Coach 9 - Official Work Thread

[Harold Downey]

After the glue dried (actually its epoxy, so it was an overnight cure), I cut 5 degree angles on all four sides.  This was not as simple as it looks, but I did it on a large bandsaw after a couple of different setup attempts. 

[Harold Downey]

Then I attached 4 sides to the top half, to form the core box. 

[Harold Downey]

Then I finally was ready to separate the two halves.   Shown first is the mold half, which will form the top of the seat frame.   Since this mating assembly as I constructed it, splits on the back surface of the seat frame, this mold will get built up by the thickness of the frame (about 3/16"), and also the side webs and other features will be added. 

[Harold Downey]

This is the core box which will form the bottom side of the seat frame

[Harold Downey]

Here is another view of the bottom side core box, with the seat frame sitting on it, so you can compare.   As you can see there are lots of features to be added to this. 

But the hard parts are done, and the rest will just take some time.    I promise to show the completed versions. 

Harold

[James Patten]

In the Top Side Mold picture we see the lattice work, but don't you need the negative of that?

[John Kokas]

I can't wait to see the first rough casting come out.  I hope you know there are tourist/historic lines that are looking for someone to make new seat frames for restored coaches.

[Harold Downey]

In the Top Side Mold picture we see the lattice work, but don't you need the negative of that?

James, the pattern is a positive shape.  A sand mold gets made from this by packing sand around it, and then extracting the pattern.     Similarly, for the bottom side core box, it is packed with a special chemical curing sand, and extracted from the core box.  This sand core then drops in the sand mold made from the top side pattern.  The resulting space between the two will be the seat frame once filled with iron. 

 The way I am building this is --  that right now, if a mold and core was made from these two as shown, the net space is exactly zero.   So I add material to the top side pattern on the baseline form that exists now.  The lattice work is like that - I just set it on there for the picture.   I know this may not make a  lot of sense.  I keep having to make sketches to keep it all straight in my mind.    Maybe I should post one of those to better describe it. 

So - the lattice is a positive shape.   

[Steve Smith]

Harold, what splendid work! Thank you so much for taking the time to explain.

[Carl G. Soderstrom]

Beautiful work!!!

I am glad you know where you are going - I got lost shortly after the lattice.

The original helped.

[Jeff Schumaker]

Simply amazing work, Harrold.

Jeff S.

[Alex Harvilchuck]

My shop just received an upgrade two days ago. It's replaces a circa 1908 version of the saw with a "new" early 1950's version. It will saw up to 34" wide and 18" thick. It cuts a might fine veneer also. Looking forward to maybe cutting some stuff for Coach 9 with it...

[Stephen Hussar]

WOW.

[Harold Downey]

I am adding all the details to the top side mold.  I thought this would be easier.  But many of the edge pieces have 3-D curvature, and I couldn't just bend them out of thin pieces.   For example, here is one of them.  I start with a cube that contains the part I want, and glue paper patterns to two sides.  I cut it on a bandsaw in one plane, then keeping the stack together, cut it in the other axis.   Here is the cube with all the cuts done.

[Harold Downey]

Then the cube is separated into the three vertical stacks.   (the part I want is in the center of the middle stack).