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Quick question:-

 

Did the humble 12' diameter wagon Turn Table accommodate 9' or 10' wheelbase wagons maximum?

 

 

Kev.

 

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  • RMweb Gold

Thanks Mark,

 

I was aware that Buffers, coupling, dangly-bits and wagon overhangs didn't matter - (as long as they didn't interfere with adjacent tracks, especially running lines) - but it is the wheel diameter and its' flange that will protrude into the fixed rails around the table thus stopping the turn table spinning!

 

I'll post some CAD which illustrates the problem.

 

 

Kev.

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  • RMweb Gold

Here I have drawn a 12' diameter wagon turntable to see where the Bachmann 10' wheelbase flanges come above rail the top.

 

image.png.f757199df8788bd145322b57a3ca314c.png

 

A 12' diameter turn table will have rail lengths of 44.77mm in OO gauge.

The 10' Wheelbase Wagon's flanges will come above rail tops at centres.

 

image.png.03ca445951b359c7cf55967360159357.png

 

It's the scale 3" flanges that are the problem.

If I use a 13' diameter table then everything clears - just - but how common were 13' wagon turntables?

 

Even at 13', the wagon would have to be positioned to within 0.8447mm!!

So an even larger table would be prudent to turn 10' wheelbase wagons?

 

 

Kev.

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Posted (edited)

You also need to keep the wagon from moving as the table turns.

 

I've filed a slight dip in the rail top on a table I used, this helps spot the wagon as well.

 

 

See here for a completed view:

 

Edited by Stubby47
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Thanks Stubby,

 

I thought the same thing, with notches in the rail tops, to stabilise wagon positions.

I then thought that a small shim, added to the TT surface next to the rail ends, would also work.

I then thought about having this shim in the gap between the running rail and the check rail would perform the same function but would also be out of sight.

 

If the wheel flanges are 1mm then I need to add something so that there is only 0.8mm from that to the rail top. The Wheel will then have to climb 0.2mm to exit the TT.

With these "shims" located out on the circumference then the "slight bump" just looks like the transition from TT to fixed track.

 

I tried this with a cut down sleeper. I seemed to work well.

20200528_121257.jpg.7e4a11a2f5124b4c94731eacba2d8375.jpg

NOTE! - 9' wheelbase.

 

20200528_121458.jpg.3c4d3922ce91f82fe3b55a1820896bd5.jpg

 

 

This is an "ATLAS code83 90degree X-ING"

The rail lengths are exactly 2inchs. This gives a TT diameter of 53.41mm or 13'4.23".

20200528_121805.jpg.81894d2bda31b546262676736e07ea85.jpg

 

13'4.23" is an odd size so I'm going to call it 13'.6".

image.png.b9a4ba505c32d473eaa0cdda6c9257bd.png

 

Here is a 10' wheelbase wagon.

I really wouldn't want a smaller diameter table than 13.5'!

20200528_101537.jpg.13548a98cc8a216f08c1a3c969c5fb31.jpg

(I know I've got it on the wrong rail...)

 

The ALTAS 90degree X-ING has the advantage that it is ready made, but also, each rail is electrically connected along its' length.

The disadvantage is that (in one direction) any wheel flanges, that are too deep, will short out the two parallel rails, (it's about 1.8mm deep so Lima pan-cake cutter wheels are not allowed) . You can see this in the above photo. The other disadvantage is that the gauge is wide! I varies between 17.0mm and 17.2mm but the check rails worked very well!

 

 

I still don't know if the UK 12' Wagon TT could turn 10' wheelbase wagons or not!

 

 

Kev.

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Posted (edited)

Nominal 12 foot diameter wagon turntables were usually actually 12 ft - 1 in diameter and this just enabled them to turn 10 foot wheelbase wagons. However the clearances were very tight and a 13 foot diameter turntable was preferred anywhere where 10 foot wheelbase wagons were turned regularly. The diagram shows just how tight 10 foot on 12 ft - 1 in was.

WagonTT.jpg.e3fc8fe26423487acf356f260a38f776.jpg

Edited by bécasse
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  • RMweb Gold

Fascinating!

So much quicker, and easier, than I ever expected. Such a wealth of information.

 

 

Kev.

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  • RMweb Gold
59 minutes ago, bécasse said:

Nominal 12 foot diameter wagon turntables were usually actually 12 ft - 1 in diameter and this just enabled them to turn 10 foot wheelbase wagons. However the clearances were very tight and a 13 foot diameter turntable was preferred anywhere where 10 foot wheelbase wagons were turned regularly. The diagram shows just how tight 10 foot on 12 ft - 1 in was.

WagonTT.jpg.e3fc8fe26423487acf356f260a38f776.jpg

 

Thanks becasse,

 

That's pretty much what my CAD work showed - just about possible if everything was perfect but really not possible in the real world - unless anyone knew better!

In OO, you need a bigger diameter table for 10' wheelbase wagons.

 

Just spent an hour watching follow-on films after enjoying the LNWR "Electric Capston" use demonstration/safety film.

 

Many, many thanks.

 

 

Kev.

 

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Posted (edited)

The LNWR, which was a major, perhaps the principal, user of wagon turntables*, had mostly 12 ft diameter tables. These were fine for 19th-century 9 ft wheelbase wagons but when they wanted to go with the early 20th century trend for larger wagons, wheelbase was increased to only 9'9" rather than 10'0" as adopted by other progressive lines, as @Guy Rixon says. This may be why the earliest LMS vans had 9'0" wheelbase even though the design was derived from Midland vans with 10'0" wheelbase. However, the best photo I've been able to find is at Curzon Street, with an LMS fitted van of 10 ft wheelbase being turned - this looks like a 12 ft table. Here's another good view, at Windsor Street.

 

In 00, the narrower gauge gives slightly longer rails but this difference may be offset by the deeper than scale flanges. 

 

*No doubt as a result of being first in the field.

Edited by Compound2632
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Some turntables -- I think not the LNWR ones --- had stops for the wagon wheels, such the capstan man could run the wagon on hard against the stop. Presumably this saved the need for a second man on the brake. I've seen an archive film of this somewhere but can't find it. It may be that the stops made it feasible to position a 10' wheelbase wagon accurately on the table.

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  • RMweb Gold

Thanks Compound,

The extra length of rail due to the narrower gauge is not much (45.07-44.15=0.92mm in 00) but the extra flange depth really takes up a lot of extra rail (44.14-47.35=3.21mm in 00).

(Constants used in the above calculations:- 16.5 18.83 12' 10' 1" 3" Pi)

 

Great Phots - a wealth of detail there.

 

 

Interesting thought there Guy - thanks.

 

 

Kev.

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Talk about timing - I've been meaning to design a better wagon TT for my layout for literally months now; finally got round to starting it this morning:

 

WagonTurntable01.jpg.25d92002237105037bc5e24c92bba9c4.jpg

 

I came across a query & just did a search to try & find the answer, and discover this thread!

 

Jonathan

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  • RMweb Gold

Hi Jonathon and welcome,

 

Although I must say it's partially your fault that I am designing a wagon TT - Your lovely Mills are just crying out for a WTT or two!

 

I know you use LibraCAD but which CAD program did you use for the above 3D rendition of a TT?

 

 

Kev.

 

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Posted (edited)
3 hours ago, SHMD said:

Hi Jonathon and welcome,

 

Although I must say it's partially your fault that I am designing a wagon TT - Your lovely Mills are just crying out for a WTT or two!

 

Thank you Kev! That's exactly why I'm designing this...

 

3 hours ago, SHMD said:

I know you use LibraCAD but which CAD program did you use for the above 3D rendition of a TT?

 

That turntable above is in SketchUp. Although I'm going to have to make it bigger now, as I made the assumption that a 12' turntable would actually be 12', therefore it's only 48mm diameter!!!

 

I'm unsure whether to do this as a 'cosmetic' turntable only, or go the whole hog & try to make it work... :unsure:

 

 

Jonathan

Edited by jrb
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A long time ago I was stripping out an old VCR for salvageable components. Well, you do don’t you.

 

Anyway I took the head assembly out and looked at it. Hmm,  nice spinny bearing that. Very, well, spinny with no wobble. You know what, thats about the size that a wagon turntable would be. Nice wee project, keeps me out of harms way using bits from the junk boxes.

 

So with some copperclad and bits of rail it ended up looking like this;

 

2071468460_wtt1.JPG.c61c51703a7a9ba5936e13756eb14cba.JPG

 

Fine, but what if I wanted to run a vehicle over it, or even turn one ? I accept that this would not be done in reality with a loco of any weight, but perhaps a wagon with a motor in to make it look like it was being hand or horse shunted?

 

So underneath ended up like this. Electronic drive, position sensing and automatic correct feeding of all the bits of rail.

 

621605233_wtt2.JPG.e7fc08db09df57996c011776615e3b47.JPG

 

 

 

Then I bought some capstans, whitemetal, can’t remember from where.

 

952766998_wtt3.JPG.2288bc371508d90727f836477a08f43e.JPG

 

 

Sensible folk would just make them cosmetic really, but meh ….

 

829564527_wtt4.JPG.442b1a1a541e75e3b7b09e688845fd96.JPG

 

One of these days I might make a wee shunting plank and actually use them. Hope thats not too off topic, but might give a few ideas.

 

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Just to clarify: standard gauge steam locomotives may not pass over a wagon turntable? If this is the case, would the same rule apply on industrial narrow gauge lines - in relation to steam and/or diesel and/or petrol locomotives?

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The turntables at either end of the Glyn Valley Tramway, which were obviously used to turn their three tram engines (but not the Baldwin), were almost certainly standard gauge wagon turntables with narrow gauge rails and strengthening plates. While no photos exist of them "stripped down", there is a photo showing the hole that remained post-closure/clearance and it matches exactly what one would expect for a wagon turntable. Circumstantial evidence suggests that they probably came from the Caledonia Foundry at Stoke which was later owned by Kerr Stuart.

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Posted (edited)

There were wagon turntables in the Up Sidings at the west end of Exeter Central station, with a notice restricting their use to certain classes of (small) locomotives. So yes, standard-gauge loco could and did pass over wagon turntables.....

notice.jpg

 

The notice was fixed to the post of the signal which controlled the exit from the sidings. One day the Western Region painters came along to repaint the post......hence all the drips of aluminium grey paint :-(

 

Edited by RailWest
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  • 2 months later...
  • RMweb Gold

I've decided to go for the 13'6" TT, (54mm) instead of the 12' (48mm) version - but as a freelance design with a one road deck, as a through road, and two sidings sharing a common frog coming off it.

That's only 3mm extra each side!

 

Here's the basic design. (I know the planks are too wide, I'll narrow then down a bit in the next day or so).

image.png.5e841c49319bb6c4f32b613ffa66bd12.png

 

A common frog right next to a Turn Table has always fascinated me.

 

Track building wise - it is a challenge.

Electrically - it was a nightmare of the brain teaser of the brain bending variety!

 

I've never built track so using a Peco short crossing is the solution - just use the same crossing angle of 24 degrees and cut off the unnecessary bits.

image.png.0b57d9c87f2e35981b3b37e8f69e8839.png

..and if I mess up the first attempt - I have the other side to get it right before I have to buy another one!!

 

Getting the CAD right was a bit difficult.

 

Here, I have the basic (winning) design with all the (important) construction details shown...

image.png.49152340712c3b85f3b0c8411989ddf0.png

 

..a clearer picture of the electrical circuits required to, not only keep the bridge rails the correct polarity, but also to power the frog correctly..

image.png.b72931ab3bb965883e5f9154a5e515d1.png

(The three purple circles are the electrical contacts to make it all work.)

 

The machined (underside) PCB should come out something like this...

image.png.0531339c083a00138d3e6e1b487fc0b2.png

 

This is the virtual view of the machined single-sided copper clad PCB which will form the basis of this model.

image.png.8f79b191697f38a2149413db6ff8807b.pngNot only will the rails be powered correctly for the road currently set, they will change polarity  if rotated the other way so being 180' out. Not only that, the frog polarity is correctly set for each road and the TT  orientation. (It seems easy now, presented, but this did take a lot of thinking!)

 

 

Kev.

 

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  • 3 weeks later...
  • RMweb Gold

Top deck...

It's a bit age-worn and distressed with some patches added.

 

image.png.e20b9db90d6dec8ffa8f46a3cbf13933.png

 

I'll see about machining this this evening.

 

 

Kev.

 

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