trunnels/treenails

What are people's considered thoughts on the shape of trunnels? Should they be circular, oval, octagonal? I'm building a traditional framed shed, hence my reason for the question.
Cheers.

To the best of my knowledge my grandfather always used octagonals and I use octagonals if I need to... although I prefer wedged construction. :shrug:

He told me that the arris makes 'em 'bite into' the hole for a tighter fit, but in all reality my preference is simply 'cos they're easier to make. And I suspect his was too! :D

I can't say that I've ever heard of anyone making oval ones before. Not deliberately, anyway. Of course, if you make round ones from imperfectly seasoned timbers, then they'll end up oval once they do dry out thoroughly. (FWIW, I strongly, strongly recommend using seasoned pins, even on green frames.)

would love to see photos the shed build.

Thanks for that info skew c, oval wasn't the correct way of describing the shape (sorry) the book I was reading mentioned the shape as oblong (shaving the sides) and also octagonal both designed to prevent splitting.
thumbsucker, so far just have the slab down. As soon as things dry out I'll be getting back to milling my shed timbers and taking photos along the way
Cheers

Cheers Houn

My only advice regarding trunnels is split them out do not saw them and make sure they are bone dry <5% moisture. And choose a flexible yet tuff timber claret ash & white oak or even better hickory comes to mind. Not hard & brittle like many eucalypts.

Huon, I suspect that there is no correct shape, although some will argue that they should be tapered the full length. Round or octagonal is likely to be the result of the method you use to make them. For example, I will make draw bore pins using a dowel plate. This results in a round pin. I then whittle a taper to the end, which makes it easier to insert.

The important part of the pin/tree nail is its construction. For strength when flexed it needs to be made from rived stock. I split the pins from the straightest grain I can find, and then bang them through the plate. Those who do not have a suitable plate will whittle them to shape. Octagonal is on the way to round.

Regards from Perth

Derek

I've been splitting stringybark using a froe (I'll post a pic on progress tomorrow). Yes the tapered end makes sense, stop or reduces blowout on exit.

Hello Huon,

I am rather new to the forum here, but have worked as a Timberwright and traditional green woodworker for a number of decades now on and off...

Trunnel, peg and/or wooden nail types are vast in variety and number...Much of it depends on culture the timber frame is meant to emulate, and being a contemporary form of you own design and choosing...You could go with many different modalities and still be in good shape....No pun intended...ha, ha...:U

I specialize in the Asian and Middle Eastern styles most often and for that we are looking at square pins and/or wedging systems within the frame.

Unless you go with purchased Trunnell few are turned on a lathe though this is an option if the blanks are riven out and not sawn...or...sawn well with the grain orientation being well understood and adhered to...

For many (most??) Timber Frame DIYers here in North America the riven blank then sawn to an Octagonal shape is probably most common...and well suited to the task of a proper draw bore joint (understanding that the given joint has been Draw Pinned first...which is best practice whether timber frame or furniture.)

Trunnel should be as dry as possible before use and/or well oiled. Drying fast over flame and case hardening is an acceptable system with several methods of approach I have seen or practiced/taught.

Wood Species choice is vast and variable too. Hardwoods are most common with some pretty broad variations of choice from region and culture. Osage Orange, Dog Wood (aka Dagger Wood,) Hop Hornbeam, etc are just some of the more excotic domestic forms. I have seen (and used) Black Walnut, Maple, Cherry, Chestnut/White Oak, and Ash as well...

As for tapper...there is huge debate on this topic (usually among novice and those not broadly experienced in the Timberwright craft, but focused on only one style and/or region/circa date.) For the most part the Draw Pina takes care of a draw born joints ential tightening. Thus the Trunnel only needs an ever so slight rounded or tapered end. Historically this is reflected in most timber frames, be it domestic or agricultural (aka Barns.) When you find extreme tappers in Pins/Trunnels this is often indicative of a structure that has be moved, reworked and/or repaired within the contemporary time period...and...very often by someone new or not well versed in the craft. It does not reflect the historic standard nor is in necessary or any great value (overall) to have an extreme taper.

Hope that helps? Let me know if I can offer more details on this subject...

Regards,

j

First things first, welcome to the forum White Cloud and thankyou for your advice and information. That was the type of taper I was thinking of using. The books that I've been using for reference are those written by Steve Chappell, Jack Sobon, Roger Schroeder and Ted Benson.
These are a couple of photos of stringy bark trunnels (The first stage of the process).

I had a bit of a read of some post replies..after 40 years experience with post and beam construction and the same duration splitting shingles, palings, slabs,pegs,pins...whatever there are a number of good answers in your replies...riven (split timber), dry, hard tough eucalypts would be great...from straight grain material, octagonal in shape..this was traditionally done with a side (1 sided) axe, and done fairly quickly so exact shape isn't important, a champhered end that is going in first to resist blowing out the material....a slow lead in taper of about an inch but hardly any....and...place the annual year rings in the riven peg so that they are in the working direction....within the joint.

Big Stan, excuse my ignorance but can you explain the annual year rings in the riven peg thingamebob,please?

Hello Huon,

The books you are referencing are some of the most referenced today for contemporary timber framing and pretty good choices. I know all these authors and three of them personally and/or have worked with them on various project here in North America over the decades. I have an suggested reading booklist available online (found at Amazon for only ease of access and not a business venture) that I share with students and clients that has additional (and germane) texts that you may find interesting or useful.

Per your query to Big Stan about..."annual rings"...and trunnel, if I may add to whatever he may offer in the follow suggestion:

Having worked with a team of PE that founded our North American Timber Framers Guild, (aka Fire Tower Engineered Timbers) I can share that this subject too has a great deal of academic examination over the years. This area of study within timber frames ( which I differentiate from..."Post and beam"...architecture as P&B employs large metal plates and/or iron fixtures unlike true timber frames that are all wood and wood joints) has reflected a full range of understanding. There are also cultural differences within regions and type of timber frames found in them when regarding pin, peg and trunnel grain orientation.

Thus in your case, when a Trunnel is engaged within a joint matrix (aka driven home through a joint union in within a timber) a cross lateral load scenario is set up. These are shear loads across or perpendicular to the grain or the Trunnel itself. As such the grain (as you would perceive it on the end of the Trunnel) should run along with the grain of the timber that is going to receive the most notable tensioning during a load event.

For example if you have a Tie Beam going into a post, the grain of the trunnel (from an end view of the Trunnel) will run with the grain orientation of the Tenon of the Tie Beam and be seen as perpendicular to the Post's grain orientation.

It is worth noting here (academically) that a trunnel is not really...weaker...(per se)... if the grain is oriented in other direction It is just more prone to bending forces than in the other orientation. So you can think of it as bending in one orientation and stiffer in the other orientation.

I would note...from your photos...(this isn't super critical just more along the lines of Best Practice)...to avoid (if possible) any sapwood in the Trunnel and only employ heartwood if at all possible. Again, this isn't a super critical issue, yet the heartwood Trunnel tend to be of higher quality and performance.

Regards,

j

Hmm, food for thought, thanks j. There's plenty of stringy around here so gathering heartwood wont be a problem.

I think I'll dip the ends of the split timber in some paint before they start splitting where I don't want them to split. It'll be a little while before I get to the lathe.