Is Atlas wrong about their bridge?

[palallin]

The Atlas double track bridge to be protypically correct, should have much larger exterior trusses than its single track counterpart.  From my observations, the double track Atlas bridge is just the single track Atlas bridge, widened. 

 

You're right:  the prototype is a single-track bridge.  A double-track would need to have deeper, beefier trusses. 

The model does support my die-cast Frisco Mike (about 11 lbs) + train.

[Buckeye Riveter]

I'm surprised that no one mentioned the Bollman Truss used by the B&O. It is historically significant in U.S. engineering.

http://www.du.edu/~jcalvert/tech/bolltrus.htm

As to warren trusses, this is a double portal warren truss bridge. Look at the top cord of the center truss and you will see that it is significantly larger than the top cords on the exterior trusses.  It is designed to carry twice the load.   

The Atlas double track bridge to be prototypically correct, should have much larger exterior trusses than its single track counterpart.  From my observations, the double track Atlas bridge is just the single track Atlas bridge, widened. 

[FJ and G]

Thanks for sharing your bridge thoughts and facts. The topic is rather interesting. Too often, modelers just choose a simple girder design or an old fashioned trestle. Nothing wrong with those but there are other options as well out there.

These bridges all started out wood in 19th century but in latter part of that century, iron and then steel replaced the wood, though each type of bridge can still be found in some part of the world today!

[envfocus]

Just thought I'd share a reference my son brought home from school last year. 

 

[FJ and G]

FWIW, Atlas neither knows nor cares.  I have been in contact with several of their people, and none could identify it or even work up the gumption to try.  Thye rely on their own catalog, and anything beyond that is as foggy as a graveyard on Halloween.  In a reply to my inquiry about the origins, an Atlas rep wrote:

"The documents that the bridge was based on only had Missouri Pacific bridge noted."

Sometimes getting responses from individuals and organizations can be like pulling teeth or beating a dead horse.

I sent out questions to Lionel and MTH more than a month ago asking if TMCC and DCS are compatible with any remote control systems on the market.

I got the initial acknowledgement of receiving the email but not replies.

I tell myself that they are busy trying to turn a profit and that my questions don't really translate to profits.

My friend fired off an email to Atlas. If they reply, I'll be pleasantly surprised and post their comments.

Reg. Lionel and MTH, I've received excellent technical service from them, so I just wanted to add that positive note.

[palallin]

It's a Warren Truss pridge.  They sell the same design in HO and N and call it a Warren Truss.  The vertical bracing isn't an issue, the direction of the angled bracing is.  Warren Truss is easy to spot as the angles look like .......  W's

http://www.matsuo-bridge.co.jp/english/bridges/basics/truss.shtm

The only thing I can think of is the specific model goes over a body of water called Pratt or the actual engineer that designed the bridge was named Pratt.

 

As Historic Bridges puts it, "Two-span through truss bridge over Black River on the Iron Mountain mainline between Poplar Bluff and Hilliard."

 

Thanks for the weblink to the discussion of the truss types.

[palallin]

Just so people can see, I'll post the link to the prototype here:

http://bridges.midwestplaces.com/mo/butler/mengo/

 

FWIW, Atlas neither knows nor cares.  I have been in contact with several of their people, and none could identify it or even work up the gumption to try.  Thye rely on their own catalog, and anything beyond that is as foggy as a graveyard on Halloween.  In a reply to my inquiry about the origins, an Atlas rep wrote:

"The documents that the bridge was based on only had Missouri Pacific bridge noted."

I suspect that someone dug up an old set of engineering plans while simply looking for any RR bridge that sould be used.  They did a great job of engineering the model from those plan (as you can see by comparing with the prototype pics)!  But no one at Atlas is a bridge engineer or knows a Pratt (/\\//\) from a Warren (/\/\/\) from some of the more exotic (such as whipple or Pennsylvania), and someone in development at Atlas misread an identification chart somewhere.  As Chuck notes, it's the angles that count.

[FJ and G]

Thanks, Chuck, for clarification. Atlas is normally fastidious about details

[chuck]

It's a Warren Truss bridge.  They sell the same design in HO and N and call it a Warren Truss.  The vertical bracing isn't an issue, the direction of the angled bracing is.  Warren Truss is easy to spot as the angles look like .......  W's

http://www.matsuo-bridge.co.jp/english/bridges/basics/truss.shtm

The only thing I can think of is the specific model goes over a body of water called Pratt or the actual engineer that designed the bridge was named Pratt.

[FJ and G]

http://www.atlaso.com/bridge.htm

Is that bridge a warren or pratt as advertised?

I ran it in Sunday photo fun and now I'm not sure.

My friend, who owns the bridge, writes:

Dave ... I would need to defer to Atlas! Its advertising for its bridge
says it based its bridge's design on a reproduction on a Missouri
Pacific Railroad prototype.

Is the jury still out? According to multiple references I checked, the
Warren truss has no vertical support members.  Here is one excerpt: "The
Warren truss is a more common and simple truss bridge than the above 3.
The Warren is a pattern of repeating triangles.  It has no vertical
supports as the other bridges and is therefore lighter."

However, another engineering source depicted a Warren truss bridge that
incorporates vertical supports, and it sure looks like the Atlas design.

Why not punt this up to Atlas, forwarding your link and mine, to seek
resolution?  I'm surprised a question has not been raised before this!

Interesting!

Gordon