CAG Meeting Reports 2017

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Will L
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CAG Meeting Reports 2017

Postby Will L » Tue Mar 14, 2017 11:29 pm

CAG Meeting Sunday 12th March

The Crewe Area Groups March meeting was help at Dick Petters home and was well patronised with 8 members plus soon to be ex-EditorJames in attendance. The attraction was, as always when we visit Dick, the chance to play with his rather fine train set. Although he was also taking the opportunity to try and divest himself of some surplus kits, magazines and tools, the residue of which will appear again on Scalefour Norths bring and buy stall.

Having arrived at about 11 we all settled down for a cupper and in due course our lunches. After a very pleasurable chat, where we put the model railway world to rights, we adjourned upstairs to play trains on Dick’s Knutsford Junction layout.

The highlight of the day was when we did some timed runs, what Nigel Gresley would have called brake trials, which were inspired by a recent article in MRJ252. We may not have a P2 to hand, but we did have a re-wheeled to P4 LMS diesel 10000 which was happily pulling 13 coaches through Knutsford Junction’s measured ¼ mile at a scale 93mph or there abouts, no hesitations, no derailments and no steamroller wheels.

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10000, blasts through Knutsford Junction station at a little under a ton. Note no yellow lines to keep behind in those days.
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The lady herself as she approaches the camera man.
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Although probably rather faster than the real thing ever went, in truth, the scale 93 mph wasn’t actually all that visually impressive a speed, but it was all 10000 seemed capable of. I’m sure that Dick’s normal stock list of LMS express motive power actually whirls that 13 coach rake round rather quicker.
Anybody interested in knowing more about what sort of challenge 13 coaches on Knutsford Junction represents, may like to read an account of previous trials documented here.

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Will L
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Joined: Sun Jul 20, 2008 3:54 pm

CAG Meeting April 9th 2017

Postby Will L » Mon Apr 10, 2017 3:48 pm

At Your Servos

Last Sunday at David Burton's home saw our best attended meeting for a long time. It must have been the quality of the promised entertainment that attracted 12 of our 15 members. Lets hope the other three don't feel too left out. Before starting out on the days entertainment we were please to welcome a new member, Barry Lingham, to the group. Lets hope that he finds us the friendly and welcoming bunch we think we are, and that he gets considerable advantage from mining the combined experience of the group.

The subject of the day was a talk by member Phil Bourn on the use of Servos to operate signals points and other bits of ancillary equipment around the layout. Phil, a member of MERG (Model Electronic Railway Group) and with lots of relevant experience from his professional life, provided servo power for all the signals on Knutsford East as well as the operating private siding gates.

The curious may want to know that, while servos could have been used for the points, they were not because the decision to use tortoise motors was taken early in the layout development, before the servo option was understood to be realistically available.

Phil's talk had to walk a line between getting too deeply involved with he technicalities/terminology involved in the hardware being used and the fact that many/most of us had little knowledge of the electronics which underlies it all. I think he judged this very well, it certainly worked for me. He started from what a servo was in general terms, and moved on through the sort of servos likely to be of use on a model railway, and the electronic equipment needed to drive them and adjust their action. He pointed out that the electronics needed to drive the servos is not expensive, particularly if you are a member of MERG, and that the servos themselves can be remarkably cheap, although, as with many things, the cheapest purchases often come with a down side.

The servos he demonstrated give you the ability to control the movement of an operating arm within very fine limits, in terms of both speed and position. Just the thing for operating signal arms etc. However while those limits to the movement can be finely controlled, the power it does it with isn't, and the things don't push or pull gently. The result being that a mismatch between the movement of the servo operating arm and the movements required to control, say, a signal arm, can prove significantly destructive. A fact that needs to be taken into account when designing a servo activated operating mechanism.
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Phil is seen here with a number of test rigs he had made while developing the servo controlled mechanisms for Knutsford, which he used to illustrate his talk. The one pictured below was for the private siding gates seen in action in the video clip above.
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Phil finished his talk by covering the whole topic of Twitchy servos, that is unwanted/unexpected movement of the servo arm either when being powered on or as a result of electrical interference during use. This is a topic not unknown on the forum, but I have to say his explanations made much more sense of the problem for me than the forum discussions ever have.

Having seen the demo, would I be attracted to their use were I to be designing a new layout, well very much so, but it is also clear that you need to be very aware of their personal habits if you don't want to be disappointed.

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