How would you build this bridge?

[jymbee]

I've got two sections of railroad track-- about 20 feet long each-- spanning a small stream, resting on two very large rocks at each end. Next step is to add some planking but not sure just how the best way might be to do that. Pretty hard driving nails or screws into that iron!

I'm thinking the final bridge should be around five feet wide. The heaviest load on it would be our John Deere 748 garden tractor. Any suggestions?

 

[M5farms]

If you can secure the track where it will not separate you could cut 2bys to span inside the rail and then run another 2by6 beside the rail to give you a stringer to nail too. then your planks can lay on top and fasten

 

[M5farms]

Pardon the rudimentary drawing but you should get the drift .

 

[jymbee]

Right. I had thought about something like that. Keeping the rails from separating is another issue that I'd like to incorporate into the final structure as well. I suppose some kind of cross section welded in would accomplish that but I don't have a welder and it's in a pretty remote spot to get at.

In the past we've had a pretty simple wooden bridge here but the stream really rises with a good rain storm and that washed away often. The iron is quite a bit higher now and given the extra weight the hope is that even if the water were to get that high it would stay in place. Probably add some kind of "anchors" to make sure of that.

 

[jymbee]

Looks interesting but not quite sure what I'm looking at with respect to materials?

 

[M5farms]

If the rails were upside down it would simple to lay the planks and attach a cleat to the under side to secure them and much cheaper

 

[check]

<img src="http://www.tractorbynet.com/forums/attachment.php?attachmentid=507571"/> Pardon the rudimentary drawing but you should get the drift .

Interesting project. How long is the span? Maybe you could drill holes in the bottom part of each railing, and then bolt something across the bottom every 4 feet or maybe 8 feet. Then bolt A few boards in between the channel, and then run your main boards longitudinally.

 

[jymbee]

Interesting project. How long is the span? Maybe you could drill holes in the bottom part of each railing, and then bolt something across the bottom every 4 feet or maybe 8 feet. Then bolt A few boards in between the channel, and then run your main boards longitudinally.

Might be really tough to drill any size hole through the rails? They're pretty darned "dense". I think the issue with the longitudinal route would be simply a matter of strength. I envisioned setting the distance between the rails to match the wheelbase of the tractor thus providing maximum load bearing.

 

[2LaneCruzer]

I would think that once you figure out how to keep the rails separate (welding angle iron spacers would work if you have a welder), you could attach a plywood base with U bolts, and nail or bolt planking to that?

 

[RedNeckRacin]

I don't think I would recommend using those rails for beams. You better check the bending deflection and have enough bracing to prevent the rails from rolling. While in theory they may seem ideal, the distribution of the material in the cross section isn't quite right for a beam application. I'm not saying it can't be done, its just no ideal. What type of weights are you thinking about running across this bridge?