HI all:
Very interesting topic and replies.
I ran across a very interesting tie beam and vertical post joint in an 1846 muley blade saw mill. The tenon that passed through the post was dovetailed on the bottom side only and on the upper flat side of the dovetail it was wedged from the outside. This seemed to do away with the shrinkage problem hat may have happened over the 150 + years that could have loosened the frame.
Hope this helps
NH

Hi Northern Hewer,

Up until now we have been discussing buldings experiencing fairly static type loads or loads regularly applied from the same direction e.g. the prevailing wind. You have now crossed the threshold into an entirely different field where reciprocation and rotation will result in frequent stress reversal on joints. There is no room for any kind of slop in joints on those types of structure and hence joints will need to be fashioned to take regular tightening up into account.

To explain further, for example, the spokes on a gin wheel or donkey wheel will change from being in tension to being in compression as the spoke moves from the 6 o'clock position to the 12 o'clock position thus depending on the speed and regularity of the the turning operation the spoke joints will become quite vulnerable to wear and deterioration and will quickly pull themselves apart if reliance is made on simple dovetail joints.

You should send a measured sketch copy of your joint configuration to Jack to add to his collection.

Regards

Ken Hume

Hi Ken and all:

Thanks for the thread Ken, But I don't know if I am in complete agreement with your assesment of this joint. This historic structure also has received many years of wind weathering. these huge cross tie girts 13" by 18" by 30' are double braces on both ends, along with the dovetail and wedge connections, this setup seems to have weathered the years and still show very tight shoulders and no side sway.
Another connection for conversation is the full through tenon on the old world dutch barns that are wedged on the outside of the vertical posts, some are also pinned , these are and will remain very tight over time.
NH

hey, my students and I got the frame up a couple of weeks ago. I did put a bit of a gap at the teazle shoulder(3/16) and did not wedge the dovetails. there is a photo of the frame here:
http://www.wpltree.ca/tools.html
that would be me laying out the ridge.
thanks again to all who added to this thread, and I encourage anyone interested to cut the english tie joint... it is a good teacher.