What gradient required to start train rolling?

[Titan]

Just a quick one to drivers or anyone else in the know, what is the shallowest gradient that will certainly start a train to roll when the brakes are released? Assume we are talking modern stock - i.e. roller bearings throughout. I am hoping it is somewhat less steep than 1:184!

[LMS2968]

Many variables, but 1 in 200 was certainly considered enough to require brakes to be applied to Mk 1 stock.

[great central]

Bear in mind the runaway from Quorn to Loughborough on the GCR. According to the RAIB report the average gradient is 1 in 330 at Quorn 

[njee20]

Well, no, not any gradient. At some point the friction of the wheels on the rail and in the bearings will overcome the potential kinetic energy. Or something sciency.

[Gilloverland]

'Modern stock' with roller bearings has been known to be blown by the wind on perfectly level track - hence vehicles should be secured properly at all times on any level.

[Edwin_m]

HMRI considers 1 in 500 to be a "safe" gradient for no roll-away, so has a preference for gradient less steep than that at places where drivers may leave their trains.  I think it's rather less rigid these days with modern parking brakes. 

 

As to a gradient where trains will definitely roll, I guess it depends on the condition of the bearings. 

[roythebus]

I helped prepare a class 40 in Finsbury Park depot one day on one of the outside roads. My driver told me to take the handbrake off in the back cab, which I did. With that, the loco, without the engine running, started to roll. It rolled to near the exit point; it rolled back again, and back agin, despite both hand brakes by this time being applied! It was only after my driver started the engine and built up enough air to apply the loco  brake that it stopped.

 

There was no noticeable gradient on that siding.

[TheSignalEngineer]

With old fashioned stock the requirement for run-back catch points started when the gradient got to 1 in 260. As bearings improved, stock could roll at a considerably shallower gradient. The current requirement in Railway Group Standards requires new platforms to be located on track with vertical track alignment (ie average track gradient through station platforms) no steeper than 1 in 500.

[TheSignalEngineer]

I helped prepare a class 40 in Finsbury Park depot one day on one of the outside roads. My driver told me to take the handbrake off in the back cab, which I did. With that, the loco, without the engine running, started to roll. It rolled to near the exit point; it rolled back again, and back agin, despite both hand brakes by this time being applied! It was only after my driver started the engine and built up enough air to apply the loco  brake that it stopped.

 

There was no noticeable gradient on that siding.

Following an unattended EE Type 4 runaway at Monument Lane in 1965 (by the Great Train Robbery engine D326) there were special instructions about securing them as the brakes were not sufficient.

[96701]

When I was working at Carlisle Kingmoor in the mid 70s, there were occasions when we had to move locos using pinch bars. I was much easier to start them off and get them rolling south to north than it was to get them rolling north to south. A spirit level on the rail showed no noticeable difference between the two. It was a bit tricky to stop them once you'd got them rolling in whichever direction they were going.

[stovepipe]

Following an unattended EE Type 4 runaway at Monument Lane in 1965 (by the Great Train Robbery engine D326) there were special instructions about securing them as the brakes were not sufficient.

 

There are a number of photos showing EE type 4s chocked at various depots, .......I understand they had quite a reputation.

[modfather]

96701 - amen to that, I'm pretty sure I can tell you every subtle change in angle at Spm.