Hi
I keep seeing geometry cars on Rail Pictures and was wondering just what is their purpose.
Thanks
Lee
They measure the geometry of the track. There are 4 basic measures.
Line is how straight or curved the track is compared to how it should be.
Crosslevel is how high one rail is relative to the other.
Surface is how much vertical variation there is in the rails.
Gauge is how far apart the rails are relative to each other.
The FRA sets limits on how much those measures can vary and sets speeds based on that variance. There are track geometry cars, which can be a "car" like a former passenger car, a small rail bound vehicle or a modified truck (or even as small as an ATV). In addition there are now "autonomus" track geometry vehicles. Many class 1 railroads have sensors mounted in engines that do basic track geometry measures and report it back to the AAR, the AAR then forwards that info the various railroads that own the track (an NS engine on the UP will measure UP track and the data will be sent to the UP via the AAR). There are also boxcars set up to be detector cars, they are put in a train and just travel like any boxcar. They normally are a regular old boxcar with an 18" thick layer of cement on the floor and electrical and diagnostic gear inside.
The benefit of using an engine or rail car is that they measure the track under load.
Dave H. Painted side goes up. My website : wnbranch.com
A few more details.
https://en.wikipedia.org/wiki/Track_geometry_car
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Thanks Dave, Rich
Great answers for my questiion.
I had to sit at a crossing one time while a Herzog track machine worked its way across. I now know how the railroad knows when the Herzog is needed.
Cheers