Perhaps an engineer could answer this question, how much pulling load is actually applied to the post, exerting pressure the tie beam joint? And with these hydraulic pulling machine they test with, how much more pressure is applied to the joint that will be seen in the life of the structure at worst cast scenario? Is it like testing tire load ratings and putting a load on a tire to the point is bursts where we would see failure in broken springs, or bent things before the tire blows? I am presuming these test are performed to build number that will lead to specifics, a broken joint is not necessarily the end goal, more degrees of failure at given pounds of pressure.
Peg and wedges, a belt and suspender approach, I wear both, btw. The belt holds things and the suspenders keep my pants up when in use and when the zipper is run down for other purposes, a perk, I guess.
I can see times where just pegs could fail with relish blow out then there is not back up plan, a wedge adds a back up plan in times of need. Were the original builders adding a wedge for the future, or unforeseen needs, like shifting foundations and the such?
Yes I get the point of the theoretical exercise of joint busting aside from it being a lot of fun in some way perhaps. Soort of like, nobody actually wears that crazy Paris cat-walk kind of clothing. But belt and suspenders? I could never really get my head around that one, still can't. It's why you have pocket-knives, for those times when your outfit includes over-all or suspenders and you leave your fixed knife or your multi-tool in its belt holder on the bureau. I look at the joints cross adaptation. Could it be that it began as a remedy addressing something very specific like the various forces exerted on a particular component of a horse driven mill in and around the late middle-ages, and from there just got taken into the barns that got built. Today we still got barns but no more horse driven grinding mills, well, an acquaintance is building his but this is an exception.
Loc: Albany County New York
For the record on a few points...
Having strong ties to the Textile arts and trades...they very much do where those "cat-walk kind of clothing"...actually quite often...just not in too many areas you will find many practicing Timberwrights ...Greenwich Village, Milan, Hamptons, Beverly Park, Marseille...to name just a few...have "nightlife" and social gatherings where these types of attire, especially for Women, are very common...
The "Belt and Suspender" metaphor was about perfect in my view, as they do work much better together if you carry stuff in your pockets...Actually, when you really look at all the folks that do where suspenders, especially cultural groups I have always worked with through the years like the Amish, River Baptist, Mennonite etc....all...wear belts and suspenders. I suspect for the same reason Tim shared (and their common cultural habits in attire.)
From the literary and conversational comparative the reason we have the "peg and wedge" setup...is very much for that same reason...Wedges are much better at really drawing a joint tight. Nevertheless wedges can work themselves out of place (in some applications) when in the horizontal position. This is why we find the vertical orientation so often in furniture, which actually must endure a great deal "human created" tectonic loading...A horizontally wedge on a "Trestle Table" will need more "tapping in" and retightening than its vertical wedged cousin...I should clarify from one of my comments above that when I said this joint was "rare" in timber framing...I meant in exactly this configuration...As for "vertical wedging" joints in general...they are extremely common and in many different styles and applications...yet outside the context and understanding of most "Western Timberwrights."
We are actually only getting to "scratch the surface" of testing and videos of them, when we are lucky enough to get folks like Ben and Joe of FTET...Joe is our current PE on the project we are working on currently. We spoke of this very video over lunch just a few months back, and there work testing these many joints is invaluable to the rest of us in the field working with timber frames...!! For those of our readers that really like this type of testing and timber frame examination, I would strongly encourage learning some other languages as it relates and applies to our craft. The Japanese (et al) not only "timber frame" way more than most other timber frame cultures (now and historically) but they produce literature and video of actual competitions to present different wall assemblies under load and failure. They do similar empirical comparative analysis of traditional joints like we get from our wonderful FTET gang as well, at many such events. They even have competitions where the only event is to see how well you can tune and use a Kanna (plane.)
Here are a few more video (tip of the "iceberg") that folks may find interesting...
I added this one as you can see the many examples of both horizontal and vertical wedging joints that are used...
This is an example of "Nuki Beam" testing (also a wedged joint and why I included it here in this post)...one of the most common "horizontal bracing" modalities employed in timber frames architecture, and perhaps the oldest in application and understanding, as it is highly resistant to "catastrophic failure" in tectonic loading. It is a very keen point of interest even today as there is a very clear rift that has formed between "big construction businesses" and their "industrial housing" methods as compared to the traditional builders still holding out that these "traditional systems" (overall) are much better in application. The draw back is that "Big Industry" can manufacture and sell these methods as profitably and fast as they can lesser "stick framing" and metal fastener methods...It is a normative "building culture" as much as it is actual aspects of good practise....
Point of interest to the many groups like it in Japan...
Mortise and tenon joint testing
Another spline joint with "vertical wedging" common and one I like to use on frames...
Loc: Albany County New York
Hmmm...in the beginning of entry no doubt...
Yet, to actually implement a true "wedging force" I think the "wood element" being driven...whether square, rectangular, round, or having some other general geometric shape...must be forming an ever increasing "inclined plane"...(i.e. a wedge)
We know that a "screw" is a type of wedge as it maintains all those elements of having multiple "inclined plane" within its helix.
So...is a drawbore peg/trunnel actually a wedge??
There is wedging in the beginning, yet after that it seems to me to act more like a "spring shaft" or perhaps even a "cam" of sorts...not a wedge because the sides of the trunnel are typically of a consistent geometry...
I have seen "square wedging pegs" that also "draw bore" yet those seem uncommon for the most part...
Loc: Albany County New York
It is truly awesome, each decade that passes the more I learn and get to observe in the area of Asian joint design modalities.
The "keyed spline joint" or more apply translated as Shachisen tsugi ..."plug joint"...Shachisen for short and most Diaku would know what you are asking about...Does not fail the way most would think...
Like so many of the Asian joints, particularly in Japan with their massive tectonic load needs...the joints are meant to "stretch" and fail very slowly...Thereby rendering the building much more enduring and flexible...compared to "oblique bracing" which not only put extreme fulcrum forces on most joints near it (especially when under 4' in oblique length...the also fail rapidly and catastrophically once over loaded...They do make a frame ridged, yet there application in Japanese framing (they do exist) are in very key and critical locations that you typically do not see in Western framing systems...Glad you enjoyed the video...
Loc: the Netherlands
I chop a point on the peg and then bevel it 1/3 of its length which is twice the thickness of the beam. But there is no taper after that, no intentional taper at least but generally those pegs are so irregular. The point and bevel I see as guiding the peg into the off set hole of the tenon and then gradually initiating the draw so I wouldn't characterize the action as wedging at any time. A tapered peg though that would surely be a wedge too. What's the point of a tapered peg?
Loc: Albany County New York
I have exhaustively search for a "mechanical phrase" to describe what a "drawbore" actually does...I agree too Sean..drawborn trunnell/pegs...by their overall affect and geometry...are not wedges...as the one I employ are typically square and only sometimes round...both are only tapered about 25mm to 30mm at most.
What is the mechanical effect they do have???
I have seen some (limited) text that use the term "wedge" in relationship to them but considering the "text" this was published in and the authors I don't give it much countenance, as these where "novice articles" about timber framing joints, described by "non" Timberwrights.
One my mentors (Amish) referred to it in broken Dutch to English as a "spring shaft" effect, but I feel that might be to much local vernacular even though it does describe the mechanics of how the peg/trunnel functions once driven home.
So...the best I can come up with for "mechanical force" is in the name itself..."drawn" or "pulled"...by means of offset mechanical action between the planes of to passing members...There has to be a way to shorten that...??..So, perhaps "drawn joint" is simply the best?
Then again...a wedged joint is a "drawn joint" by the..."effect of an inclined plane."
While a trunneled or pegged joint is working as an "offset"...??...shear plane, or cam...It would seem?