Trailer design

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First off I would like to say I am not new to welding or fabrication, but I am trying to rebuild a flatbed trailer, and not have to need a 1 ton truck just to move it.  I normally really overbuild anything, and am trying to get this right where it needs to be.  So a little back story I was given a homemade flatbed trailer that was way underbuilt.  It is basically a 10-12ga 2x4 frame with 1" square between the rails to hold the floor.  With a 3x3x1/4" tongue that runs all the way back to the axles.  It has had some bracing added to try to strengthen it up, but I can jump on it, and it flexes bad.  Basically I want to remove the axles, and build a better trailer.  It has 2 3500# axles right now.  So I am trying to keep it as light as possible, but still be able to use the full 7000# capacity of both axles.  Attached is a drawing of what is going through my mind as to how to build it, but being deployed I cannot look at any pre-made trailers for a sanity check.  It will be a 8x16deck, and I am thinking or 2x4x1/4" tube for the frame, and bending it in to the coupler (fishplate the joints where it bends of course), 2x2 10 or 11ga on 16" centers for the cross pieces, and 2"x3/16" flat bar to cap off the 2x2.  I came up to roughly 700# of steel.  I will make drive over fenders, and have a plan in mind for how to do them.  It is planned to have a 2x6 deck as well.  I basically am curious if I am thinking heavy enough, but not too heavy, or if I am basically retarded with the design.  Black = 2x4x1/4"Blue = 2x3/16" flat barRed = 2x2 11 gaugeLast edited by clemet; 09-29-2011 at 05:15 PM.
Reply:What are you going to use to pull it??Over what type of roads, terrain, speeds, etc??What max loads, what type of loads???You sort of got to match up the power source to the trailer capabilities. I got a 16" trailer about like you describe but my power source is only a Ford F-150 6 banger, 5 speed and I have lots of hills with more like back roads. So I can't really haul anything up to what the trailer might do. Can get peeps cussing back there, why is he going so slow up them hills.If I was under powered I might go lighter on the trailer, would use that as the starting point.Plus you got to think about the braking. Does the trailer have any assisted braking itself? Scary if you are mismatched, way more trailer than motive power abilities with a big load on the wrong hill and only them brakes on your lil truck.Last edited by CosmicRambler; 09-29-2011 at 05:42 PM.Reason: spelling
Reply:If you want to keep a trailer as light as possible and still stay at 7K, I'd suggest you invest the $40 or so for one of the trailer plans that Northern tool and others sell. They are engineered plans so there's no guess work or overbuilt materials ( They are probably slightly over built, but since they don't have control over the weld process, they add a small bit of fudge) Your other option would be to go find a 7K trailer you like and make an EXACT copy of it. Most commercial trailers are specifically engineered to have zero extra weight. Extra weight means extra steel, and that cost money.I'll toss out the usuall safety blurb. Trailers are not begginer or learning projects. They also are not projects for those who think "it's ugly but it holds" as far as their welds are concerned. You must be capable of making code quality welds EVERY time in ALL positions . Many so called "welders" I've seen can't do this, even if they "make their living" welding. You also need to have the right machine capable of making good welds. 110v machines don't fall in this catagory ( a few might but lets keep this simple). Add to this that a trailer is a fairly complicated design structure. The design by the seat of your pants idea isn't going to work if you want to push the envelope and try to go to the bare minimums as far as materials is concerned. Spend the money for a set of plans someone has already done all the work on, and live with that..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Good advice so far.  If you need ideas google will find lots of trailers you can look at from manufacturers that should be similar to what you are trying to do.  Nice sketch too, lets us see what you are talking about.I think I would go a little deeper with your main frame and add a couple cross members of equal depth on the main frame.  The deck cross members could be 1x2 or channel to save some weight.  Depth and spacing depends on what the deck loads will be.Suggest you use an angle iron instead of flat bar to tie the ends of the deck cross pieces together.  A 1.5x1.5 placed on top will protect the wood and transfer load from one crosspiece to adjacent pieces.Good luck with your deployment, and thank you for your service."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:You'll also be able to save weight by going with 24" on center with your cross members the 2x6 will handle the weight so long as the cross members can as well. I second what DWS said about getting plans. it'll have the metal sizes and everything you need already for you.Last edited by ThorsHammer; 09-29-2011 at 11:58 PM.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:I have used the plans from Northern tool and they were detailed and good.  I took it a step further and went to a couple of trailer retailers and took measurements/pictures plus asked questions from pros on this site.  The plans are indeed a big help.  I purchased the 18ft car hauler plan but modified them some and got myself into trouble on axle placement. Specifically, getting the proper "empty"  tongue weight. I am sharing this with you as a word of caution if you deviate. Have built four more different trailers since then and all is ok, once I learned a value added lesson the hard way.GeezerPower Mig 255C185 TIGBlue 175 MIGRanger 8 Kohler 20HP1974 5K Lincoln/Wisconsin Powered (Cherry)Victor/Harris O/AK 487 Spool Gun
Reply:Thanks for the insite everyone.  I have changed my plans a lot now.  It will be more or less like ones I have seen.  I am looking at 4"channel frame with 3" channel stringers on 24" centers.  Then a 4" channel tongue that sits under the frame.Actually this is the one that really got me thinking as to how to build it, and make it easier/less material.http://weldingweb.com/vbb/showthread.php...flatbed&page=2I still have to get my other welder before taking this one on since right now all I have is a 220v Lincoln 180a wire feed.  I plan on welding it all up with an older stick welder that my dad is giving me.  I forget what brand it is now, but it's what I learned on, and have welded on my share of farm equipment back in the day.  I do plan on practicing quite a bit to get back in the swing of things before taking on a project such as this, and if I don't feel my welds are up to the task I will be getting help because I really don't want to look like an idiot if it brakes let alone hurt someone hence the reason that I usually tend to overbuild things.To answer a couple of other questions I saw right now my main plan is to carry my quads, and every so often my truck, but ultimately I will upgrade from this to a 10k equipment trailer when my truck is done so that I have no concerns as to the trailer.  That also brings in the 1 ton truck to pull said trailer, and that means even more money.
Reply:Don't forget to also consider where you are going to put the spare tire. (The What?????) Maybe a tool box with jack / tools. And where are the tie down points, hopefully built right in. It doesn't need to depend on the pulling truck for support, which will probably be forgotten.Some trailers also have a way to put a battery / winch in temporary. You would be surprised how many over loaded hulks there are roaming the highways and byways with no spare, or even a way to get a tire off. You say spare, the answer is "What". When one tires goes, another is not far behind if you got too limp.