Small Deckover Trailer

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Hey everyone,I've been in the process of building a new trailer for about 8 years now, and I am finally approaching the point where I have everything except the steel to build it. (I've been slowly collecting parts for it, just picked up an axle this past weekend, bringing my part count up to: axle, leaf springs, ubolt kit, leaf spring hanger kit, tongue coupler, lighting for trailer. All I'm missing is some small parts and 2 tires.)Because I want this trailer to last a long and healthy life, I will be using C-channel for the construction of the frame. I'm not a fan of steel tubing that can rust from the inside out, at least with the C-channel I can paint it all, and see the rust to deal with it before it destroys the trailer. I may use angle iron for the cross members to support the decking, but I'm not sure yet. Now the trailer is gonna have a 3500lb axle. I know this isn't a very heavy duty trailer, but I'd still like to go with a deckover design. The question comes, how large do I make the trailer, and how do I go about building up frame height so my tires don't bottom out on the structure? My axle has 58" spring spacing with a total width of 72" hub to hub (at least that's what I was told, I'll have to measure it to confirm). A 6' wide trailer would seem appropriate but I'm not sure how far my tires will stick out at that width, so I may need to go with 6' 6" or maybe even wider (I suppose I should pick up some tires so I can measure the width I actually need...) length, well if I'm doing 6' wide, 10' long would be the minimum I'd want to do. Any opinions on the length? I don't want to build it too big, nor too small. I'm not sure of the best size for this.For building up height for the deckover, this is where it gets a little complicated for me. I want to run C-channel around the perimeter of the trailer, but that means I need to add cross members to support the axle. If I do that, I could add a couple of C-channel running 90° to the other crossmembers underneath to build up height for the axle.... thoughts?I may have to break out the pencil and paper if none of this makes sense to anyone... I'm hoping I can hold off until after I get some input.It's a shame aluminum would cost me so much for this trailer... it would be awesome to tig weld this together using the tig welder I haven't used yet (I'm getting there, just need a tank of Argon). It would set me back a few months too while I learn how to tig weld aluminum before doing something structural like this.Thoughts on aluminum instead of steel?If the women don't find you handsome, they should at least find you handy!
Reply:A trailer should be designed for what it is used for. If you know what you will haul, then that influences design. Starting with the weight.Most deckover trailers have frame rails that run the length of the trailer and that is what the springs mount to. The crossmembers sit on top of the framerails and run side to side. Then the flooring sits on top of the crossmembers.If you want a c-channel perimeter it usually welded to the ends of the crossmemebers.Often the height of the floor is determined by the size the tires. If the height of the frame rails isnt enough to gain the clearance between the tires and the floor a subframe can be made below the frame rails to make up the difference. A subframe just needs to be long enough to mount the spring hangers and usually runs side to side to increase stability.Often the best way to figure out what you want is to go look a similar trailers and see how they are designed.Lincolin Power Wave 450, Lincoln Powermig 255, Lincoln Pro Mig 140, Lincoln Squarewave Tig 275, Miller Big 40 G(with Hobart Hefty suitcase), Thermal Arc 95S and Esab PCM875 in an already full machine shop.
Reply:I favored a complete sub frame that mounted beneath the main carrying beams.

You can adjust your height accordingly with fillers.  I believe, IIRC, my total clearance between top of the tires, and bottom of the deck, is about 4", or so, when empty.  Trailer springs compress a lot less than you think.  


Reply:BTW, in answer to your question about steel vs. aluminum.Aluminum if properly sized is strong, but it has limited fatigue durability.  It will crack after a finite number of stress cycles.  This requires upsizing structural shape sizes to reduce flexing.  For this reason, I don't like aluminum for anything that's going to be used hard, or required to undergo a lot of stress cycles.  Loooominum trailers are fine, until they start to crack here and there...............then you're chasing cracks for the rest of the lifetime of the trailer.Add to this............aluminum is much harder to weld correctly.  I just don't think it's a winning combination.
Reply:

Originally Posted by farmersammm

BTW, in answer to your question about steel vs. aluminum.Aluminum if properly sized is strong, but it has limited fatigue durability.  It will crack after a finite number of stress cycles.  This requires upsizing structural shape sizes to reduce flexing.  For this reason, I don't like aluminum for anything that's going to be used hard, or required to undergo a lot of stress cycles.  Loooominum trailers are fine, until they start to crack here and there...............then you're chasing cracks for the rest of the lifetime of the trailer.Add to this............aluminum is much harder to weld correctly.  I just don't think it's a winning combination.
Reply:Why size welder you got? A aluminum trailer will take a lot of skill and and probably need to preheat a lot of area with a torch before welding
Reply:

Originally Posted by motolife313

Why size welder you got? A aluminum trailer will take a lot of skill and and probably need to preheat a lot of area with a torch before welding
Reply:Aluminum is great when used properly. Look at semi trailers. Problem is the material is often alloys that are heat treated to increase strength and rigidity. The pieces are typically rivited with solid rivets or in certain situations bolted as welding would typically affect too large of an area regarding the heat treatment.
Reply:

Originally Posted by M J D

Aluminum is great when used properly. Look at semi trailers. Problem is the material is often alloys that are heat treated to increase strength and rigidity. The pieces are typically rivited with solid rivets or in certain situations bolted as welding would typically affect too large of an area regarding the heat treatment.
Reply:I'm amazed at the strength and rigidity of the rails on a semi trailer. The force needed to straighten them is about the same as the same thickness in steel. I always wondered what alloy is used as it makes 6061t6 seem like 5052 or 3003 alloy, very little bending before it cracks
Reply:

Originally Posted by motolife313

Why size welder you got? A aluminum trailer will take a lot of skill and and probably need to preheat a lot of area with a torch before welding