Size question

[DollyDiggerParticipant @dollydigger]

[DollyDiggerParticipant @dollydigger]

Just to help me sort out sizes for the garden i am playing with drawings but i really want it to be accurate, long story but might tell at the next online mtg

What i really really need is the precise dimension of the 3.5" track so i can make a track gauge, or am i not allowed to do that?

Many thanks, Malc

[old martParticipant @oldmart]

Could it be 3.5"?

[Jon LawesParticipant @jonlawes51698]

This isn't exactly what you are after but it may help you derive the answer. My understanding is that it is 3.5 between the rails, inner edge to inner edge, but I would need to confirm.

http://www.cheltsme.org.uk/index-wheel_standards.html

This seems to confirm about the width between the rails:

https://www.homemodelenginemachinist.com/threads/3-5-gauge-specification.20158/

I guess it doesn't actually matter if you are running on wide rails or narrow ones, the only critical dimension there is how the wheels/flanges sit between the rails.

[noel shelleyParticipant @noelshelley55608]

An interesting point in this vein is that our Standard Gauge was originally 4' 8" but was found to be too tight and hence the extra 1/2" ! This was also true for The GW Broad gauge which was in fact 7'1/4" for the same reason !

Noel.

[DollyDiggerParticipant @dollydigger]

Well at first i thought people are going to go well its 3.5" doh, but since when in life has any size that has been quoted is correct to that size? i have 2 size 9 shoes that are different 😀
so i am taking 3.5" to be inside the rails and nothing to do with wheel track and also my question i suppose is 3.5" is it 88.9mm or is there an accepted figure allowance of that?

@Jon, thats mint, you have no idea how long i spent trying to find that type of info, brilliant thank you.

@noel, i wonder what dictates too tight with 4'8", is that the radius curves ? surely you could narrow the wheel track,

need to read on that, new knowledge.

@old mart, 😀 i wasnt trying to be funny just maybe should have put some more text behind it, cheers all.

[old martParticipant @oldmart]

3.5" is 3.5", what ever more would you want, any other answer to your stupid question would be superflous.

[DollyDiggerParticipant @dollydigger]

Wow thats strong words no wonder beginners dont want to ask on forums anymore, some people feel so above us !!!!!!!!!!!

There was nothing wrong with how or what i asked un my mind, having just read the links from jon i am amazed at how important the dimensions are to what was before today a simple wheel.

I really truly hope you never get the need to ask a question to any one about something you dont understand, and dont forget dyscalculia might not be in your blood but it is in mine, should i really have to announce that?

Edited By NUFCBernie on 20/12/2020 20:24:17

[Jim NicParticipant @jimnic]

Ouch!!

Whatever happened to "There's no such thing as a stupid question"?

Jim

[Jim NicParticipant @jimnic]

Double posting removed

Edited By Jim Nic on 20/12/2020 20:26:43

[GeorgineerParticipant @georgineer]

Mart,

It's so nice to be on a forum where people are nice to each other, isn't it? I've heard tell of other forums where people are sometimes quite rude.

George B.

[Paul KempParticipant @paulkemp46892]

Treat it as 3.5" between the rail heads on the straight, depending on the radius curves you might be thinking of using then you might want to consider gauge widening of the track on the curves, the amount depends on the wheel base of the loco's you are intending to run. For example a short wheelbase 040 would probably cope with an 8' radius in 3.5" but a 6 coupled might need the gauge pushing out by up to 1/8" if you want it to go round the corner! For example a 6 coupled 5" gauge loco won't go round much less than a 30' radius curve without slight gauge widening. The back to back dimensions of your wheel sets will also govern points and check rails. Best to go with a standard, there are a few around certainly for 5" gauge, if you can't find one for 3.5" then you can scale it within reason.

Paul.

[john halfpennyParticipant @johnhalfpenny52803]

Bernie, I thought your question quite sensible. The very intemperate response deserves a forum ban.

[Phil super7Participant @philsuper7]

You can see why i don't post very often.

[Peter G. ShawParticipant @peterg-shaw75338]

Hello Malc,

I don't run locos of any description, but in an attempt to make up for the rudeness shown earlier, may I point you at Tubal Cain's Model Engineer's Handbook, specifically pages 13.15 to 13.18 where he discusses track & wheel standards. For 5 inch gauge, he shows back to back wheel standard of 4.687 inches or 119 mm. There is a lot more as well, but nothing that states that the track standard is anything other than 5 inch. or 127mm.

Hope this helps,

Peter G. Shaw

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 20/12/2020 20:17:15:

3.5" is 3.5", what ever more would you want, any other answer to your stupid question would be superflous.

.

Don’t people use +/- dimensional tolerances where you come from ?

Malc’s question seemed perfectly reasonable to me … but I don’t do trains, so had no idea of the correct answer.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Malc,

Here’s a tolerance for ‘full size’ track:

HOW WIDE ARE RAILROAD TRACKS?

The US standard railroad gauge is 4 feet, 8.5 inches (Gauge means width between the two rails). The U.S. federal safety standards allow the standard gauge to vary from 4 ft 8 in (1,420 mm) to 4 ft 9 1⁄2 in (1,460 mm) for operation up to 60 mph (97 km/h).

Ref: **LINK**

Railroad Facts… Construction, Safety and More.

… Presumably there must be something similar relating to 3.5” track, although I doubt if it’s directly scaled.

Please don’t give up on us just for one member’s rudeness.

MichaelG.

[Nigel Graham 2Participant @nigelgraham2]

Right, some numbers at last… And amplifying Jon Lawes answer.

My source is Martin Evan's Manual of Model Locomotive Construction, and differs little from the Cheltenham table cited by Jon. See his reference for a diagram.

3.5" track gauge : Min, curve radius 14ft, recommended min. 30ft.

Note that Evans does not go into track design so gives no figures for gauge-widening on curves, but a study of the dimensions and some drawing should give you a guide. The wheels are meant to run with a slight gap between rail and flange, on the straight, but obviously not overdone! So, this is what Mr. Evans gives

Wheel-set Dims, inches rounded to 2 dec. places

Back-to back (i.e. between the inside faces of the flanges): 3-9/32 = 3.28. (important for point-work and crossovers)

Wheel width (or thickness if you like): 13/32 = 0.41 (Cheltenham quote 0.375)

Flange thickness 5/64 = 0.08

Flange Depth (root to tip) 1/8 = 0.13

Coning (taper) 1 in 20 or 2.8º ( 5 – 6 º included. Don't exceed the angle)

That gives an outer flange dimension, or front to front as it were, of 3.12 inches. That does not account for the root of course, which takes up much of that 3/16 " a side difference

The thinner wheels the Cheltenham club specifies are probably nearer scale, but the Evans dimension may allow for more latitude in practical building of tracks. The Cheltenham society's track is of aluminium rails and their site says, for its longevity will not allow access to locos and rolling-stock with wheels not to specification. (I imagine other societies with similar rails would say the same.) These are all for models of Standard-gauge prototypes.

So – I am assuming you already have the loco and rolling-stock. I would first verify their wheel-sets' dimensions in case you need alter the track gauge slightly to allow for that, in proportion to the above dimensions. Be careful though because that may preclude future running of a locomotive built to standard.

Otherwise build your track to 3.5"g., but determine if you need widen that slightly on the curves, and by how much.

My own club has a ground-level 5 and 7.25 " g track, and uses two groups of setting-gauges each consisting of an aluminium bar with notches milled in it, one for the straights, the other for the curves. Two or three gauges are a placed a few feet apart on the track as it is laid. Ours is of flat bar, not prototypical section, but the principle is the same.

'

I tried to view the homemodelenginemachinist reference but it obviously contains something Very Naughty, because my BT "Parental Controls" blocked it! BT asked if I want access – yes – but then the page came up as " can't be displayed " . Good thing I am over 18.

[Martin WParticipant @martinw]

O Mart

I would think that an open apology would be in order after such an acidic post – perhaps the old advice of " If you haven't got anything good/constructive to say then keep quiet ". As others have said it was a perfectly reasonable question as tolerances can vary and the given measurement/dimension may only be valid under certain conditions i.e. straight runs of track or whatever.

Martin W

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I'm interested in railway locomotives and a general interest in railways and I do like a good railway journey, but as for track laying technical information, I know next to nothing, so I think the OP's question is valid. No question is ever stupid.

Regards Nick.

[Peter G. ShawParticipant @peterg-shaw75338]

Hi,

It seems I made a mistake by thinking it was for 5 inch gauge when it's actually for 3.5inch gauge. Nevertheless, the reference I gave still stands although the figures I gave are irrelevant for this question.

Sorry about that.

Peter G. Shaw

[Nigel Graham 2Participant @nigelgraham2]

Bernie's question is indeed valid, and he and some of the responses show an interesting point.

There is plenty of information, hand-books etc. on building locomotives and rolling-stock, but I do not recall any similar literature on building the track.

I don't know how much there is the homemodel… reference Jon Lawes gives, but that's because my ISP and computer won't let me read it!

Yes, individual articles appear from time to time on such matters as making points, individual clubs' own track-building projects, HSE advice on line-side clearances… but a hand-book that collates the design side? Maybe one for the TEE 'Workshop Series' – that's the sort I have in mind.

I suppose the difficulty is someone with sufficiently broad experience of building railways from outdoor 16mm-scale up to 7.25 " gauge, permanent and portable, coming forwards to write it.

I might be prepared to help write one but as a technical writer, not a technical consultant. I have helped build fixed and portable tracks, but not design them. (Apart from a 7.25 " g oddity outside of model-engineering, and using wood and old bed-frame angle-iron!)

[David Davies 8Participant @daviddavies8]

Nigel Graham wrote "There is plenty of information, hand-books etc. on building locomotives and rolling-stock, but I do not recall any similar literature on building the track".

Martin Evans wrote a book 'Outdoor Model Railways' in 1970 which contains chapters on track and track laying. The content includes reference to gauge widening on curves, super elevation and transition curves or 'easement spirals'.

There is also much information on rolling stock, passenger cars and signalling.

Copies will surely come up from time to time on the second hand market. I bought mine for £2 as an impecunious 12 year old in in 1970,' hot off the press'.

HTH

Dave

[Nick Clarke 3Participant @nickclarke3]

This is a link to the Bristol table of wheel and track standards, which itself is a reference to the SMEE standards of 1976.

**LINK**

But just because these are 'standards' does not mean that all published designs follow them – Martin Evans gives 13/32 for the with of the bogie wheels of 'Columbia', to give just one example.

[Dave HalfordParticipant @davehalford22513]

Malc,

You can gauge how you want, it's your track.

Personally I think you have to gauge it to fit the garden as a Black Five needs a much shallower curve than a Tich for the same gauge.

Most published info is meant to cater for club tracks with a necessarily broad spread of wheel layouts to cater for everybody. You can go much tighter is you have to.

Just use your longest truck (riding truck?)

[Author]

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