Track Choice
Track Choice |
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Rail
For 5" gauge there are generally two rail profiles available.
Left 16mm or 5/8" fell rail, available in aluminium. Right 21mm available in steel or aluminium
The cost of steel and aluminium are very close so usually it is other factors that influence the choice.
STEEL - Profiled rail - 21mm from MRSC
Advantages
- Very strong, needs less support (less sleepers if required)
- Can be welded for rigidity or for example constructing crossovers
- Lower expansion rate. Half that of Aluminium
- Good impact resistance - hard wearing - especially good for areas such as point blades and frogs.
Disadvantages
- Rusts - with constant running isn't really a problem
- Hard to bend. Good for staying in shape once bent but is hard bending by hand. Can be bought from Miniature Railway Supply Company pre curved but for flexibility I would recommend one of our rail benders
- Heavy - not very good for portable track as you will only be able to lift 3 panels at a time.
- Hard - may save rail from excessive wear but this may be taken out on your rolling stock.
ALUMINIUM - 16mm and 21mm
Advantages
- Easy to bend - Good for laying, bad for un supported track
- Light weight - good for portable track - I can easily pick up 15m
- Doesn't rust
- Soft material - doesn't wear the wheels - very important if you have a £8k steam engine
Disadvantages
- Soft material - With sharp corners sign of ware show quite quickly, also derailments can damage track.
- Point blades and frogs made from aluminum can show signs of wear very quickly.
- High expansion rate. Hot sunny days can see track snaking as it expands. - Must allow for expansion at joints.
Left - Aluminium rail - this piece was nearly 8 years old in use on our bottom curve which is an 11 foot radius. I would consider that we are reasonably heavy users so I don't think this wear is unacceptable. We could have re gauged the track and carried on using the rail but decided to replace it with steel.
The rail won't we wasted as it will be straightened, turned and used in our new siding.
Suppliers
Bar Track
While many clubs use bar track there can be problems. The running edge of the bar needs to be rounded or else it can easily cause excessive damage to the wheels. In the garden environment with tighter corners the sharp edge can destroy wheels in quite a short time. We have seen a Trojan with the front right and rear left wheel returned in under 6 months with major serrations to the flange and complete loss of the radius on the flange. Trojan number 21 had to be re wheeled due to running on bar track on a raised line.
Sleepers
1) Timber roof battern - 225mm long - 32mm x 25mm - Timber is tanalised but we also immersed them in creosote(or new alternative) for at least a fortnight. Rail fixed with 3/4" x 8 pan head screws with M4 penny washers.
2) Aluminium - Jubilee rail - copy of the narrow gauge sleeper for temporary track ie used on peat bog systems. Advantage of not rotting but major diadvantage is that the track sits on top of the ballast and the track is prone to movement. Only for 16mm rail.
3) Timber battern as per number 1 but with plastic chairs as supplied by PNP Railways.
4) PNP Railways plastic sleeper. Offers pre set gauge and possibility of gauge widening + rot resistant.
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| 6 sleepers per metre Temporary use or hidden sidings/sheds |
9 sleepers per metre. This is what we found looked good. |
12 sleepers per metre Just too much although near standard gauge track standards |
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Hardwood vs
Softwood Many people have written on the subject of sleepers and quite a few have written off softwood as a short term investment. The picture on the left is of sleepers which have been down for 8 years. There is no sign of rot and still have many years of life yet. In comparison we have seen hardwood supplied with a point kit degrade quite badly to the point where they needed to be replace. It didn't help that they came with live woodworm in. Recycled Plastic Recycled plastic sleepers have many advantages but one major disavantage. In the sun they can curl. Do not use on points as the distortion in the longer sleepers can affect the operation of the point. |
Thermal Expansion
Why should this bother me?
Below is a table showing the thermal expansion of three materials. Concrete has been inlcuded as a comparision.
Product |
Linear Temperature Expansion Coefficient |
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(m/m. oC x 10-6) |
(in/in.oF x 10-6) |
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Aluminium |
22.2 |
12.3 |
Concrete |
14.5 |
8.0 |
Steel |
13.0 |
7.3 |
Column two shows the expansion rate per degree in temperature rise. If for example we say that it could easily get to -10oC in the winter and easily get to 50oC in the summer (if the track sits in the summer sun all day) we will get a temperature range of 60oC.
Therefore a
2.5m aluminium track panel will be 2.5 x 22.2 x 10-6 x 60 = 0.00033m
2.5m steel track panel will be 2.5 x 13 x 10-6 x 60 = 0.000195m
So for a track in the sun you will need to leave movement for 3.3mm for aluminium and 1.95mm for steel. Yes movement.
Fishplates should not be bolted tight - use nylocs or double nuts.
Regularly grease or oil. This also helps reduce electrolytic action that can lock up fishplates and stop the rail moving.
Over drill the holes in the rail - use 5 or 6mm drill bit for 4mm bolts.
If laying rail on a very hot day the rails should butt each other. At 20oC the rails should be mid way through their movement.
Don't worry too much. If you get it wrong the rail will find its own way to expand. On corners it will push out and on long straights it can even lift the track into the air. Over a period of time you will soon learn where you need to allow for more expansion.
Above - This is the inside of a curve and taken at 3pm on a sunny June day. The gap between the ballast has been left as the rail pushes out the curve as we had not allowed for expansion in the fish plates.
Restaining the sleepers can allow the rail to slide on the sleepers and the expansion to be taken up in the gaps left in the fish plates. It is not recommended to try and totally restain the rail as you will find at some place the rail will find a way to move to accommodate the expansion.
On the full sized railways welded sections are often laid stretched so the any expansion can be taken up in the spring of the steel. With most miniature rail supplied in 2.5m or 3m legnths I think you would be hard pushed to lay rail pre tensioned.
Points
Why are they so expensive? The simple answer is that they are complex and complicated. Our point, as pictured above, is made up from 168 parts and takes us the best part of a day to assemble.
From experience we found that cast aluminium frogs fail quite quickly (medium to heavy use) as the aluminium is not strong enough to cope with the impact of the wheels. To combat this we use a laser cut steel frog. Also on the market are cast iron frogs which also cope better. That said and done, the aluminium frogs are not expensive and can easily be replaced.
Notes
The check rails are to protect the frog and stop the wheels straying up the wrong side. Make sure they are located correctly and not just bolted on to the adjacent sleepers.
The curve on the turn out has more than one radius
Check rails need 6mm clearence. Point blades also need to clear at least this
For your first point - buy ready made. Kits may sound cheap but without reference to how it should go you will easily lose a couple of days constantly tweaking it to get it right.
Next Stage - Curves and Gradients
