How big should a wedge be to secure a 1 inch dowel in place on each side of the two poles being secured? Eg tapered 5mm to nothing, length 60mm? I guess needs to avoid splitting the dowel inside so not too long?
I think I have more questions first before I can give good advise to what I think you are asking??
In timber framing there is a big difference between a "wedge" and "trunnel or peg."
"Draw boring" a joint with a wood trunnel (wood peg) works on similar principles but the applications are vastly different. Even with "draw boring" there is a huge range of application and material types, so I would really need to perhaps see a photo or drawing of what you care to build, and how you would like to...wedge it...or...pin/peg it.
Pegs and wedges both come in all shapes and sizes (and species.) Each region has there specific commonalities...Ash is common in some regions, like parts of Pennsylvania and Ohio, in others they are all Oak, and Beech. With the Oaks overall being the most common here and in Europe, then Beech, Locust and a few others, though almost all strait grain hard woods are more than sufficient to doing the job in most applications. I parts of the Midwest they can be Locust, Cherry, Maple, and Horn-beam or Dogwood. Some areas of Michigan and Wisconsin sees a lot of Black walnut and catalpa.
Hope that helps and let me know if I can help further...
Thankyou Chadwick and Jay. Cool photo of bent dowel..
Small building already underway. Have been using Ben Law style butterpat joints. Dowels and wedges are seasoned oak and the logs/poles are mainly ash. I will attach drawings which explain my question hopefully better.
I like Ben...so I do want to stress that (met twice at conferences.) He is doing a great service to promoting green building...He is also really "pushing extremes" on "load paths" and "reinventing wheels" sometimes on some timber joints...
Now that is a "warning" not a "don't do it."
Anytime we employ trunnel for "shear loaded" pathways of horizontal members (that are not housed completely) we are subjecting the trunnel/peg to some pretty significant stresses along its load path....be it a house or furniture...
Now that does mean...again...we can't do this, but one must really understand the dynamic being created and whether a catastrophic fail of one or a few pegs will create a cascade effect in other failures?
With that out of the way, your work concept looks just fine. I only wrote the above as "warning" just incase there is some major loads being placed on these members.
This method you are illustrating, is used traditionally a great deal (just as you show it) to mount heavy planking on wood ships ans sailing vessels. It is also employed to "lock" certain timber joints that otherwise might "breath out" there peg.
I don't know enough now about the "loads" to suggest "safe" or "unsafe."
Interesting re shear loads. It did cross my mind a lot thinking how could it be stable. In our case the horizontal beam is between A-frame and post so this helps. We couldn't have catastrophic collapse.. as we have so much timber and bracing in a tiny building. What are your thoughts on wedge length/whether pic A or B is better?
Preliminarily the wedge looks just fine and even 3 to 4 mm thickness is sufficient in most traditional applications such as this... Width is same as trunnel typically. Length of taper is usually congruent with size of peg and kerfing modality selected. I would test the current peg stock to see how it reacts to your wedges. I am not sure of what "kerfing" tool you are using, as the wedges can't just be driven into the endgrain of the peg.
I also wrote "preliminarily" as I have concerns this "pegged fixed" horizontal member maybe a critical bent or connecting timber. This "pegged lap joints" is not meant for:
Connecting Primary purlin (secondary is often acceptable)
Or any other critical frame member. Braces add nothing to most frame accept single direction compressive strength in most applications and in many applications act as "fulcrum" that can actually stress joinery intersections further. They do not work in "tension" and typically are not peg themselves accept to aid in assembly. If the obliques bracing has a tenon longer than 200 mm then"tension strength" can be gained in some configurations.
I love that you are building this way, and hope you post pictures of your efforts when complete. These are marvelous ways of building and not as complicated as many think they are. All are based on millennia of "working examples." I am sure you will be pleased.
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