Risers for RPODS

No the FR ones aren't adequately designed either.

The problem is not the riser itself, as you say the frame tubes are too light for the application. The weak point is the rear attachment for the axle or riser to the frame tube. Because it is a torsion axle if you hit a pot hole or curb you get a fire rotating the axle up and back and trying to lift the trailer at the same time, placing high stress on the frame right at that spot. The risers make it worse because the moment arm from where the wheel hits the pothole to the frame is longer, but either way it's a well known weak spot in any torsion axle trailer.

When I did the calc for my 179 I got a design safety factor of about 1.8, meaning that it only takes about a 1.8 g bump load to bend there. That is very low, most guidance says that heavy truck frames should be designed to about 2.5 g, and passenger vehicles (which are lighter so get thrown around more) are generally designed to handle 3g or more.

The fix is to spread out the twisting load from the axle or riser farther along the frame tube. One of our members had his frame bend at that point. He had to straighten the frame and then add another piece of 4x2 tubing under the frame tube. That creates a doubled frame section which greatly increases the ability of the doubled frame to handle load and spreads out the load. It also provides a 4 inch lift, just slightly more than the 3.5 inch lift kit.

If you have access to a good welder then I'd suggest talking to him about welding a doubler tube under each frame tube and reattaching the axle to that. The weld doesn't need to be continuous as the weld is at the neutral axis of the doubled frame section so doesnt see a lot of stress.

As for doubler length, you want it to extend farther behind the axle than in front to spread out the higher forces which occur behind the axle. I did a post on that a few years ago, you can probably find it by doing an advanced search. IIRC the doubler tubes needed to be around 4 ft long, extending about 2.5 or 3 ft behind the axle, but my memory might be wrong.

If you do that reinforcement I'd suggest you also reinforce the axle tube at the same time. There have been many bent axles on rpods, that is another and probably the weakest link in the chain. I posted a simple reinforcement I did on mine which involved U-bolting a steel angle under the axle. The angle needs to be bent slightly upward in the center because the axle itself is (or should be) crowned. You would need 4 square U-bolts, two at each end of the axle just inside the wheel, oriented at 45 degrees to the vertical to mate the angle to the axle tube.

If you do those two reinforcements and also add the floor outriggers FR sells or you can make then you'll have a pretty robust trailer. The next weakest point is the toungue frame around where it goes under the front of the cabin, but I haven't heard of any actually being at that spot yet.

Should FR have designed their trailers differently to being with? Sure but they are motivated by cost and weight to keep things as light as possible, even if that kind of design won't hold up to long term ownership or use on some of our not so perfect roads.

I agree, if you don't need to raise your pod for clearance either from the ground or the wheel wells then don't add the risers. In addition to putting more stress on the frame they will increase drag (because the trailer sits higher and presents more frontal area) and lower your fuel economy a bit.

If I were to get another trailer with a desire for rougher road travel I'd try to find one with a conventional leaf spring axle rather than a torsion axle. Much more forgiving design because the load on the frame is at 4 points not two and there is no rotational moment imposed on the frame by the suspension.

Some folks (I'm one) much prefer the narrower body style of the rpods. But there's no obvious reason FR couldnt make the narrow bodies with more robust leaf spring axles and frame rails. My European built horse trailer is compact, lightweight, well balanced, and has dual leaf spring axles and dead simple bullet proof inertially activated brakes. Tows great.

The rpods are narrower in the trailer body improving rear visibility. So I didn't need extension mirrors with mine, keeping everything overall narrower and cleaning up my TV. My horse trailer is the same way, narrow body with outboard wheels. I like it that way. And there will be a difference in drag/fuel consumption. It's just hard to measure due to all the other variables.

We've had this discussion before LA, it comes down to being a personal preference. I think your trailer design is fine and I'm glad it works well for you. It would be a boring world indeed if there were only one right answer for everyone. Certainly no reason to argue about it.

+1 

The stock mirrors on our F150 lets us see behind the Rpod pretty well. The narrow body on our Rpod is a real plus to me. I think the biggest issue with older Rpods is that they made the frame too narrow, which created the cantilever axles, which required outriggers, etc. etc.