Angle iron is about the least efficient shape, and therefore the worst possible choice for the frame. I-beam or channel is way more efficient, as it is the extreme fibers (the upper and lower flanges) of a beam which carry the loads
It's a trailer with an 800 lb load. I beam? Let's see the sizing you would recommend for that
Torsional fatigue is an issue to address because many suspension movements will impact only one of the trailer tires. Even with a solid axle, you'll end up with a twisting moment if for no other reason than the axle is so much lighter than the load and has a much lower MOI.
exactly right. Angle is useful because it's many times better than just a flat bar which has useful stiffness in only one plane. Angle gives you a bit of stiffness in two planes. But it's still far behind an I beam or Channel. Put the metal where it's actually carrying stress.
Yes, the ratio of sprung to unsprung mass matters. With a somewhat heavy axle flopping around back there, it can manhandle an underweight trailer into structural failure.
From OP's original post: "The camper shell will put about 800 pounds on the perimeter of the trailer" you have assumed (wrongly) that the static load of the shell was the only load being applied.
I did not assume that. I still ask, what is the I beam sizing that you recommend?
I don't recommend it. Only pointing out that angle is possibly the very worst choice. Do your own research if it interests you. It isn't that hard.
well, there are internet engineers. Then there are engineers on the internet.
Most I've seen and read of use a SIP like floor - 1/4" ply on both sides of foam. It will easily span 2' or more.
About 20 years ago, some RV manufacturers tried using honeycomb plastic (fiberglass skin?). It was very light and worked well for a short time. After about 2 or 3 years there would be a noticeable sag in the floor where people walk. Some very large people actually put a put through. Never heard of this type of composite subfloor.
Nothing wrong with honeycomb geometry-- it's brilliant and effective.
Your suggesting 4 wheels for a 800lbs static load plus trailer frame and personal ****, maybe 2000lbs total max?
coosa board with e glass/epoxy skins is the floor to have.
I would expect a homebuilt camping trailer with cabin for an 11' x 5' to be nearer 1000 pounds, and easily accomplished.
I think you missed the whole point. Use Timbren (or anyone else's) smallest, lightest independent (i.e. just spindle, no axle) on each end of a walking beam. THAT is 10x or more travel than anything else and gives ability for very different displacement side to side.
For the trailer yes, but I am including water, gear, food, ice, ect, things that make nearly every commercial camper/rv overweight.
Not sure which one you are referring to, but the video I thought I lined is their live axle with one leading and one trailing torsion set on a walking beam. actually very simple, but I think that is their 3500 lb. one.
That is almost identical to suspensions I started building about 25 years ago. I think I have only done 2 coil (automotive coilovers for very light and delicate loads) the rest in air. Small air suspensions are easily made with the air bags from semi cabs. Absolutely the best way to make fully independant, but if you want a LOT of travel the air bags are larger and go between the pivot axis and the spindle axis. Note: they are using a complete automotive spindle (stub axle), disc brake and probably matching hub and bearing unit and caliper. I have been doing that for almost 40 years.
Sorry, that part was supposed to be deleted. My bad, Yes it the model you showed was a walking beam with rubber suspension outboard on the beam.
Self preservation.Pretty sure the OP bailed on this conversation days ago.
No doubt.
he just wants to build a little trailer and its turning into the undercarriage for a jumbo jet.But the timbren unit you showed is not a walking beam. Its just two single units back to back.
For the trailer yes, but I am including water, gear, food, ice, ect, things that make nearly every commercial camper/rv overweight.
I understand what your saying, I just think its way over complicated and unneeded.
The aussies adopted and have used the same type of independent suspension on off road "caravans" for several decades now.
Either Air or coil springs.
If the jumbo jets you fly on have landing gears that are that low tech I wouldn’t fly on them! That is about as archaic of an independent suspension as it gets.
these over engineered discussions turn so pedantic because the stakes are so....small.
The purchasing agent bought what the salesman was selling. Price beats everything !
4'x8'x34" sheet is over $200 !!
voice of reason,
The vast majority of what is offered in the trailer world are horrible pieces of **** due to the race to the bottom in price. Once you go off road, the suspension you NEED has to have a huge amount of travel or the act of driving WILL destroy the trailer and its contents in a fairly short time.
Did you compare it to marine plywood? a piece of "cheap" hydrotek 3/4" thick is around 230 dollars, okume is 250 dollars from the local Johnsons workbench. Hell even crappy ACX is 55 dollars.
Most builders use ACX. The real problem is, if the roof or windows leak (very common) water sits on the floor and it rots. Replacing the floor correctly requires removing all of the cabinetry inside. Using Coosa on a 24' travel trailer would add about $1000. Using commercial grade TPO roof instead to the residential grade EPDM would probably add another $500.
