Been there done that - a long time ago. Great little stands and yes - very economical.
Don't really need any plans.
1/2" or 3/4" conduit? NFW! Use the 3/4" for the steps and angle braces though. 1" will suffice if you keep Hoss off the things. But I wound up using the 1-1/4" top rail fence post (for chain-link fence applications).
Make the 2 risers by simple using a bender and going 90-degrees or a little more open. Using the top rail fence post gives you an extra 6" in height because it comes in 10"-6" lengths vs. EMT @ 10"-0"".
You can just weld the rungs on to the risers but I went to milling slots in the risers and fitting the rungs into the slots and then welding. Rungs are nothing more then 3/4" EMT with 1" of each end flattened in a vise and fitted into the slots.
Set the whole thing up with ratchet straps holding it together, nice and square, spot weld here and there. Check for square and finish weld it. I set mine on a steel welding table but a good flat concrete floor should suffice.
WELDING (IMPORTANT!)
1.Practice welding on some scrap tubing to get the feel. It is thinner material and if you get into hot you're gonna blow holes.
2. I find it welds better if you gring some of the galv off where you want the weld. If your a really good welder you may not need to.
3. It is galv! The fumes I believe put out cyanide gas? Anyway the fumes are bad for you. I have a large exhaust fan in the shop and I place a fan behind me blowing the fumes away and to the exhaust. At a minimum use a fan to blow the smoke away from you!
HARDWARE
1. (2) 1/4"-20 eyebolts with (4) 1/4" flat washers, (2) 1/4" nuts and (2) 1/4" nylon insert lock nuts. Weld the eyebolt so it can't open up. Run a nut on the eyebolt all the way and a washer. Put thru the 5/16" hole drilled sideways under the platform, another washer and the locknut. Tighten until just barely snug. DO NOT DEFORM THE ROUNDNESS OF THE TUBING BY TIGHTENING THESE EYEBOLTS. This is where you hook your ratchet strap hooks.
2. (4) 1/4"-20 X 3" bolts, (4) 1/4" fender washers, (4) 1/4" flat washers and (4) 1/4"-20 nylon insert locknuts. Attach the platform with bolt thru fender washer thru platform, thru tubing, thru flat washer and secure with nylon insert locknut. AGAIN - DO NOT OVER TIGHTEN AND DEFORM THE TUBING.
PLATFORM is 3/4" plywood. 3' wide X 2' deep. Put a "V" in it as shown to center on tree. Holes for bolts should be 5/16". I drill holes for some extra slugs to be handy.
IMPORTANT You DO NOT want your legs under your thigh to be hanging hard on the front edge of the platform while you are sitting. So measure and place your top rung carefully to keep the back of your thigh unpressured when sitting. Consider all the different people who might be on there. Make it for the shortest set of legs. Place your remaining rungs evenly the rest of the way down.
KICKERS. Put (2) 3/4" EMY kicker braces as shown in drawing. These may or may not be needed depending upon ow much weight is in the stand.
OTHER We have seatbelts on ours as they are nearly exclusively used to sit in gun hunting. I go to the boneyard and pull seatbelts out of older conversion vans. Lap belts. They are attached to the seat frame and easy to get to. Most are standard nuts and bolts but be prepared and bring your allen and torx ratchet stuff too.
All our stands stay out all year. We check ratchet straps every year and replace platforms when necessary. We keep a spare supply of platforms up in the barn, some extra seatbelts and a bunch of 1/4" hardware. When we need to replace a platform we just bring a cordless drill out with us, tear off the old platform, lay it on top of the new and matchdrill the holes one at a time dropping a new bolt thru after each drilling to keep it all lined up.
Now keep in mind these stands only get your butt up about 9' at best but they work fine for us I'll tell you that.
*** DRAWING TO FOLLOW SHORTLY ***