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  1. #1
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    Default Building a Aluminium I Beam Trailer

    hey guys i have seen some really nice boat trailers come out now i'd like to build one my self but i require assistance, ive found some i beam 130x80mm 6082 aluminium by a google search and it comes up as structural and transport use http://www.onesteel.com/products.asp...Name=Aluminium the trailer will be around 5.4m long and around 2.3m wide possibly 2.4m wide it will carry a boat weighing around 700-950kg

    will this grade of aluminium i beam bend or roll and is it a ideal grade?

    the cross members will be 50x50x3mm SHS aluminium will this be sufficient?

    draw bar is undecided yet possibly 100x100mm not sure on thickness?

    i'd like to build something along this design by with flat cross members http://www.tradingpost.com.au/Automo...=D555902476618

    last of all do u think im dreaming and its all too complicated?

  2. #2
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    Boy oh boy Gazza, you are one for a challenge!
    If I recall correctly, you haven't had the most successful of runs in your ally endeavours thus far. What have you got to weld this up? You will want a decent mig with some punch as you are working with 5mm+ thicknesses for a start plus you will require a high degree of proficiency in order to create a safe and sound trailer. Next you need to be aware that taking a steel design and substituting ally will not work. A weld in steel is relatively strong compared to the parent metal, the same cannot be said for ally. Particularly in the higher tempered extrusions, there is a degradation in the weld zone.
    Attaching suspension will be more difficult as the commercially available kits will not work due to their use of steel bracketry which obviously will not weld to ally.
    All in all, more trouble than it is worth for you Gazza, in my humble opinion.

  3. #3
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    hey karl, the aluminium boat trailers are actually bolted together there is no welding, just bending of the I beams thats all

  4. #4
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    Quote Originally Posted by gazza2009au View Post
    hey karl, the aluminium boat trailers are actually bolted together there is no welding, just bending of the I beams thats all
    Oh, okay. They must be a different design to the few I've come across.
    How do they fix the cross members? Plate them and bolt through the web of the channel? Surely they wouldn't bolt through the flange of the channel.
    Some photos would be good if you have any.

  5. #5
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    Quote Originally Posted by Karl Robbers View Post
    Oh, okay. They must be a different design to the few I've come across.
    How do they fix the cross members? Plate them and bolt through the web of the channel? Surely they wouldn't bolt through the flange of the channel.
    Some photos would be good if you have any.
    hey karl the cross members use SHS and bolt to the bottom sides of the I beams they are pretty simple

    check out this link http://www.easternmetal.com/boat_tra...t_trailer.html
    Attached Images Attached Images

  6. #6
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    I see what you mean Gazza. Normally you wouldn't drill the flanges of a chassis if you could possibly avoid it, but you are certainly correct and that is what has been done.
    You would need to put some tubes in the shs to prevent it crushing when you torqued the bolts up, but that would be easily done and bolts would need to be stainless steel to prevent corrosion issues.
    That only leaves the suspension as an issue to overcome. I guess that some SS brackets could bed made to overcome this. The bending of the side rails would be something worthy of much thought as a good bend here is critical to your strength. No heat, no cracking and minimal deformation of section will be your requirements. In all probability you will need to make some sort of press/former arrangement to achieve this.
    I strongly suspect that as a one off, this could be an expensive exercise although it would be pretty individual once completed.
    As a side issue. Where did you finish up in your Ally welding journey?

  7. #7
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    Quote Originally Posted by Karl Robbers View Post
    I see what you mean Gazza. Normally you wouldn't drill the flanges of a chassis if you could possibly avoid it, but you are certainly correct and that is what has been done.
    You would need to put some tubes in the shs to prevent it crushing when you torqued the bolts up, but that would be easily done and bolts would need to be stainless steel to prevent corrosion issues.
    That only leaves the suspension as an issue to overcome. I guess that some SS brackets could bed made to overcome this. The bending of the side rails would be something worthy of much thought as a good bend here is critical to your strength. No heat, no cracking and minimal deformation of section will be your requirements. In all probability you will need to make some sort of press/former arrangement to achieve this.
    I strongly suspect that as a one off, this could be an expensive exercise although it would be pretty individual once completed.
    As a side issue. Where did you finish up in your Ally welding journey?
    i was thinking of using 130x80 i beam and 80x80 stainless steel angle for the suspension to attach stainless steel spring hangers

    i thought i would post the trailer idea here as its a metal working forum section and thought people would know all about the strength of i beams etc.. by the looks of it no body knows much

    the trailer doesnt seem that much of a big cost, the main i beams are only $240 each and $140 each bend from rollco if they can bend it, a new aluminium trailer cost $4000+ i think i could make one for half of that

    im giving aluminium welding a miss mate however im still keen as mustard to TIG weld steel and im willing to try TIG weld stainless steel if it isnt much harder

  8. #8
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    Small aluminium trailers are still a rare sight on our roads so that is possibly why there have been few replies.
    If the correct grade and temper were used I have no doubt that 130X80 would hold up fine. My only reservation as mentioned earlier is the drilling of the flanges of the channel. Traditionally you would avoid drilling flanges like the plague however your photo's show clearly that this is the way they affix the cross members.
    One problem that you face is actually knowing the grade and temper of the alloy used in the proprietary trailers.
    If you check out a steel trailer, you basically know what steel has been used straight up as RHS and SHS are generally only the one grade. Ally is not so easy. There can be multiple temperings of a given grade. One may be as hard as a goat's forehead and the other comparatively soft. Using excavator loading ramps as an example, they are made from a much tougher grade of ally than that you would be sold if you went to Ulrich/Capral etc. This may be the case with the extrusions that your sample trailers are made from. Often, these higher tensile extrusions are not available to the general public due to an exclusivity arrangement. If you get it wrong, chances are you will not suffer a catastrophic failure, but you will build a trailer that will constantly crack and/or bend.
    You would be surprised how many commercially available aluminium truck trailers, designed by engineers and built to the highest standards suffer ongoing issues with cracking in certain areas. Ally can be a strange creature to work with sometimes.
    One question that needs to be asked is what you are hoping to achieve by the use of ally? Corrosion resistance? Weight reduction? Appearance?
    This will not be a simple build as there will be many obstacles to overcome along the way. Not saying you shouldn't do it, just saying that it won't be as straight forward as you hope. Stainless bolts will eat up dollars quickly. Stainless brackets will need welding and fabricating, (stainless electrodes?), mudguards will need consideration.

  9. #9
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    hey karl the temper is T6 these aluminium i beams are designed for supporting structures and for transport use, i looked up T6 temper the other day and it says its harden and good for 29,000 or 45,000 PSI and it mentioned something about 1500kg

    page 39 is the i beam spec's http://www.onesteelaluminium.com/pub...alogue2013.pdf

  10. #10
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    Quote Originally Posted by gazza2009au View Post
    hey karl the temper is T6 these aluminium i beams are designed for supporting structures and for transport use, i looked up T6 temper the other day and it says its harden and good for 29,000 or 45,000 PSI and it mentioned something about 1500kg

    page 39 is the i beam spec's http://www.onesteelaluminium.com/pub...alogue2013.pdf
    Okay, that extrusion is 6082 T6. That means you have a aluminium and Silicon alloy which is heat treatable, tough to bend in it's tempered state, (bendable all the same, just needs a large radius bend), has good weldability, good corrosion resistance and will have a tensile strength of 340mPa. Steel RHS and SHS are usually Grade 350LO and this has a tensile strength of 430mPa. What this means for you is that your Ally I beam is around 80% of the strength of a comparable steel one, but around 1/3 the weight. So no doubt that your I beams will carry the load. Your cross members will need careful selection though as the most common box sections appear to come in at around half the tensile strength of steel rhs.
    This project will need very careful planning and costing from start to finish so as to avoid nasty surprises. Find a trailer, measure and photograph everything if you are able.

  11. #11
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    karl, thanks mate i was looking to use the 130x80 i beam for the main frame, probably 100x100 RHS aluminum draw bar and something around 80x80mm cross members but im unsure of what thickness,grade and temper of aluminium i would need?

    edit: actually looking at onesteel they also sell the other aluminium sections i need i could go 100x50x3mm cross member T5 6082 material

  12. #12
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    Just make sure when selecting your cross member material that you use a size that will be easy to fix rollers to etc.
    Don't forget to incorporate some anti crush method where your bolts pass through a hollow section.

  13. #13
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    will do karl thanks for the advice mate , do u know if the aluminium i beams i suggested are stronger than 2.5-3mm steel C channel around 75-100mm high by 45-50mm wide? (my old trailer design)

    also i was thinking of maybe using stainless steel square U bolts to attach the stainless steel spring and mudguard holder plus the cross members, good or bad idea?

  14. #14
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    No heat, no cracking and minimal deformation of section will be your requirements.
    Yeah ally can be a strange beast to work with.

    Glad back when used to play with SS that I wasnt paying the bill!!!! One of my local steel merchants describes it as "drug money".
    www.lockwoodcanvas.com.au

    I will never be the person who has everything, not when someone keeps inventing so much cool new stuff to buy.

    From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".

  15. #15
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    Quote Originally Posted by gazza2009au View Post
    will do karl thanks for the advice mate , do u know if the aluminium i beams i suggested are stronger than 2.5-3mm steel C channel around 75-100mm high by 45-50mm wide? (my old trailer design)

    also i was thinking of maybe using stainless steel square U bolts to attach the stainless steel spring and mudguard holder plus the cross members, good or bad idea?
    The ally beams will be well and truly stronger than your 100X50X3 steel channels. Channels are prone to twisting far more than a symetrical section such as a box or I beam.
    Stainless would be required for your U bolt attachments in order to provide corrosion resistance.
    I would be inclined to look at drilling the web of your beams to attach your mudguards. You could also make a S/S frame with your axles and springs mounted to it along with mudguards etc and u bolt this complete to your I beams. This approach allows the axle group to be slid forward and backwards to fine tune the balance of the trailer.
    One word of advice with your Stainless U bolts, if bending them yourself, take care that the bends are not too tight as stainless U bolts can be prone to cracking. Also, lubricate the threads well when tightening any stainless fastener. If you don't, the bolt and nut will weld themselves together and lock up.

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