Model Railway Forum

Rather than using documented data on preferred heights etc what I did was much simpler. I placed a piece of rail flat on the baseboard and put on it my tallest locomotive and rolling stock that I intended to run on the track. I then placed a straight edge across it supported on both sides with anything that came to hand until the loco/rolling stock could just pass underneath without touching. I removed the track and measured the distance between baseboard and straight edge, added 5mm and that then become my datum. Simples.

Walkingthedog wrote: ↑Mon Jan 03, 2022 2:16 pm When I added a bridge I measured from the top of the rail to the top of my tallest piece of rolling stock then added a bit for clearance.

I didn't see your reply Brian before adding my own LOL. Great minds etc etc.

I agree Terry, not often my mind is referred to as great. Thank you.

Steve M wrote: ↑Sun Jan 02, 2022 5:26 pm Yes, I did look - very carefully.

I think you're worrying about nothing there, it looks like more than a coach length so should be fine. This is what I've found when discussing inclines, some modellers seem to think they are far more trouble and difficult to construct than they really are. My technique was slapdash and I've never had any kind of problem. Heck you can see from this image how slapdash I was:



I didn't even take the time to lay the track straight!

As for easements I just worked out the length based on 2% then made it 'a bit longer' and when constructing the ramp left gaps at either end so that the rail would sag 'as it saw fit'.

I have diesels, a 4-6-2 and even a 0-6-0 that can happily pull a metre long train up my inclines. There are some basic rules about inclines but I see nothing in that layout that violates them and if the OP says trains will run then all seems fine.

I’ll not apologise for offering sound advice based on a good few years experience. It’s up to you whether you take it or not.

Sorry all responders, but anything over the tracks on a OO layout needs to be a minimum of 60mm above rail top of the lower track to the underside of that above. This is the very minimum space needed.
Its never taken from the lower level of the baseboard surface, but is taken from the rail top of the lower track to the underside of anything above!

When I look at track plans I do not see what others see. Sometimes advice is given and is not what the OP wanted in the first place. That is one reason I do not offer any.

What I look at is the possible scenery that is to be added to a plan. Once that scenery is in place how easy is it for maintenance of track etc.? Some plans look simple to maintain, others look a nightmare. Not many, (in fact very few) plans that are a nightmare, last long.

Like I said I am not offering any advice. Just my take on things.
I wish Mick B well in his endeavour.

Glencairn

No, commercially made model bridges do not use a common deck height/thickness, if that is what your asking?

Brian wrote: ↑Mon Jan 03, 2022 8:20 pm Sorry all responders, but anything over the tracks on a OO layout needs to be a minimum of 60mm above rail top of the lower track to the underside of that above. This is the very minimum space needed.
Its never taken from the lower level of the baseboard surface, but is taken from the rail top of the lower track to the underside of anything above!

Brian, I can only think that this 60mm minimum height above rail tops referred to is for prototypical appearance rather than actual necessity on 00 gauge models as is proven by the photo attached. Given the space restraints that most of us live with, sometimes it is just not possible, or even desirable, to achieve certain limits just to stay in line with prototype practice just for the sake of it.

In my particular case, referred to in post #16 above, I have a branch line that runs under another line. The two lines, though never connected to each other, reach the same height at the far end of the layout. This is achieved using the 50% up and 50% down method. This lower branch line is ONLY ever served by a pair of diesel railcars and so they these were used in determining the lowest safest height for the over bridge. As seen in the photo, the steel rule (resting on the rail tops) shows a distance of 55.5mm and an ample clearance above the railcar's roof of approx 7mm. After many hours of running I can confirm that there have been thus far no incidents of contact between loco roof and the bridge

I'm not trying to be contentious here, just merely pointing out that sometimes hard and fast "rules" can be manipulated in certain circumstances to achieve personal requirements.

Hi
The OO 60mm rail top to underside of a structure is from the BR structure gauge scaled to 4mm/foot. Which is roughly 15ft above rail top.
It is the minimum allowed on the real thing. What individuals set their layout too is up to the owner. I'm just stating the scaled minimum which should easily allow clearance for all OO items.

As can be seen in this picture of the Hornby Breakdown crane fully lowered and passing under my own bridge that is at 61mm above rail top. It just passes under with about 3mm spare.