Advice & sanity check on car trailer project

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My car trailer was stolen New Years Eve.  I was going rush and buy another one just to spite the whole situation, but decided to build instead.  Please give me your input by doing some sanity checks, answering questions and offering recommendations.General: 16" long, 82" between fenders, tandem 3500lb axles, 7000 lb GVW, dovetail, 22" deck height.Deck: 1/8" diamond plate steel. If I use aluminum, what thickness should I use?  If I inset the deck (plate sits inside the outer frame rather than on top), would it be sufficient to weld angle to the inside perimeter of the outer frame to hold up the plate?Dovetail: 2' with 6" drop. Is this too much drop or too short of a dovetail?Tongue: 5" channel, 1/4" thick.  Would tube be better? (What size & thickness?)Tongue cross member: Is it necessary to position a cross member at the center of the "A"? I'd like to leave this open for recessing a storage box and winch enclosure.Outer (main) frame: 2"x4",3/16" thick. Would 1/8" be okay?Frame cross members, longitudinal (front to back): 2"x3", 1/8" thick. 16" apart (4 cross members).  I may place the 2 outer members about 10" from the outer (main) frame and space the remaining 2 evenly. I figure this is about where the average car's tires will roll.Frame cross members, lateral (side to side): 3" channel, 1/8" thick. 20" apart. Could I use 3" angle, 1/8 thick instead?Ramp storage: I'd like to have the ramps slide into the rear of the trailer, positioned in width about where the tires would go. What can I do to reinforce the back edge of the deck since holes are being cut into the frame for those ramps to slide into?Is there any benefit to to tilting if you have a dovetail? I'm also considering making it a tilt bed, just because it seems cool and doesn't seem like much more effort.Most car trailers seem to be made by adding a deck frame on top of an A-frame. Is there some advantage to this as oppsed to just extending an A-frame out the front of the deck frame?  I'd think the latter would be better because it would be simpler, less material / lighter, and the deck would be able to sit lower. The only disadvantage I can think of is a lower deck would cause the fenders to sit higher above the deck, making it harder to open car doors.Thanks in advance for your responses.  I've been reading these forums for hours the past few days and it's really helped me visualize my trailer.Last edited by moocowman; 01-06-2010 at 06:23 AM.
Reply:Welcome and sorry to hear about your old trailer.Steel design is complicated. If it was me, I'd either do an exact copy of an existing trailer, or get a set of plans from say Northern tools for $40 or so. There's a lot that goes into picking steel besides just how strong it is. Some shapes resist loads better than others, taller lighter steel can often carry more loads than short fat members. It's definitely not simple. The landscape trailers can be light because the rails act as a truss instead of a solid beam. It's all about design.You asked for a reality check OK. This would be my biggest concerns. What sort of machine do you have, and what sort of welding skills do you posses? Trailers are NOT beginner projects. You really have to have good skills to even attempt this sort of thing. Also even if your skills are top notch, what sort of machine are you going to build this with? You really need at least a 220v machine. A good 200amp+ output mig or decent stick machine as well as the skills to use it is mandatory. This pretty much rules out almost all cheap units. I won't say you have to be a pro to do this, but your skills had better be at that level for this sort of project.You might also start doing a bit of price checking. If this is a tandem axle, 7K trailer the materials won't be cheap. Start adding up the costs, say thru Northern Tools, to start, 2 axles, elect brakes, battery, tires, rims, wire and plug, coupler, lights, fenders, jack, , safety chains and hooks, springs and hardware, paint, wood deck, tie down rings... let alone steel, wire and gas, rod, grinding disks, cut off wheels... and I'll bet you will find you are starting to get pretty close to the cost of a factory unit. I've got most of the steel to do one myself, and unless I can get some super deals on tires, axles and brakes, it just doesn't pay for me to build onePersonally from the questions you are asking, I really wonder if you have the skills and tools to be able to accomplish this job. Remember 7K rolling down the road will KILL if things go bad. If you've got a nice race car, or restored classic, you might just be kissing it good bye if the trailer takes off on it's own because your welds fail..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:utilitytrailerkit.com has kits. Everything except the steel to build what you need in every design and option. I have priced out items separately and you wont beat their deal, even after paying to ship it all you will save several hundred dollars.
Reply:If you use the materials you mentioned, I'd estimate your trailer to be in the 2300-2500 lb range empty.  That means that you are left with a 4300-4500 payload capacity.  Hauling a full size truck would be out of the question unless you go with heavier axles.  Be prepared for a sore wallet to do it right.My name's not Jim....
Reply:Experience & skills: I've built two trailers by myself before, but they were smaller single axle.  One of my mechanics will be doing most of the welding.  He was a welder until I hired him at one of my shops.  I've seen a Miller 220V in his garage. I only have a small Lincoln 110V wire-feed MIG myself.  Cost: One of my customers owns a steel yard.  He's agreed to barter materials for service on his vehciles.  Another customer owns a trailer supply store. Torsion axles, brakes, hubs, etc. for $350 all.  I already have wheels and tires.  Breakaway kit uder $50 on eBay.Weight/materials:  Boostinjdm, thanks for the input on the weight.  What would you suggest I use in lieu of the materials listed?It doesn't really come down to cost.  I figured it could cost as much as 150% the price of buying a factory-made trailer and I'd be okay.  I want the satisfaction of having the exact trailer I want.  Every trailer I see has one thing or another I don't like and can't be easily modified.  If I happen to come across anyhting that can be modified to my taste I'll do that.  But for now, this is what I've planned.
Reply:actually, I kinda like the materials you have mentioned.  If you want, take a look at my thread for ideas.  It's called "boostinjdm's trailers".  I use a lot of 2"x3" 1/8" wall tubing and 1/8" deck plate.My name's not Jim....
Reply:Boostinjdm... Actually, I did see your posts in my reading of the forums and your use of tube instead of channel is what gave me the idea of incorporating tube as much as I could in exposed areas.  I liked how "clean" your trailers looked.  I know some will say it's unnecessary or overbuilt, but I never liked seeing exposed angle or even channel.  I'm especially interested in your tandem axle flatbed.  That's pretty close to what I want, minus plate covering the tongue because I want to drop a battery & winch enclosure into that area and plus a dovetail.  I'm looking for sleek and simple.  I don't think I'll even add stake pockets.  If I do, I may have them inside the deck. It looks like you took that same flatbed and made it into a tilt, right?  I noticed in the 1st picture of the flatbed (in front of the garage door), the tongue was a single 2x4.  In the 5th pic ot that trailer (hitched to your Dodge), it looks like you added another 2x4 wrap-around underneath the original tongue.  Did you do that because the tongue was flexing? That trailer in its original state, do you think it would have been suitable to haul cars?
Reply:Originally Posted by moocowman  I noticed in the 1st picture of the flatbed (in front of the garage door), the tongue was a single 2x4.  In the 5th pic ot that trailer (hitched to your Dodge), it looks like you added another 2x4 wrap-around underneath the original tongue.  Did you do that because the tongue was flexing? That trailer in its original state, do you think it would have been suitable to haul cars?
Reply:Was the frame of that trailer you sold to the farmer similar to the replacement you're building?  It looks like it's all 2x3 or 2x4 (1/8" thick).  Based on what you have, I'm now thinking of doing 2x4 1/8 for the frame. 2x3 1/8 for the cross members (front to back) spaced apart 20".  3", 1/8" thick angle for the cross members (side to side).As for the tongue, I had originally planned to use 5", 1/4" thick channel wrap-around under the deck frame.  But now I'm thinking I might just use 2x4 1/8 extending out of the deck frame like yours.If I can keep the height of the trailer low, I may also forego the dovetail.  I'll hae to measure and see how much ramp I'd be able to save by doing a little dovetail.What did you mean by "choppy" roads.  Like pothole choppy or rythmic, evenly spaced seams in concrete highway choppy?
Reply:Evenly spaced seams I think is the problem.  There is a stretch of highway that I travel on a daily basis and about five miles of it seems to be bad.  Without a trailer you don't notice much, but with a trailer it gets pretty bad.  I've prolly run 5 different trailers down that road and all of them have shook the truck.  Except my new dump trailer.I would use angle thicker than 1/8".  Not for strength reasons, but because of rust.  1/8" seems to dissapear faster than 3/16" or 1/4".My name's not Jim....
Reply:Feel free to PM me with specific questions.  I might even have a drawing for ya showing my member spacing and tongue layout.My name's not Jim....
Reply:Originally Posted by BoostinjdmFeel free to PM me with specific questions.  I might even have a drawing for ya showing my member spacing and tongue layout.
Reply:Originally Posted by MoonRiseNow that just sounds obscene.