Lever frame mk 2 and the locking frame

Discussions of the prototypes and how to model them. Show us how you do it.
davebradwell
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Re: Lever frame mk 2 and the locking frame

Postby davebradwell » Sun Feb 09, 2020 8:17 pm

I once heard a twist to potential design for electrical locking: you don't need a separate lock for each lever, you can just lock them all at once. As long as there is only one signalman the fact that the levers you aren''t trying to pull are locked is irrelevant.

The system needs to know which lever is being pulled so either the catch handle or first lever movement should actuate a microswitch. After that a diode matrix should do your locks. I never came up with a tidy mechanical arrangement.

Think about it, it's potentially easier and less complicated than a row of servos. I didn't advance the idea because my 60 lever frame was no place for a try out.

DaveB

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grovenor-2685
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Re: Lever frame mk 2 and the locking frame

Postby grovenor-2685 » Sun Feb 09, 2020 8:33 pm

I have seen proposals for such but my take has been that they are more complex than the row of servos which I have seen done well. Fitting a microswitch on a catch handle is considerably trickier than just on the lever throw, and if you go for the first bit of movement then don't forget you need it a both ends of stroke so now its 2 microswitches, and the locking has to either apply or release very fast to avoid inconvenience/lockups/damage.
I would stick with the row of servos. The one I have seen has a rotating slot on top of the servo that can be either in line with the lever movement or at right angles, the lever tail passes through the slot so giving a positive lock in both N and R positions.
Regards
Keith
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davebradwell
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Re: Lever frame mk 2 and the locking frame

Postby davebradwell » Sun Feb 09, 2020 10:43 pm

Reflecting on it a bit more you gain a microswitch and lose a servo on each lever - to me that was worth a look. The system is dead until a lever is moved when it reads the lever positions and decides by diode matrix or whatever if the lever movement is permitted. If not then all levers are locked so release lever and try another.

DaveB

JFS
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Re: Lever frame mk 2 and the locking frame

Postby JFS » Mon Feb 10, 2020 1:11 pm

davebradwell wrote:... and decides by diode matrix or whatever ...


Hi Dave,

I think you might find a thousand devils lurking in that tiny detail! To me, the biggest ADVANTAGE of an electircal approach is if it is implemented digitally (I know of a very large layout with over 500 levers done this way) and I have written a BBC Basic programme which (would) run on a Raspberry Pi under SDL. That way, if you make a mistake in the locking logic, it is easy to correct. However, I gave up when I realised a mechanical solution was much more interesting!

What I am puzzled by is in what way any of this electical stuff is any "easier" than mechanical locking - given that Tony has demonstrated that a complete beginner with basic skills can succeed with the latter.

I reckon to have done my fair share of both - here is the electrical locking on the Leeds City Junction frame:-

Locks testing_s.jpg


This only does the simplest of stuff (locks with the Blocks, Track Circuits and a couple of remote releases) yet the control circuitry is not insignificant:-

Control Box.jpg


[I did design all that but I did not build it all! ] More details of the locks here:- https://www.rmweb.co.uk/community/index ... m/page/41/

I think the biggest problem with the servo-based solutions I have seen is the slowness of their reaction to a lever pull - it feels like waiting for Christmas to set up a route - and with a "one servo locks all" approach they are very easily defeated. Kieth has already pointed out the problems of detecting a lever pull - we chose to use "Economiser" plungers for each levers - see the RM thread bove. This has worked fine in actual use.

Looking forward to hearing how some of these electrical concepts work out in practice - perhaps some should start a new thread?

Best Wishes.

davebradwell
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Re: Lever frame mk 2 and the locking frame

Postby davebradwell » Mon Feb 10, 2020 2:28 pm

I wouldn't disagree at all, just wanted to get the idea out there in case it appealed to someone. Certainly electronics can become a lot of work and I baulked at the thought of 60 servos and drives - just the wiring would have taken an age. I was doodling with some kind of solenoid operated lock to get a fast response and using the catch handles gains a few milliseconds. Someone might give it a go, I'm only passing it on.

My own locking ended up as traditional mechanical with bits produced very easily in the mill, stepping out the pins and notches with the leadscrew to get accurate parts quickly. Could have done with reading the tips in this thread to reduce the number of parts required but I did end up with a similar number of rows to the prototype.

DaveB

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Tonycardall
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Re: Lever frame mk 2 and the locking frame

Postby Tonycardall » Fri Feb 21, 2020 4:13 pm

I am sure you will spot further issues - please feel free to let me know.


It has been mentioned that there are plenty of spare nibs and bridles etc. within the etch. So, (here I place my tongue firmly in my cheek and I use the word 'cheek' advisedly), there is one thing that I can think of that is missing from the excellent etch. Anyone embarking on creating a mechanical locking frame will obviously want to work it in as accurate and proper way as possible. Therefore, they will need some lever collars!
Just a thought. I'll go back to trying to dry out my flooded railway cabin now!
Tony

collar.JPG

JFS
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Re: Lever frame mk 2 and the locking frame

Postby JFS » Fri Feb 21, 2020 8:40 pm

Hello Tony,

Very sorry to hear about the flood - I trust there is no permanent harm.

Is this something like you had in mind:-

Collars.jpg


They take only seconds to bend-up and blow over with a bit of red rattle-can. I will ask Jeremy if he thinks they might be stocked in the stores.

Does not help with all the spare nibs though ...

Best wishes for a speedy clean-up.

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Tonycardall
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Re: Lever frame mk 2 and the locking frame

Postby Tonycardall » Fri Feb 21, 2020 9:37 pm

Is this something like you had in mind

Howard,
I should have known you’d have it covered.
I look forward to them appearing in the stores.
Mind you, I hadn’t thought about reminder appliances to be used for Rule 55, section K or whatever it is called at the relevant time of ones railway, I was thinking of using collars as a genuine preventative to stop a lever from being used when, if you can imagine such a thing, a point fails during a running session.
Not that it has ever happened to me obviously. :twisted:
Tony

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Tonycardall
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Re: Lever frame mk 2 and the locking frame

Postby Tonycardall » Sun Aug 30, 2020 11:07 am

Having lived with and thoroughly benefited from my locking frame for a few months now I suddenly realised that there is something missing. The signals are silent! In the current world of weird and wonderful sounds emanating from our locomotives surely I should be able to hear the iconic clunks of my semaphore signals returning to ‘on’.
Does anyone have any idea how it can be done in coordination with the operation of the signal?
To operate the signals I am using a Megapoints Controller servo driver which I would have thought could network to some form of sound generator?
I hope that I am not being over optimistic.
Tony


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