cone. The cone was then inverted and the marking repeated.

The razor-saw then removed the top and bottom of the cone, taking care to rotate the cone to ensure the cut didn't stray from the lines.

A small section from the side of the base of the cone was cut-out to fill the hole left by the trigger mechanism. Although the diameter of the removed section of the cone was larger, I felt it would not be too noticeable. This was glued into place with Superglue.

Next, a 2.5mm wide piece of plasticard micro-strip was superglued into place around the base of the cone. I found gluing the strip in stages and then trimming off the excess on the final stage to be the most reliable - certainly in terms of keeping the glue from sticking to my fingers!

I considered various ways of making the upper inverted cone of the churn, such as discarded plastic golf-tees and screw-cups. However, none of these looked remotely appropriate and so I revised my knowledge of basic geometry and worked out how to draw the net of a truncated cone of the right dimensions. It actually turned out to be a simpler shape than I expected - basically two semicircles - one radius 20mm and the other radius 15mm. These were drawn on 0.75mm thick plasticard ....

.......  and carefully cut out with scissors - a small 2mm tab being left on one end.

The nets were then curled and glued with a dab of superglue.

Once the glue had set, the overlapping tabs were carefully filed and sanded,........

......... before the cones were slipped on to the top of the churns and held in place with superglue.

The rim was then formed with a fine 0.5mm square section of microstrip.

2A little more research on the net unearthed a couple of pictures showing the churn lid. Again, the design of these seemed to vary according to manufacturer.
 Source: http://www.thecowshed.co.uk/img/p/225-457-large.jpg
Source: http://sandfordstation.co.uk/wp-content/uploads/2013/04/ChurnRestored1.jpg













I decided to keep things simple and went for a plain disc of 1mm plasticard with a diameter of 17mm.

The knob was simply cut from the pivot for the toy's trigger mechanism.

The manufacturer's plate was made from a very thin oval of plasticard attached with Superglue.

A quick look at the photos of the churns on the above website revealed that there was a range of different types of handle - some hanging down, some pointing upwards. The position for the handles was marked at 19mm from the base.

Two 1.5mm holes were drilled 4mm apart ........

..... and copper wire stripped out of some twin and earth cable was threaded through the holes and bent with fine nosed pliers to represent the handles.

I probably should have used finer gauge wire but this was all I had to had - and I generally tend to over-engineer things destined for the garden!

The completed churns were then given a coat of plastic primer using a Plasticote aerosol and then given a couple of thin coats of silver-grey acrylic paints (a mix of silver, black and white) - with a dab of gold on the manufacturer's plate.

The finished churns were then ready to enter service.
 


The future

I have kept what I consider to be the best-made churn unpainted as I intend to use this as a master to make a mould for resin-casting.........

.... and I can then go into mass-production. As I now potentially have an unlimited supply of churns, I am considering a creating lineside industry on the railway of a creamery similar to that found beside the Leek & Manifold Railway.
Standard gauge milk tanks on transporter wagons on the Leek & Manifold - Source: http://www.kachuzyn.fsnet.co.uk/ecton2.jpg
Of course, that might one day lead to the construction of some standard gauge transporter wagons. (For more information about the Leek & Manifold Railway see the entry on my Narrow Gauge Railways blog).

2 comments:

Pat G said...

Lovely work!

I am modelling these to make up on my 3d printer.

Ge Rik said...

Sounds like a really good application of 3D printing. Would be really interested in seeing the end-product.