Suspension bridge

[Darren]

The original hangers look like they were made on site by cutting to rod material length, forming hooks on the ends and then bending and cinching them on the wire rope. The wire rope cannot be unthreaded and rethreaded.

I can make new hangers. I just need to figure a way to maintain the distance between the top and bottom rope while I'm fitting and attaching the hanger. I looked at a 300' suspension bridge last night that had been built
by families living in the area in the early 1900's and was still used by vehicles until recently. The vertical stays were much heavier than mine. They looked like at least 2" diameter. What caught my eye was that the stays were attached to the ropes via clamps that had a built in eye.

Finding something like that would make my job easier. I could use those clamps on both the top and bottom rope to attach a come-along on both sides to maintain the vertical distance between the top and bottom ropes while fitting the new hangers.

The problem today is that the average hardware store has no source for something like that. Even the closest wire rope supplier has told me finding the bridge rope isn't going to be simple unless I buy an entire roll. Even getting J bolts to attach the planks meant finding a hardware store that special ordered them.

When you look at the hardware made over fifty years ago, everything is heavier even the nuts.

 

[Darren]

I lucked out today. After searching the internet for wire rope fittings, my third phone call was to a salesman at a company that told me they had the patterns for the original Roebling fittings. The name for what was looking for is a type "A" clamp. No one else had any idea about what I described.

The company does their own forging so any product even if not in stock is available within a few weeks. I should be getting a catalog sheet in a few days.

 

[RobS]

Sounds like you hit paydirt Darren. Be sure to post some before, during and after pictures. You've likely got one of the more unique projects on the board /w3tcompact/icons/smile.gif

 

[Anonymous Poster]

HI DARREN
I WAS READING ABOUT YOUR PROBLEM AND HAD A COPPLE OF THOUGHTS
(1) IF YOU DON'T MIND SACERFICING A PAIR OF VICE GRIP'S TRY USING A PAIR OF C-STYLE VICE-GRIP'S CUT THE GRIPING END'S BACK TO ACOMADATE A SPLIT TYPE SHAFT COLLER THAT IS THE SAME DIA. AS YOUR ROPE. CLAMP IT ON THE UPPER ROPE AND USE A COME-A-LONG TO WINCH THE UPPER AND LOWER ROPES INTO PLACE WHILE YOU REPLACE THE STAY. I WOULD THINK THAT THE CLAMP WOULD HOLD THE COME-A-LONG FROM SLIDING DOWN THE ROPE.
THOUGHT #2
LOOK IN THE OLD BOY SCOOT MANUAL IM SURE THEY GOT SOME SORT OF ROPE KNOT THAT YOU CAN TIE TO HOLD YOUR COME-A-LONG IN PLACE ?
I PERSONALY CAN'T SEE HOW ANY TYPE OF TROOLY WOULD WORK SEEMS TO ME THAT YOU WOULD HAVE TO KEEP HAVING TO PUTTING IT ON & OFF TO GET AROUND THE STAYS?

JUST A FEW THOUGHTS DON'T KNOW IF THEY WOULD WORK OR NOT
ANYWAY GOOD LUCK.

 

[Anonymous Poster]

Two systems of scaffolding are common to the construction of suspension bridges, one being a bosun's chair on a trolly system, and the second is to install a temporary manscaffold using Cyclone Fencing attached to working cables. If you use fencing, be certain to use cross ties on the temporary suspension cables to preclude strain from ripping the fencing apart. This system was used on the Golden Gate, and many bridges since. If you elect a bosun chair and trolley, you will definitely need a helper to crank the chair back and forth.
You should be able to reuse the old suspender rods, assuming they aren't rusted beyond use, by reheating the eyes, and punching the cables out of them with a tapered drift. The tapered drift will leave the eyes open sufficiently to allow for the threading of the replacement cable. After the cable is threaded, you can cold close the eyes around the new cable with a hammer and bucking block.

 

[Hawkflyer]

The trolly idea will work. You need to get a rope and anchor it at one end of the bridge to control the trolly. The rope must be at least 1/2 as long as the bridge. Go to a climbing store and look for either a pair of Jumar or Gibbs assenders (you need 1 pair). You attach the assenders to the trolly using 2 short ropes (one should be a little shorter than the other), the assenders will clip on the rope. The assender is designed to slide in one direction and grip in the other. You will be able to control the movement of the trolly down the cable to the center with great precision. When you reach the center, untie the rope from the anchor and move it to the other end of the bridge.

 

[Anonymous Poster]

Another way of accomplishing travel control is to use a cheap boat loading winch at the bosun's chair, and a travel rope. You put 3 or 4 complete turns of the travel rope around the drum of the winch, and tighten up the travel rope with a comealong at one of the towers.
When you want to move the chair, you just crank it in the direction you want to go.
This gives you fairly positive control of chair position, and doesn't require dependance on gravity. If the chair is on a taught line, you have excellent control.

 

[DocHeb]

<font color=blue>I lucked out today. After searching the internet for wire rope fittings, my third phone call was to a salesman at a company that told me they had the patterns for the original Roebling fittings. The name for what was looking for is a type "A" clamp. </font color=blue>

Did they get you what you needed? Could you pass on the company name?

 

[Darren]

The name of the company is Houston Structures Inc. (713) 678-7998.

 

[Darren]

It's been awhile but the bridge still needs renovation and I still need suggestions on replacing the cables and walkway. This time I have some pictures. The first is the lower stream crossing into the property. At low water as in the picture the crossing is about 50' wide. The creek can go up 12 to 15' several times a year.

 

[Darren]

This is a view looking east at the access stairway at the south end of the bridge.

 

[Darren]

This shows the anchors at the south end with the turnbuckles connecting the cables to the anchors. A quarter is lying on the end of a turnbuckle for scale.

 

[Darren]

This a view from the creek looking east. this gives you and idea of the height of the walkway above the water.

 

[Darren]

These are the anchors on the north end. The walkway is level with a path around the hillside on this end. There are no turnbuckles on this side.

 

[Darren]

This picture was taken standing on the walkway at the north end looking south showing the ends of some of the hangers clinched around an upper main cable.

 

[Darren]

This shows one of the support boards that is attached to the lower main cables with "J" bolts. You can see the nut on the exposed threaded end of one of the bolts in the center of the picture. There are about fifty of these boards on which the walkway is fastened.

 

[Junkman]

Interesting bridge. Who built it and when was it built? I am not sure that I would want to cross it, it seems like a long way down if a board was to fail. I wonder what those turnbuckles are anchored into?

 

[Henro]

Darren,

How about just leaving the old stuff in place and stringing new cables beside it, sort of building the new cable structure around the old...then either just leaving the old there, or taking it down in pieces. You could use a torch to cut the old stuff away in pieces sized so you could manage them...

By doing it this way you could work off the old bridge, perhaps somewhat safely...

Just an out-of-the-box thought... /forums/images/graemlins/smile.gif

Don't know if it is a practical idea or not...but I would consider doing it that way if I were doing it myself. Of course if I were standing next to the bridge I may see a dozen reasons why this would not work... /forums/images/graemlins/tongue.gif

 

[Darren]

The bridge was built by a gas company (maybe Hope Gas) in the early 50's to allow the pipeline inspectors access during periods of high water. Before that the highest flood on record took out all the bridges on the creek. I think that's the reason they built the replacements high off the water. I'm not sure when they turned it over to the landowner, but it was quite awhile ago. The company uses helicopters these days. I've carried tons of stuff across the bridge usually one 50# feed sack at a time. That's usually when I find out that a board needs replacing.

Henro, stringing a second set of cables along the existing set is a problem because you need to tension the cables to attach the hangers. The top cables go through an eye welded on top of the upper cross support on the towers to prevent them from slipping off. You'd have a tough time threading another set of cables through the eyes. It's a thought though.

 

[daedong]

Darren can you still walk on the bridge /forums/images/graemlins/confused.gif