1922 Iver Johnson Truss Bridge Roadster

[UncleFester]

eBay item number: 131732779470

 

[Dweber]

Great Looking Iver!
Why are some Iver Johnson truss bars shaped differently than others?
Year, Type of frame?
Ebay# http://www.ebay.com/itm/1922-IVER-J...779470?hash=item1eabe2b1ce:g:0ZkAAOSwll1WyJls

 

[UncleFester]

Depends on seat tube height?

 

[Handyman]

Thats a great question Dweber and I've never heard a reasonable explanation for it. Why does the back side of the truss attach so low on the seat tube on Unclefesters small frame (20") Iver................yet on Bowersmb's small frame (20") the rear of the truss bar attaches much closer to the top of the seat tube (see pic)?????? I've seen dozens of examples of both styles but still don't quite understand why? Is the difference all about the type of truss??? Special truss frame vs regular truss frame ??? Pete in Fitchburg

 

[UncleFester]

Thanks Pete, I am speculating all I can understand is maybe they cut all those center tubes to a uniform length and the frame center tube jig was gauged for the height range of the model requiring more drop at the rear to accommodate a more shallow head tube height? It creates a very elegant swoop in the truss bridge. 20" frame fenders have a different mounting point in the hole punch as well. than the standard 22' ctt height?

 

[IngoMike]

I grabbed this description from a Columbia Truss Bridge Bike that is currently listed on Ebay out of the UK, I think it explains why the truss bar moved, maybe.....

IVER JOHNSON v COLUMBIA PATENTS

Patent litigation between the major American cycle manufacturers took almost as much of their time and effort as building bicycles.

In America, the original patent term under the 1790 Patent Act was decided individually for each patent, but 'not exceeding fourteen years.' The 1836 Patent Act (5 Stat. 117, 119, 5) provided (in addition to the fourteen-year term) an extension 'for the term of seven years from and after the expiration of the first term' in certain circumstances. In 1861 the seven-year extension was eliminated and the term changed to seventeen years (12 Stat. 246, 249, 16) from the initial grant date.

Iver Johnson's truss bridge frame was introduced around the turn of the century. If the 17 year patent term was applicable, then the introduction of the truss bridge frame by Columbia in 1917 may have related to the expiry of Iver Johnson's patent.

Is it a coincidence that Iver Johnson changed their truss bridge frame design slightly at this time - the fitment between the truss and top bar was elongated - but the 1917 Columbia Archbar has the older style fitment? Perhaps the patent lapsed on the original Iver Johnson design, and that's why Columbia was able to introduce the model at this time?

The Archbar model was obviously important to Columbia as it was heavily promoted after WW1.

 

[Handyman]

Interesting angle IngoMike, definitely food for thought...........Pete in Fitchburg

 

[keith kodish]

Thanks Pete, I am speculating all I can understand is maybe they cut all those center tubes to a uniform length and the frame center tube jig was gauged for the height range of the model requiring more drop at the rear to accommodate a more shallow head tube height? It creates a very elegant swoop in the truss bridge. 20" frame fenders have a different mounting point in the hole punch as well. than the standard 22' ctt height?

larry,thought this one was yours?!?