Euclid Randy Stahl Euclid I remember seeing main line switches that had a 180 degree lever connected to a about a 2.5" diameter rod that ran across the track under the rails right at the points. Welded to the rod were two big blocks of steel near the location of the nearest stock rail. When the switch was lined for the main line, you threw the lever over 180 degrees and it rotated the rod, bringing the two blocks of steel up so they contacted the side edge of the rail base of the stock rail and the base of the point against the stock rail. So it created a very strong impediment to the sparation of the point from the rail. I always wondered if you could run through and split a switch with that locking feature. I assume it was just intented as a backup feature to make sure that wheels could not pick the switch on a facing move. I've used these point locks too. Some have the bar like you describe and some have extra latches with a foot pedal. Both are locked with a switch lock. Operating these switches can cause injury if you do not know they are there. People have tried throwing the switch with point locks and hurt themselves. They are to prevent the points from opening under a train on a main track. Randy, Would that type of point lock derail a train if it ran through the switch in the trailing point direction?
Randy Stahl Euclid I remember seeing main line switches that had a 180 degree lever connected to a about a 2.5" diameter rod that ran across the track under the rails right at the points. Welded to the rod were two big blocks of steel near the location of the nearest stock rail. When the switch was lined for the main line, you threw the lever over 180 degrees and it rotated the rod, bringing the two blocks of steel up so they contacted the side edge of the rail base of the stock rail and the base of the point against the stock rail. So it created a very strong impediment to the sparation of the point from the rail. I always wondered if you could run through and split a switch with that locking feature. I assume it was just intented as a backup feature to make sure that wheels could not pick the switch on a facing move. I've used these point locks too. Some have the bar like you describe and some have extra latches with a foot pedal. Both are locked with a switch lock. Operating these switches can cause injury if you do not know they are there. People have tried throwing the switch with point locks and hurt themselves. They are to prevent the points from opening under a train on a main track.
Euclid I remember seeing main line switches that had a 180 degree lever connected to a about a 2.5" diameter rod that ran across the track under the rails right at the points. Welded to the rod were two big blocks of steel near the location of the nearest stock rail. When the switch was lined for the main line, you threw the lever over 180 degrees and it rotated the rod, bringing the two blocks of steel up so they contacted the side edge of the rail base of the stock rail and the base of the point against the stock rail. So it created a very strong impediment to the sparation of the point from the rail. I always wondered if you could run through and split a switch with that locking feature. I assume it was just intented as a backup feature to make sure that wheels could not pick the switch on a facing move.
I remember seeing main line switches that had a 180 degree lever connected to a about a 2.5" diameter rod that ran across the track under the rails right at the points. Welded to the rod were two big blocks of steel near the location of the nearest stock rail.
When the switch was lined for the main line, you threw the lever over 180 degrees and it rotated the rod, bringing the two blocks of steel up so they contacted the side edge of the rail base of the stock rail and the base of the point against the stock rail. So it created a very strong impediment to the sparation of the point from the rail.
I always wondered if you could run through and split a switch with that locking feature. I assume it was just intented as a backup feature to make sure that wheels could not pick the switch on a facing move.
I've used these point locks too. Some have the bar like you describe and some have extra latches with a foot pedal. Both are locked with a switch lock.
Operating these switches can cause injury if you do not know they are there. People have tried throwing the switch with point locks and hurt themselves.
They are to prevent the points from opening under a train on a main track.
Randy,
Would that type of point lock derail a train if it ran through the switch in the trailing point direction?
Yes, locked points will derail empty cars, seeing is believing/
Randy
BaltACDThere is very little chance of a derailment on ANY movement that trails through the switch, no matter the speed.
To eliminate an impending source of confusion: what Balt says here is true for switches without positive point locks. The situation I was discussing earlier specifically involves the points being locked against any motion, which implicitly would 'protect' the point bars, rods, or joint at the switchstand from damage that would allow the points to open.
More speed over a point-locked trailing-point switch would put geometrically more energy into the near-elastic lifting and other interactions of wheel and rail, unless the welds on the locking blocks fail or their actuating rod deflects. You can see the quandary designers have here: you need to keep the facing point deflection ABSOLUTELY minimized under what may be great shock to the switchstand or debris trying to 'pick' a point, but still allow 'safe' trailing-point action.
I suspect there will be patents on devices that can accomplish these two disparate things reliably, safely, and cost-effectively. At least in the patent description...
LithoniaOperatorOn a trailing-point move, does the risk of derailment increase as train speed does? Or does it perhaps decrease with more speed?
There is very little chance of a derailment on ANY movement that trails through the switch, no matter the speed. Reverse movement through a run through switch is where the fun starts.
Never too old to have a happy childhood!
On a trailing-point move, does the risk of derailment increase as train speed does? Or does it perhaps decrease with more speed?
Still in training.
petitnj That is called a traiing point move. Usually the pionts will realign to the direction of the train and the train will not derail. The arms holding the points in place are connected to the switch stand thru a long rod. Typically the switch stand is spiked to the ties holding the rail. The switch stand will move if the rod is pushed by the train's motion. This usually means the switch no longer works correctly and will have to be respiked to work.
That is called a traiing point move. Usually the pionts will realign to the direction of the train and the train will not derail. The arms holding the points in place are connected to the switch stand thru a long rod. Typically the switch stand is spiked to the ties holding the rail. The switch stand will move if the rod is pushed by the train's motion. This usually means the switch no longer works correctly and will have to be respiked to work.
The switch point pedals that I have seen were only used on switches that were very close to road crossings. The purpose being to keep the points in place if a train collides with a vehicle and takes it through the switch the facing points don't come open and derail the train.
.
In my experience, which now dates back a few years, in CTC territory there were two types of hand-throw switches. If it was no more than a company siding, where the train would lift or set off a car while continuing to occupy the main track, the protection was often simply a switch circuit controller. All it did was show a track occupancy if the switch was not aligned for the main track. You would see a second rod leading to a flat metal case; very simple. The electric lock was as already described, and was used where a movement could enter the main track from a service track or industrial lead. The dispatcher could unlock it, or I believe for a train wanting to clear the main track, there was a timer that would release the mechanism once the train was waiting at the facing point.
MP173 What is an electric lock?
What is an electric lock?
It's been covered in other posts, but think of it as an interlock in this context.
A CTC system knows what switches need to be open or closed to line a safe route. For many applications, terminals or crossovers for example, powered switches can be installed: these can be unlocked, the points moved by motor to full opposite engagement, and locked again by machinery.
But these are expensive, require a significant reliable power source to run, and may be difficult to move if for any reason the CTC control goes down. So for sidings and the like, you use a hand-throw switch that the CTC system can lock whenever it 'shouldn't be thrown'. The device used to do this is the electric lock mentioned.
You may be familiar with some of the card-access facilities used on building doors, which use a magnet or latch to prevent opening an otherwise manual door unless 'permission is granted'. This is a similar principle; the power needed to lock and unlock a switch is much less than the power to physically move it.
Note that there is a similarity with what an electric timer lock does to keep the switch points from being physically moved, but the reasons for the latter's use can be very different.
EuclidWould that type of point lock derail a train if it ran through the switch in the trailing point direction?
A highly increased risk, in my opinion at least. The flanges will be cammed up and may not follow the groove between point and rail; if even one wheelset drops a flange outside the gauge it's 'game over' and there may be a "statistically-significant" number of flanges involved, perhaps all subject to abrupt locking-up from braking as the contact patch essentially goes to near zero, by the time the train is stopped.
Again. Thanks, all, for the excellent info.
Ed
edblysard You can run through any switch, at least once!
A normal switch (hand or power-operated) will be damaged if equipment makes a trailing-point move over it when it is lined the wrong way. This is referred to a "running through a switch", and usually results in the points "floating", not tight to either stock rail, and the next facing point movement will most likely derail. But the equipment running through the switch simply forces the points over and damages the throw rod and/or switchstand, but usually does not derail. As was mentioned moveable frogs or other fancy things for higher-speed turnouts may cause other issues.
Spring switches are designed to be run through from one direction, the wheels force the points over and the spring pulls them back. One must never back up while pulling over a spring switch without first manually lining it for the proper route, or a derailment will result.
Semi-automatic switches are designed to be run through without damage, on these the points simply snap over and lock in place when run through, and the mast rotates to change the target colour displayed to approaching movements. But it is essential to run a full car (4 axles) through the switch before reversing, or the points may not lock in place and "float" instead. This can result in a car attempting to simultaneously occupy two different tracks.
In Canada semi-automatic switches have diamond shaped targets for identification. All other hand-operated switches have square or round targets. Spring switches have a circular white sign with the letters "SS" on it, mounted on a separate signpost next to the switch.
Greetings from Alberta
-an Articulate Malcontent
23 17 46 11
In the Chatsworth crash that brought on the congressional PTC mandate, the Metrolink engine went through a trailing point move with the switch lined against him. The damage to the mechanism was evident and apparently no derailment occurred until the Metrolink engine hit the UP engine head-on.
Just worth of an example.
Thanks, guys.
Spring switches are of course designed explicitly for this.
All the reports I can remember reading say that a train will successfully negotiate a locked trailing-point switch with little derailing hazard but the mechanism will be permanently damaged. I do not know if there is an added tendency to damage the initial wheel flanges that do the forcing.
Your mileage may vary with switches with active frogs or similar elements that would abruptly kick wheels into flange bearing and then drop them again. I do not think this would constitute a direct derailment hazard (see the Army film about how not to derail a train) but the indirect hazard posed by broken flanges or wheels would be relatively great.
If the switch points are facing away from an approaching train (facing the direction of the train's motion), can a train on, say, a main track ever pass safely through a switch that is lined for the turnout (not the main), and continue along the main?
That is, will the wheel flanges force the switch points to conform? Or will a derailment always happen?
Are switches designed to absorb such inadvertant harsh treatment? (I kind of doubt it.)
I have wondered about this for a long, long time!
Our community is FREE to join. To participate you must either login or register for an account.