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Aluminum trailer - but too much flex

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  • #16
    Education can cost a lot or a little and spending more doesn't always equate to better. I sacrificed my Sugar Crisp box and guess what I discovered?

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    • #17
      Maybe install a torque tube?
      https://www.pjtrailers.com/options/torque-tube/
      ---Meltedmetal

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      • #18
        Originally posted by Meltedmetal View Post
        I could be smarter then I look...? I'm not. But the link to the torque tube suggests other wise? Thank you.

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        • #19
          Looks like I need to go shopping some 4x2 tubing, or maybe I should be 4x4, or maybe 2 pieces of 4x2 channel spread out. decisions....
          www.silvercreekwelding.com

          Miller Trailblazer 325 efi
          Miller extreme 12vs
          Thermal arc 186 ac/dc
          Lincoln power wave 455m/stt with 10m dual feeder

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          • #20
            Or a 5 1/2" od pipe with .237 wall thickness....

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            • #21
              No desire to pee on the Sugar Crisp intended, but it may sound that way.
              First, the connection between crossmembers and rails is insufficient. Fortunately you're seeing that before stress fractures appear.
              Aluminum is a strange animal when it comes to flex/crack.
              Were I building that frame there would be angles connecting crossmember to frame at every possible point, preferably 4 per crossmember.
              Look into cements(glue) for aluminum, more strength and less future problems than welds or rivets.

              That will get you part way, but it ain't far enough.

              Swing by a truck stop or trailer yard and look at how an aluminum flatbed is prestressed. Empty the trailer had 6" of upward bow over 30 feet from axel carrier to pin. Put 20 ton on it and the beams and deck are flat. Those beams are a lot heavier than what you're playing with.
              THINK about prestressing NOW while it's easy.

              While you're there eyeball how the Xs are attached to the beams. STEEL.
              Were I building that trailer it would already be inverted with the X coming off so a SLIDING carrier assembly could get installed. Trust me, sliding X carriers are a gift from the gods!
              Again, adhesives are your friend in this attachment, especially over the life of the trailer when you don't have to deal with wallowed out holes.
              The frame side of the carrier WILL strengthen the rails too.
              Build the carrier to accept a second X even if you don't put the second on now.

              TORQUE tubes are your friend, once you understand them. Connecting the tube to the frame is where the fun starts. A LOT of diagonal bracing needs to connect the tube to the frame or the tube is just extra weight.
              Since the frame is aluminum, bracing gets more complex because aluminum bends, flexes, wows and cracks a lot easier than steel.
              Also learn how the tube functions and the diagonals work in tension, not compression.

              There is also a lot to be gained on that frame by some simple trussing. Look at a cheap landscape trailer. The cheap sides that look like a ladder are a TRUSS. The truss allows light weight material to be strong enough to haul a lot of load. Same applies to a 53 foot fiberglass sided box trailer.

              Creating a monolith from components that share load is fairly well known. Every joint becomes important, In 2019 we use a lot of adhesives to make the joints less self destructing and longer living. It ain't new, Piper built plenty of planes from wood, cardboard and adhesive 70 years ago. Many are still flying.

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              • #22
                The young bull said to the old bull, lets run over the hill and get us a cow. The old bull replied, let walk and get them all?

                I'm not sure what the solution will end up being, but if there's one thing I do know is a bit more thinking on the solution isn't going to hurt or cost as much?

                https://edmontonjournal.com/news/loc...ders-to-buckle

                Win some, lose some, and some you manage to save?
                While It could be adding more, or backing up and redoing what's been done (been there and done that more then once), I'm sure a solution is close at hand that's affordable, practical, and suitable for your needs.

                It was suggested wind did that to the bridge girders? Lol... It wasn't me but someone thought so? Thank goodness for engineers eh?

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                • #23
                  Originally posted by Noel View Post
                  The young bull said to the old bull, lets run over the hill and get us a cow. The old bull replied, let walk and get them all?

                  And a savvy old bull says "Son, I'll just hop on my buttbuggy and ride along with you so I don't tire myself and waste energy better spent on them cows. On second thought, you just amble on down there, tell them cows there's a party here at my place, lead em back here and stop at the store on your way to pick up a 12 of Molson for yourself and whatever the cows want to drink. I'll catch a nap while you're gone."

                  That old bull knows the youngster will be tired when he gets back with the cows, and probably 6 beers into the 12 pack. Guess who gets more cows by end of day?

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                  • #24
                    Franz you seam to know a lot about trailer so maybe you can give some some good ideas here to stiffen it up. I understand and know what your saying about the pre stressed beams on big flat deck trailers. You got to understand though, I'm not looking to put 60 tons on this thing. More like a couple thousand pounds max. So you mention 4 angles to connect each cross member. The only way I see to do that is one on each side of the frame rails so I guess thats what you mean?

                    Some of the other stuff you talk about I dont quite understand. I just want to come up with a solution without spending a ton of money on material. Im kind of starting to regret building this thing out of aluminum.

                    I bolted some light channel to the bottom of the frame rails but that didnt do too much. Here is what Im thinking of doing, let me know if Im on the right track. Im thinking I should get some flatbar and box in the channel for the frame rails. Then welding on some angle braces from the rails to the cross members. 1 on each side. Further to that im thinking of cutting pieces of square tubing to go between the top and bottom channel cross members to turn them into trusses basically.
                    www.silvercreekwelding.com

                    Miller Trailblazer 325 efi
                    Miller extreme 12vs
                    Thermal arc 186 ac/dc
                    Lincoln power wave 455m/stt with 10m dual feeder

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                    • #25
                      Wilvis, you explained where you created the problem in your first post. Probably a lack of experience caused the instant problem, We know the problem, now it's a matter of working around and out of it at minimal cost and time.

                      What you have may look like a solid frame, but in reality it is a self destructive pile of Non-Connections, and each of them interacts with the others to develop more flex than you want or need.

                      " I wanted to avoid any welding on the beams as that would take the temper out and weaken them. So I thought I was being smart by simply bolting the cross member to the top of the beams"
                      The law of unintended consequences jumped in and bit you hard. Bolted joints move. Worse, you probably used steel bolts in aluminum structure, and each and every one of them moves and chews the bolt and hole each time it moves. It's called Steam Locomotive effect, building something that is known to self destruct over use life.
                      Your bolted connections are also minimal connection between 2 structural elements that really need the strongest possible connection. Honestly, in aluminum, welding wouldn't have provided much more connection if you welded all 4 sides.

                      Your further reference to bolting the deck on and still having flex says more poor connection.

                      At this stage, we need to overcome the initial problem and build some connection.
                      I misstated 4 angles thinking you also used tube for the X members. You can only employ 2 angles using adhesive and small self tapping screws to enhance the joints.
                      An angle running down the back of the channel and fixed to side of the rail will give you 500% more contact area in the joint. It will also stiffen the joint.

                      There is also the possibility of gaining stiffening from the X members by running diagonal rods from the center of the X member to the bottom of the rails. The connections at both ends of the rod will become important so I'd suggest steel rod with end plates that can be stuck to the aluminum with adhesive and self tapping screws.

                      I fully understand your goal is not to build a 50 ton capable trailer, but I remain an advocate of pre-stressing and trussing for more strength at minimal cost.
                      Your X members offer a trussing possibility by strapping them together at the top of the X member above the main beam. Since you're using aluminum and given the intended load, I'd pre-stress the assembly by supporting 4 corners and letting the axle hang. Add weight to the hanging axle to get yourself at least 2" of bow above the axel. Preferably I'd opt for a steel axel carrier/slider at this point as well.

                      Sequence of operations comes into play as well.
                      My thinking is I'd pre-stress the beams first, weld in the strapping at the top of the X members and then while still supported at the corners install the angle connectors from X member to rail. Diagonal rods can go in sitting on the tires since that geometry won't change much at that point.

                      You didn't specify what you're using for decking so I'm at a loss as to what can be gained in that element.

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                      • #26
                        Franz the decking is 2x8 rough sawn fir. Right now each board has 2 carrige bolts on every other cross member. Bolting to every cross member might help but I dont want to do that yet incase I have to pull them off to make working on the frame easier
                        www.silvercreekwelding.com

                        Miller Trailblazer 325 efi
                        Miller extreme 12vs
                        Thermal arc 186 ac/dc
                        Lincoln power wave 455m/stt with 10m dual feeder

                        Comment


                        • #27
                          Holy smokes...there's some serious smart-guy stuff going on in here. It's fun to watch. I wonder how much you'd have to pay to have a set of drawings done up by some engineer types for this sort of thing?

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                          • #28
                            Originally posted by Willvis View Post
                            Franz the decking is 2x8 rough sawn fir. Right now each board has 2 carrige bolts on every other cross member. Bolting to every cross member might help but I dont want to do that yet incase I have to pull them off to make working on the frame easier
                            KRAPPP, not enough gain to be had there to make it worthwhile.

                            3/4 plywood (form grade) would offer some potential if it gets glued to the frame with Liquid Nails & screwed, but planks offer nothing.
                            I got a hunch the planking weighs more than the frame.

                            Lets look at Plan Q-7.39-a.
                            Rubrails + gussets or diagonals.

                            How much overhang have you got beyond the frame on the X members?

                            You got a stash of 3/16 aluminum plate, plasma cutter & spoolgun?

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                            • #29
                              Originally posted by ryanjones2150 View Post
                              Holy smokes...there's some serious smart-guy stuff going on in here. It's fun to watch. I wonder how much you'd have to pay to have a set of drawings done up by some engineer types for this sort of thing?
                              You got any idea how much I charge per page for correcting "engineering" and producing a workable assembly/build plan?
                              Iffin I were smutr I cudd charge more.

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                              • #30
                                I'm told there's three ways to build something? Under, enough, or over built.
                                I'm also of the impression, the same can be said for thinking? No offense intended, lol...I think all three are present much to my amusement. Benefit as well. So I'm going to push on.

                                Just so we are clear... as far as mud goes anyways, I'm not over thinking it. My Sugar Crisp box while demonstrative of a singular design stiffener, such as the torque tube mentioned, comes as after thought to solve a problem with the original design. If I hadn't all ready thrown it, the crisp box out, I would have gone thru the effort to fab a second one with twin inner rails to stiffen things up.

                                I worked a 5 year stint in and around trucks and trailers. I don't know it all but I've seen a lot of them and the design. This one is all perimeter and no middle or center supports as it exists to prevent twist over length. Sure, boxing crossmembers will help up to a point but a box will still twist over a span length? What needed is shortening of the span is it not? I get X members, I'm not seeing any?

                                But you could make the perimeter a box to stiffen thing enough enough to resist deflection in twist? I guess?
                                Flat panel cereal box. Boxed edges? Hmm? Probably do just fine with a trussed railing around it however or sides and a top? Or a center stiffener, back bone, torque tube?

                                https://forum.millerwelds.com/forum/...num-car-hauler

                                Now Franz, Willvis, with all due respect, get out a pencil and paper, draw out what you think this should look like, what you think should be done, take a picture and post it. Clear the muddy water.
                                Other wise, poor Willvis, and the rest of us reading, or maybe it is just me (?), require another 372 more words to clarify things completing the picture of what you suggest he's doing, should do, to make things right?

                                I do however agree Franz with some of what your saying. Suggesting. Some, not all. But I also buy into your suggestion for adhesive usage. I'm a fan of the stuff actually. I'd also disagree with a bit as well, maybe because I'm un clear of what that is, if I was more inclined to do so, thankfully I'm not, I'd beat the horse to death. I'm holding out for a drawing.

                                Willvis however has to come to a solution, soon I'm sure, avoiding excess work I expect, and affordably.

                                All that said, back to the drawing board.

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