Any of you engineers know how much it takes to bend railroad track?

[Dargo]

The reason I ask is because I built a zip line across my lake and used a 10' section of 1945 dated standard railroad track for the termination post. I sank 5' of it in the ground, digging the hole with a 24" excavator bucket, and filled the hole with 32 eighty pound bags of concrete mix; figuring that would give me 2 yards of concrete on the post. I also welded various 'appendages' on the lower portion of the track to give the concrete more to hold.

I wasn't planning on putting a tension wire off the back side of the short post to help hold it. Unfortunately, I think I bent the track. I'm still working on finishing the project, but it's operational and has had dozens and dozens of runs on it. The starting point is at the top of a 26' long 12" I beam with 3/8" webbing and 5" wide sides. With that I beam, it's buried 6' deep and concreted like the train track but it does have a guy wire off the back going to the bottom of a tree in the woods. The 20' I beam also sits on top of a 5' tall hill; giving me a full 20' of drop over the 350' distance of the zip line. The speed and action of the trolley seems to be just right.

I am going to start the process of building a platform around the I beam (rather than the temporary ladder that is attached to the beam) with bench seats and even a fiberglass slide off one side. I'm going to use six 6X6 posts for the platform as it will also be used to prevent the slight side to side motion I get from the beam when someone heavy gets a bit wild on their zip line ride. Anyway, it seems to be holding fine, but it looks like the railroad track has bent about 2".

Is that possible? I have 2 different trolleys and each are commercial models with a 14,000 pound WLL as does the 3/8" cable. Do I need to add a cable and turnbuckle to the back side of the railroad track or maybe has the cable just stretched a bit and I just need to tighten the turnbuckle on the main cable and the guy wire cable on the tall post? Thoughts?

 

[Bill_C]

Railroad track is relatively easy to bend, when I worked in a mine 30+ years ago we had a portable track bender (could easily be carried by one person) that was basically just a big screw jack.

Track is great for rolling stuff over it, but as far as structural use, IMHO it's not that great.

And putting cables with turnbuckles on the back would definatly help.

 

[BHD]

I can not tell you how much it takes, but a lot depends on the leverage one has to bend it, and the depth (height) of the track and the direction of the pull, to the structure of the track,

but if you take a zip line, and stretch it out straight and add a few hundred pounds in the center there is a tremendous amount of pull on the anchors,

take a look at this first chart PNNL: Hoisting and Rigging Manual - Slings

even to get the cable straight one has a fair load on it before any additional load is added, and when you have a cable that stretched out straight supporting a load the load on the cable is multiplied (according to that chart at 5 degree, and your most likely less than that, the cable is 11.490 the original load), and if it is less than 5 degree angle it may be much more, so a 200 pound load on the cable is in excess of a 2000 pound pull on the anchors and the stress on the cable is in excess of that as well, then put a little bounce in it and you could possibly be exerting 10 to 20 tons of force on the anchors and cable, depending on where the bouncing takes place, and the amount of it.

I would my self consider 2 dead men anchors, on the post with about a 30 degree spread, so it helps eliminate any sides way forces exerted on it as well,

this is the way I am seeing it,

 

[Baby Grand]

I second all of BHD's comments - especially the use of multiple guy wires to avoid buckling the RR rail "mast". What you have constructed is basically a toggle mechanism - think "chain binder". This mechanism is capable of greatly magnifying the applied loads that it supports (trolley + riders + cable weight + cable tension + dynamic/bounce loads). Examine how a suspension bridge requires massive anchorages to hold those spindly, long cables to get an idea of the forces you are dealing with.
-Jim

 

[Kernopelli]

Interesting but impertinent.....during the civil war, in order to disable the rail ways ( supply lines), troops would take the rail sections loose from the tracks and place the center section of a rail in a "camp" fire. After a little heating, 6 men could bend the rail into a pretzel around a tree, rendering it unusable. Moral of this tidbit: RR rails aren't necessarily as stout as they appear to be.

 

[doall]

just tie your old ford behind the railroad rail. but first beat it back straight with your hf claw hammer.

 

[Willl]

Ah c'mon Dargo,,,,You built a cable run and didn't post pics of it ?

Me and my brother have long talked about one across his creek valley.

Pics please.

 

[Bedlam]

:thumbsup:YES pics ...

 

[Dargo]

These old arthritic hands are having a hard time moving this morning, but I'm working on building the "launch" platform as well as sinking a 8' long 6" I beam completely into the ground on the termination end so I can help the wimpy 5' section of railroad track above ground (5' below ground with 2 yards of concrete but track bends). In this pic it was just setup for temporary use for a graduation party.

My daughter graduated valedictorian of her HS class and we had a big party here and I just got the zipline operational. You get to travel 350' over the pond, over the edge of the island and, if I move it, through the fountain, as you cross the pond. Can't see much in the pic but my old hands are moving slower each day and the launch deck may take another couple of weeks to complete the way I want it; with seats on the sides and a 10' slide off the side in case you change your mind.

 

[Travelover]

Dargo, we want to see a picture of YOU on that zip line! :laughing:


Congratulations to your daughter.