Dog Star
Western Thunderer
Some months back, maybe even last year, I promised to write about making switch rails for 7mm track using bullhead rail. My interests are pre-group... when most railway companies were using straight cut switch blades although the GWR had started to install "curved" straight cut blades (not a confused ideal... the rail was clamped to the bed of a planer and the area to be planed was then curved to the appropriate radius for the switch. The switch blade would then be machined as a "straight cut" switch whereupon when the clamps were removed the rail would return to the original shape and the tapered portion of the blade would be curved).
The switch blades for a turnout are handed in that there is a LH blade and a RH blade with the taper being, apparently, on one side of the blade. So, given that we need to produce a pair of handed blades, we need to be aware of which side the taper is formed. Here is a photo-sequence of the work in forming the tapers and shape of a RH straight-cut switch rail for a LH turnout. In the photos / captions note is made as to which way the filing is done in relation to the head of the rail.
This piece of rail is going to form a RH blade and the "first" taper is put onto the rail face which is against the RH stock rail... which means that the head and foot of the rail are filed away so that the taper is across the full depth of the rail. This blade is for a LNWR 18'0" switch which is (roughly) equivalent to a REA "D" switch. For this blade the taper is planed over a scale 11'0" so the rail is covered with black permanent marker and the required length marked in the web. Here the face of the blade marked up prior to metal removal - in this photo the foot of the rail is against the ruler.
This photo shows a blade which has had the taper formed on the face which is against the stock rail, the head and foot of the rail are filed away until the taper has just started to cut into the web (where "just" is about 0.5 - 1.0 mm).
At this time the toe of the switch rail is greater than the full thickness of the rail web and so metal has to be removed from the running face of the blade. Here is the running face of the blade marked up prior to metal removal - in this photo the head of the rail is against the ruler.
Whereas the head and foot of the rail are removed for the rail face against the stock rail only the head of the rail is removed from the running face of the rail. This photo shows the switch blade after the head and web have been filed until the toe thickness is circa 15 thou. There is no removal of metal from the foot of the rail.
In this photo the tip of the running face is filed to provide a lead-in so that a wheel does not "jolt" when taking the diverging route. The permanent marker was applied before this step so as to show the extent of the lead-in.
So now we have a rail with a taper filed on both faces... we shall to change that situation so as to leave the switch blade with a taper only on the face which abuts the stock rail. Place the rail in a vice with the mark on the web against the jaw (this is the mark from photo 1 and indicates the planing length for the switch blade). Gently bend the rail so as to remove the taper on the running face and leave all of the taper on the non-running face - a straight edge against the side of the rail head can be used to check that there is no remaining taper on the running face..
regards, Graham
The switch blades for a turnout are handed in that there is a LH blade and a RH blade with the taper being, apparently, on one side of the blade. So, given that we need to produce a pair of handed blades, we need to be aware of which side the taper is formed. Here is a photo-sequence of the work in forming the tapers and shape of a RH straight-cut switch rail for a LH turnout. In the photos / captions note is made as to which way the filing is done in relation to the head of the rail.
This piece of rail is going to form a RH blade and the "first" taper is put onto the rail face which is against the RH stock rail... which means that the head and foot of the rail are filed away so that the taper is across the full depth of the rail. This blade is for a LNWR 18'0" switch which is (roughly) equivalent to a REA "D" switch. For this blade the taper is planed over a scale 11'0" so the rail is covered with black permanent marker and the required length marked in the web. Here the face of the blade marked up prior to metal removal - in this photo the foot of the rail is against the ruler.
This photo shows a blade which has had the taper formed on the face which is against the stock rail, the head and foot of the rail are filed away until the taper has just started to cut into the web (where "just" is about 0.5 - 1.0 mm).
At this time the toe of the switch rail is greater than the full thickness of the rail web and so metal has to be removed from the running face of the blade. Here is the running face of the blade marked up prior to metal removal - in this photo the head of the rail is against the ruler.
Whereas the head and foot of the rail are removed for the rail face against the stock rail only the head of the rail is removed from the running face of the rail. This photo shows the switch blade after the head and web have been filed until the toe thickness is circa 15 thou. There is no removal of metal from the foot of the rail.
In this photo the tip of the running face is filed to provide a lead-in so that a wheel does not "jolt" when taking the diverging route. The permanent marker was applied before this step so as to show the extent of the lead-in.
So now we have a rail with a taper filed on both faces... we shall to change that situation so as to leave the switch blade with a taper only on the face which abuts the stock rail. Place the rail in a vice with the mark on the web against the jaw (this is the mark from photo 1 and indicates the planing length for the switch blade). Gently bend the rail so as to remove the taper on the running face and leave all of the taper on the non-running face - a straight edge against the side of the rail head can be used to check that there is no remaining taper on the running face..
regards, Graham