Author Topic: WW&F No. 11 - Official Work Thread  (Read 200390 times)

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #315 on: January 15, 2015, 04:34:33 PM »
Here is an image of the solid model that Alan did in Solidworks.  It gives a pretty good idea of the complexities of this casting.  There are washout holes in the corners that are at 40 degrees -- how can this be pulled from the sand if these are to be cast in? 

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #316 on: January 15, 2015, 04:44:52 PM »
To answer Bernie's question, I will explain how we decided to make this pattern.

If you look at the picture, we are creating a split line on the pattern along the dashed line B-B, so that the sides with the washout holes are separate, and can be withdrawn from the sand at the angle of the washout holes.  Then the back portion comes out perpendicular to its plane.  That way we get all the holes without cores, and the amount of draft required is minimized. 

Bernie Perch

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Re: WW&F No. 11 - Official Work Thread
« Reply #317 on: January 15, 2015, 10:32:11 PM »
Howard,

WOW!!!!!!!!!  I love how you solved some of the complexities of this casting.

Bernie

James Patten

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Re: WW&F No. 11 - Official Work Thread
« Reply #318 on: January 15, 2015, 10:54:06 PM »
If you look at the picture, we are creating a split line on the pattern along the dashed line B-B, so that the sides with the washout holes are separate, and can be withdrawn from the sand at the angle of the washout holes.  Then the back portion comes out perpendicular to its plane.  That way we get all the holes without cores, and the amount of draft required is minimized. 

I've looked at this a couple of times and I can't say that I understand.  Since there are "wings" on both forward and rear, that means the whole casting has be to pretty deeply in the sand, and there has to be sand (or maybe its a core, not sure of terminology) around it to make the wings.  So how do you remove the wing with the washout hole without messing the rest of the casting?  Do the wings fold back so you can then remove the main part?

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #319 on: January 15, 2015, 11:08:45 PM »
James,  the back side of the pattern will be filled completely at first with a wooden construct called a follow board.  It will be flush with the back surface, where the mold will split, and extends out top and bottom a few inches.    After sand is rammed up over the outside of the whole thing, the follow board is removed, the sand is dusted with parting compound, and more sand is rammed up in place of the follow board, forming a core.  The core comes out; then the pattern is removed in three pieces, then the mold is put back together for pouring. 

See Alan's sketch below; the follow board is the red part:

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #320 on: January 16, 2015, 02:35:45 AM »
Daily progress update: 

I glued up material for the top and bottom flanges of the side wings.  I cut the 40 degree separation line where the back will join to the sides, and also made the flanges that stay with the back portion, and glued them on.   

The 40 degree cut was interesting, since I could only achieve 45 degrees on my table saw with the pattern laying flat.  I then used a hand plane to bring it down to the line. 

The flange sections started as glued up plywood to the thickness I needed, then planed to get a 2 degree draft on both sides (using the planing jigs that Alan came up with).  I printed out full size patterns for their shape, glued it on the surface, cut them out on a bandsaw, and used my hand plane to flatten the mating/gluing surface.  Note the dovetail feature which will interlock with the corresponding flanges on the sides (once I make them).


Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #321 on: January 17, 2015, 02:32:55 AM »
I didn't have too much time to spend today, but I got a start on the top and bottom flanges of the two side wings.  I printed out the drawing full size (it took four pieces of paper to fit), glued it on the wood stack for both the left and right flanges, then cut it on a band saw.

The second photo shows how it fits on the main back portion of the pattern. 

Each of these I will need to taper to get the required 2 degrees of draft. I can't think of a way to do it with power tools, so I will mark the finished width along the outer edge, and use a hand plane to taper it from the inside down to the final outside thickness.  Since there are four of them, it will take a while.

Stephen Hussar

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Re: WW&F No. 11 - Official Work Thread
« Reply #322 on: January 17, 2015, 01:36:55 PM »
Amazing!!

Stephen

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #323 on: January 19, 2015, 01:01:55 AM »
Rear extension casting pattern:

Sorry, no pictures today.    Progress is not quite so visible.   All four of the flanges for the two sides were cut out, cleaned up to their lines, then tapered by hand on both sides to achieve the required draft.  I then made a full size template for the inside of the "U" to use to fine tune the fit of the flanges to the back portion of the pattern.  They are now all tuned up and ready to go.

Next I need to make the vertical portion, the web the connects the top flange to the bottom flange.  I am going to stack laminate them from plywood, so each layer has the shape of the cross section.  I am preparing two templates to use for these, since I will need to cut out and stack 16 pieces of 3/4" thick plywood for each side.   It is really amazing how much plywood a pattern can eat up.  Just the four flanges took almost a 1/4 sheet of 3/4 ply. 

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #324 on: January 21, 2015, 01:13:38 AM »
Pattern progress:

This pattern seemed to go really fast at first.  The back portion was large but relatively straight forward, so it went together fast.   The two side wings are taking a lot of time.

Over the last couple of days, I have cut out all the pieces to stack laminate the two sides.  There were a total of 36 pieces required.   In the picture below, you can see where I have glued up two stacks, which will make up one side.   In the foreground are the two templates that I used to generate them.    After I glue up the pieces for the other side, I need to do a lot of hand work to fill the voids exposed in the plywood, smooth the surfaces, then cut to final height.   I am debating whether to cut out the large oval holes for the clean out plug access before final glue up, or do it in each individual piece first. 

Harold Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #325 on: January 23, 2015, 02:18:40 AM »
Today's pattern update:

I finally got one side all glued up, as you can see in the picture.  There was a lot of tedious hand tweaking to get it to fit properly.  You can see that I cut most of the oval hole before assembly, except for the center web -- which I will cut out later.  The problem with stack laminations, is that they can skew during glue-up, and then nothing is square because it parallelograms.     I am probably looking at two more days of work to do the other side.  Despite spending more time on the stack glue ups, they are worse than the first set. 

Keith Taylor

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Re: WW&F No. 11 - Official Work Thread
« Reply #326 on: January 23, 2015, 02:28:27 AM »
Harold on the laminations, could you put in a couple of holes in a set location on each layer and then use a dowel as a register pin to ensure that all of the layers line up perfectly?

Keith

John McNamara

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Re: WW&F No. 11 - Official Work Thread
« Reply #327 on: January 23, 2015, 03:57:47 AM »
The slipping laminations reminds me of my mother making a fancy dessert for her bridge club. It involved slicing an angel food cake into about five layers, putting a filling between the layers, reassembling the whole thing, frosting it, and then chilling it in the refrigerator.  She had failed to make the slices absolutely parallel, and the chilling process somehow made the filling more slippery. No number of toothpicks (similar to Keith's dowels) could stop the impending sideways collapse. The result was too ugly to serve to the bridge club, but my father and I found the taste was unaffected by the disaster.  ;D

-John

Alan Downey

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Re: WW&F No. 11 - Official Work Thread
« Reply #328 on: January 23, 2015, 06:25:32 AM »
Keith,

I can't speak for my dad, but while dowels would be an effective way to assure the pieces stayed aligned for a glue up, brad nails also work stupendously. as long as you're sure that you won't need to cut anything later. But my dad and I have differing philosophies on the use of brads.

I was at home last weekend, so I grabbed a couple pictures of the pattern while Harold was working on it. They give a much better sense of scale for the whole thing- it's really huge. I've been working with the drawings and 3D model for the casting for the last few months, and I still was taken aback when I saw it in person. And it's even larger now that the wings are going on.

It was a nice 70 degree day, so we rolled up the door and enjoyed the fresh air!





Filleting has been the biggest time suck for the pattern making process. If we could speed up that portion of our work, I believe that we could really increase our pattern output. Thus, we've decided that the Rear Frame Extension would be a great test bed for us to use commercially available wax fillets. So we ordered some loose ball bearings, and I've spent part of the week making ball end fillet tools. I've got a little Sherline lathe in my apartment that makes short work of little projects like these. We're looking forward to finding out how they work. Hopefully well!


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Bernie Perch

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Re: WW&F No. 11 - Official Work Thread
« Reply #329 on: January 23, 2015, 11:51:29 AM »
Harold, Alan,

I am an advocate of the brad method and when making core boxes, I use wallboard screws to keep everything in place.

Bernie