WIGGLER VALVE

[Anonymous]

Does anybody have any information on a steam locomotive device called a wiggler valve?  Apparently this was a device that sensed differential motion between the locomotive frame and the frame of the lead truck, and if it exceeded a certain amount, the device dumped the train line in order to prevent a derailment that was likely to occur due to rough riding of the locomotive.

[Anonymous]

I conclude that the wiggler valve was not too common.  I have only heard of it being applied to N&W 4-8-0s.  It strikes me as a rather odd, but nevertheless practical solution to the problem of poor track and locomotive instability.  If the ride gets too rough, the wiggler valve dumps the air and stops the train in order to prevent the engine from derailing.  I wonder how much comfort engineers derived from this remedy for bad track.

[BigJim]

I have never ever heard of a "wiggler valve". There was a valve that was placed on the pilot truck of steam engines that put the train in emergency if the pilot truck derailed. There is a name for this valve, although it escapes me at this time. However, it wasn't called a "wiggler valve". Maybe something like "Wright's Little Watchman".

[Anonymous]

I have never ever heard of a "wiggler valve". There was a valve that was placed on the pilot truck of steam engines that put the train in emergency if the pilot truck derailed. There is a name for this valve, although it escapes me at this time. However, it wasn't called a "wiggler valve". Maybe something like "Wright's Little Watchman".

Thanks Jim,

That sounds a little different from what I understood the wiggler valve to be, which was to put the train into emergency before anything derails.  What you describe raises another question.  It suggests that an engineer might not immediately realize that the piolt truck has derailed.  I never thought about that before, but I would have assumed that if the pilot truck derailed, the rest of the locomotive would almost immediately derail.  Maybe not though.