Good day gentleman. I've been contemplating a few ideas to get a full size spare somewhere on my truck, since a 37 will not really fit in the old spot. I've come to realize I'm am probably stuck it hanging off the back somewhere. Somewhere along the line my truck had some 3" square tubing welded on the back underneath the rear bumper. It serves its purpose pretty well by extending out further than any point in the rear, protecting the back somewhat, and it keeps you from tearing off your license plate off road! So I figured I could incorporate it.
I was trying to figure out geometry to give the truck a place on the rear drivers side to be strong enough to support a 37" tire when it was swung out all the way. I built a couple of these bumpers for my old jeep and bronco so thats were my brain was focused. I'm fairly confident that could be accomplished and it would probably work fairly well. But with the amount of steel that it would take I started thinking of some different idea's that are a little non-traditional. Since its going to take a lot of steel therefor a lot of weight to make some kind of tire rack I came up with an idea to utilize the square tubing on the back of my truck and design a "slide" out tire rack. I spent a few hours crunching numbers and calculating moment's of inertia and came to the conclusion that it should probably hold up. Especially if you added a second area to pin the mechanism higher up on the truck for when the truck is moving. I was thinking that a piece of 1.5" x 2.5" square tubing could be inserted into the lower square tubing and ride on a set of rollers that you would whip out in the lathe. The entire assembly would then slide out 40 or so inches so your spare tire can clear the rear drivers door.
At first I was contemplating use PTFE (teflon) or something like that and having it slide through it like a boom on a crane. But since its located at a mud gathering spot I didn't think that would be a terrific idea. So I came to the conclusion of some kind of roller set up. My dad has a light plant that just has a square tubing boom that they cut out slots and just welded a shaft with bearings to provide a telescoping bearing setup. So that can be tweaked as needed. But the general idea is to just unpin the thing and have it slide out to the point where it clears. The important thing to this design is when it is in the "go down the road, or off the road
" position it be secured higher up on the rear bumper somewhere. That way it is pinned in two places and should have no issue with being able to handle anything the rest of the truck is experiencing.
Another idea I had since either of the two require 75 pounds of steel is to make a pivoting rack that swings out side ways. Utilizing an ATV winch to raise and lower it. You can buy a decent winch for $100 and it would have more than enough strength to lift it. They winch weighs about 26 lbs. It would take about 800 lbs of force to lift up the "200 lb" tire I threw in a little safety factor. Utilizing a similar Pin or locking device you wouldn't worry about it going down the road since there would be no tension on the winch. The only time the winch see's strain is lifting and lowering. I think it would be pretty easy to hide compared to a big old swing out tire rack. Just a thought.
