I work in an old converted factory in Brooklyn, NY. Built back in the late 1800's - It is made of exterior brick walls with (huge) timber frame internal layout. There is an interesting feature that I am trying to understand more and I wish I could just send a photo but since I cant I will try to describe it.

In a particular location where a post would have been, there is a device that I can only describe as being like a spreader on a sailboats's mast. It consists of a closely-spaced pair of "arms", about 2 feet long, that protrudes downwards from the ceiling about two feet to rest on two horizontal iron rods - 3 inches thick, the rods slope up and away in opposite directions to disappear into the top of the walls on each side of the room. Where the rods meet in the center under the arms, there is a pair of turnbuckles that that join them together and they are simply huge. Also of interest is the beam, which is not solid like the others in the building, it is more like a flitch beam , it consists of three stacked (on edge) 3 by 12's that are spaced apart with spacer blocks at intervals. Where this beam sits on the walls - the space between the 3 by 12 is where the rod disappers.

It seems to be some kind of truss that allows a greater floor space underneath. I am very intrigued by the engineering behind it and have many questions.

So if you are still with me, my basic question is: Where can I learn more about this and other devices like it, which allows you to span wider gaps without a column.
I am planning my own timber frame shop with dwelling above it and I want to know my options for the widest space possible with a minimum of posts.
Let me know and I will email pictures of it to you.
Anthony

Period books would aid your research, I found a copy of "The Civil Engineer's Reference Book" by John Trautwine at a local used book seller. Trautwine's was in publication from 1872 into 1930's. The later additions were titled as "reference book" and the earlier as "pocket book". Trautwine was a railroad engineer and is strong on wood and steel construction. If I understand you correctly, you are looking at a trussing method.

Anthony:

My shop is in an old warehouse building, and there are several areas where interior support posts have been removed, and replaced with rigging just like you describe. Roger's right: it's a makeshift truss.

Yes, a simple truss, simplicity in it’self. The timber becomes the top (usually) and compressive chord, the rods are the tensile (always) chord and the standoffs you describe are the webs. These are, in some circles known as Strong-arcs.

These became semi common in the late 19th century, were, and as you are supposing, are an affordable way of creating clear-spans while still incorporating wood as a major component.

Here in NH they were retrofit (posts removed) into many of the buildings at Canterbury Shaker Village and all are still performing as intended.

I am aware of one timber bridge, the Burkeville Covered Bridge in Conway Mass which incorporates these to augment the bottom chords of the bridge trusses and am guessing this particular use is not more common only in that obstructing more of the space between the bridge deck and high water is a precarious balance and a bit of a gamble on most rivers/sites.

I have not seen such a system built as heavily as you describe and would be interested in seeing photographs should you find a way to share them. Also, the built up beam is of interest to me, are these spacer blocks, or are they shear blocks which have been dapped (let in) into the 3 X 12’s ?

Here is a shot of Anthony's shop:



And here is a close up of the iron work: