Author Topic: joinery help on kingpost truss (Read 23144 times)

Jim_Rogers · « **Reply #20 on:** April 21, 2005, 08:27:00 AM »

Don P:
Here is another view of the connector plate:

I have a page from the BMF catalog but it's all in "German" so I don't know what it's called. The part number "80" means it's 80 mm wide, and they come in different widths based on what you need.

It seems that Simpson Strong-tie bought out BMF who makes these, and they are available in Europe.

The Simpson catalog has some things call VPA (adjustable variable pitch connectors) shown on page 71 of the catalog C-2005.

About your drawing.
When a board was used as you have drawn, it was called a "raising plate". As most timbers are named because of where they are in a frame.
Whether to use a board or more commonly a plank, is determined by the span from ceiling joist to ceiling joist and the load.
And this type of assembly was shown in Jack Sobon's book, and in the "Historical Joinery" series.
It was and still is a good method to support common rafters that overhang the wall plate.

Jim Rogers

Don P · « **Reply #21 on:** April 21, 2005, 09:38:17 PM »

Thanks for the explanation and terminology Jim, neat stuff

What caught my eye on the connector was that angle iron "shear foot

". Now if it had a knife plate in the middle to hide the straps... It looks like a good piece of hardware.

Hardway, I'm southwest of you, down 81/ 77 near Galax.

Thehardway · « **Reply #22 on:** April 26, 2005, 02:50:59 PM »

I picked up my new bandmill on Fri. morning and have begun to cut timbers from some blown down pines I have.

I think I will build a 1/2 scale truss for practice and see how it looks/performs on a shed. Will give me a chance to practice on some shorter timbers and spans and work out any potential problems before I get too deep. Milling the timbers is a lot of fun although my back is very sore today. I was just given a nice Pin Oak today which should be large enough to provide all my struts. I"ll have pics coming soon! Now I've got a bunch of questions about sawing. One thing leads to another but I'm still having fun!

Thehardway · « **Reply #23 on:** May 03, 2005, 01:53:02 PM »

Well, I slabbed the Pin Oak and got two cants 9.5' long. One was 11"X11" and one 6"x6". I can't believe the weight of that 11"X 11" timber.

How would anyone ever handle a wet green 12" X 12"oak timber 24' long? It is mind boggling what the old timers accomplished without power equipment. I would be curious to hear what the largest timber those on the site have ever handled in a frame.

I have read that in The Old World timbers became shorter and shorter due to the lack of availability. I wonder if much of it was not also the fact that 1) joinery technology evolved and 2)the realization that shorter timbers were easier to transport, handle, cut assemble and raise.

Perhaps some long timbers (sills and such) were even cut into multiple pieces and scarfed together to make them easier to handle without the neccesity of gin poles and horses or 40 strong men.

My newest challenge is an uprooted poplar that is over 30" through and laying on the side of a steep hill. I want to cut it into fireplace mantles. Not sure how to get it off the side of the hill to move where it is level enough to cut without it rolling away and taking out half the hillside with it. $:-\$

Gilman · « **Reply #24 on:** May 04, 2007, 03:06:54 AM »

Is the top of a kinpost normally set at 7 degrees or should it be changed to fit your truss? (I just guessed at the 7 degrees from a standard dovetail)
??

Don P · « **Reply #25 on:** May 12, 2007, 10:45:45 PM »

Gilman, I realized when I looked up this post, nobody answered.
I'm no expert, on the truss here I laid out a plumb cut and then swung the base in 1" to create a seat. There is a 2x6 tennon laid out from the bottom of the rafter sticking in the king.

This is a more metal connected bent than the first one.

I kind of used a picture from above for an idea for a rafter foot on this bent. After this pic I welded an 8x8 plate from the heel angle iron up the rafter and sank 4 lags to help lock it in place. There are 2 more lags in the holes in the angle at the heel .

That way didn't save any time or money, but it is alot stiffer than the splined truss.

Thehardway · « **Reply #26 on:** May 13, 2007, 09:05:51 AM »

Gilman, I have seen a lot of different configuarations and flavors for kingpost tops in books and pictures. Some have no angle at all. In many later designs, an Iron rod was substituted for the post which had no angle. I like the angled version. The greater the angle the better the rafters lock the kingpost in place. I believe the angle should be increased as the pitch increases. I say this because thrust and compression increases in the rafters as the roof pitch decreases, holding the kingpost tighter. The reverse happens as the pitch increases. It is a Chinese finger trap principle. Also much depends on the pitch of your roof and the size of your kingpost. An important thing to remember is that the kingpost is the only member in tension and all of the weight generated by the kingpost has to be transferred to the rafter foot joint. I started another post sometime ago on kingpost top configurations. I will try to pull it back up in a search.

Don, What is the purpose for the strap visible on the top of the tie-beam in the lower picture? What does it attach to, the bottom of the rafter?

Gilman · « **Reply #27 on:** May 13, 2007, 01:06:16 PM »

Thanks

Don P · « **Reply #28 on:** May 13, 2007, 02:25:09 PM »

The strap with the 16-1/2" lags is the thrust resistance for the rafter foot

. It extends under the rafter and is welded to the angle iron behind the rafter. To get assembly room and proper spacing that got kinda long. Think about the amount of "meat behind a 1/2" lag and then the amount of shear resistance in the notched foot of bent 1. Just a different way of restraining that thrust.

Its unseen from ground level. The "spline" on this bent is 2 fish plates ~14' long let into the bottom chord across the king. There are 3-1" bolts in tension there on each side of the king.

Thehardway · « **Reply #29 on:** May 14, 2007, 02:19:08 PM »

OK. Think I see it now.

Forestry Forum
Sponsored by: