Monday, May 11, 2009

Smells Like Progress

It's been a while since my last post - busy with work and hard to keep up.

The painters have started which is a huge milestone. They are just sanding and priming at the moment. There's a bit of back-and-forth between the painters and the plasterers - they use the primer to help identify wonky spots, then the plasterers come back to fix it up. The whole house smells like primer progress.

We had a designer - Jennifer Hale - come by last Friday to give us a hand picking out paint colors for all the various rooms. It didn't cost us all that much ($260) and was very helpful. She steered us away from a few choices that she thought "would be tough to live with" (like super-bright orange in the exercise room), found a couple of great colors we never would have picked but that should look awesome, and endorsed some of our other choices or made minor tweaks to the direction we were already leaning. The next step is to see some samples to see if they still look good on the walls at full-scale.

The pantry also went in last week, looking good, and very useful. The drawers slide out on full extension slides so we should be able to get to everything.

Oh, and the replacement tile was installed and the master shower grouted:

Everyone really likes it so far! (Or at least the ones that hate it haven't said so ;-) )

Overall, the whole project has gone remarkably smoothly - that's due mostly to Drew and Fred of DMC, our contractor. However, we did have a minor catastrophe with our kitchen bar top. For those of you who have been following along, the kitchen bar is supposed to be made from an orange ("Tequila Sunrise") quartz material called Caesarstone, which looks like this:

We heard in December that that color was being discontinued, so we snagged one of the last few slabs on the West coast. It's been in storage at our countertop fabricator in Redwood City waiting until the bar was framed and the steel sub-plate was installed:

But, we got word last week that the fabricator *dropped* our slab off the forklift. Apparently the corner hit the ground and split it up the middle. They were able to salvage some of it, but not enough to do the whole bar top. Here is the sad looking remains:

We went by to assess the damage, and to look at a "replacement" chunk that they were able to find, however the replacment slab has some issues - it looks like it was left outside where the UV from the sun darkened a big stripe right down the middle. Since this counter is right in the middle of the main room, we decided we couldn't live with that kind of blemish.

So, the countertop guys are trying to scramble to find another piece, someplace, perhaps even on the East coast. We will keep you posted. There really isn't a Plan B at this point.

We are pretty disappointed to say the least, but we are expecting that they'll find a piece...someplace...

In other news, I've been trying to design our stair railing. I've come up with a cool design, but it's structurally challenging. The main feature is that there isn't a "normal" middle post on the long (13') railing - which is, of course, what makes it so cool. Well, that and the fact that "balusters" aren't - they are horizontal rods carried down all the way down from the upper landing.

I've been trying to figure out how to actually construct it so it will be sturdy, pass code inspection, can be made from available metal shapes (harder than it sounds - stainless steel comes in surprisingly few sizes in this range).

In order to get it to be structurally sound, I've been doing a bunch of "finite element analysis" (FEA) with my Solidworks CAD program. FEA is a way to predict the way structures will bend and distort, and what the mechanical stresses will be when that happens. I use FEA in my day job all the time, so I'm already equipped with the software tools.

The output of a typical "run" gives two plots - one of "deflection" (how far it will move when a certain force is applied), and one for "stress" which is how much "pain" is in the metal, which will tell me if it will break or not. Here's a typical "deflection plot":

The rainbow scale on the right shows the color-coded range of deflections, in inches. So you can see that the red portion (middle) of the railing (where the 200 pound "code" force is applied) will move about 0.4" (0.396", just over 3/8 inch).

How much is too much? Well, I didn't know, so naturally, I did an experiment :-). I clamped a piece of aluminum bar in my milling machine vice (everyone has one, right?), then grabbed the bar at various points along the length and wiggled it back and forth.

The "Test Railing":

I found the spot that I considered "too wiggly", the one that was "ok", and one that was "wow, that's plenty rigid". I then used a dial indicator (a precision distance measuring device) and a hand-held force gauge. Here it is being measured at the "OK" point:

By measuring how far the bar bent at each of the 3 locations, and knowing the force that I applied to each location I was able to simply divide the two to get "pounds per inch" (which are units of stiffness). I could then simply calculate the equivalent deflection that would occur at the 200lb test force:

So, then "all" I had to do is to design a railing in Solidworks that wouldn't bend more than say 0.600" when the 200 lb force is applied. I can also animate the movement in Solidworks so I can visualize how things move under load (click to run the tiny video):


One other issue (there are many) is that the building inspectors test to see if a 4" diameter ball can be shoved through the balusters - in my case the horizontal rods. I guess I could have done an FEA on this too, but instead I did the other usual thing - build a mockup.

In this case the mockup is just two 1/2" diameter steel rods, spaced at the distance I'd like to use (3.75"). The rods are 52" long, which simulates the longest span that will be used in the railing. If I push *really* hard, I can get the 4" disk between them, but I'm hoping that "absurdly hard" will be good enough for the inspector.

This test is supposed to (I've been told) to simulate a child getting his/her head stuck between the bars, which would clearly be bad. So, unless the inspector is trying to simulate a toddler shoving his/her head through the bars with over 75 pounds, I think it will be ok.

Oh, and one final thing - they concrete guys have returned and have formed up the front porch and steps. They should be pouring the concrete on Wednesday. It will be nice to finally get rid of that ramp to the front door, the ditches, and all the mud. Yeah!


Post a Comment

<< Home