Cheap observer's chair



I decided one day that my back just couldn't take standing/kneeling/lying down to find the eyepiece and that an observer's chair was destined to show up in my kit. Being basically cheap (the banker/wife insists) I couldn't spend $100 on one of the beautiful chairs that a member of the local RASC makes.

I did some research on building a chair and found the Denver Chair in several websites that looked like something I could build (I'm relatively challenged carpentry-wise). With plans in hand I went to the local lumber yard and bought the needed supplies. My total expenditure was $16.00, but I had a few parts on hand that might have put the price up to about $25.00

Part list
  • 2 2x4 remnants, pressure-treated and about 4' long
  • 1 3/8" bolt 6" long (with nylon lock-nut)
  • 1 1x4x3/4 piece of plywood.
  • A hand-full of wood screws**
  • A hinge**
  • Something to use as a spreader bar (or anti-spreader bar)**
  • One small L bracket**
    ** Items I had lying around

    Originally I just used some aircraft cable that was lying around the garage (from what I don't remember) to keep the spacing of the legs right; but you could use nylon strap, an old belt, some rope... whatever. Of course, this won't keep things spread, but it will keep it from spreading too much. As you'll read, I replaced the aircraft cable with a proper spreader bar.
Tool list
  • Jigsaw
  • Screwdriver
  • Drill
  • Chisel
  • Dremel tool with some bit that can 'hog out' a mortice
  • Sander (or not)

Layout
    The Denver Chair is basically two 2x4s hinged at the top with a single cross-piece like a T at the bottom of the front leg. I put the cross-piece on the rear leg to have less lumber swinging around the tripod. It seems to make no difference. I cut the front leg 34" long and the rear 37.5" long. This does give the seat a tiny bit of forward tilt but it means that the front leg folds against the rear leg and the seat folds up for a pretty flat package. If you want the seat riding flat, just make the spreader longer.

Seat plans
    http://members.tripod.com/denverastro/seat.html

    I cut my seat supports as per the original Denver Chair plans (below). I didn't bevel the seat rear to fit the angle of the support and it seems to make little difference with my design. If you're following the Denver Chair plans to the T you'll want to do this to put more bearing on the anti-slip tape that they call for. As you'll find out, I don't use the anti-slip tape.



    The seat is all cut from 3/4" plywood. Some places sell 24x24 pieces which is all you need. I had to go with a 12x48x3/4 piece as it was all they had in pieces.

Top hinge
    I had an old hinge around which I used at the top of the chair to connect the two 2x4s. It wasn't 'spec' and it's not pretty, but it works darned well and I wasn't out of pocket for it.



Keeping things up
    The 'traditional' Denver chair uses non-slip tape down the front of the fore-leg. I didn't do this as it would have upped the price by $40... to keep things from sliding around I drilled a pair of holes every 2" down the rear of the front leg and hammered in some metal dowels in that I had lying around. This gives me 'pre-sets' and not a continuously variable seat-height, but it's close enough. Instead of dowels you could put in wood screws and just cut off the heads when you're done. Leave about 3/8" of the screw proud of the 2x4. The dowels don't take a lot of 'down' pressure, they just keep the seat from sliding down the leg.


The spreader bar
    The Denver chair uses a piece of 1/8x1 aluminum bar stock as a spreader. I didn't do this but used a piece of 3/8" aluminum channel that I had left over from another project. To put it in place I just carved out some mortices in the 2x4s with a chisel and a Dremel tool; deep enough so that the aluminum channel was level with the 2x4. Then I drilled a small hole in each end of the aluminum channel and into the 2x4 while the channel was in place. For a pin I screwed in a wood screw and cut off the head of the screw with the Dremel and smoothed the end. To keep the spreader from falling off I chopped up an L-bracket with the Dremel and screwed it into the 2x4 above where the channel sits with enough pressure that I can swing it out of the way to remove the aluminum channel.
 


The last part of this project will be paint and possibly a pad for the seat. I know I have the paint lying around (it may be a funky colour) and I'll hold fast on the pad until I know that the wife has leftovers from some craft. Like I said... I'm cheap.

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