4-SF on the web
4-SF is also known as 00-SF ( for EM add 2.0mm to all relevant dimensions below )
(See also the 00-SF Yahoo Group.)
See Supply of Gauge Tools below for details of how to obtain track gauges for building 4-SF track.
4-SF v Peco
( 4-SF is also known as 00-SF )
This diagram above shows the huge improvement in the appearance of the crossing (frog) when the narrower 4-SF flangeways are used. You can see from the orange areas how much the gap area in front of the vee is visually reduced. Although visually the reduction in the length of this gap is the most noticeable difference, it is the reduction in the width which brings about the big improvement in running quality. The width of this gap at its widest point must be less than the width of a wheel. It is then physically impossible for a wheel to "drop in" -- it remains fully supported on the rails as it runs through the crossing. All 00 wheels are wider than the gap for 4-SF. But many are narrower than the much wider gap in the Peco turnout, and bumpy running is inevitable as they run across the unsupported area.
A is the check gauge. It is the most critical dimension in pointwork. If this dimension is too small, wheels running from left to right can hit the nose of the vee and very likely derail, or at least bump. If this dimension is too large, the wheel backs will bind or jam on the check rail. To make sure it's correct, the check rail is set using check gauge tools. For 4-SF and 00-BF this dimension should be 15.2mm. You can use the same check gauge tools for both these standards (they are both running the same wheels).
(But where the check rail is combined with a wing rail in complex formations such as a tandem turnout -- i.e. in parallel-wing V-crossings -- it must be the same as B.)
E is the check span. It is not usually necessary to set this dimension directly if the gauges are used correctly. For 4-SF this dimension shouldn't be more than 14.25mm. For 00-BF this dimension shouldn't be more than 14.0mm.
For best-running 00 models:
a. Measure the width of the wheels.
b. RTR wheels will be around 2.8mm wide. Assume the flanges are 0.8mm thick and set the back-to-back to 14.4mm.
c. Romford/Markits wheels will be 2.5mm wide. Assume the flanges are 0.7mm thick and set the back-to-back to 14.5mm.
d. Kit wheels such as Alan Gibson / EMGS will be around 2.3mm wide. Assume the flanges are 0.6mm thick and set the back-to-back to 14.6mm.
e. For 4-SF make sure no wheels have back-to-back less than 14.3mm.
(For 00-BF make sure no wheels have back-to-back less than 14.1mm.)
f. If you want to use the same back-to-back for everything, make it 14.4mm. Kit wheels won't run so smoothly, but they will run.
Adding some detail to that:
RTR models such as Hornby and Bachmann normally have wheels 2.8mm wide conforming to the NMRA RP25/110 profile with flanges 0.8mm thick. They should be supplied set to 14.4mm back-to-back, which is also the DOGA-Intermediate setting -- see: DOGA wheel standards
Sadly the manufacturers don't always have the best quality control. For 4-SF, such RTR wheels should be 14.4mm maximum, 14.3mm minimum, back-to-back. Unfortunately I don't know of a 14.4mm back-to-back gauge available anywhere, you could measure them with calipers if you have them. If the flanges are thinner than the 0.8mm maximum, RTR wheels would likely be ok set to the traditional 14.5mm 00 back-to-back gauge.
Most modern RTR models will be found to run fine on 4-SF straight from the box. But there is always the possibility that you will get a rogue wheel set which needs adjusting as above (or ideally returned to the supplier for replacement).
Locomotive wheels from Markits/Romford are 2.5mm wide with flanges 0.7mm thick. These are the traditional BRMSB "scale 00" wheels which should be set to 14.5mm back-to-back. Using the Markits/Romford squared axles you don't have much choice over this. For 4-SF, these wheels should be 14.5mm maximum, 14.3mm minimum, back-to-back.
Rolling stock kits such as Parkside Dundas are usually supplied with Alan Gibson or similar wheels which are either to the EMGS profile or the very similar NMRA RP25/88 profile. These wheels are 2.3mm wide with flanges 0.6mm thick. For 4-SF, these wheels should be 14.6mm maximum, 14.3mm minimum, back-to-back. Ultrascale wheels are similar.
These wheels may be supplied set to 14.7mm or 14.8mm back-to-back which is intended for the DOGA-Fine standard and is too wide for good results on 4-SF. They should be adjusted as above.
· Some non-UK "code 88" wheels have flanges thicker than 0.6mm, and should therefore be treated as RTR wheels, as above.
If you are not sure of which wheels you are dealing with, measure the width of them:
Wheels 2.8mm wide -- back-to-back 14.4mm MAX.
Wheels 2.5mm wide -- back-to-back 14.5mm MAX.
Wheels 2.3mm wide -- back-to-back 14.6mm MAX.
For 4-SF the MIN back-to-back is 14.3mm for all of them.
(For 00-BF the MIN back-to-back is 14.1mm for all of them.)
But for best results, ignore your back-to-back gauges. If you have 4-SF check gauges you can make yourself a simple wheel checking fixture which I described on RMweb recently. This not only gives better results, it ensures your wheels are matched to the actual track you will be building.
Here's the link for that -- see this and subsequent posts on RMweb: 4-SF wheel setting fixture
1. Fix this rail first. It represents the crossing vee. There is a flat on the check gauge so that it can be used where the vee won't fit in the slot.
2. Fix this rail second, using the check gauge tool. It represents the check rail.
3. Fix this rail third, using the 1.0mm shim. It represents the wing rail. it doesn't engage with the check gauge tool.
4. Fix this rail last, anywhere you like. Its sole purpose in testing the wheels is to support the wheel. It represents the opposite running rail. A good way to identify it in future is to fix it upside down, or make it longer or shorter than the other rails.
Mark which rail is which. Don't get rails 1. and 4. muddled up.
In using the fixture,
1. hold the back of one wheel against rail 2.
2. gently lower the other wheel onto rail 1.
3. the wheel flange should just clear the side of rail 1. without rubbing, but ideally leaving only a fraction of daylight showing between them.
4. the back of that wheel should easily clear rail 3.
With care, a testing fixture like this if accurately made is a better way of setting the wheels than using a back-to-back gauge, because it allows for different flange thicknesses, and the actual track you are building.
The diagram above shows an A7 turnout in 4-SF, radius 53". This is typically the size of turnout which a modeller in 4-SF might use in place of a Peco Large Radius turnout, radius 45". Both turnouts are shown truncated to the mid-point of a crossover. In 4-SF double tracks are closer together at 45mm centres (as prototype) than for Peco at 51mm centres, so that although the 4-SF turnout is an easier radius than Peco, it is actually slightly shorter to the crossover mid-point. The 4-SF turnout has had the lead length to intersection adjusted slightly in order to match the Peco turnout exactly (purple line). This is a screenshot from Templot .
The diagram above shows the nearest exact match to a Peco Large Radius turnout. It has a GWR 10ft curved switch and a 1:6 curviform V-crossing. That's not a common size, it was generated simply to get as close as possible in 4-SF to the Peco dimensions.
The diagram above shows the same turnouts printed out as a track construction template. The difference in appearance of the 4mm/ft scale UK-style timbering for 4-SF is very noticeable.
( 4-SF is also known as 00-SF )
diagrams © Martin Wynne 2008
Please note that these 4-SF gauge tools are no longer available from Brian Tulley.
**Please Note: Track Gauge design dimensions were derived from C&L Code 75 Bullhead Rail. However, rail (including Flat Bottom Rail) from other manufacturers (SMP, Marcway, Peco, Exactoscale etc.) may also suit.
16.2mm 4-SF Roller Track Gauges
15.2mm 4-SF Check Rail Gauges
16.2mm 4-SF Three Point Track Gauges
1.0mm 4-SF Crossing Flangeway Gauges