Thanks, Will. Great pics and it clearly demonstrates my lack of knowledge regarding braces as tension members. I think it also demonstrates WHY we see so few braces as tension members!

Will,

Very nice pictures.

It’s tough to tell from the pictures, but it appears that the roof system is a straight gable without additional support other than the eve plates. The thrust at the plates do to gravity loads would introduce the destructive tension loading. Designing to avoid tension loads do to vertical loads by use of queen posts or canted purlin plates eliminates that problem. I’ve been successful minimizing tension loading by use of those methods. It’s the lateral loads that are presenting a problem for me.

If you peg your braces, they will carry tension loads during a wind event. If you do not peg your braces than achieving a viable frame design using ‘standard’ engineering practice can be extremely difficult, at lest it has been for me.

Derek,
What type of loading is generating a 3.1k tension in the dovetail brace in your picture?

How do you engineer your frames for wind loads??

Thanks, pete

We've a common problem in the north east, hay tracks. They would tell farmers to remove queen ties to accomadate hay tracks and roof loads went right to the plates and overloaded the tie beam/ post connections. Many smaller frames , like carriage barns had no rafter support system at all. Most agr. buildings in this area where not deep and pegged brace which agravated the design flaw. Then the iron man was called.
I have used steel and with a little artistic flare in can greatly compliment your work.

They are great pictures too! It looks as though maybe shrinkage of the brace may have started the problem, dovetails have to stay tight. I saw a dovetail like that once with a bolt in it. It loked about the same , but held. That is alot of tension on that joint , wow

MTF – Yes, I tried to accurately describe the situation and said I was posting the images only as a “sidenote” I saw them myself as only tangential to the nature of your thread, but food for thought all the same

I will try to find the time speak to your greater point. Today is spoken for and I’m not sure there’s a short answer.

thanks Will,

understand, no short answer, ever!!

pete

Great thread:

Long braces were used by the better millwrights to steady structures such as the Mulley saw mills of the 1846 vintage and earlier.
One that I am familiar with had no short braces but relied only on 4" by 6" long braces crisscrossing each other in the outer wall cavities, and repeated for each every bent, notice none were pegged either, lets make that clear here. These braces ran from the sills up to within 12" of the upper plates, and were on an even run and rise.
They were intentionally inserted to steady the building as the sawing equipment ie; the log frame carriage started forward and stopped between each stroke of the pitman during the sawing action.
The building was 2 storey, and had identical bracing on the lower floor.
The huge timbers over and under the saw blade guides (20" square by 30'long) had double braces and double supporting posts on each end, the timbers sat in dovetail sockets between each set of supporting posts with wedges to ensure that they could not move,
even with all this lateral support the building would still respond to the sawing action slightly, and uncanny as it may seem you could feel the frame respond even to a person walking around.

NH

I've got some photos of NH's mill from TTRAG '02:

This one shows the big beam that holds the top of the saw blade guides:

(That's NH in the center)

Here's an end-on view of that beam, showing the double posts that hold it up:


And here's the unpegged overlapping long braces he was talking about:


CB.

Thanks Diaku:

Those pictures tell it all especially the ones of the long braces that go with the conversation thread.

This old mill was a wonder of building technology of years gone by, and the use of the long braces a good example of historic mill wrighting, in conjunction with a good Historic Timberframer, with whom I suspect worked closely with the prospective operator or mill owner of that time.
Many things had to be understood before the frame was cut, for instance a good understanding of the waterpower to be used, and how it would be installed after the frame was up. What direction the inflow of water would be coming from, the topography of the surrounding land, and the list goes on and on.

Once again thanks for taking the time to post the pictures for the enjoyment of all.

NH
Richard