Scratchbuilding Towers for a Vertical Lift Bridge

[mbinsewi]

Looking good Rich .

I didn't realize that the actual lifting was done at the control house, and the big sheaves on top were just part of the counter weight set-up.  

With all the pictures in the link that Ed posted, I had to look through them until I found the cable and sheaves along the top of the bridge, and then I seen the picture with the two huge pulleys on each side of the control house.

Have you found something decent to use as the cable?

Mike.

[richhotrain]

mbinsewi

Looking good Rich .

I didn't realize that the actual lifting was done at the control house, and the big sheaves on top were just part of the counter weight set-up.  

Have you found something decent to use as the cable?

Mike

Thanks, Mike. I have not yet settled on cable. I have been checking various alternatives, but I need to physically view the possibilities. If you noticed on that diagram that I posted, there are two different types of cable which I depicted in red and blue.

The cable (red) that is strung over the sheaves up on top of the tower platform connects the bridge to the counterweights. On the prototype, there are 16 cables running over each pair of sheaves, for a total of 64 sheave cables.

The cable (blue) that is strung over the pulleys on the bridge is a single cable. It connects near the top and the bottom of the tower.

Currently, the bridge is raised and lowered from a remote location 3 miles north of the bridge. But, for many years, the bridge was raised and lowered by the bridge tender in the shack on top of the bridge. The system is powered by two 220-volt, 300 HP motors inside the bridge tender's shack. The motors rotate the four pulleys located just outside the bridge tender's shack, which is turn rotate the other eight pullleys via the cable.

As the pulleys rotate, the bridge responds by raising or lowering as the counterweights provide balance in the form of equalizing the loads. So, in effect, the bridge itself and the counterweights do the heavy lifting with the sheaves acting as a sort of fixed fulcrum.

Rich

 

[toptrain]

My son Steve has been working on one to be apart of a rolling section that when the layout is being run would be put in place. 

[Track fiddler]

The bridge is really coming along and looking excellent Rich.  I can hardly wait to see it finished and a picture of it on your layout,  hopefully. 

Now get back to work on that thing, I need to see some more progress,  you can't just park this thread on page 4 

TF

[richhotrain]

Track fiddler

The bridge is really coming along and looking excellent Rich.  I can hardly wait to see it finished and a picture of it on your layout,  hopefully. 

Now get back to work on that thing, I need to see some more progress,  you can't just park this thread on page 4 

TF 

TF, not to worry. I had to put the towers aside last weekend while out of town to attend two of our grandchildren's graduations.

However, I am about to install handrails around the sheave platforms up at the top of the towers. And, I need to fine some suitable chain to hang from the towers to the underside of the counterweights. These chains are used on the prototype to balance the added weight of the pulley cables.

I still face a big task in terms of installing the bridge and towers on the layout. At the moment, I have a 30" wide open space on the layout that the bridge must span. Trains run over a temporary plywood sheet that spans the open space. That 30" wide open space needs to be further opened to accomodate the towers.

So, I have some sawing and trimming facing me before I can complete the installation of the bridge and towers on the layout.

Stay tuned.

Rich