Roorkhee Chair v. 2

chair4_sm

My original Roorkhee chair was comfortable, but it was very low to the ground and deeply reclined. I prefer a more erect seating style, and thought I might raise the chair and make it less tilted. This proved to be considerably more difficult than I anticipated. It was easy enough to test the effect of taller legs by putting the first one up on blocks, but what happens if I decrease the seat tilt? I made some new back legs in pine with holes in different spots for testing and I found that raising up the back to make the seat more level wasn’t enough by itself. It wasn’t comfortable like that. It needed some other changes like a decrease in seat depth. I didn’t have a good way to prototype that. Decreasing the seat depth also leads to decreasing the width (if you want to keep the frame square to avoid complicating the assembly) and it’s not clear that would be a good thing.  In addition it seemed like the location of the pivot point for the back rest needed to change.  What seemed like a small change to the design turned out instead to requires global alterations.  So I gave up and made a chair whose seat is farther from the ground, but with no other changes.

chair1_sm

Another change with version two was the choice of leather. For the first one I used discount leather. That leather was too stretchy, especially for the arms. So this time I took a look at leather from Wickett & Craig, which Schwarz had used in some of his later chairs. Schwarz used the Oiled Latigo, but when I looked at the samples, all of the oiled Latigo leathers were almost black. I ended up choosing the English Bridle leather which is apparently the same leather, not oiled. The Latigo comes in a 6-8 oz thickness but the English Bridle is not split, meaning the leather comes off the cow the thickness it is. I could have paid an extra $1.10 per square foot to have it split and re-dyed, but decided to go ahead and use it as it came in a 8-10 oz weight.

One problem with the original Roorkhee was the narrow width of the arms. I noticed that I would try to rest my arms on the arm rests and they would fall off, so I corrected that in this version with arms that are wider.

chairdetail4_sm

The wider arm rest is definitely an improvement.

For the first chair I cut the leather and put it on the chair. But I subsequently learned about finishing the edges, which definitely produces a much nicer look. To do this I first beveled the edges with a leather edge beveling tool. Then I applied burnishing compound and burnished the leather vigorously with a leather burnishing tool. Finally I applied edge finish to the burnished edges.

chairdetail2_sm

The top edge is rounded and smooth after burnishing and edge painting.

chairdetail5_sm

The roundover on the front edges was intended to make the backrest more comfortable, though the leather is so stiff that it may not matter in this case.

For this chair I made the legs from canarywood scraps I had on hand—the only 8/4 material I had enough of. The wood is pretty, but I think it is harder than the ideal for hand powered reaming. (It is a good bit harder than hard maple.) I had more trouble cutting the mortises than on the first chair, and the finished joints were worse. I used maple dowels, and I ended up making the back supports out of some bland apple sapwood. From sitting in the original chair I had noticed that my shoulders and back would rub uncomfortably on the edges of the backrest supports, so for this version I was careful to give them a big roundover, though in the end it may not have mattered so much because of the heavy weight of the leather.

Here you can see the process of folding over the leather of the back rest. On the first chair, this part of the project was a little irregular, so I took more care this time, making measurements, keeping everything parallel, and clamping the pieces together before making the holes for the rivets. As it turns out, this particular measurement produced a very snug fit with the stiff leather I was using.

chairdetail1_sm

I determined the fold for the seat back by clamping the rail flush with the edge and folding the leather over for a snug fit. I marked the fold, removed the rail, and then clamped the leather down to punch the rivet holes.

The original design calls for square legs with a turned recess near the top and a turned taper towards the feet.  Schwarz implies that the turned recess at the top is important because it gives you a place to grip the chair.  My first one didn’t have this.  For the second one I cut an octagonal recess.  In order to do this I made a series of parallel crosscuts with the bandsaw and then cracked out the waste.   This produces a rough square recessed area.  Then I smoothed it out with the router plane, chair2_sm and then I marked out the proper edges and used rasps to remove the corners to transform the square into an octagon. The result looks pretty good, but in the end, the only function it serves is that it gives a space for the leather that is wrapped across the backrest to go when the backrest tilts.  I never grab the chair by these “handholds” because the frame just twists.  If I do another chair I think I might just make a single shallow cutout on the inside of the back legs for the leather and skip the rest of them.

Unlike the recess in the middle of the leg, the taper to the feet is simple to do without a lathe. I started by marking the octagon on the bottom of the leg and choosing the length of the taper to be 10.5 inches. Hand planes quickly removed the corners of the legs up to the octagon’s edges, leaving the shape shown below.
legtaper1Next I measured from one triangular facet to the opposite facet to find the spot where the thickness was equal to the 1.75 inch thickness of my leg stock. This is the right spot to start tapering the legs to get a regular octagonal cross section. I marked this starting line and then tapered down to the octagon’s boundary marked on the foot, finally obtaining the completed tapered octagon:

legtaper2When I picked 10.5 inches I figured vaguely that the length of the taper on the square sides would be a bit smaller, perhaps by a factor like the square root of two. But working out the correct formula would have revealed that if I tapered the corners 10.5 inches I would only get a taper on the faces that went up about 4.25 inches. If I do this again I’ll run the taper up much higher. The length of the taper on the flat side is (ST)d / (S2T) where S is the thickness of the full leg, T is the desired thickness at the tapered end, and d is the length of the taper on the corner of the leg stock.

chair3_smSo how does this chair work? Alas, it is not as comfortable as the first chair. One observation I made after sitting in the first chair for a while was that the way I constructed the seat, which seemed initially like an unfortunate mistake, was actually a fortuitous move. The seat came out considerably looser than I had intended, and this made the seat more comfortable by giving it mobility. I was careful to model this second chair after than one in that respect.  (I marked a line eleven inches from each edge and folded the leather to that line.)  However, the stiffer leather makes the back of the chair less comfortable. With the softer leather, the bottom part of the back rest conforms to my lower back and seems to give a remarkably comfortable support to the lower back. With this stiffer leather, the bottom of the backrest is simply too close to the seat and it pokes me on the butt without conforming at all.  This isn’t so comfortable. After giving the chair more use I may try trimming off a few inches from the bottom of the seat.

chair5_smBut if I do that I’ll need to solve another problem first. Often when one leaves the chair the back ends up in a strange position. I have tried various schemes to stop this from happening. A perhaps related problem is the propensity of the bolts holding the back on to loosen themselves. I tried to solve these problems by inserting a lock nut under the wing nut, by using a wing nut and a thumbscrew, by inserting leather washers to increase friction, and by inserting Belleville spring washers to try to create tension that keeps everything together. None of these things worked—it always unscrews itself with use. If I remove leather from the bottom of the seat I’ll be taking more weight from the bottom and I’ll create an imbalance that will be even more troublesome. The only solution I can see is to add weights to the bottom of the seat supports, though that still doesn’t address the problem of the chair unscrewing itself.

chairdetail3_sm

The backrest connected using a wingnut and a brass thumbscrew in an unsuccessful attempt to create a locknut combination that would keep the chair from unscrewing itself.

Roorkhee Chair

When Christopher Schwarz started talking up the Roorkhee chair I was intrigued because the project looked so easy.  Why not give it a try?  It would supply a use for some of the mahogany scraps left over from my table.  After completing the table and moving it out of the shop I started tidying up, and ran across those scraps.  In the blink of an eye the joinery for the chair was complete.  (Meanwhile the finishing of the table was proceeding at a glacial pace in the other room and wasn’t even half done.)

roorkhee2_sm roorkhee1_sm

Schwarz says that this project is very forgiving, and I have to agree.  A variety of things went wrong, and yet the chair still works fine.  This chair requires tapered mortise and tenon joints.  The tapered mortise and tenon is  new to me and is nice because the joint wedges together and is remarkably tight without glue.  I made a paper towel holder for the shop to test the joint and the requisite special tools, a reamer and giant pencil sharpener.  These tools enabled me to quickly and easily cut the joint.  Or not so easily.  My wrist got tired of spinning the tenon cutter on the hard maple dowels.  As I was finishing up the last one my eyes fell to the instructions sheet which read, “As supplied, the cutting edge is adequate for rough work in most woods; however, accuracy and surface finish will be improved with additional sharpening.”

After cutting the tenons I made the mortises by drilling a hole (which I did on the drill press) and then tapering it with the reamer.  Schwarz has a video where he shows how to test that your mortise is square using one of the rails you have cut, and how to correct when it’s not.  I carefully followed this method.  Once everything was done and I was assembling the chair I discovered that the tenons weren’t straight.  So in fact my test that the mortises were square was no good, and instead had encouraged me to produce crooked mortises.  Despite this problem, the chair works.

The challenge in making this chair is the leather work. The Popular Woodworking article gives detailed drawings for the woodworking part of this project, but is vague about the leather work. Advice is lacking on how to fit the leather parts to the structure. Schwarz has also simplified the design since he wrote the article, eliminating two straps that are screwed to the legs and substituting a pair of buckles on the wide strap that runs from side to side behind the front rail. In doing the leather work I had trouble cutting the leather the right length. The seat sags. When I made the aforementioned wide strap it was about a foot too long. I kept having to cut the buckle part longer and add more holes. When I made the back rest, I made one side a bit too tight, so you have to force the wooden rail in. Despite all of these problems, the chair works great and is remarkably comfortable: a very forgiving project indeed.

Another gotcha is the choice of leather. I used leather from Brettuns Village because it was cheap and Schwarz mentioned them. Brettuns Village is a leather discounter that gets random shipments from tanneries. The leather I selected was the only one in stock at the time that appeared suitable: it was 6 oz leather available in a “side”—that’s half a cow. I suspect, however, that this leather might be a bit stretchier than the ideal. And it also has a surface that is very easily marked by the lightest touch or scratch. The article gives no advice at all on how to lay out the leather pieces on the side of leather. It seems that leather does have a grain direction and in principle you should line up parts along the grain, which means parallel to the back of the animal. And you should avoid the belly area, which is weaker and more stretchy, and use the area along the back for parts that need to be strong. The leather arm rests are remarkably comfortable because they give a little and can twist and flex. But even though I tried to make the arm rests as tight as possible, you can see in the picture that they are sagging quite a bit. Perhaps I need to try making them from a double layer like Schwarz does in his later chairs. I asked Schwarz about choice of leather and the answer that emerged was that you can’t judge the leather by its weight. Despite being thick, it could be too stretchy or too soft. Instead, ask the leather vendor if the leather is suitable.

Schwarz warns on a blog post that if you don’t use straight grained dowels for the rails they may split.  He said only 10% of the dowels at the home store were straight grained enough.  I ordered mine from McMaster and found that all of them were nice and straight grained.

An interesting property of this chair is that the frame is not rigid and none of the joints are glued, so it can shift and flex. You don’t notice this when sitting in it, but if you pick it up, the structure moves. As a result, the structure can shift to accommodate uneven ground. Even with one leg a couple inches off the ground, all four legs rest solidly on the floor.

roorkhee3_sm

No wobbling on uneven terrain: all four legs stay on the ground.

This chair, as designed, is low to the ground. My next one will have longer legs. This chair also has the seat tipped backwards more than I’m comfortable with. I’ll make my next one closer to flat. I wonder if it would work to make a chair with two configurations, a more reclined option and a more level one. In the published design, the chair has handholds turned into the legs near the top. I figured I could dispense with these, since they were a complication to make with no lathe. However, I noticed that without them, the leather on the back rubs against the leg. These spaces provide clearance for the leather on the seat back when the back of the chair tips down. A problem not mentioned in the article is that the chair tends to unscrew itself in use. I asked Schwarz what he does about this problem and he said he puts in a square nut to jam against the wing nut. Why square? Because square nuts are earlier historically—not something I care about. I wonder, though, having deployed hex nuts, if the square ones would be easier to jam tightly without tools. I have trouble holding onto the hex nut.