Monday, October 26, 2009

Drawing in Steps

As I waited this morning for my student to arrive, I couldn't resist this photo.

Alan asked if he could do his comb back rocker with a shield seat instead of the oval that I usually use and I thought the redesign required would be a good way to show the drawing process step by step.
I began by designing the seat pattern full scale. I used other chairs and just a basic sense of what I wanted to locate the legs and proportions.

The first step in the drafting/design process is to block out the seat in the 3 views.

Then I located the legs by measuring the pattern that I made.

Next the seat shape can be drawn from the pattern. The location of the coves cut into the side are very helpful.

This is where I leave the pattern and start designing on the page. These are the leg angles. On a rocker, it's important that the locations of the front and rear legs will give a nice looking taper effect to the rockers as they exit the rear legs. Notice that because the seat is drawn parallel to the floor line that the rockers unnaturally pitch up at the back, I'll correct this later by redrawing the floor below the side view.

Below, the armposts and rail set in place. I used the same curve from my normal comb back to get a lot of these measurements but I did lengthen the arm 1 inch to account for the deeper shield seat.

Next come the spindles and spindle spacing on the seat, arm and crest. Once again, each drawing informs the others.

Finally, I add some details to help the overall feel and proportion. We'll have a chance to see the finished chair at the end of the week!

Sunday, October 25, 2009

Fall Day

Here is a little birds nest that Sue spotted in the sugar maple that we planted near the goat barn.

It's made out of my shaving pile. I can't tell you how many times folks have commented that I should find a use for my shavings (I do mulch and burn them), and I assure them that my market research has come down heavily on the side of chairs being the more valuable outcome of my labors. But leave it to this little bird to prove me wrong, as far as a housing material, what a jackpot.

Below is an orthographic projection of a chair that I am designing for a class next year. It's a more realistic view of the actual look and process that I follow.

I start with "stick" drawings, like the one that you see in the front view and then use the various views to inform my design. Once I like the basic skeleton, I'll add some thickness to some of the parts to get a better feel for the proportion, like in the side view. I didn't know how to draw orthographic projection until Dave Sawyer showed me how, so don't mind if I back up to explain it a bit, figuring that maybe you didn't arrive with this info either.

Basically, it's a means of taking information from one view and mapping it onto another. The creepy looking floating eyes show how the views relate.

For me, it becomes a game of give and take, playing what looks right in one view against how it affects another. On the given drawing, you'll notice a large square that connects the same point on each drawing. Notice that by "refracting" the side view at the 45 degree line, the information from the side view can flow correctly to the overhead view. This is a vital piece of info for the techniques that I am moving towards showing.

I generally begin with the seat shape, of course I draw it as a large block and then later create the actual seat shape. I really suggest giving the drawing board some time, it may not become your process, but it will definitely help cement the chairs elements in your head.

This is a pretty easy drawing because the only curve (the bow) is parallel to one of the sides. Later I'll go into what happens when a curve follows a sightline off the square axis.

For those of you who have been following the progess of my goats etc... here is the finished goat barn!

Here is the milking room, which for now is where I am storing the hay for easy access to the built in manger.

The manger is in the wall that separates the milking room from their "loafing" area.
The hay that they love to pull out and then disregard forms a bed that they can enjoy while laying in the sun coming through the front door, we should all have it so good!

It looks like we've found a proper suitor for our Maggie and hope to get her in "the family way" in the next few weeks.

Monday, October 19, 2009

Back to the Drawing Board Part 2

During the class at Highland Woodworking, Curtis and I were chatting about the trig tables that we use and teach for figuring out the sighting lines and resultant angles. He mentioned that someone had shown him a means for arriving at the solutions by mapping them out, as opposed to going to Drew Langsners book "The Chairmakers Workshop" or some other math route for the charts. This really appealed to me, but Curtis couldn't recall how it was done. So, I set out to figure my own way.
The sight line angle wasn't so tough, it's really just the overhead view of the chair and I've been drawing those for years, but the resultant angle for drilling was a bit trickier. After a bit of thought and doodling, I had one of those lovely eureka moments.

Below is the first step, which picks up where we left off with the diagonal of the rectangle which gives us the sight line angle. Simply draw a line at a right angle to the diagonal and the same "common rise" as used on the front and side views.

Then, complete the triangle to the other side of the diagonal line. And there it is, the resultant angle is opposite the diagonal line.

Hopefully, the drawing below will help clarify what it is that you are seeing. It is the profile of the plane that the leg is in.

Sorry for the crappy images, my scanner is down and photos are my only solution. Even more exciting and useful for me (it's still faster to use the trig tables) is that while doing this, I remembered a technique that I came up with years ago (and then forgot how it worked) for viewing a chair that I am designing from any angle. Once again, I know that computers can spin an object in space with no effort, but to see it emerge on the page still gets me going.

I know that I am not the first person to figure any of this out, but I see this kind of problem solving as skill building for working with the complex geometry in chairs. So with a little more primer on orthographic projection, we'll get to the real fun stuff.

Saturday, October 17, 2009

Back to the Drawing Board

Over the past years, I've abandoned full drawings of my new chairs in favor of thumbnail sketches. The techniques that I developed for getting the chair together have gone a long way for me. Now curves of all sorts and in all places don't intimidate me, but as I honed the geometry of the pieces and wanted to set them "in stone" as it were, I heard the drawing board calling.

Above are some of the tools that I use to draft my chairs. Before I go any further, I know that I should probably get this out of the way. Yes, I know about Sketch Up, Cad, Solidworks etc... and agree that they are amazing. If I didn't think so, I probably wouldn't be paying someone $150 an hour for drawings of the new Caliper parts! But I've been drawing since I was a kid and its one of my most pleasurable and productive habits, so for now, I'm sticking with it.

Below is the basic look of the three view drawings that I use to render the chairs. Of course this is a sketch to get the point across, the actual point to point drafting will come later along with a fourth view that is incredibly useful.

I'm going to cover a technique that I use for mapping the angles for drilling the legs. The most common way of referring to these angles is the rake and splay. Rake is the angle that the legs projects when viewing the chair from the side, splay is the angle that the legs project when viewed from the front.

One important fact that will help out later is to note that both angles share a "Common Rise" which is the length of a line dropped straight to the floor from the top of the leg. The rake and splay are great information, but most chairmakers that I know prefer to distill this information into something a bit more manageable.

Below is the overhead or plan view of a sightline. The sightline shows the plane that is perpendicular to the seat bottom and travels through the center of the leg. When you look at this plane from the side, the leg cants at an angle that is neither the rake or splay, but when the chair is viewed from the front or side, the rake and splay will be correct.

One simple way to "get" the sight line is to turn a chair in front of you until the leg looks perpendicular to the floor, now you are staring down the sight line.

Now this may seem like an unnecessary complication, I mean, you know the two angles, why not just drill them with two bevel squares set parallel to the front and side of the seat?
The beauty of using the sightline and drilling the leg at what is called the "resultant angle" is that it reduces one of the angles to 90 degrees. Not only are we surrounded by lines that are vertical (think door jambs etc...) but we all have an innate sense of what is upright, otherwise standing, drinking, and walking would be quite problematic.

It's also helpful because it frees us from the front and side views and allows each element in the chair to be seen for the one deviation that it has along a vertical plane, which becomes even more important when we talk about curves later.

To translate the rake and splay angles from a drawing or known numbers, start by drawing the horizontal and vertical axis on the paper.

Then, measure off a common distance for the "Common Rise" on the axis. The actual length doesn't matter so long as they are the same.

Also draw the rake angle below the horizontal axis and the splay to the right of the vertical. I included the sketches of the chair to help the significance of the lines make more sense.

Then draw a rectangle that has the length and width of the rake and splay distances along the axis.

And finally, draw a diagonal from across the rectangle, this is the sight line angle.

This angle is used by connecting the two front legs (or rear) by a line on the seat blank (or pattern) and then using the sight line angle to mark the sight line.

Hopefully, the drawing below will help clarify what the line means in the chair.

So this is one piece of information, next it's a short step to getting the resultant angle.

Monday, October 12, 2009

New Sharpening Tool

Anyone who has followed this blog probably knows that I am not one to recommend buying a lot of tools. I've seen too many tools marketed as bestowing or replacing a skill as opposed to enhancing one. While teaching with Curtis (another crusader) this summer, I sometimes thought that we should be teaching a soap box making course.

But sometimes you come across something that you have been needing and it's love at first sight.

I was ambling around the showroom at Highland Woodworking and this one jumped out at me. It's a mandrel for the lathe that has the ability to run three different wheels at once. When coupled with a variable speed lathe, this becomes a sharpening tour de force. It even inspired me to get the defunct old lathe gathering dust in the corner back into working order. The mandrel needs a No. 2 morse taper and a live center on the tailstock. It runs about $50 and can be bought at Highland (you might need to call, I couldn't find it online) or from the maker Beall.

Any of the students that I've worked with around the country this year can describe the multiple grinding and buffing tools that I drag to class. I've found that no matter what the schools have to offer, they just don't add up for the special needs of chairmaking tools.

I set up my mandrel with a large grinding wheel for drawknives, next to a smaller one for drill bits and the fuzzy buffer to remove the burr from carving tools. I used the lathe tool rest to dress the wheels and a Veritas tool rest for grinding. Now I just need someone to manufacture an adjustable toolrest that fits in my lathe banjo and I'm in business.

Besides not having to drag my clunky old pillow block setup around the country, my favorite thing about this setup is that the height of the wheel on the lathe is perfect for freehand drawknife grinding. As a matter of fact, I've never had such an easy time achieving an even grind.

I must say, this is not "essential" to most folks, but if you are looking for a way to get yourself more sharpening real estate in the shop (which is almost always the case in my shop) without bringing in more motors etc... this might just be for you.

Thursday, October 1, 2009

Curves in Action

I realized that I haven't shown the final results of the curved stretchers. This is the chair that I brought along on my trip to show the class and to discuss with Brian.

I learned a lot on this one and am looking forward to working more with the curved stretchers. Having the curve between the front legs offers a number of benefits, mainly that the sitter can slide their legs under the seat. In doing so, the center of gravity shift towards the rear which naturally reclines the chair. Also, sitting in this position puts the feet closer to the contact point of the rocker and floor, which allows the sitter to push the rocker with less motion. And finally, if the sitter is shorter, having their legs under the seat allows them to extent their toes to the floor to rock.

When I make my next chair like this (very soon), I'll detail the measuring and drilling techniques that I use to get it together.