What size girder bridge?

[DavidEnghauser]

As I have outlined before I am incorporating an 009 gauge section with my 00 gauge main area. Using the Bachmann Baldwin loco. on one stretch of track I am planning to use a girder bridge with the 009 portion, crossing over the 00 gauge track. What gauge bridge should I use? N gauge or 00 gauge?

Hope this is clear.

Thank you. David

[Bandit Mick]

I would guess OO for the girder bridge because track is n but buildings would be scaled 4mm to the foot. I may be wrong. Hopefully someone else will confirm.

[Walkingthedog]

If 009 is 4mm to the foot then you will need an OO bridge otherwise the permanent way staff who may need to walk across it will bang their heads.

[Mountain Goat]

N gauge will suit some 009 layouts but the only downside is that any rivits or bolts will be half the scale. 00 gauge girder bridges can look a bit overdone as standard gauge axle loads are normally much greater then they are with most narrow gauge lines. There are exceptions to this...
My advice is to look at as many photographs of both to help you decide.
Girder bridges came in many sizes according to the expected loads the railways were built to take along with the length of span etc. So what maybe an idea is to decide if your narrow gauge railway is a lightweight, mediumweight or a heavyweight type of line. You mentioned a Baldwin. You are close to a heavier built narrow gauge line to begin with so that does give a rough guide, as Baldwins...Even the smaller ones were pretty large compared to many of the UK narrow gauge lines. Railways like the Welsh Highland or the Ffestiniog were able to carry heavier loads, and be able to take Baldwins (Though I seem to remember that the Ffestinion only had so much width to play with) but lighter lines like the Tal-Y-Llyn or the Corris so they only had lightweight locos to take much shorter loads means that they did not need such heavy duty rails and therefore their bridges and viaducts did not need to be so strong. It does not mean they did not make them stronger then needed with the hope that traffic would increase... As it was always a gamble. One could build a viaduct half price if one could predict the future and assume that traffic will stay the same, only to find one was wrong and have to replace the viducts and strengthen the bridges at a later date and thus spend a whole lot of extra money then one would do if one had planned ahead.

But in general, to have some idea of your lines traffic... A Baldwin sized loco would be expected to pull fairly lengthy trains at faster speeds.. A little Hunslet would be pulling shorter trains at generally slower speeds.
I would probably consider a smaller 00 gauge viaduct. One built for branchlines? But first take a look at the prototype for examples.

[Mountain Goat]

If 009 is 4mm to the foot then you will need an OO bridge otherwise the permanent way staff who may need to walk across it will bang their heads.

Good point.

Actually, I would follow prototype practice and scratchbuild a suitable viaduct to suit the location. The real narrow gauge pioneers would have done this and had their engineer do their calculations.

[teedoubleudee]

I now this is an old thread (June 2022) but as I shall soon be embarking on a new 009 layout project I have been collecting as much information from this and other on-line sources before I begin early next year (not long now ).

My (current) proposed layout will have two rail-over-rail bridges which will be very short and I've been looking at various options. There is a very nice N gauge laser cut mdf kit available which would have been perfect width wise but it has overhead cross members which the Bachmann Baldwin locos would not have passed under. So I've decided on the ubiquitous Peco lineside girder bridge sides in N gauge (image below). The reason being is the width is as wide as you want/need and the length will suit my requirement for a short crossing.

I'd dearly love to know how the OP, David got on with his project and maybe a picture or two.

[Walkingthedog]

June 2020 TWD

[teedoubleudee]

June 2020 TWD

Mmmm, should have gone to you know where!