South Wayne Truss 2 done

All went well and truss 2 is now done. Four days to layout, cut, clamp and drill. Not bad if I do say so myself!

This time the parts were pre-finished. At the left you can see the wheel borrow full of chips that
were produced from the holes that were drilled!

Along those lines I can tell you that I did a test and drilled one of the holes through the full six layers and can tell you that it took 8 minutes and about 150 revolutions of the auger to do the job. Drilling all the holes by hand, in one truss would take over 14 hours!

The Hole Hawg does the job in about 1 minute. With all the time I saved I will spend the next 10 days in Chester, New Hampshire working on a 24 foot covered bridge at Wason's Pond.  This project is being done by the Timber Framers Guild. Should be a good time and lots of serious fun!

Puzzler - What kinds of new things will I learn in the next 10 days?
Tech Vocab - Pratt Truss

Why did I save that piece of broken mirror...?

I save a lot of "good stuff".  At the time I did not know that I was going to need a nice piece of mirror to make a bridge but I know now.

This would be a good puzzler to figure out just what is going on in the picture above, but I'll save you the trouble. The mirror is placed on the opposite side of the chord when sawing to the kerf to get a tight fitting butt joint. This way I can see how close the saw is getting to the chord piece above or below the cut without stopping. Don't want cut to deep and nick the other chord piece!

Above you can see how the butt joint has opened after the camber was put into this chord. This can be a significant gap and any load would not be transmitted evenly through a poorly fitting joint like this.

The solution?

My American pull saw! I was having a great deal of trouble with the saw binding during this process then it dawned on me. Pull the saw instead of push it. I also gave the saw a good coating of bees wax. Mirror, wax, Vise-grips, works like a charm! Tomorrow should lay on the web layers, maybe even start the inside chords.

Puzzler - What ideas can you come up with to improve the process?

Tech Vocab - Pull-saw, Vise-grips,  bees wax, Sawing to the Kerf,  Gear wrench

Table Reset...

Alex is back from vacation and we have begun the process of removing the clamps.

There is no turning back now. After some careful study and explaining how the layers and individual pieces of each layer are identified it was off the to the races and we had the clamps off in no time.

Each chord layer has a letter ID. Assembly will start on the left when viewed from the bottom chord.

Using the playing card system the ends of all butt joints are ID. Each piece is also stamped on each end with it's layer number with a steel stamp. Hopefully the pieces will be kept in their own layer piles during the finishing process!

And here you have it, table re-set and ready for truss number two. In the background you can see the pre-finished material ready to go. Tomorrow Alex and I will have a go at it!

Puzzler - What could go wrong?
Tech Vocab - Falsework, Annual Rings, Bow, Parallel Clamps, Blocking, Camber, Sawing to the Kerf

Cribbage anyone ?

While waiting for Alex to return from vacation I kept myself busy with a little work at the bridge site.

This bridge will require assembling on site and so cribs of the correct height and in the proper location (one at each chord butt joint) will be needed. In the picture above you can see the abutments and the cribs for the bottom chord. The local highway shop had a good supply of 6x8 guard rail posts and blocks that they let us borrow for this work.

Here you can see the cribs built and I have placed some 4x4's on top to simulate the first layer of chords that will be placed on them.

From this portal view you can see how the bridge truss will be assembled and then raised to vertical. This process must then be repeated on the other site for the second truss.

I can now relate with some tiny amount of personal experience what Milton Graton did in 1968 when he built the 140' Union Street Bridge in Woodstock, Vermont. The pictures in his book on  pages 98 - 101 are beyond belief! Surly if you are interested in this type of thing by all means get a copy of his book, The Last of the Covered Bridge Builders. The engineering and design of moving this bridge by hand over the river and into place is the stuff of legends! Truly Milton was a master of his craft.

Puzzler - How will loading and unloading of the truss parts need to be managed and what difference will it make?

Tech Vocab - Crib - Capstan - Needles - Rolls - Shoes - Rocker Blocks - Abutment - Track

Swiss Cheese anyone?

Let the drilling begin! Imagine the time and effort involved when the bridge builders of years ago did the drilling like this. Makes my arms tired just thinking about it.

Can't wait for the high school helpers to get here and give this a try!d

Which one do you think they will want to use?

These are some mighty fine looking holes. Even with the Milwaukee Hole Hawg it took several hours to layout and drill the 108 - 1.5" diameter holes. If placed end to end the hole would be over 75 long!

Built a little "hole locator". Worked well on the Web but had to do some adjusting when it came to the 3 holes in the chords. Had to make sure that there was a minimum of 2" of wood from each of the 3 holes and the edges of each of the 3 pieces. Wow. The success of this will become known only when the pieces are taken apart!

Also, each and every hole needed to be backed up with a scrap piece to prevent the drill from "blowing out" the hole as it came through the material. This was tricky but the falsework helped and with a few wedges the job was done.  And here you have it. First truss done and ready to be dis-assembled and taken to South Wayne where it will be finished.

Puzzler - How will all the pieces be kept in order so that no piece is flipped,  flopped or flip-flopped?

Tech Vocab - Metal Stamps, Playing Cards, Assembly Schematic, Layers,

Clamp Fest !

When Milton spoke of using several hundred clamps in the process of building his bridges I was surprised. Now I realize he wasn't kidding. Shown above is nearly a "full set" of clamps required at at each butt joint assembly in the truss chords. Missing is the clamp that would is placed to the left of this group. The clamp would squeeze the inside and outside chords and web together (all six layers).

With all the truss chords clamped and cambered it was time to install the end verticals and wall rail that the Secondary Rafters will be attached to. This will prevent any "racking" of the bridge.

And here you have it! Signed sealed and nicely clamped. The casual observer may not realize the importance of the location of each and every clamp. All 101 of them! Each clamp must not interfere with the false work, another layer clamp or soon to be drilled trunnel hole. Lots to think about and plan for.

Puzzler: Here is my "helper" can you figure out what his job is when I am "sawing to the Kerf"?

Tech Vocab - Parallel Clamp, Edge Clamp/12", Surface Clamp/4", Layer Clamp/12", Diagonal Clamp/19", Wall Rail Clamp/23" Threaded Rod

Web worthy, layers and inside chords

Pretty hot today. How hot was it?  It was so hot, that I didn't even have to light the grill... all had to do was turn on the gas! Getting some practice for the Burlington Liars Club contest in January.

Things went as planned and all is well. Did some reinforcement bracing on the falsework. Lots of load bring applied to it by the camber in the outside chords. Want to secure it before I form and clamp the inside chords in place tomorrow adding more load to it.

Did a lot of measuring and double checking. Placed a 2" drywall screw in the edge of each web piece to hold it in place while I am placing the Inside Chords on them.

Finished up the day with the pieces that make up layer five and six ( the Inside Top and Bottom Chords ) in place and clamped on the edges and face to make them straight. Tomorrow I will form the camber into the Inside Top Chord first. This will be done by clamping it to the Outside Top Chord that is blocked in place to the falsework. I can use a come-along to pull the ends into place. Then I will form the bottom chord by using a jack working against the top chord.
Should be drilling trunnel holes this weekend!

Puzzler - Took a couple of pictures of some small but very annoying problems that only the end user can appreciate. Take a look and see if you know where the "manufacturers" went wrong and why this is such a pain.

  Tech Vocab - Burr,  Chamfer, Thread File, 100%,  Re-work operation, Cost overrun, Lost Time, Made to Order.