This is the fanciest one I

This is the fanciest one I have ever seen. I worked on this about 10 years ago. If I recall correctly it is 6 railcars welded together, off site, in pairs. This is a county road that used to just run through the creek. This is an affordable solution for us in more rural counties. I am not looking to build something like this, but I thought it was a pretty unique example. 

A more typical example

This is a more typical example. This used to be a culvert but a significant and very active land slide had us bring this flat car in. While it may look temporary, this bridge, and one just like a few miles south of this one, are most likely there for good. I wish they would come to us with the reporting marks still on them so I could research the flat car a bit. 

this one is private driveway....

in Gowanda Ny

https://www.google.com/maps/@42.4475956,-78.9417725,3a,32.8y,43.1h,79.61t/data=!3m6!1e1!3m4!1sLhdcU-UqVjXGb_Ggvuhfkg!2e0!7i13312!8i6656

Peace Bill 

yes

I see them quite often installed on private property as well. 

....I just never see them modeled. 

I've seen the private driveway ones.

That one is actually pretty high class, having guardrails and all.

For modeling, I'd stick with the shorter cars, for a couple reasons. The first is we never have enough space. The second is that a shorter flatcar is more likely to have been sold off at some time in the past.

I  actually recently had the

I  actually recently had the thought of doing this but I don't have any "junkbox" flatcars lying around and don't want to sacrifice a good one.

Arizona

in the middle of no place Arizona over a wash is a Sothern Pacific flat car bridge over a wash

Jeff

I agree with using a shorter one. I would love to see someone who has modeled one. 

UP uses them on their access roads

Over the last 20 to 30 years the UP has used old flat cars to eliminate a number of fords and dry gully crossing on their trackside access roads.  Otherwise, the other times I've seen old flat cars used as bridges they were nowhere near the tracks.  And very few of us have the room or desire to model the stuff that isn't next to the tracks.

Scott Chatfield

Following through

I'm following through on this idea and I'm about to order a couple of "junk" flatcars on E-bay for a scene on my module. My thanks to the OP for the inspiration. I think I'm going to do something similar to the pic Bill posted of the private drive. If anyone is interested in what I'm doing, they can check out my blog entries on the module. I'm getting excited about how this might turn out!

Abutments under the bolsters, please

Remember to put the abutments under the bolsters of the flatcar, not all the way at the ends.  I've seen at least one real-world example of a flatcar-turned-bridge installed wrong.  I'm sure my SUV would safely cross it.  But I wouldn't drive a full size truck (dump truck, tractor trailer, etc) across it.

Just sayin'

Scott Chatfield

...

Scott,

Nobody in the real world cares if you think they were installed wrong with the abutments under the ends instead of the bolsters, because most people install them with the abutments under the ends.

What you ask would sacrifice a good 10-20 feet of useable bridge on each end and that's just not necessary.

Ends vs. bolsters

Hi,

that is an interesting question - is the flatcar bridge supported at the ends or the bolsters... I'd guess it's a question of load capacity.

What kind of load does a typical, somewhat older, flatcar carry? Let's say 80 tons (~160 thousand pounds)? If supported by the bolsters. Now, a typical road car does not weigh that much (some SUV are close

If the flatcar is supported at the ends, I'd guess the load capacity is half that or less, which would be between 20 and 40 tons (~40-80 thousand lbs). That would still be rather good for a driveway or a less-traveled road.

I've seen driveways built from just a slab of pre-stressed concrete. Mostly in places where agricultural equipment would use these.

Obviously, that doesn't take into account any dynamic effects of a car bumping its way across the bridge, nor the weight of the road surface itself. And it is just a rough estimate.

Have fun and stay healthy

PS: just last week an old military bridge was installed as access road over a creek not far from where I live. Just as non-permanent a solution Though, an old flatcar would look more nicer!

Dark2Star

Engineer here, your biggest concern will not be span so much as whether or not they've put the support onto the central beam or not. If it's off, or if the weight shifts to the outside of the flatcar, that can cause a twist to the general structure. If you secure the central support beam of the flatcar, you probably only increase the overall span length by about 4'-5' (2'-2.5' on either end), which will probably only decrease the loading capacity by about 10% or so. Considering a 45' flatcar's maximum loaded weight of 180,000 lbs (we're using 1940's numbers here), and a flatcar weight of 51,000 lbs, you'd be looking at a maximum weight of 64.5 tons on the flatcar. A 10% reduction would keep you at 58 tons, well above most equipment.

Load capacity

Well, in my little freelance world at least, this bridge will be on a secondary mountain road. Practically speaking, I'm using it as a view block. I doubt I'll do much detailed modeling of the abutments, only the end and one side need be done because the rest doesn't show. I may even set one end right into the "rock" of the mountainside.

Here are a few more

 This one was placed as a detour while our erstwhile bridge crew repaired the covered bridge. I know for a fact that the bridge crew would rather leave the flat car and knock down the covered bridge. People love covered bridges...county bridge crews, not so much. 

scary one

 Looks ok...at first, but it was just set on old redwood logs that rotted away. 

this one has reporting marks.

My thanks Devin

I was just about to get around to doing some research and pic searches. Those are some great examples and they give me a lot of inspiration.

No problem

I could post photos of these all day long. We employ these bridges quite often.

this one...

This one goes in each summer when the river gets low...and when the river rises, we pull it out. Gives the people on the other side of the river a shorter drive to 'town'. 

A Rail Served Industry

There was a company in Oregon who deals with cleaning up derailments along with doing some contract and railroad operations that purchased a bunch of old auto racks. They then shoved them to an end of a spur where they would cut off all the super structure leaving the flat car. They would then stack the flat cars up and ship the scrap out in gondolas. The trucks and air systems were salvaged for parts and hauled away. The flats were then taken to a location where railings could be added at the customers specification, they would then truck them to there new location and set the bridge. 
 

I always thought it would make for an interesting modern rail served industry. 

Example of modelled bridge on this site

You said you were looking for an example of someone that modelled a flatcar bridge.  That reminded me of an amazing diorama that I once saw right here on MRH.  Eventhough it is used as a bridge on a small little gravel road, it has always stuck with me, and I have always kept it in the back of my mind to model something similar on my own layout one day.  Here's the link:

https://model-railroad-hobbyist.com/node/13383

There is also a video of this diorama on Youtube I think.

Regards

Stefan

@Stefan

That is exactly what I was looking for. Thank you for sharing that. What an example!