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Posts Tagged ‘Merg turntable controller’

Wear and tear occurs on anything mechanical over time and model railways are no exception, especially when subjected to the rigors (and occasionally operator error) of exhibiting for hours on end at shows. One of the focal points on Fisherton Sarum is of course the turntable which during an exhibition seems to be pretty much constantly on the go especially when younger viewing eyes are present.

My T14 is turned on the turntable at Fisherton Sarum

I have posted before about the turntable on Fisherton Sarum in my Controlling Interests #2 post here., but as a quick recap the turntable comprises of a Peco LK-55 kit where I have utilised the well and deck, whilst adding scratch built sides to represent the turntable installed at Salisbury; and it is controlled by  MERG turntable control kit which drives via a stepper motor and gearbox.
During the last couple of shows I attended with Fisherton Sarum I noticed that the operation of the turntable was getting less and less reliable mainly due to issues of the plastic drive shaft mounting hub on the underside of the table deck starting to disintegrate and wear to the  track power feed split contact ring.  I therefore decided to hopefully remedy the issues by removing the deck and trying to replace the drive shaft mount and also effect a repair on the power feed ring. However having examined the removed turntable and due to the lack of the original plastic now remaining at the mounting point it proved difficult to align my replacement metal bush accurately, both vertically and centrally, to give reliable running.

The original scratch built side sides have been grafted onto the new deck

I have now therefore obtained a replacement turntable kit and built a brand new replacement deck (if anyone wants the kits well components that I now have surplus to requirements let me know, free to a good home…) and carefully added the scratch built sides from the original deck to the new one.

The replacement split ring pick up bush in the middle of the well

I have also replaced the now worn power feed split ring in the turntable well as the plungers on the underside of the deck over time had worn a groove and then starting to catch on the edge of the copper split rings.
In order to make future maintenance easier and allowing easy removal of the deck, if required, I have also now incorporated new direct coupling with grub screws. I carefully drilled on a pillar drill to ensure vertical alignment, the bush in the underside of the deck to suit a 4mm OD silver steel rod to match the output shaft of the gearbox and the coupling,  as the Peco LK-55  kit is designed to be interference fit  for a standard Meccano imperial Standard Wire gauge 8 shaft.
I had tried as an experiment a  Ruland Aluminium Flexible Beam Coupling, from RS Components to link the drive shafts of the deck and gearbox, but although these are designed specifically for use with stepper motor drive systems where no back lash is a requirement a certain amount of juddering occurred as they flexed, so I have gone back to a fixed brass coupling but one with two opposing grub screws at each end to ensure a good grip on the shafts (which as per good practice have a slight flat filed on them to ensure the grub screw can grip properly.

The replacement turntable has been fitted and tested on Fisherton Sarum and means that the layout is all ready for its next outing at the Hampton Court MRS, Tolworth Showtrain, on 11th / 12th November at the Tolworth Recreation Centre, Fullers Way North, Tolworth, Surrey, KT6 7LQ

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This coming weekend, 10th / 11th October 2015, Fisherton Sarum will be at the Great Electric Train Show organised by the Hornby Magazine at the Heritage Motor Centre, Gaydon 

Fisherton Sarum’s last outing at the excellent Worthing MRC annual exhibition two weeks ago proved that the relocation of the main control panel from the rear of the layout to the front left hand corner worked really well and it will be retained in this position for future shows. It certainly, as hoped, made interaction with the audience easier and more pleasant, whilst keeping things in the shed area moving.

T14 No. 30461 is turned on the turntable as Merchant Navy 21C14 heads East.

T14 No. 30461 is turned on the turntable as Merchant Navy 21C14 heads East.

Unfortunately towards the very end of the weekend at Worthing the turntable operating mechanism failed, which upon further inspection was due to a fairly catastrophic failure of the plastic boss that connects to the operating shaft on the underside of the Peco deck itself. This has now been drilled out and replaced with a new turned steel boss and refitted. Limited time available has meant that it will have to be tested and the MERG indexing system reprogrammed for the first time tomorrow evening once set up at the GETS show, so fingers crossed it all works properly again!

1848 catches late evening sunlight as she rounds rounds the curve leaving the station

1848 catches late evening sunlight as she rounds the curve leaving the station on Rob’s South Brent

Hopefully on Sunday a guest engine will be making an appearance on Fisherton Sarum, in the form of the Bachmann N Class No.1848 that I repainted and numbered into post war SR black livery for friend and fellow post war period modeller Robin Sweet (Gwrrob on RMweb) for use on his excellent, albeit GWR,  layout‘Brent’ based on South Brent in Devon. 1848 will in a way be coming home as she was in fact a Salisbury allocated locomotive during this period.

This is the third year that Hornby Magazine have organised this show which already has a reputation for being a quality show with a great line up of layouts and traders, with the added bonus of visitors also being able to also wonder around the Heritage Motor Centre (Banbury Road, Gaydon, Warwickshire, CV35 0BJ). The show is open to the public between 9.30am  and 5pm on the Saturday and 9.30am and 4pm on the Sunday.

Once again I will be kindly and ably supported by fellow members of the High Wycombe and District MRS to operate the layout over the weekend and on the Sunday there will be four generations of my family involved (if you count the model of my Grandfather as a Ganger on the layout) as my Dad and teenage Nephew will also be helping!
I hope some you are able to attend and I look forward to seeing you there.

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My recent Controlling Interests #5 recent modifications completed…and working post  included an update on the Model Railway Electronic Group (MERG) turntable control unit that with the grateful help of fellow HWDMRS member Mark Riddoch I am now using to drive the turntable on Fisherton Sarum.

The purpose of this #5-xtra post is to demonstrate how the operation now looks via the short video I have put together below, enjoy:

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In my previous Controlling Interest posts I have discussed changes being made to a number of layout control items on Fisherton Sarum. For the last number of weeks the layout has been set up in its entirety at my local Model Railway Society , the High Wycombe and District MRS (whom have a nice new website also worth taking a look at..) initially to enable a photoshoot for a future magazine article to take place along with preparation for its planned appearance at the Basingstoke show.  Unfortunately, due to ill health I was unable to attend this show (but is now booked to attend next years show instead) and the layout has stayed at the Society Rooms enabling it to be running at this Saturday’s HWDMRS open day and also means it can fully prepared before its visit to the Hornby magazine exhibition at Hartlepool in July.

This prolonged period of having the layout set up has enable a number of items of work to be carried including:

Signals
East Signal_2
There are two working LSWR lattice post signals on Fisherton Sarum, built from Model Signal Engineering components, based on two actual signals at Salisbury. These will be the subject of a View from the line post in the future, but I have recently repaired the east end bracket signal that was damaged at the last show and both have had their paintwork touched up.

Remote Signal Operation
Before the last show I attended I added a third controller to the set up so that each fiddle yard operator can now drive trains towards them, whilst the third controller allows shunting the shed area to be carried out. This balances the workload between each yard operator, and to enhance this further I have now added a remote signal switch to each of the fiddle yard indicator panels to allow them to operate the approach signal at their end without having to move across  to the main control panel. This is controlled by a ‘Local/Remote’ switch on the main panel, this provides an interlock to ensure that only the panel or fiddle yard switches can operate the signals at any one time.  After a bit of head scratching and the addition of a couple of diodes in the circuit this is now fully functional.

Turntable
Fisherton Sarum - LR - 4
As per my Controlling Interest#2 Turning Tables post with the grateful help of fellow HWDMRS member Mark Riddoch the Turntable is now controlled by a  Model Railway Electronic Group (MERG) turntable control unit.  After initial installation there appeared to have been an issue with the counter clockwise alignment (to take up any slack when turning counter clockwise the MERG unit is designed to rotate past the selected track and then move clockwise back for final alignment) this has now been identified as being due to a small amount of slip in the connector joining the turntable drive shaft and the output shaft from the gearbox and this has now revised and I am pleased to say the turntable rotation and alignment is now quiet smooth and accurate in both directions.

In addition to the above I have also carried out a general touch up of the scenery in some places and paid attention to some of the track joins to improve running.

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In my controlling interest #1 post I mentioned the change of turntable control system to the Model Railway Electronic Group (MERG) turntable control unit.  Since I first built Fisherton Sarum the turntable was powered via a Frixinghall motor and gearbox that did not have any form of automatic indexing. This meant that the rotational speed of the table was not easy to control and track alignment had to be done by eye (sometimes hitting the mark easier than at othertimes) via a toggle switch.

The turntable on Fisherton Sarum is very much the focal point of the layout.

Friend and regular operator of Fisherton Sarum, fellow High Wycombe and District MRS member and electronics wizard Mark Riddoch has very kindly built for me a MERG turntable control kit which drives a stepper motor and gearbox.
This clever bit of electronics can give up to 63 different positions (I only need 8 i.e. each end of 4 roads, on Fisherton Sarum) to an amazing precision of 0.03 degrees.

The stepper motor and gearbox installed on a new cross member on the underside of the turntable well

The turntable is simply operated from the panel via a rotary switch (a binary hex coded switch, for those that understand such things) to select the desired road and then pressing the start button. The controller then automatically works out the shortest distance to the desired alignment. When turning clockwise the deck is stopped automatically at the correct place or if turning anti-clockwise it over runs slightly before stepping back clockwise to the correct position ensuring any slack in the gearbox is taken up. The controller has a learn mode to allow the desired positions to be accurately set up which it then remembers.

The Meccano shaft locked in position with a brass pin through the boss and shaft. (apologies for the poor image)

The typical bank holiday weekend weather, just passed, encouraged working inside rather than other pursuits so the installation was completed. Installation has required a few slight changes to the control panel: firstly to incorporate the rotary switch,  mounting inside the control panel the controller PCB card and changes to the wiring harness to get the required five wires to the stepper motor and gearbox that is being mounted directly under the turntable itself, replacing the previously installed traditional motor, gearbox and worm and wheel drive.

It is imperative that the link between the gearbox outlet and the table deck is positive and has no possibility of slip. The Peco deck is designed to be an interference fit on to a Meccano shaft so to ensure no unwanted movement is possible I have drilled through the boss and the shaft at 90 degrees and pinned it with a short section of Brass wire.

A close up of the motor, gearbox and drive coupling arrangement.

This shaft matching  the gearbox output shaft has had a flat filed onto it and a brass collar joins to the two with grub screws ensuring a positive connection.

Programming the turntable in learn mode has not gone 100% to plan and I did not yesterday  manage to get it working correctly, so need to some additional advice. Once I have mastered the programming I will upload a video of the turntable under its new control in action, so watch this space.

I am once again indebted to Mark, and offer my my sincere thanks for his time and assistance with this addition to the control of Fisherton Sarum which should, when fully up and running,  improve the operation and visual effect no end.

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Although Fisherton Sarum is not currently set up, I am using the time between shows to make a few changes and additions to the operating system. These modifications include: the addition of a third controller for main line operation (see below), the installation of a Model Electronic Railway Group (MERG)  turntable control unit with stepper motor, moving of the signal control to the fiddle yard panels and changing all the point motors to slow acting Cobalt types. The other modifications will form the subject of future posts so to coin a phrase watch or follow this space.

N1 Class No 1822 trundles west with a rake of dia 1774 40T ballast hoppers. In the new scheme of things this will be driven by, and towards, the west end fiddle yard operator, with the signal operated from a remote switch on the fiddle yard indicator panel.

Whilst operating the layout at the Doncaster Festival of British Model Railways my fellow operators from the High Wycombe and District MRS, naming no names (Roger and Mark) hatched a plan for improved operation of the main running lines. Currently the layout has two Gaugemaster ‘W’ handheld controllers for traditional DC Cab control allowing either controller to control any section of the layout.

Our default operation is one controller for the shed area and one for the main lines. This does mean that only one of the fiddle operators actually drives the main line trains and does so in both directions. The suggestion was to add a third controller so that two can be used on the main lines, i.e. one up and one down, allowing each fiddle yard operator to drive the trains towards their end. This will also increase the likelihood of trains passing on the main too (already possible but meaning the shed movements having to stop). The plan also includes the addition of remote signal controls to the fiddle yard indicator panels to ease operation too.

Time has been spent this weekend modifying the control panel wiring for the new controller, along with the installation of the new Turntable controller (but more of this soon). The final part of the controller installation will be the wiring on the west end baseboard to a socket for the new controller (the wiring harness is already in place with suitable spare cores). Fisherton Sarum’s first outing with the new operation will be Tring and District MRC show 13th October 2012.

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As part of the layout control changes currently being made to Fisherton Sarum (more of which later)  involves the turntable I thought it was about time I posted about the turntable itself. The turntable at Salisbury was originally a 65’ foot heavy over girder type. In 1958 this was replaced by a larger diameter under girder type.  An unusual feature of Salisbury shed was the the access to the stores building unloading platform was via a shunt across the turntable and I have replicated this feature on Fisherton Sarum and it often raises a comment at exhibitions.

N15 Class no 744 is on the turntable. Barrels of steam oil and other engine lubricants are stored in front of the turners mess hut.

On Fisherton Sarum I wanted to represent the original style of over girder table installed at Salisbury. I used a Peco kit for the well and the deck, modifying the deck by scratch building the heavy over girder sides and a the addition of the turner’s platform.

The shed pilot, T1 class no 10, shunts a box van of spares from Eastleigh works to the stores building unloading platform.

Thick plasticard and Plastistrut sections was used for the girder sides along with an overlay embossed with a punch to represent the rivets along the top of the sides. A small outbuilding was provided to act as a mess room for the turners employed at the shed, on Fisherton Sarum this is a modified Wills kit.

The turners work hard turning 21c151 'Sir Winston Churchill'

Ironically the Peco kit unmodified matches the later style at Salisbury.

Since I first built Fisherton Sarum the turntable was powered via a Frixinghall motor and gearbox that did not have any form of automatic indexing. This meant that the rotational speed of the table was not easy to control and track alignment had to be done by eye (sometimes easier than others) via a switch. This is in the process  of being changed to stepper motor and gearbox controlled via a Model Electronic Railway Group (MERG)  turntable controller kit, kindly built by Mark Riddoch, more of this in a future post.

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