Designing the track

The lot is only approx 30 x 60 meters (100 x 200 ft) in size - in no way ideal for a 7 1/4" live steam layout, so for the track plan shown, the minimum curve radius would have to be around 7 meters (23 ft) for this layout. This should be possible with a small 4-4-0 in 7 1/4 gauge - has anybody got any experience with curves this tight? As you can see, my latest track plan sneakily steals some space from the county, but since the track is removable, I don't think I'll be thrown into the slammer for it... Any suggestions for a better layout?

Here is the intended track superimposed on an aerial image of the lot:

The only really steep grade on the entire plan currently is around 1:11, but slight excavation should enable me to get it down to 1:25 or 1:30 - but this may still prove troublesome to run on, especially as it is on a tight curve.

Has anyone built a removable track in 7 1/4 or 7 1/2 gauge? Southern Finland is at the same latitude as Anchorage, Alaska, so you can imagine how the yard looks like in winter - up to 3 ft of snow on everything... Suggestions?

Calculating the trigonometry, and making a short piece of 7 meter radius curved test track (shown here, depth of a 1400 mm cord is a little under 40 mm), I surmise that the gauge widening in the curves needs to be around 6mm (1/4") in order to let the 3003 engine negotiate the curves without the wheels climbing the track (i.e flanges getting squeezed) or falling between the rails. Fortunately, the front bogie is of the swinging type, and has a generous lateral movement:

Then, the track itself: I have two options: Iron or aluminum? Iron is by far the cheapest, if the track is constructed of band iron (one suitable dimension is 5 x 25 mm, or 1/5 x 1") on wooden sleepers that are slotted to a depth of about 15mm:

In fact, this is how I constructed the test track piece for the above experiment... Cost of this type of track, including sleepers, is only approx. USD 2.10 per meter, or 70 cents a foot!

This is how it looks, unpainted, placed on the lawn:

The other possibility is real rail-shaped profile of aluminum - about 3-4 times more expensive than the band iron. If a large enough order is placed, the factory will extrude our own profile! I had planned one looking like the sketch at left - the hole in the rail head would enable quick, exact and safe joining of track pieces, by inserting a pin in one of the ends to be joined, securing it in place with Loctite 603. The other end of the pin would be a sliding fit into the next piece of track. Of course, the two sleepers closest to the join would need to be attached together! The cost of extruding a profile like this would be a few hundred USD for the tool, and then around a dollar a foot - in 150 kg (320 pound) lots...

The total cost for this type of track, which would need a lot of fasteners, too, would be around 8 or 9 dollars per meter. All these prices do not, of course, include the cost of preparing the ground - sand, gravel, the plastic sheet that needs to go under it, etc.

Yet a third way to construct a removable track entirely of hot-rolled iron: 10 x 10 mm for the rails, 5 x 25 mm for sleepers, all welded together. Cost, around USD 3 per meter (a dollar a foot), including the welding supplies. This track can be laid out "Lionel-style" on a very smooth (and well-mowed!) lawn, without any foundation. Thanks to the dark color of the iron, this is the least "offensive" type to the rest of the people in the house... ;-)


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