Ok, I'm editing the first post with the final drawing files and some instructions. If I can't figure out how to get photobucket to work I'll try and come up with something else, maybe just put a PDF up on google share, dropbox, or something like that. (Ok, I think I got pictures to work but... why are they so freaking huge!?!
The twist here is we (me and several of you that participated, mostly roguebuck) created 2 complete ladder designs. The original "tube" design is a few small sheet parts for steps and brackets along with the large side bars made from common 1 inch square steel tube. The "sheet" version idea started around page 4, cuz hey, if you have or are going to find a local shop that does sheet cutting and bending anyway, why not? Then a little after that I got into my head to try it with aluminum, and my project that way. Roguebuck and a few others have mentioned getting in on it and I hope to have a picture gallery of these things eventually.
If you recognize me you'll know that I can't get technology to work most of the time. Photobucket doesn't want to let me share pictures, my phone deletes everything I type right before I post, even this website swallows PMs into a black hole and I never get them. If I sometimes sound angry at the world, it's probably just the stupid glowing screen in front of me that seems intent on not doing what I want to do and wasting time I could be spending outdoors... So, on to the build steps.
1. Get your materials. You'll need a little over 8 feet of 1 inch steel tube, (2) 49 inch chunks are fine. (If you can only get 48", you can still get by with a little extra welding and creativity.) My first test used 14 GA steel, wall thickness of about 0.075" and it felt beefier then necessary. 16 or 18 GA would probably be fine, 20GA is pushing it 2 ways - it may not be strong enough and it's tougher to weld for beginners. (Too easy to blow a hole through it.) Around here Home Depot has 14 GA and 1/8" and thats it. If you have a full-on steel distributor like Alro (is <5 miles from where I live) or maybe get lucky at a scrap dealer. Best steel price I get is around $0.50 per pound. Scrap value is $0.05, but only if your selling.
So, you've got some steel tube, now you need my super awesome flat steps. And the mount brackets. That's the tricky part, you will be lucky to have contact with a nearby fab shop that does plasma / laser / waterjet cutting. (plasma is usually cheapest though not quite as accurate) You can give then the DXF files from the zip file and they can easily cut a set of steps and mount brackets for you. So that's the easy way. You can also just get some small pieces of sheet and cut them with angle grinder and cut-off wheel. Print the templates, cut out on the lines, trace with sharpie on steel, grind.
Final part of step 1 is bending the brackets and steps. If you have or found a nice shop they will be giving you a small package of already bent parts. If you either only got flat parts or had to cut them yourself, you get to bend steel. It is possible without the proper tools. It will be hard. If you at least have a bench vise you can get brake jaws that will do a fine job once you practice up a little. Otherwise get a hammer, find a hard object to beat on, and try not to hurt yourself. (Are you really sure you looked hard enough for a local metal shop?) When you have a set of sheet parts ready it should look kinda like this:
2. So now you have some bent sheet parts and a couple 4 foot chunks of straight tube. It's time to get out the sharpie, tape measure, and a copy of roguebuck's drawings.
Start from the end and mark each length noted on the drawing (4", 19", whatever), just go in order and make a line across the tube. If you're good at carpentry this is just like mitering a door frame except with really wacky angles. I just kinda guess and draw a "V" that looks like when you cut it out and fold it up you would end up with something that looks like the drawing. Got a protractor? That's good too. Using the cut-off wheel cut those "V" notches and adjust until you're happy with the angles. Oh, and in case it wasn't obvious, you only cut 3 sides. The tip of the "V" can be left completely uncut and when you grab the ends it should nicely bend right along that line. Even if you accidentally cut it completely off, hey, you're going to be welding it anyway, right?
3. Tack time. So, if you're a beginner welder you may not know that tacks are only for verifying fit up and somewhat holding things in place while you get the real work done. If you wimp out, it will fall apart. If you go all Biff on McFly you won't be able to adjust alignment, squareness, etc. And you can almost always just pull out the cut off wheel and start over so don't panic. In this initial part of step 3, tack up the tubes and verify the angles and end to end distance. You can stack and clamp them to help get them identical, may need to grind a little or insert spacers between the tubes.
3a. When the side tubes are ready, I start assembly with the top mount bracket. Get it positioned from the drawing info and give it 2 tacks to each tube. If you put 2 in a line, it can bend when you pick it up or turn it over and they will probably break. Try and find diagonal or out-of-plane places to tack and things will be less frustrating.
3b. Go straight down the line? NO. Well, if you want to go ahead. I usually go to the other end, then back to the middle, in some attempt to not build up too much heat in any one area. I admit that I think my fabrication skills aren't great. So for now, unless you know better, just go tack the bottom bolt bracket.
3c. Steps. Do you want the 9" step height that I chose? (I like it for leaning on, it fits right on the sweet pain-free spot between my shin and kneecap.) How may steps, 5, 4, 3? You can be as creative as you want with that. Just take your time positioning and 2-tacking one end of the step to the tube, verifying squareness to the tube, then 2-tacking the other end of the step. The steps are inserted by tilting one side higher, liging the tubes up with the slots, then tilting it back to horizontal. There should be about 0.040" gap for the weld joint so the steps should fit into place easy. When you've finished tacking all the steps, you're almost done!
4. Optionally, inspect / test / rework. If it looks good and you want to go for it, you don't need to go put it on the hatch. I did because I wasn't sure the design was right. (First 2 tries it wasn't...) But if you trust your prep, layout, and tack skills (and me and roguebuck to give you a good design) you can go ahead to fully welding the joints. The design of the lower bracket is pretty forgiving. There's a 1" contact range for the side bar to hit without hitting the hatch. If you hook the top and bottom brackets and it looks like about a 0.5-0.75" gap between where the bolts go, you did fine. (The gap will close up to 0.0-0.25" when you tighten the bolts during install, this pre-flexes the ladder so when you climb on it doesn't flex and slip the bottom mount off the hatch.)
5. Fully weld. Honestly, On my steel test I was jumping up and down on 4 tacks per side and it held fine. I had planned to weld pretty much any joint you can see, but if you only do the 1" up the front and down the back it's probably more than enough.
6. Paint as you wish. I picked white because I happened to have a can laying around. Got almost 1 full coat but there wasn't really much left. It might be cool to mask off and paint the window area parts of it black, kinda "stealth" ladder that you won't really notice unless you're looking for it.
7. Rubber hatch protection pads. In our family we go though lots of bike tubes. A tube that hasn't been patched 3 times yet is still considered a new tube. Anyway, I had a crappy 26er tube with valve stem damage due to be cut into yet more patches, so I just cut a few really big patches. I'm no expert but after I wiped the metal clean with soapy water a few drops of super glue gel stuff held the rubber patches on great. A few minutes later, trim with razor blade. If not obvious, do this to the top and bottom brackets, and glue it on the side that will contact the hatch. (Yeah, I figured you didn't really need that level of detail...)
8. Install. I did it standing on the bumper. Gently drop the top hook down in the gap and slide aft to hook in place. Try and keep the other end of the bar from damaging your paint, if you care. Hop down, pull the ladder off the hatch a few inches, hook the lower bracket up so it lines up, drop the ladder down so the side bars contact the bottom bracket. If you did it right you've got nothing but rubber touching the hatch, 2 bolt hole pairs that line up, and a gap of about half an inch between the bolt plates. I used 3/4" long 1/4-20 button socket screws and nylon insert lock nuts, but you can use whatever hardware you prefer.
9. Warnings - yada yada at your own risk yada no liability etc. If you lean it against the wall and hold on to something while test climbing your ladder that's probably reasonable and safe, or maybe it'll break and you'll fall and possibly die. Just because me and roguebuck put some effort into getting a "good" design out to the public doesn't mean you aren't fully responsible for whatever you do with that info. You can probably tell by my writing that I am not teaching how to use any tools - that's on you and assumed you either already know or will at least figure out a safe way to learn.
1. Getting materials on this path should be easy. Just say, "I want this file cut in 1/8 inch aluminum please." (You really need a friendly local shop contact.) For reference, my ladder needs about $9 worth of aluminum but cost me $12 because the sheet layout leaves leftover scrap that the shop can't use. Beyond that you're paying them for the equipment usage, labor, and whatever they think they can get you for and you agree to.
2. If you were given flat parts, you will now need to find a brake to use. Trying to do this version with a vice brake or hammer is just foolish. Really. Because it is actually quite easy to crush and/or sever fingers when learning and / or careless you can probably expect most shops to just do it for you. (It's easier than cleaning up finger bits.) Discouragement complete, I suggest you learn sheet work, it's fun.
In my case I didn't have access to a large enough brake to do the frame all at once so I split the cut file between the 19 in segments. (should be clear in the picture) For the top section I formed the C-channels first then the profile angle. For the bottom I formed the bolt area first, then the C-channels, then the profile angle.
The steps are pretty much the same as the tube version as far as bending goes. The notch area is a little different. You may thank me for making a new version for 1/8" sheet. I foolishly originally drew it for 14 GA steel, but chose to cut it from 1/8" aluminum. So many little notches that were too tight and had to be filed or ground...
3. Assembly. This part was super easy. (After those stupid little notches got fixed.) Just tilt in the steps the same way. 90 degree steps on the vertical segment, 75 degree steps on the segment that leans in over the rear window. You can't really put them in wrong - upside down, backwards, it really only works one way without looking obviously wrong. Due to the split, I had to be careful keeping the 165 degree joint tacked well.
3a. With all the steps dry fit and fairly snug, tack the top bracket.
3b. No bottom bolt bracket. Yay, easy! (You should still weld around the bend joints to make the bolting area nice and strong.)
3c. Steps self-position. Yay, easy! Just tack if they aren't snug enough to not fall out, or if you just really want to.
4. Exactly the same as #4 above.
5. Mostly the same as #5 above. Take special care at that split from vertical to leaning section, if you also cut and bent the frame in 2 parts. This is the weakest spot and the weld must be good. You can probably see in the pictures that it is the only step I fully welded. That way not only is the frame welded, but the step itself and all it's weld material is helping transfer the force over that joint.
6, 7, 8, 9. Pretty much the same as above.
Original-Original post deleted cuz "error too big"? Go check post #77 if you care what it was.
EDIT: Roguebuck's drawing file package for the sheet version is in post #80. DIY: Hatch Ladder