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  1. #1
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    Question Trailer Rack for Roof Top Tent - good first welding project?

    I have no experience in welding other than a 20 minute tutorial by a now ex-in-law who's a boilermaker. The 'ex' means he is not available to answer questions any more.

    A couple of years ago, when Masters was still around, I picked up a Stick Welder on special. Cigweld WeldSkill Turbo 140. It has been sitting in an unopened box since. Now finally a project has come up that might make use of it:

    I want to build a rack to sit on top of my 7x4 trailer. That rack will hold a roof-top tent and an awning plus I want to keep the option open to transport a kayak or similar as well.

    That rack will replace the cage that the trailer came with. I have identified the strongest parts of the trailer that are best suited to take the load - basically the same spots that the cage was connected to, and lower down, the main frame of the trailer.

    Before I start buying materials, I wonder if someone here with welding experience can answer a few questions.

    The parts of the rack that will be subject to the most lateral stress will be the horizontal supports that hold the roof top tent. About 60kg for the tent when towing, 200kg+ when stationary and tent is in use. Those supports need to go across the whole trailer width.

    Looking at options I can get sufficient load rating with a very comfortable margin from either square 40x40x2 tubes, rectangular 50x20x2 tubes or 40x40x3 open equal angles.

    The open angles have the highest strength, lowest weight, lowest price and, being 3mm thick, should be easier to weld for a beginner with less risk of creating holes.

    Question 1) other than aesthetics, is there any reason that I might have missed that makes tubes preferable over angles or should I just go with the angles seeing all the advantages just listed?

    The vertical parts of the rack will face much lower lateral forces, I would be happy to use smaller material. I.e. if I go with open section: 30x30x3mm open equal angles. The main advantage I see from that: weight reduction. The trailer is unbraked and will be towed by a smallish 4WD. I would like to keep total loaded weight to below 450kg.

    Question 2) any reason not to mix different sizes in a project like this?

    Question 3) I will probably have a choice of plain or galvanised steel, my preference (less need for protective painting) would be galvanised. I have become aware of the toxic fumes that welding galvanised steel produces. I would weld outside wearing a respirator. Any other downside to using galvanised other than slightly higher cost?

    Question 4) since I am a beginner in welding, how can I test the strength of my welds? Or should I, just to be on the safe side, add nuts & bolts as extra protection in case a weld fails?

    I might ask more questions later, but I want to make sure I take into account the answers I get to these ones here.
    Last edited by PeterWA; 25th Nov 2018 at 09:00 PM. Reason: fixed a typo and formatting

  2. #2
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    Hi
    First up let me welcome you to our forum.

    With 30x 30 x 3 gal angles I don't see a problem if the angles are electrically plated not hot dipped.

    Hot dip, however, reacts more with the arc pool in my experience. The stuff penetrates the pores of the metal and a lot stays there.

    With the off the rack gal angles, give the surfaces to be welded a hit with the flap wheel to remove what thin coating there is and just weld it.

    A respirator and a decent cooling fan behind you will stop the fumes coming your way.

    I would encourage a bit of practice on the material to weld.

    Say cut out all your frame pieces and practice with the offcuts.

    Check the practice welds by holding one element in a vice and belt over the other with a hammer.

    If it hangs on until the end, it should be ok. If it falls off at first tap, you are in trouble, practice more.

    If you can achieve that, there's no need for nuts and bolts. 25mm of bead will hold a remarkable weight.We used to do a demo for the kids were a 25mm x 6 bar was tacked to some equipment weighing a 1000Kgs and lift it with crane. Once you welds beads without major defects you are home.

    When you start constructing, remember to tack it all together first and then small welds in placed diagonally opposite to one another- it spreads the stress from weld bead contraction so less warping will occur.

    Grahame
    Last edited by Grahame Collins; 25th Nov 2018 at 03:26 PM. Reason: more info added

  3. #3
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    Hi Peter and Welcome to a Top Forum also.
    As Grahame suggested practice welding on your offcuts. weld images.jpg
    To test your welds, mount the piece in a vice and cut across the weld to check your penetration, it should look like this;weld ends beads.jpg
    Then get a strong vise, or a way of holding the test piece in there, grab the hammer you have, preferably not a claw hammer and hit above the weld to try to break it. Have a look at the quality of the penetration, it should penetrate about half way or better.
    Hope this Helps,
    Kryn
    To grow old is mandatory, growing up is optional.

  4. #4
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    Thank you so much for the friendly welcome and all the tips.

    I am sorry that my formatting all disappeared and you had to read through such a blob. I think I figured out how to fix it, I'll try to edit the post to make it better to read.

  5. #5
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    Thank you so much Grahame and Kryn for your well thught out replies. I certainly feel encouraged to continue with this project and also to learn more about welding in general, now that I know where I can turn to if I get stuck.

    To summarise what I take from your replies: using 30x30x3 and 40x40x3 open angles should do the job. If galvanised then use zinc plated rather than hot dip. Do lots of practice beads on off-cuts to get my welds right, then cut across the weld to check visually and with a hammer.

    I found what I believe is a good link explaining the importance of rod angle, gap size and speed here: https://www.wcwelding.com/arc-welding-tips.html

    What I haven't found is a clear and easy to use selection table helping me decide what specific rod to use for this project. With the limited knowledge I have I'd stick with the 6013 rods and probably go for 2mm. Would you suggest something different?

    Is there is any one book that you would recommend to a beginning welder?

  6. #6
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    Hi Peter,

    Unless you be of stout heart and steady hand, 2mm electrodes can be a bit difficult to obtain continuous coverage over the join.

    I'll explain this in saying running the bead down a join requires a spread of the electrode "footprint' pretty much equal on either side.
    The footprint ( weld pool) of a running 2mm electrode does not allow much in the way of deviation to one side or the other.

    Any bit of shudder or wobble sees you run off to one side leaving the opposite unwelded and unsealed in many cases.

    You often get a nice bead to the point where it is unwelded and there is an area of slag inclusion that's hard to remove and looks crap. Joints that are nicely welded with no slag inclusion look great under paint and there's no need to to dress them with a grinder.

    The 2mm electrodes have their uses in light wall welding but the problem remains.

    The 2.5 electrodes will bite well into the 3mm wall thickness and leave a very nice profile once you have practiced a bit.

    That is my experience with 2mm and 2.5mm electrodes for what it is worth.

    Also 2.5mm are cheaper than 2mm due to the fact that there are more 2mm electrodes to the kilo and therefore more handling .

    Grahame

  7. #7
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    Hi Peter,

    Grahame is right about the 2mm rods. Sometimes it can be like trying to weld with a wet piece of spaghetti. That thin rod will whip around like you wouldn't believe and any movement of your hand will be amplified at the hot end of the rod (+ its tendency to wobble about by its self) which is not great for a beginner's confidence. Once you get some practice with thicker rods on thicker metal, these thinner rods will be much easier to use. If the waving about still irritates you too much, cut the rods in half. 2mm rods are great for welding "thin" material that is closer in thickness to the rod's diameter. You can use lower welder settings which will reduce the amount of warping and the chance of blowing holes through the material. That's what you would want to use if welding stuff like 40X40X2 SHS. If you weld rusty tip finds like I do, then you'll certainly get some practice welding up holes that happen when your weld pool falls through.

    For 3mm and 4mm steel, I would use 2.5mm rods as Grahame suggested. You could use 3.25mm rods, but then we're back to getting your welds pretty hot, introducing more chance of pulling your work out of square. They are good for thicker material and to fill up larger gaps. Even with 2.5mm rods, some steel will shrink heaps as the weld cools, hence the need to tack your joints first in the suggested diagonally opposite fashion. For corner joints in angle iron, a cope joint is a good alternative that is easier to keep square than a mitre joint. See here for instructions: Coping Steel Corners - NewMetalworker.com - How-To's

    cutsmade250.jpg

    There's no problem mixing sizes of steel, as long as your joints are suitable and the welds are good. 6013 rods are a good choice for what you want to do and are readily available. The weld pool will solidify quickly which will help as you learn, but at the expense of weld penetration (compared to say 7018 which is a deeper penetrating, low hydrogen rod = stronger if the situation warrants). Unless I am doing something like welding quick hitches on to round hay bale handlers, I generally use 6013 rods and I have no problem getting plenty of weld penetration. 6013 welds also look nicer than a lot of other rods and that can give you a fair amount or satisfaction in your work.

    Welding hot dipped galvanised steel can give you a case of metal fume fever and if you don't enjoy having the flu, you wont like that either. You need some good ventilation, a suitable respirator and to be prepared for your welds to smoke and give off very bright light (like burning magnesium ribbon in high school) even after you have cleaned the galvanising off the area to be welded. The new Duragalv steel isn't so bad and I believe that there is no requirement to grind off the coating, just weld through it. Get some colour coordinated cold galv/zinc type spray can paint to protect your welds.

    While you are practising, have a look at some Youtube videos from Welding Tips and Tricks like: https://www.youtube.com/watch?v=TwCxsMOoahM
    and ChuckE2009 like his "Teach yourself to stick weld" series: https://www.youtube.com/watch?v=NjYPJ-CxxW4
    These guys know what they are doing and can teach.

    Don't forget all your personal protection gear like gloves, welding helmet, leather apron maybe and don't weld with your sleeves rolled up. Forearm protection is especially required if you are using a hand held face shield type mask (that probably came with your welder) to avoid severe burns to the underside of your arm.

    I'm sure that you'll have heaps of fun with your new drug habit - welding.

    Simon

  8. #8
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    Thanks for filling Peter in on the PPE side of things. Sometimes us older blokes take things like that for granted.
    Kryn
    To grow old is mandatory, growing up is optional.

  9. #9
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    Thank you so much everyone! This forum is amazing compared to all the others I've seen so far. Instead of 3 people 4 opinions as everywhere else, here everyone is co-operating and filling in gaps while at the same time confirming the main important bits. That, plus the quality of the replies, made sure I felt confident to tackle this project.

    Maybe a bit over-confident in that I didn't do enough practice welds in all the different configurations that came up in the project. As a result some of my welds are quite ugly (the vertical ones especially). But I am happy with the overall result, happy that it came together reasonably quickly and quite sure it does have a lot more strength than required. Here's a photo of the rack on top of the trailer. Don't zoom in too much, it ain't pretty, but it is sturdy. ;-)

    IMG_20181207_143550.jpg

    To reply to some of the points made by you: I went for mild steel for all the open angles, but I happened to use some scraps of galvanised 2mm plate to make small brackets that go over the side walls of the trailer. They are mostly there to even out the thickness and give a little lateral support, but aren't crucial. Working with those pieces however clearly confirmed that going for mild steel for all the rest was a very good choice. So much easier to work with.

    I went with 2.5mm electrodes, 6013, as recommended by you and also by the place I bought my steel from. All good. Not sure why sometimes they were sticking to the steel several times in a row, I didn't consciously do anything different then compared to other times where I found it easy to establish an arc. Could that have to do with the quality of the electrodes? The steel place had a 2.5kg pack for $10, seemed very cheap compared to prices I had seen at Bunnings.

    As to safe working: that's probably the only thing I remembered well from the introduction I had a few years ago from my ex-in-law. I had already bought all the safety equipment at the same time with the welder, proper welding gloves, apron, auto-darkening helmet. I had a respirator with suitable filters from other projects. Thanks for putting the details into this thread though, I am sure other newbies will stumble across it over time and benefit.

    Just one question: my helmet is an el-cheapo from Ebay. It reacts extremely quickly when it comes to darkening, but sometimes it didn't open up again afterwards. Maybe because I was outdoors and the sun came in at an angle. But that didn't inspire a lot of confidence. Is there any risk that it lets UV rays through while blocking visible light? I don't have any reason to think so, just wondering whether a $30 helmet can be trusted.

    I am looking forward to play a bit more with my welder. Maybe an art project next, a sculpture from scrap metal perhaps. Who knows. Not right now, first I got to use the trailer for camping )

  10. #10
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    Quote Originally Posted by PeterWA View Post
    I went with 2.5mm electrodes, 6013, as recommended by you and also by the place I bought my steel from. All good. Not sure why sometimes they were sticking to the steel several times in a row, I didn't consciously do anything different then compared to other times where I found it easy to establish an arc. Could that have to do with the quality of the electrodes? The steel place had a 2.5kg pack for $10, seemed very cheap compared to prices I had seen at Bunnings.

    More to do with the technique used than the electrode quality. Electrodes can stick when the current is set too low.

    The electrodes will stick if the flux at the strike point is chipped off. Also a bad earth where the alligator clamp connects to the item to be welded does not allow full current to get to the work.

    Clean with A/grinder -shiny- before placing clamp. I still use 10 year Korean electrodes bought for pennies.

    Keep the electrodes dry - store in plumbers PVC tubes with caps and anti moisture silica gel packs -as found in a lot of medications- They will keep for ages.


    Just one question: my helmet is an el-cheapo from Ebay. It reacts extremely quickly when it comes to darkening, but sometimes it didn't open up again afterwards. Maybe because I was outdoors and the sun came in at an angle. But that didn't inspire a lot of confidence. Is there any risk that it lets UV rays through while blocking visible light? I don't have any reason to think so, just wondering whether a $30 helmet can be trusted.

    You get what you pay for. Even so, that cheap helmet won't allow your eyes to come to harm while you are wearing it.

    If sold in Australia your welding sheild must comply with the safety standards. The A.S.Code standard lays out performance minimums that will state the criteria the helmet must adhere to. These are not advisory they are used by legislators when he safety laws are enacted.

    Your screen might be slow to react and that "flash" is no more harmful than being flashed by the high beam when driving at night. The clear filters will stop the harmful UV's. Many think they are eye damaged from the welding sheilds but in fact get flashed when the helmet is not in postion-ie accidental arc strikes-thats why you wear the clear safeties under the welding helmet. A real flash is when the eye waters and stings and usually needs medical treatment. The momentary loss of vision is NOT a flash and not harmful.
    Congratualtions on having completed your first project. I hope there are many more. Don't be embarrased to show close ups and guys here can "read" those beads and and constructive advice on what steps to take to improve those beads you may lay down in the future.

    Cheers
    Grahame

  11. #11
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    Thanks for the explanations

    Ok, I'll take you up on your offer to explain problems with individual weld beads.

    The first one the issue is clear, the junk bitten out of the right side of the upright. I have a fairly good idea why it happens too: being on the edge the heat has a lot less options where to spread to. Also the angle of the electrode changes from maybe 60 degrees to 90, sending more power. What I don't know is: how to avoid that issue other than perhaps stopping welding at least 5mm before I get to the edge.
    IMG_20181212_090126.jpg

    The other one the problem is obvious too. I went off course in the second half and the bead doesn't connect the two pieces. In this case I left it as is. The first part is strong enough for all forces expected on that piece and there is a nice bead on the other side in addition. But in general: how could I clean this up to re-do the weld if I need to? Given how close it is to the corner I can't reach it with my angle grinder.
    IMG_20181212_090225.jpg

  12. #12
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    Happy to help!
    Pic 1
    To start with. The beads are not real bad for a beginner.
    yes you can improve them.

    If the bead is welded from one side to the other, heat concentrates to the outside edge ie the last bit to be welded.
    A better option is to tack both ends so the end of the bead can run into a slightly thicker area-hold a moment then quickly reverse back over wgere you already welded.do it to the count of 1 ,2. At the same time the weld current is higher and at a short arc. -see more on that below.
    Pic 2
    Never never never stop and restart at the inside corner or I absolutely guarantee you a slag hole there, 99% of the time.

    If you really need to seal the inside of the angle start the bead at a tack,run in and while the arc still burns swivel 90 degrees and run out to the opposing tack.

    I do not want to mislead anyone, it does take some practice but still, it is quite possible after a few practices.

    The trick is to treat that corner as the pivot point of the turn as you manipualte that operating electrode through the 90 degree turn.

    Another thing to emphasise is short arc length which is the distance from the unburnt portion of the electrode ( while it is arcing) to the parent metal. Don't be timid,turn up the current up to another 10 amps or so and keep it consistently short.
    The above applies both to pics 1 and 2

    Observe the molten pool-it should take the oval form of a football. That will give you a speed of travel to go by.

    Also on pic 2 note the possibly unfused line along the top of the bead. This is caused by the electrode angle being to steep.
    Drop the electrode angle down a bit so say half of the arc is bearing on the vertical surface. Again, all the things said about short arc applies.

    Changes of arc length change the arc voltage produced and in turn this affects current-amps.

    Re <Also the angle of the electrode changes from maybe 60 degrees to 90, sending more power>

    That's where you lock your wrist as you weld. Pivoting at the wrist cause the change in electrode angle. Consistentcy is the key to better welding

    Theres probably more but I have to go now.
    Others will come along and offer help too.

    Grahame

  13. #13
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    Okay, I'll add slightly to Grahame's comments. Bear in mind, I am not a professional welder, but I think that I can pass on a couple of tips from my experience.

    Pic 1: Good job, it wont fall off, maybe panicked a bit at the start and went too fast. Try striking the arc behind where you want to start and then "quickly" move forward to your intended starting point.

    Pic 2: Arc too long and too little time with the welding rod pointed at the vertical surface. I always spend slightly more time with the rod directed towards the vertical surface than the horizontal surface as the weld pool will naturally flow towards the lower surface. If your welding rod is too far away from the metal, the arc will wander towards the shortest path to earth and deposit weld metal there, making the problem worse. In the second half of your weld, that's what happened (the weld built up on the horizontal surface leaving trapped slag in the corner) and at points you were travelling too fast for the weld pool to keep/fill up. A weak arc where the current setting is too low will also cause the arc to wander, but based on your pictures, your settings aren't too far away. Don't worry, it's easy to leave worm tracks, especially if you are not comfortable, but more of that in a moment. I always think of it like I am trying to drag the flux on the end of the welding rod along/over the joint and that encourages me to "sew" the parts together with the shortest arc I can.

    Pic 2: Starting your weld in a corner of a joint will often lead to a slag inclusion right in the corner where your grinder wont go, more so when welding the other half of the joint in the same fashion. The metal generally starts out cold, so the weld metal can stack up at the start and then flatten out as the heat starts to build up - you may have to pick up the pace a bit to compensate. That corner is a great place to make ugly worm tracks as the more weld that builds up, the harder it is to get the rod in there close enough to make a good weld - bring out the plasma cutter to blow the bad weld away (been guilty of that a couple of times myself).

    Vertical welds are more difficult to do well - practice, watch those youtube videos, practice, practice, rinse and repeat. Wherever I can, I try to get the piece to be welded in the flat position so that I don't have to be too worried about the look of my vertical welds - Cheater!!!! This helps me to make stronger welds because I am more comfortable. If you aren't nice and comfy and braced for the entire length of the weld, you will shake, stretch the arc out too much, weld off on a tangent to where you wanted to etc. As soon as I feel uncomfortable, I have to try and make myself stop welding. If I don't stop, there is always some fault with the weld. It helps if you do a bit of a dry run first to see if your body position etc suits.

    As far as rods sticking, check that you have a really good earth first like Grahame suggested. The second thing is your current setting. A slight adjustment up can make all the difference. Sort of the reverse problem can happen where the flux will stick out too far or there's some other insulator on the end of the rod for the arc to strike and you have to scrape the end of the rod a bit on a file or a piece of brick. In the case of 7018 rods, the end of the rod will glaze, and restarting your weld can be entertaining if you don't give the end of the rod a scuff up first. 6013s are no where near as bad, but still need a bit of a scrape occasionally. The more old paint and rust that you try to weld through, the worse the problem is.

    Simon

  14. #14
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    You have been given some good advise Peter.
    To correct the weld in pic 2, I'd get the angle grinder out with a thin cutting disc, and slice the weld against the angle, hopefully there's enough flex there to be able to lift the offending weld out of the way and slice against the angle to remove the weld and then start again.
    Kryn
    To grow old is mandatory, growing up is optional.

  15. #15
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    Quote Originally Posted by PeterWA View Post
    But in general: how could I clean this up to re-do the weld if I need to? Given how close it is to the corner I can't reach it with my angle grinder.
    IMG_20181212_090225.jpg
    If the situation and the budget warrants it most can be removed with a long shank tungsten carbide burr driven in a air die grinder.The burr needs to one of the tapered ones .
    Unfortunately this requires some expenditure.
    PS anyone using such a rig beware that the slivers get every where and sharp slivers could end up in your eye.
    Correct PPE recommended.
    Grahame

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