For a equal weight per foot, and an equal height (IE: 6", 8", 10") what shape would be stronger? And in what order?
1. I beam (wide flange)
2. I beam (S type)
3. C channel
4. Rectangular tubing

Application is for a trailer frame approximately 20 - 24 ft in length.

toomanydaysoffwithtoomuchtimeonmyhandslookingattoo manythingsthatIcanplaywith Shortround out

 

enter here...

http://www.engineersedge.com/materia...e/strength.htm


edit....
that maybe hard to find the info in.
but from my experience the rec tube i believe would be at the top.
Norm

 

I'm no engineer, but I'd say that rectangular tubing is going to be the strongest for a given weight.

I't obvious to most people that vertical orientation is stronger than horizontal for supporting a weight against gravity. So, when thinking of cross-sections, imagine that you have a component designed to carry weight, and another (horizontal) component mostly designed to stabilize and support the weight carrying component.

I-beams are very strong but quite heavy. They're not used in most pickup trailers for a reason. Look at certain kinds of flatbed trailers for Class 8 rigs and you will see that they have one big I-beam running down the middle, with smaller I-beam perpendicular ribs at regular intervals (usually 15" or 18"). While this makes for a VERY strong trailer, it's also not very stiff torsionally (twisting). It's not really an option for making a trailer yourself, because the axles you will be working with are MUCH different than a Class 8 setup.

Rectangular tubing allows for lighter weight and more rigidity while still being nice and strong. If you can find some 2" by 4" rectangular tubing with .120 wall, then it should be plenty strong for home trailer fabrication.

JMO as fellow what-iffer

 

I'd say rec. tube also...........has incredible strength!!! The I beam is great for a load bearing structure with all it's wait resting on top, but as far as twisting I wouldn't be comfortable with it for a trailer unless you did some serious bracing. But all that extra bracing will make that sucker weigh a TON!!

I'd shoot for the rec. tube!!!


~Nick

 

I think you'll find that all better brand RV's are built on an I beam frame for a reason.

 

Although I will retract my statement to a certain extent............One of my gooseneck dump trailers is an I-beam frame, just went outside and looked at it.


The I-Beam will work great, I just think it will take a little more bracing to stiffen it up from twisting...............sounds good in my head anyways


~Nick

 

all depends on the wall thickness.

 

aluminum.....

 

This might sound dumb, but I vote for The tube too, BUT, I would rather see two pieces of channel stood up a welded then a piece of rectangle or box tube. If you look at the inside corners of channel v.s the inside of tube it is much beefier.
Now, if weight is an issue the channel will kill you.
The last trailer I had was 6" channel, tough as can be. My outlaws have an enclosed race car trailer that is build out of 6" rec. tube. The wall thickness is WEAK, but weight v.s strenght wise it may have been "better" than my channel frame.
When you get into longer lenghts, the lb. per foot starts to matter more and more as your empty weight starts to mess with your final loaded weight(s).

 

For what it's worth, (prob'ly not much!), I build trailers pretty regularly and I will NOT use rectangular tubing unless someone holds a gun to my head. Tubing tends to sweat on the inside and will rot from the inside out. The way you find out about it is when the frame bends in half.

For lighter trailers, (up to 7 ton capacity), I use channel. 8 thru 20 ton capacity trailers get wide flange beams with channel cross members. I give all my trailers a 10 year structural warranty and so far, building about 10 to 12 a year, I've not had one warranty claim.

chaikwa.

 

Interesting take on all this.
My plans are to build a 20 - 24 ft GN flat deck trailer. 12K - 14K capacity.
Deck width no more than 96".
Spring centers of ~80" with 6K - 7K axles.
Frame rails of W6x12 I beam (6"x4"), or S6x12.5 I beam (6"x3.325") or C6x13 channel (6"x2.16"). Maybe bump up to 8" so the gooseneck would be same size and strong enough.
Cross beams for the platform would be probably a C3x5 channel (3"x1.5") on 16" or 24" spacing, with "not really sure" for edging.
Channel looks to be easier to work with since "angles" are easier to cut and weld.
All thoughts and opinions are appreciated. Keep it up.

realizingnowthatalotofpeopleinherearesmartatbothen ds Shortround out

 

usually, when ever I get involved in something like this, when I'm all done it would have been easier and less stressfull to shop around and just buy one than try to re-invent the wheel building it.

i realize that you probably can't buy exactly what you want so thats probably why you are in the market to build.


remember, a factory built trailer will always sell faster and for more $ than a home-maid trailer

good luck!

 

please do not take offence

quick question if its 12k-14k capicity and you use 6k-7k axels your really only hauling 9k-11k on the trailer? or did i miss a third axel? seems very light for a 24' trailer...just asking?

 

Most of what I will haul will be bulky. If I go larger than 7K axle, I get into duals. Only other option would be a third axle (ain't ruled it out). I'm probably gonna stick around 20 ft.
You're right about finding what you want. Things like liftable dovetail, ramps, tilt bed, etc. I'm taking what I like from different mfg specs and going from there. Having someone else build it will cost extra. Besides, I have access to some facilities that will make the fabrication process very easy.
I will probably overbuild. I'm not too worried about overloading myself. HOWEVER, I do have a 33 yo son whose philosophy is to fill any trailer to the top of the bedrails with whatever material he is hauling, be it leaves or rock. My 12 ft 14K trailer had 23,000 lbs in it the other day. Good thing the Highway Police (DOT) that pulled him over is a family friend.
As to aluminum. I've got access to a bunch of extruded 6061T6 and 7000 series. Just don't trust our welders on the non ferrous stuff.
Rectangular tubing is very strong. However, I agree with the condensation issue. Therefore I'm leaning toward the I-beam main frame and channel deck supports. Much easier to get to both sides for welding. Right now SWAGuesstimate is ~2,000 lbs base frame weight. Axles, tires, and suspension components will add another 5-600 lbs. I think I'll be able to stay in the 2700 -3200 lb range.
What I will do is keep a detailed log of what I do and pass the info down to those of you that may be interested. Royalties are 10% or a case of cold beer.
I've found that there are as many opinions on proper engineering of a trailer as there are companies building them. Everything from 3"x5"x1/4" angle iron to 12"x19lb I beam. And this is for a 20 ft gooseneck.
Besides, I may want to put a concrete bed on it instead of wood.
Again, I appreciate all y'alls thoughts and comments.

onsecondpotofcoffeeaftereyesfailedopenat0127Shortr ound out

 

Im thinking about making a 25ft deck + 5' dovetail GN trailer. Plan on using 2 or three mobile home axles. Now dont jump all over my case, these are not one time use axles, they have the brake assembly bolted not welded to the axle meaning they are not one time use.

Im thinking about going with 12x16 or 12x19lbs/ft I beam, total is going to be about $1,000 just for the main beams and the neck steel. Add on the crossmembers, one more extra axle, wood for the deck, GN coupler. Im thinking 2500 easy, unless I find cheaper steel or go with a 10'' beam, not much cheaper.

Or sell my current 12ft tag for almost 1K and invest into a used one. But I like to have the deck low with driver over fenders that stick out just 2-4" above the deck. That way I still have a low deck and 8ft wide for tractors or full size trucks.