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Miniature Lever Frame operation

British signalling of the past (UK, excepting Northern Ireland)

Re: Miniature Lever Frame operation

Unread postby Marsh Lane » Tue May 9, 2017 8:30 pm

Mike Hodgson wrote:So pulling a lever is effectively a two-stage process, and the signalman gets a positive feedback from the lever - if the points should jam he would know not only from illuminated indications but also from the feel of the lever as he is unable to complete the lever movement. ...... It is an excellent fail-safe design for a safety critical use, but many modellers would consider this complexity of design to be seriously "over the top" for a model railway.


Mike,
As you say complex and seriously "OTT" for a model railway - but I think I've managed to work out a way of replicating it to make it work the same way, and only allow the final part of the travel in each direction following confirmation of the point detection!

I presume that such 'two-stage' process was only used on pointwork, I'm assuming it was not implemented for signals, but am I wrong in that assumption?

Regards
Rich
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Re: Miniature Lever Frame operation

Unread postby Richard Pike » Tue May 9, 2017 9:08 pm

I have wired my Westinghouse L frame to include signal indication locking in most cases. The arm has to be proved on to get the lever in the frame. The real genius in the L frame is the timing of the rotary contacts in relation to the force down ramps on the electric lock tappets. A slight maladjustment can give a 'sticky' feel to the frame. Adding spark quench diodes to the locks can do the same. There are special tools required for contact finger adjustment and a certain amount of skill/practice in using them. If you are to faithfully reproduce an L frame the need for precision will soon be apparent. If you are producing something that does the job of an L frame without all it's features i'm sure you'll end up reinventing the wheel so to speak. A lot of thought went into the design. Not all of it is apparent from just pulling the levers on a well maintained and properly adjusted prototype.
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Re: Miniature Lever Frame operation

Unread postby Peter Gibbons » Wed May 10, 2017 8:26 am

I think that there is now only two Westringhouse Style L frames still in use on Network Rail. Those, I believe are at Liverpool Lime Street and Maidstone East. The miniature lever frame at Maidstone East was the last such installation on Southern Region and was slightly unusual in that unlike other Southern 'L' frames, it only provided two aspect red / green signal repeater indications, instead of the more usual actual signal indications.

http://www.wbsframe.mste.co.uk/public/M ... _East.html
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Re: Miniature Lever Frame operation

Unread postby Marsh Lane » Wed May 10, 2017 9:32 pm

Fast Line Floyd wrote:Much more information about the complexities of these frames can be found in John Francis's excellent book 'The Style L Power Frame' ISBN 0 9514636 0 8, this book is a long way out of print but you may be able to obtain a copy somewhere (just looked there is one on the Amazon site now!).


Graham,
Many thanks - the book arrived this morning and your right! It truly is excellent and this one is in superb condition - thank you for the heads up.

Rich
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Re: Miniature Lever Frame operation

Unread postby Marsh Lane » Wed May 10, 2017 9:37 pm

Richard Pike wrote:I have wired my Westinghouse L frame to include signal indication locking in most cases. The arm has to be proved on to get the lever in the frame. The real genius in the L frame is the timing of the rotary contacts in relation to the force down ramps on the electric lock tappets. A slight maladjustment can give a 'sticky' feel to the frame. Adding spark quench diodes to the locks can do the same. There are special tools required for contact finger adjustment and a certain amount of skill/practice in using them. If you are to faithfully reproduce an L frame the need for precision will soon be apparent. If you are producing something that does the job of an L frame without all it's features i'm sure you'll end up reinventing the wheel so to speak. A lot of thought went into the design. Not all of it is apparent from just pulling the levers on a well maintained and properly adjusted prototype.


Hi Richard,
Thanks for the info. Like I said at the start, its based on a Westinghouse frame, but I totally acknowledge there there is a limit to my knowledge, skill, money and time. This is one project within a larger one (that of the model railway!) so while I wanted to get it as realistic as I can, I'll be quite happy to get similar to it. Getting into rotary contacts, as much as I would like to be able to understand and replicate, is taking it too far for me. Its a hobby project after all! So yes, I agree I think there will be some amount of reinventing the wheel, but I'll have the satisfaction that if I can do it and make it work, then its all my own work and I'll have achieved something!! :)

Rich
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