Before you set the axles in place, are you going with the traditional center of balance for a trailer or the semi trailer center of balance format? If the semi trailer format, you may want to do some research on what the ideal C/B range is so you can figure out axle placement. And if you are going with that format, you may want to reconsider your coupler due to the heavier weights.
Your current coupler might work, maybe, with a traditional trailer center of balance (10% - 15% of total trailer weight on tongue) and the center of trailer horizontal rotation would be in the center of the axles where the equalizer should sit.
I considered going tandem axle on my trailer but the amount of rework to do it would have been massive and more work than it would be worth for something that would be more for looks and with minimal other practical benefit. At least in my case.
All good information. In your post you mentioned doing extra work simply for what something might look like. That almost defines what I’m doing, which makes no sense to folks who build things for a purpose. I truly appreciate all the advice on axle placement and loading, I’m aware of most of that, but it’s always good to get reinforcement. But I am building this mostly for looks and fun, although it will be serviceable to a certain degree.
I want it to look like a little tractor trailer. You’ve already seen what I’ve done to the Road Ranger. I want the trailer to look like a traditional flatbed for hauling materials, not a lowboy for handling equipment. The travel trailer frame was just about the right size for what I wanted. As stated earlier, if I took the 14 inch wheels in tight, I end up with the same track as the cab. I also mentioned that I’m building the wheel assembly like a railroad car truck.
Before I mount the completed truck underneath the trailer frame, I am going to jack up the trailer frame and back the cab up against it to get the level I want for the look I want. Then I will mount the truck underneath it with spacers to preserve that elevation. The wheels will be under the deck, not outside it, like a typical equipment trailer.
I suspect the connection point at the coupler will have to be higher, and the deck over the “pin” will have to be even higher than that to make sure the fenders clear when I’m turning and maneuvering. Like a lot of my stuff, I am going to field fit it rather than spending a ton of time on mathematical design. But just looking at it, I suspect the level deck will end about a foot and a half behind the back of the semi, it will step up about 1 to 1-1/2 feet, and then have a narrower flat platform going forward over the pin. The final design will be based on what I feel that day.
As regards the width of the trailer, that big square back bumper will actually have to be cut down a little bit. I am going to build about 8” extensions to the deck sides to match the Road Ranger about where the fenders are over the wheels on the cab, again, so it looks like a little semi.
Back to the actual axle placement and loading, remember the way I did the floating axle on the back of the semi, it will carry a good bit of weight. It’s a 3500 pound floating axle. The original Ranger axle and cab will be pulling it more than it will be carrying it. With double 3500# springs on the axles at the rear of the trailer, obviously that will carry the other half of the trailer. The actual axles are lighter, but the pair of them will carry more than 3500.
When I originally talked about this project a long time ago, I was talking about putting thousands and thousands of pounds on it. With the arrangement and the axles, assuming the trailer weighs 700 pounds, theoretically, I should be able to put 6000 pounds on it. You all know I’m certifiable, but that will never happen. I don’t think I would have any problem at all carrying 2 or 3000 pounds after I get all the electric brakes installed properly, but I’ll probably never do that either.
There’s one other consideration before I do anything heavy duty with it. When I put the frame on jack stands, you could actually bounce it a little bit. The travel trailer frames are made out of a springy steel that flexes a tiny bit with the bumps of the road. This is on purpose, since the cabins are typically nailed and screwed together, and they would shatter apart on a very rigid frame. I plan to put a couple toolboxes under the deck on the sides, and I plan on putting carriers for two spare tires, one on each side. When I build the frames for those, I plan on doing a little lattice work underneath the existing trailer frame to stiffen the whole thing. Most folks know a light weight truss can hold the same weight as a pretty stout beam. That’s how I plan on increasing the load capacity of the deck, so it doesn’t fold in the middle, while adding my other features.
Keep all those comments coming…
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