Finishing and Installing the PRR Vertical Lift Bridge

[mbinsewi]

Looks great Rich!    Excellent work!  I can't wait to see the finished scene.

Mike.

[ATLANTIC CENTRAL]

Very nice work Rich, makes more anxious to get started on my new layout.

Again, great work.

Sheldon

[doctorwayne]

Great results, Rich!  The boys at Bertram's salute you!

Wayne

[gmpullman]

richhotrain

My thanks to all who contributed to this series of threads.

You have a real museum piece there, Rich!  Capturing the massiveness of this structure was a real challenge and you have succeeded marvelously.

While researching, along with you, I finally found the answer for the use of those heavy-linked chains attached to the bottoms of the counterweights. A very clever solution to acheiving "perfect" balance.

Outstanding results, indeed  Rich!

Regards, Ed

 

[hon30critter]

Hi Rich!!

You have definitely created a masterpiece! Well done.

Dave

[richhotrain]

Thanks everyone for your kind words. Much appreciated, and I cannot deny that it feels great to read such supportive remarks.

But, I will leave you with this thought. If I can do it, anyone can do it. A good part of the reason that I started this series of threads is to encourage others to try their hand at scratchbuilding. It can be done.

Rich

[richhotrain]

doctorwayne

Great results, Rich!  The boys at Bertram's salute you!

Wayne 

Thanks, Wayne. I am looking forward to the day when the boys at Bertram's will be able to take a short walk to visit the vertical lift bridge in person.

Rich

[Outsailing86]

How big is your layout? Do you have a track plan?

[doctorwayne]

richhotrain

...I will leave you with this thought. If I can do it, anyone can do it. A good part of the reason that I started this series of threads is to encourage others to try their hand at scratchbuilding. It can be done.

I'm in 100% agreement with you, Rich. 

Scratchbuilding (kitbashing, too) are very rewarding pastimes, and one of the main requirements, in my opinion, is imagination.  If you have it, you will learn the skills needed to do the things which you hope to accomplish.

It helps, too, that there are many here who can provide suggestions regarding tools, materials, and methods...there is more than one way to achieve most goals.

Wayne

[Motley]

Wow Rich, that is just AWESOME looking. Very well done. I can't believe you scratch built your own bridge. Your skills and new layout seem to be very good right now.

[richhotrain]

gmpullman

While researching, along with you, I finally found the answer for the use of those heavy-linked chains attached to the bottoms of the counterweights. A very clever solution to acheiving "perfect" balance. 

Here is the explanation of the counterweight chains on the PRR vertical lift bridge as related on historicbridges.org:

Observant visitors to this bridge and many other vertical lift bridges may note unusual, massive chains hanging from the bottom of the counterweights and connected to the lift towers. The purpose of these chains may not be readily apparent, however it is actually an extremely interesting and creative use of simple physics to provide a consistent counterweight effect throughout the operation of the bridge.

This bridge's lift span and counterweight is held by a system of cables, which run through a sheave or "cable drum" at the top of the towers. As the bridge raises, the cables run through the sheaves to pull the lift span up, while the counterweight receives the slack in the cable, which is pulled down by the counterweight which itself moves downward.

As the bridge is lowered, the reverse happens: the cable is returned from the counterweight side to the lift span side of the sheaves, which allows the lift span to lower and the counterweight raises. These cables actually have considerable weight to them, and when the bridge is lowered, most of the weight of the cables is added to the lift span side, while when the bridge is raised, most of the weight of the cables is added to the counterweight side.

This means that without something to address this changing weight distribution, the bridge is not constantly counterbalanced throughout its operation. The chain solves this problem. The chain is connected to the tower roughly halfway up the tower, and it is also connected to the counterweight.

When the bridge is lowered and the counterweight raises, transferring cable weight to the lift span, the counterweight also picks up some of the chain's length, and thus some of the weight from the chain is added to the counterweight system, making up for the lost cable weight.

When the bridge is raised and the counterweight lowers, receiving additional weight of the cable system, most of the length of chain is picked up and its weight held by the fixed towers, thereby removing that weight from the counterweight system.

Rich

[gmpullman]

richhotrain

The purpose of these chains may not be readily apparent, however it is actually an extremely interesting and creative use of simple physics to provide a consistent counterweight effect throughout the operation of the bridge.

 

Thank you for posting this explanation from Historic Bridges, Rich. I was kind of hoping you would 

It really makes sense when you consider the added weight of all those cables (wire rope, actually) which transfers as the rope passes over the sheaves.

Very clever.

Cheers, Ed

[hon30critter]

richhotrain

Here is the explanation of the counterweight chains on the PRR vertical lift bridge

Very interesting!

Thanks Rich and Ed.

Dave

[mrrdad]

Fantastic job Rich. Thank you for sharing. I lived in the Chicago area most of my life. I know that bridge well. You did it justice!

Well done our friend.

 

Ed

[gdelmoro]

richhotrain

I have reached the point where I need to install my scratch built bridge and towers on the layout so that I can finish the project by installing the counterweight chains and the sheave and pulley cables.

My first thread on this scratch build project covered the bridge.

http://cs.trains.com/mrr/f/88/t/274913.aspx

My second thread on this scratch build project covered the towers.

http://cs.trains.com/mrr/f/88/t/275386.aspx

So, now, I have to modify the layout surface to accommodate the bridge and towers. Here is a photo of the bridge and towers sitting on the layout, but I cannot install it in place until I make provision for the towers which must sit below grade to match the tower decks to the height of the bridge track work.

So, I have removed the track and the affected plywood surface. Now, I need to contemplate how I am going to retrofit the affected area to properly install the bridge and towers. The large open area will eventually become the river bed over which the bridge spans.

Here is a photo of the actual bridge which spans the South Branch of the Chicago River just south of downtown Chicago at 21st Street and Canal Street.

 

Somehow I missed this thread! Outstanding modeling Rich.

[mbinsewi]

gdelmoro

Somehow I missed this thread! Outstanding modeling Rich.

Gary, you faked me out with your post.    When I seen it was active again,I thought Rich was posting pics on the completed scene. 

Oh wait!  The last picture, that must be the completed scene!    Stunning work Rich!

Mike.

[richhotrain]

Thanks, Gary and Mike. The bridge is completed, but I still need to landscape the surrounding area and create the river. Right now, I am working on other portions of the new layout, but I hope to get back to the bridge scene soon.

Here is a photo of the finished bridge with the cables, chains and counterweights attached to the superstructure.

Rich

[Tinplate Toddler]

[Boiler-man]

Your bridge is Outstanding !!!

[doctorwayne]

Great results, Rich, and I'm looking forward to seeing the finished scene.

Wayne

[gdelmoro]

Sweeet!