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Discussion Starter · #1 ·
I am in the process of building a loco depot next to my station, and, having built the shed and coaling stage, a turntable is now required. The layout is 4 mm scale.

I have not got room for a huge 70 ft or 75 ft turntable of the type produced by the trade, and so I shall probably have to build my own and motorize it.

On my previous layout, I had a smaller turntable driven by an electric motor and gear box that had to be lined up by eye and then locked in position. For the current layout I need something a lot better and I have decided on the following specification:

1. It should be based on a standard design of table used by the LNER and British Railways.
2. It needs to be a scale 60 to 65 ft diameter.
3. It should not be noisy in operation (the last one was very noisy and so an open gearbox is out).
4. Once started it should turn slowly to the required position and stop automatically in exactly the right place.
5. The power supply to the turntable track needs to be reliable. The last one picked up from the track in the well and was prone to loss of power due to dirty
wipers.

Has anybody any suggestions as to how I could buy or make such a machine?
 

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When I utilise a turntable its the Hornby one and I would concede that it is a bit toy like in appearance and noisy and big and the exit and extrance angles can be a bit steep and sometimes locos cannot cope but for those locos that can cope it is reliable.

Have a look at this as a basis. A hand crank system is available and it may be possible to motorise the crank with a few reduction gears and a lever switch. If it rotates slowly enough then it should be possibly to line the track up manually:-



http://www.sefinecast.co.uk/Turntables/Turntables.htm

Happy modelling
Gary
 

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Fleischmann make a decent turntable (part nos. 6152C & 6151C) with a deck length of 310mm (about 77' in 4mm scale). Simple to control and with "thinking" circuitry.

60134
 

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For the really cheap do it yourself modeller with plenty of time available there is the Dapol kit turntable (based on the 1960's Airfix kit). September's edition of Model Rail provides info in connection with how to motorise it. It seems that the two modellers featured both rely on a very slow speed of rotation with a massive gear reduction ratio and the "line by eye" method to line up the turntable. No mention of how they keep the track circuit alive.

Peco do something aswell giving a choice of open well or with decking infill. Again its up to the modeller to electrify.

Happy modelling
Gary
 

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That's a really excellent linked article - well worth getting on record here.


Probably of no direct value on this occasion, but perhaps also worth adding to the turntable info here, my Roco catalogue (This one only ten years old, 292 pages!) devotes a couple of pages to their turntable.

Item No: 42615
Prototype diameter: 72'
Table cutout: 280mm
Total Diameter: 307mm
Bridge Length 253mm
Depth: 50mm
Track connections: Max 40 (4 supplied)
Fully automatic positioning preselectable
Twin Speed
PC controllable (with additional interface)
 

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Discussion Starter · #8 ·
Thanks for all the advice, particularly to Rail-Rider who supplied the spec. of the Roco TT. I shall be doing it the hard way as usual, I always like a challenge.

The Dapol TT kit which should be a donor for a few parts. I have also gathered together some components from various suppliers and dusted down and explored my boxes of potentially useful bits to build the Saskatoon drive mechanism mentioned previously.

There are drawings of various TTs in "British Railways Engine Sheds" by Hawkins, Hooper and Reeve, which will be very useful.

I have been to York and photographed the TT at the NRM and then made a decision to model the one that was at the top of York North Yard. This was an electrically driven machine by Ransome and Rapier and it fits in with my policy of building a layout which is a pastiche of York. There is a video clip of this TT in operation on:http://www.bbc.co.uk/nationonfilm/topics/railways/. Scroll a long way down to the fourth clips of four clips entitled "The layout of a locomotive depot". This shows a B16 being turned during the immediate post war years as there is a WD with a Westinghouse pump in the background. The rest of the videoclips are interesting as well.

Colombo

Colombo
 

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Discussion Starter · #9 ·
There has been some progress with the turntable drive mechanism over the weekend. Here is a photo published showing the drive unit mounted under the baseboard.

http://www.yith.co.uk/gallery/image.php?fi...ble%20Drive.jpg

The 12 volt geared motor drives a pulley which is fixed onto the axle of a Sturmey Archer bicycle front wheel hub. I guess any make would do. This gives a smooth and rigid drive with very little friction as there are ball bearings at each end. The holes for the bicycle spokes are just big enough for some tiny No.2x3/16" self tapping screws that I bought from Squires to fix Kadee no.5 couplings to rolling stock. These were used to fix the hub into the 3mm ply wooden frame.

A 10" record was sacrificed to make an indexing disk, and notches on the perimeter engage with a lever operated microswitch which has a wheel on the end of the lever. The turntable stops turning when the wheel drops into a notch.

So far it all works.


Colombo
 

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Discussion Starter · #11 ·
I said that I would keep readers up to date with the turntable construction project as it proceeds.

Well all did not go as well as I had hoped it would and I have had to scrap the pulley wheels and drive belt idea. The problem was that the belt, which came from a defunct video recorder, had a certain degree of elasticity and this allowed the turntable to slow down or even stop when the turntable bridge met any resistance at all. The drive pulley continued to turn, the elasticity in the belt allowed the tension to increase until the resistance was overcome and then the bridge just flicked round to the next point of resistance. Moral: smooth video drive belts are for high speed duties. You need a toothed belt or an inelastic vee belt.

Maplins do supply a toothed belt system which may well be ideal, but it is also pricey, so I had a rethink. I visited the little shop that supplies spare parts for domestic appliances such as washing machines and vacuum cleaners, but they had nothing suitable either that could be used to replace the video recorder drive belt.

The US reference quoted previously mentions a friction drive and at first I did not cotton on. Then I decided that my old portable record player probably had a friction drive so I dug it out and stripped it down, having first ensured that 20 odd years in storage had taken its toll. (I.E. that it did not work and could safely be sacrificed). There is a rubber friction wheel driving inside the rim of the record turntable and so these two components were carefully extracted and adapted to fit under the bicycle hub.

After a few attempts at getting everything concentric, the first proper test was a revelation. So much smooth power is transmitted to the turntable bridge that it is quite difficult to stop it turning at its steady 1 r.p.m. or so. All resistance is overcome without any difficulty.

I am now working on the turntable bridge (or deck if you prefer) and I hope to be able to use it in its undetailed condition quite soon.

Colombo
 

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Heljan are in the process of developing two new turntables for N and HO. This is mentioned on their their web site. These will be power operated and probably aimed at capturing part of the Flieshmann market. The Flieshmann turntable is very much over priced and not suitable for the UK steam age without extensive modification which most people are reluctant to do with a turntable costing close to 200 quid.
There certainly is a gap in the market for a decent powered indexing turntable. The hornby examples are cheap and cheerful, unrealistic, and very noisey. While Peco's turntable looks very nice, I've found the motorising kits to be unsatisfactory, and then you are well over 50quid for a non indexing turntable. The same can be said for South Eastern fine cast nice table, requires a lot of work, and a motorising kit, and then it's still not self indexing.
The Walters turntables (120ft) for turning bigboys are truely works of art and are about the same price and the Flieshmann TT's but totally unsuitable for British operation. I think I'll wait to see what Heljan offer.
 

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Discussion Starter · #15 ·
The turntable has progressed slowly because the original belt drive did not work well enough. The elasticity in the belt allowed the speed of the table to fluctuate when it met any resistance.

This was eventually overcome by using the friction drive wheel from the record player. This was fixed on the end of the geared motor and arranged to drive on the inside edge of the record turntable. The result was a perfectly smooth, slow and quiet turn.

The turntable deck was based on the one that used to be at the top of York(North) yard. This was a Ransome and Rapier non-balancing Mundt type table and was electrically driven, with power being collected by a pair of slip rings on top of a gallows arrangement in the centre of the deck.

The deck was fabricated out of a Dapol turntable kit, using just the lower halves of the girders and the plastic circle of rail. Electrical pick up is via the bicycle hub which forms the pivot and drive shaft and also from the slip ring on top of the gallows.

The polarity of the rails on the turntable deck is reversed by a reflective IR sensor detecting a white label on the indexing disk which energises a 2PST relay.

Now it all works and I can finish the scenics in the yard.

Colombo
 

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Discussion Starter · #16 ·
The scenics around the turntable are almost complete, and I still have a little work to do on the turntable deck itself. It needs a winch and a control box, and the deck needs planking.

The background is a photograph of the Corus steel works at Scunthorpe as it is today. Blast furnaces, cooling towers and chimneys predominate - nothing changes much.

Colombo

 

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there was an article on modelling the enclosed turntable at carlistle (spelling?) using a hornby donor a couple of months ago in model rail.

it was a good attempt but really i think the hornby turntable is just junk. its a pity really as i do like the elegant soloution to the indexing problem.
as i said earlier i used the hornby model buy mounting it directly underneath a SEF model. that way i could use the hornby indexing and still have a half decent looking model. my modelling skills have moved on alot since then but i think i would still do exactly the same again.

i saw a model a little while ago that used a dapol/airfix turntable bridge mounted upside down and it actually looked very good. i might try that in an SEF vac-formed well. i cant remember the name of the layout but it belonged to burt hawkins of the gloucester model railway club. i really must show m,y face in there again. i went there evry week for about 5 years and i havent been in the door since i left for university. i made alot of freinds there. and i made the lock gates on their new layout!!

i'm wafelling arnt i?

Peter
 
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