G3 Clubroom

The Forum for Gauge 3 Model Trains

Quote from: Peaky 556 on Sep 04 2013 13:52
In anticipation of 'getting away' with the project thus far, I would like to progress some concepts for the bridge design, so as to have some more things to dream about whilst at work.  I quote Andrew Foster below from another topic, and am intruiged by this metal section mentioned below:
Can Andrew or anyone throw any light on what section type and size we are talking about, where it might be available (short of digging up signposts by moonlight) and in what lengths?  The best I have come up with so far is 25mm square hollow section mild steel in about 3mm wall thickness; very very substantial but a bit OTT in terms of weight and strength. 

Regards, Tim 

I've just realised that I overlooked the question in your post (I was out of service for bodywork repairs for some time!) but have a shot of the type of post I was talking about. This in fact shows two of them, face to face, and they are 3.5" wide (but I can check that).  My friend uses them as an inverted top hat on which he lays his track. This one looks like a fairly heavy section, and I think there are some made of lighter material. You can easily get a 6 ft span using them. Around here, I think they are available at builders' merchants - unsure of UK sources.

Andrew

This looks a good way of making some garden track.  How does he create bends?

Regards
Jon

I haven't seen his railway for a while, but I don't think he would have curved bridges.  The posts are probably too narrow to allow for a curve to be made up in the usual way from short straight sections carrying a curved track, unless you use two, side by side.

Andrew

Whilst waiting for some moulding compound to arrive for stonework in the cutting, I have been giving my bridge more thought, to start on some CAD drawings for component parts.  I'm just being held up for a source of suitable steel channel section.  These will be the long straight members that carry the track bed, visible above the arch of the Arley bridge.  I am looking for something around 40 x 10 or maybe 40 x 15 mm as channel pressed from light gauge steel.  If only I could find the industry that uses this stuff I would know where to buy it.  Steel stockholders tend to stock much heftier channel section, say 3mm thick and too wide.  Far too heavy for my purposes. 
I have found some galvanised channel in my garage of approx the correct size, but not enough of it and I don't know where it came from!
I'll try and show a picture of it below, in case it jogs any memories...
Cheers, Tim

Tim,

Try this .... otherwise it looks as though square tube/box section 40 x 40 and a session with the angle grinder may be only alternative.

John

http://www.drywallsteelsections.co.uk/assets/files/literature/Drywall-Light-Steel-Framing.pdf

See catalogue section :
Heavy Gauge Channels
Code No. DSC2
C x D x E (mm) length (mm) gauge (mm)
19 x 38 x 19 (3600 long 1.6mm gauge)

Other channels from 0.5mm - 3.0mm up to 4m available upon request.

Tim,

Try googling for 'MF7' and/or 'primary channel'.
15 x 45mm section, around 1mm gauge, seems to be a standard size for suspended ceilings.
Some seem to come in a 'crinkle texture' which I guess you won't want!- I assume gives greater strength for a given material gauge.

Or a variety of sections here - http://hire.ccfltd.co.uk/productinfo/downloads/Tradeline%20Range%20Guide.pdf

Andy

It's strange that this topic is on the forum as I was going to ask;  Are there any plans available for bridges either in steel or wood?  I need to build one for my out and back layout whose start is getting closer and closer.

Regards
Jon

John and Andy,
Thank you guys very much, you have identified the channels I have as drywall sections, which I take to be for framing/erecting partition walls in offices etc. I am now in the know!
I have made enquiries with one and will ring the other tomorrow.
Jon, I don't have a plan as yet but you will be welcome to mine once I start to build.  It will be large however at 4.9m span!
Thanks again, Tim

Thanks to all, I have selected some "TradeLine" channel section 38 x 19 x 1.5mm from a local stockist at only GBP5.80 for a 3.6m length.  I call that good value!  It is also identical to the lengths I already have, so I can consume that surplus too which is a bonus.
I had already researched cable ducting companies but to little avail.
Bridge design will now commence!

Jon - what did you have in mind? I have looked at pictures of hundreds and there is a huge variety of styles, such as bowstring, girder, arch and factors such as intermediate piers, stone-built, steel, cast-iron, concrete, surrounding terrain, the need to be able to walk along yourself for retrieval, whether the train should sit on top of and be seen, or pass through, are all factors to consider.  There is also your skill at metal cutting, carpentry, resin moulding or concrete to take into account too.    My advice is to take something attractive to your eye and fudge it with the materials you are comfortable working with.  In my case I have a pond to cross and that ruled out intermediate piers.

Regards, Tim

Here is a good little book to illustrate differing bridge styles, periods, their uses, limitations and materials. Contains lots of photosand discussion.  It is by Countryside Books.
Cheers, Tim

Another potentially useful book is 'Bridges for Modellers' by L V Wood.
Originally a hardback from Oxford Publishing Company in 1985, I see it has now been reprinted in paperback.
It is definitely not a 'how-to-build-model-bridges' book (I'm not sure one exists, certainly not for the loading that G3 models provide!), but does explain different construction types, etc. Maybe a bit dated now - but worth a few beer tokens if you happen to find a copy in a second-hand box somewhere.

Below are a couple or review comments pinched from Amazon
"The author explains all major types of bridges: how they are are built, what they look like including upside as well as the underside of the bridge."
"If you are wanting instructions on how to build model bridges, this is probably not very satisfactory. On the other hand, if you looking for inspiratin as to what type of bridge will fit a particular situation, this will almost certainly provide something to meet your needs".

Andy

It would be worth taking a look at the website of MVL Bridges:

http://www.mvlbridges.co.uk/

He uses commercially available aluminium section (mainly from B&Q) to make what are very strong large scale girder and other metal bridges.

Ian

Gosh, what a lot of helpful information, thanks everyone.

I've ordered a copy of,
'Building Bridges and Viaducts for Model Railways' by Bob Alderman,
'Model Railway Constructor' Feb 1963, that has an article, A Brunel Bridge in O Gauge,
'Model Railway News' July 1965, that has an article, Timber Trestle Viaduct.

I realise that these are all a smaller scale than G3 but it should point me in the right direction.  I like the idea of a Brunel type of bridge in timber but......

Regards
Jon

Jon,

The late Robert Head had a couple of Brunel timber viaducts on his Gauge 1 line at Shifnal and they seemed to work well.  Each contained a lot of parts, but didn't look particularly difficult - though that's easy to say when somebody else is building them!  I suspect there are drawings of these model bridges somewhere.

Robert was a civil engineer and his line had many bridges.

Mike

If you want the drawings of the brunel viaduct try Pendon museum as they have a layout there with the brunel viaduct on it

Mark