Chrisreyn

I dont build trailers or know squat about engineering( though I had an electric train once ), But I do know that every horse trailer I have ever looked at has had channel for the frame and bracing. I would agree with the idea that tubing could rot from teh inside out.

BTW just for arguments sake, the strongest shape structuraly is a circle...

NORM

BTW just for arguments sake, the strongest shape structuraly is a circle...


just for arguments sake, the strongest shape structuraly is a triangle..

Hoss

I can answer this question, but it will cost you.

HOHN

Ha, Norm reminded me that I had more to say. Blame him, not me

Consider for a moment a typical beam, let's call it a 2x8 or somesuch. Imagine you are looking down the end of the beam, so that you see an the narrow end. Now imagine that there is weight on the beam and it's having to support that weight. What kinds and magnitude of stresses are on the beam? It would look something like this:

----------> 10ksi UPPER PART OF BEAM LOADED IN COMPRESSION
--------> 8ksi
------> 6ksi
---->4ksi
-->2ksi
> 0ksi MIDDLE OF BEAM HAS ZERO FORCE-- COMPRESSION
--> 2ksi AND TENSION CANCEL EACH OTHER OUT.
----> 4ksi
------> 6ksi
--------> 8ksi
---------> 10ksi LOWER PART OF BEAM LOADED IN TENSION

Now, my terrible graphic shows a linear increase in force as you go out from the center of the beam, but in reality, it's not linear (as far as I know-- maybe an engineer could correct me). It's probably more of a parabolic shape.

Now, the taller the beam is, (say we went to 2x12 instead of 2x8), the more "leverage" it will have in supporting the load. In the case of a trailer, C channel that's 1" x12" would be much stronger than C channel that's 1"X 4", EVEN if the smaller channel was twice as thick!

Also, dimensions and shape matter a lot more than just pure thickness. For example, with round tubing, a 4" .080 wall is going to be a LOT stronger in bending than 2" .120 wall. Strength difference purely in tension or compression would be a different story, as in this case is would purely be a function of the sectional area supporting the load-- shape matters little.


Hope this helps. Someone please correct me if I'm wrong.

After all, I was a Political Science major

DR3500

I think you are under estimating you weight a little, I have a 10,100# GVWR 16x6.5 flatbed equipment tag trailer that weighs 2500# by itself. the GN is gong to make it alot heavier and all of the extras you are wanting is going to add up considerably.

westcoaster

If the tube is sealed on both ends, and there are no holes drilled in it, I can't see where the rust would be a problem. The oxygen would be used up rusting the inside for a short while, but once the oxygen runs out there wouldn't be any more rusting....

j-fox

Are you planning to fill the tubing with cement, Hoss????!!!!!

Pop-Pop

I can't resist wading into this discussion about which shape is the strongest. There is no one simple answer. There are different kinds of loads on a trailer and the loads are different across the trailer, especially as it is loaded and then pulled down an uneven road. A part chosen to resist bending, in the vertical direction, may have little resistance against twisting. Pipe will resist twisting but does not carry a bending load as well as a wide flange beam. In most instances, good cross-bracing will stiffen the entire frame up so that the cross-bracing becomes more important than the shape of the structural member. Unless you can select the lightest structural components, the whole thing will be as heavy as a Sherman tank.

getblown5.9

if you were building a trailer...could you pre-stress or arc the main beam(s) of the trailer to give it strength like you see on big rig flat beds?

Rauschbo

Load across the beam is linear:

<--------- Surface: Tensile Stress
<-------
<-----
<---
<-
----------------- Load is -0- across the neutral Axis -------------
->
--->
----->
------->
---------> Surface of lower web: Compressive Stress

Note that the load bearing regions are in the actual webs of the beam

The derivation of strength comparisons and Section Modulii are a bit beyond the scope of this thread, but the wide flange (I-Beam) is stronger than a rectangle......

...if weight is a consideration (weight of the beams), you can back-calculate a required section modulus given the load + factor of safety, then find the requisite beam / tube dimensions - and weight/ft. - from any of dozens of ASME of industry handbooks.

Mexstan

We used to design and build 5-10 ton self loading trailers in Africa that were used to haul sugar cane out of the fields and then on to the mill. Same for lumber. Hauling these trailers fully loaded over rough fields and then taking them on the highway was hard on them structurally but we never had any problems like our competitors. Why? Because we used channel exclusively. We also ran a beam from the 'tongue' of the trailer to the back member to distribute the "pull' loads. This beam was lower then the crossmembers so formed a triangle for structural purposes.

Rauschbo

Note: Wow, you guys are pretty impressive, there are some good thoughts in this thread....
Rauschbo

Ripper406

Im pretty sure they use huge hydraulic presses to get the frame to bow, and then they cut small square holes in them to hold shape. Would be too difficult to do this on a personal trailer.

TIMMY22

this has nothing to do with the trailer but for the record...

the strongest shape is not a circle nor a triangle.

the strongest shape is a honeycomb (hexagon).

Pop-Pop

You can build the frame with a bow in it like the big flatbeds, then by the time the trailer is flat, it's carrying the rated load. Keep in mind though that this is work for structural (civil) engineers. If you do it by eyeball, you may have to break a few trailers before you get it just right.