I didn't want to make just another run of the mill ladder. I wanted a sleek design that didn't look like just another a ladder. The original design did not include the 4 feet extending diagonally off the bottom of the ladder. But I had to add them because the ladder had the tendency to tip over whenever a person shifted their weight close to or over the railings. I implored and pleaded with physics and gravity, but they just wouldn't make an exception for this project. Much as I don't want those feet--they ruin the look--they're essential for safety.
I also wanted a ladder that both kids and adults could move with ease. My sister suggested putting two non-swiveling casters so that the ladder could be tilted on those casters and then wheeled into place like a hand truck. That was fine with adults but I was concerned--given the height and weight of the all-steel ladder--that that would result in accidents when my nephews started rolling the ladder. No, that option just wasn't kid-friendly. And so I decided to use spring-loaded casters.
The problem is, I couldn't find any hardware store selling such casters. Hence, I was forced to design one that I could, with my paltry fab skills, build on my own. I couldn't think of an easy way of putting the spring directly on the caster so I decided on using a chassis to bolt the casters on and then mounting the springs on half-threaded bolts to function as guide pins which would mate the chassis to the ladder.
I was able to purchase a spring about 20" in length and about half an inch in diameter. I did some crude tests with a weighing scale to measure its displacement versus force characteristic. For this particular spring it came out to about a quarter inch per kilogram. The ladder was around 13 kg so each of the four springs would be bearing a little over 3 kg. I eventually ended up cutting approximately 2-1/4" lengths of springs.
For the guide pins I used 3/8" x 3-1/2" galvanized hex head half-threaded bolts that have a 2-1/4 inch length that isn't threaded. These weren't ideal but the hardware didn't have any 3/8 bolt which had 2-1/2 to 2-3/4" of non threaded section.
Among the mostly black, shoddy-looking casters in the hardware, I found gray-colored rubber 2" swivel casters that really look good and whose color would match the finish of the ladder
As can be seen in the photo below I temporarily tack welded the H-frame the tubings which needed to be drilled so that the holes would register as precisely as I could make them.
For the majority of the welds I used MIG--am far more comfortable with that process. But I had a new TIG machine and so used it for just about all of the butt welds, except for the steps of the ladder which were all MIG welded--I was just too ill-confident and lazy to TIG weld them.
After grinding down all the non-fillet welds and cleaning the metal I painted it with a coat of red oxide primer. Sanded it afterwards in the hopes of getting a shinier finish with the topcoat. Mys sister's kitchen cabinets are in gray and orange so I painted the ladder likewise.
|Te spring-loaded caster system. The two 1" square tubing pieces will eventually be welded to the ladder|
|Letting the paint dry completely before installing the caster system. Black rubber end caps are installed on the feet|