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  1. #1
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    Off grid 1/4" or 3/8"

    I'm wondering how many amp welder I would need for a mig flux wire welder to weld 3/8" plate to 1/2 " thick.

    I was looking at the hobart generator welders. I have an off-grid property and I'd like to weld containers together along the top with plate and down the sides. I dont want to just "glue" the plate on but rather make the three pieces as one/bond. I'm not sure the structural thickness of the container but it's at least 3/8 inch on the corner/horizontal beams and I'd like to use minimum one quarter inch plate or 3/8. My cousin said that it's not possible with a wire welder/mig. I also understand if it's windy I need a flux core ( stick or wire) because the gas will blow away. Stick welding weeks for 156 ft of welding to connect four containers. The connection is mainly for rain/future stability/and if there is rust it will take decades versus 1/8 inch. I plan to cover the roof with a home depot roll on roof membrane.

    I will have 12,000 Watts of solar inverters. I can make 240 volts if I want, by connecting the two inverters. I will not have anything else that is 240 volts so I think I would rather have two separate 6,000 Watt 120 volt inverters to power my RV and another for my cabin the RV inverter will be a backup to the main inverter for the cabin and used for family camping on the property in the summer. I can use my 50 amp 8,000 Watt generator for welding I also have 30 amp 4,200 watt generator. I may be able to borrow a larger generator if I need to from my uncle.

    I think flux core wire welder would be the most user friendly for a beginner, maybe more portable without gas, good for wind, and faster than stick. I have done stick welding for dozens of hours, and mig also, not tig, stainless, or aluminum. I'm definitely a beginner but with some experience to make some decent welds on thin material. I first learned welding in high school.

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    Last edited by stewbuntu; 05-09-2021 at 02:23 PM.

  2. #2
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    Re: Off grid 1/4" or 3/8"

    Minimum 300A machine. 0.045" E71T-11, 460-470 IPM, 26-28V if it's closer to ". If the material tops out at 3/8", then you could get by with 250A. About 400 IPM, 23-25V.
    Last edited by Oscar; 05-09-2021 at 06:26 PM.
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  4. #3
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    Re: Off grid 1/4" or 3/8"

    No real reason to use anything thicker than what is on the container, maybe 10ga I’m guessing. No reason to weld the full length either, they don’t when building the container, just skip weld and use seam sealer. Just pick up an engine drive, usually had 250 to 300 amps, plenty for anything you want to do. Will need a feeder for mig, or enough aux power to run a plug in unit.

  5. #4
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    Re: Off grid 1/4" or 3/8"

    I wouldn't use flux core or mig, I'd use 6011 stick rods.
    It seemed like a good idea at the time!

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    Re: Off grid 1/4" or 3/8"

    Containers have relatively thin walls, but very heavy corners. No reason you can't make multiple passes. I would think DC, 200 amp, 6010 as a minimum. I don't believe flux core is your best choice.

    If you are able to make your steel absolutely clean try 7018 1/8" rod.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by Willie B View Post
    Containers have relatively thin walls, but very heavy corners. No reason you can't make multiple passes. I would think DC, 200 amp, 6010 as a minimum. I don't believe flux core is your best choice.

    If you are able to make your steel absolutely clean try 7018 1/8" rod.
    Multiple passes for 156 linear feet of welding is not something I want to do. I need to weld 3/8 plate to 1/2" box tube for 156 feet

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by welding1 View Post
    I wouldn't use flux core or mig, I'd use 6011 stick rods.
    Why?



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  9. #8
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    Re: Off grid 1/4" or 3/8"

    A few things:

    1. AWESOME, by the way, going off grid. Thats one of my dreams.

    2. I've been poking around welding since I was in middle school - dad got a small 120v flux core machine for smaller tasks and I inherited it later (more like borrowed it for the past 15 years, but they moved and he hasn't had any use for it anyway). Now I have 2x stick machines - an old transformer (round top lincoln idealarc 250, AC/DC) and a small/light/portable inverter (Everlast Powerarc 210STL, does DC tig also). If I were to give any advice to a newcomer to welding it would be to start with stick welding. On top of that I would highly recommend an old transformer machine that does both AC and DC - DC is more versatile. The old machines that have infinitely variable current adjustment are ideal especially for lighter welding - you can finesse the current and in some cases 5 amps makes all the difference in the world. You can't do that with a machine like an AC225 that has switched taps as opposed to being infinitely variable. For heavier welding it doesn't make as big of a difference, but on the light stuff it is a godsend.

    3. You are not going to weld those containers on alternative energy. So get that out of your head about using the inverters. Though, I understand where you are coming from. I've studied alternative energy - that is one of my on-going hobbies also. We have cabins in the boonies that are actually on-grid that I have been studying on how to get off-grid. If we can replace the electric water heater with gas (and can get a sufficient gas supply) then that will allow alternative energy to work but it would still take a lot of combined solar and wind power (plus battery storage). As you well know if you are truly off-grid - you can not plan your existence on the "ideal" conditions all the time for either solar or wind. You have to plan for production in less-than-ideal conditions and have the capacity to store power that is surplus when you CAN generate it so that it is there for when you CAN NOT generate it (cloudy days with no wind for example). Then on top of all of that you need generators still because there might come a time when conditions just suck and you don't have enough battery capacity to get you through, or there is a failure somewhere in the system and you loose power from your batteries, inverters, or both, entirely.

    So add in the power requirement of trying to weld as you are questioning in to all of the above considerations with alternative energy - aint' gon' happn'.

    By the way.... There are 15kw and 18kw split phase power inverters available, if you were not already aware. They are made by Sigineer. I have had their 15kw on my "radar" for a while now and noticed they just came out with an 18kw version this season too. They will run your traditional split phase 120/240v AC power systems. They state that the running wattage is the label 15/18k and the "starting wattage" is 3x that. I am not sure if I buy that, but there is a youtube video of a guy at an off-grid property that powers a large air compressor off of one of the 15kw units. That is about as hard of a starting load as there is. I'd say thats even harder to start than a normal household AC unit.

    Link to a page where you can source the inverters in the US:
    http://store.evtv.me/products.php?cat=4

    4. You need to watch your input amps for what ever welder you get, if it is not an engine drive you will have to have power available to run it. Most inverter welders require less than 5% THD (total harmonic distortion). Not all generators are created equal. There are generators out there that will give you the power you need, but the power they produce is pretty trashy. Harmonic distortion will destroy sensitive electronics, and unfortunately the "brains" in inverter welders generally are considered "sensitive electronics". As far as the amperage goes - you want the amperage that the welder draws at your intended welding amperage setting to be within the RUNNING wattage of a generator, not the STARTING or PEAK wattage. Say the welder pulls 55 amps from the supply when welding at 250 amps - the welding voltage is less than the line voltage, so that is how the welding current is higher, if you didn't already figure the math on that one.

    Wait a minute.... Did I just mix up watts and amps? If you caught that - good. You need to understand the difference because generator manufacturers will not always be truthful about the ratings on their generators. And most of the time generators are plastered on the side with..... Wattage. So and so manufacturer may sell a 10kw, 15kw, and 18kw "model" of what appears to be a similar generator. There are two things you need to dig to find on those generators:
    1. Rated running AMPERAGE (on 240v, not 120v)
    2. MLCB (main line circuit breaker) size

    Take the Generac GP15000E for example. On the label it is a 15kw running/22.5kw starting/surge unit. What size is the biggest breaker on it? 50 amps. 50 x 240 is 12,000 watts. If you had a load that max'ed out the 22.5kw (or 93.75 amps) - where do you pull it from? Answer - you dont. They combine the power you can draw from multiple outlets, not one. So if you have one device that requires all the units' power you are SOL. In the example of your 250 amp welder pulling 55 amps (just a pulled out of my rear number, I think it may even be more than that generally - but just for examples' sake) - the 50 amp breaker on this particular generator might hang on to that welder max'ed out for a minute or so, but the current over the rating on the breaker will eventually heat it and trip it - even though the overall generator should be able to push over 90 amps. Since all that power can't be drawn from the one outlet/breaker your welder can only get what it can get = not enough.

    Moral of the example and the long post - watch your numbers and understand them. You want to have sufficient power and not set yourself up for disappointment.

    Last note - yea, engine drives might seem like expensive options but if you have your power requirements otherwise met - an engine drive is a whole world of freedom. Only run the engine when you need the power. Additionally - Miller makes dual AC/DC engine drives that will serve as a legitimate AC power generator. Lincoln, to the best of my knowledge, never produced one. Theirs are all DC so you can't use them for conventional AC power. There are some mods/upgrades people may have done to get some AC power, but I think the easiest route to go with them and AC is to run an inverter off the starter battery. That doesn't really count, in my book, for "AC output" because it isn't coming from the main alternator like the welding power is. Yeah for some drilling or grinding in between welding it might work, but not if you're trying to power your house or do other fabrication stuff. That's where the Miller engine drives might be the way to go there.

    Good luck and keep us posted on your project. It sounds really cool. If you're going to learn any welding process I say start with stick. Its a much more versatile process and I wish we had stick all these years and didn't start off on flux core.
    Last edited by FlyFishn; 05-10-2021 at 12:01 AM.

  10. #9
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    Re: Off grid 1/4" or 3/8"

    Its almost always windy on our hill, and I wont leave a chance for leaking with seam sealer.

    I need to weld plate to the thick beams


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    Last edited by stewbuntu; 05-09-2021 at 09:57 PM.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by stewbuntu View Post
    Its almost always windy on our hill, and I wont leave a chance for leaking with seam sealer.

    I need to weld plate to the thick beams


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    You had better scrape off the mile of seam sealer that is on the container already then. I will be very surprised if you are able to make 40' of weld in ideal conditions that is water tight, much less in windy conditions. So you are going to need to use sealer regardless.

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    Re: Off grid 1/4" or 3/8"

    I think the OP is way way way over thinking it. Skip weld and if wanted continuous go back and skip weld again to get a full weld. Still need to worry about warping and pulling with that much weld. If the material is that thick I'd use 3/16" 7024 (production rod) but someone less experienced could use 5/32". You could pretty much tell by looking at the bead if 7024 is going to leak. Any gaps could be welded with 6010 or 6011 and then covered by the 7024. 156ft. of welding is not that much. I started my apprenticeship in a tank shop. You weld all the shells together on the inside and 156ft. is nothing.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by Welder Dave View Post
    I think the OP is way way way over thinking it. Skip weld and if wanted continuous go back and skip weld again to get a full weld. Still need to worry about warping and pulling with that much weld. If the material is that thick I'd use 3/16" 7024 (production rod) but someone less experienced could use 5/32". You could pretty much tell by looking at the bead if 7024 is going to leak. Any gaps could be welded with 6010 or 6011 and then covered by the 7024. 156ft. of welding is not that much. I started my apprenticeship in a tank shop. You weld all the shells together on the inside and 156ft. is nothing.
    Good luck with that 7024 especially on the sides. 6011 would be a better choice.

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    Re: Off grid 1/4" or 3/8"

    I was thinking flat along the top. 6010/6011 down hill on the sides would be the best. That's used a lot on tanks too. Could use 5/32" or even 3/16" rods. Would have to practice the whipping motion some. Minor pin holes and such aren't going to leak. 6010/6011 on the flat could work but jet rod (7024) would be easier.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by Welder Dave View Post
    I was thinking flat along the top. 6010/6011 down hill on the sides would be the best. That's used a lot on tanks too. Could use 5/32" or even 3/16" rods. Would have to practice the whipping motion some. Minor pin holes and such aren't going to leak. 6010/6011 on the flat could work but jet rod (7024) would be easier.
    It would depend on the coating and is removal of it cost effective, as for effectiveness off 7024. Personally never really cared for it and used 7018 instead. Either way I don't see the need for a full weld and see no problem using caulk provided it's decent stuff. Sika flex urethane is good stuff and pretty reasonable.

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    Re: Off grid 1/4" or 3/8"

    E C Crosby & sons was a grain mill built mostly of wood. In 1967 it was destroyed by fire. They built it new from steel. The whole thing was done with 1109 5/32 & an old Marquette welder looked like a robot. It was AC only, to change amps you unplugged & chose another tap. I later learned the bulk 1109 was actually 6011 upside down. Nothing sophisticated, but you need LOTS of duty cycle.

    Since you are off grid I feel you'd be best served with an engine drive. Miller, Lincoln & I bet others offer great 250 amp engine drives. If you got your heart set on Flux core, they fit with wire feeders.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by Willie B View Post
    The whole thing was done with 1109 5/32

    I later learned the bulk 1109 was actually 6011 upside down.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by M J D View Post
    It would depend on the coating and is removal of it cost effective, as for effectiveness off 7024. Personally never really cared for it and used 7018 instead. Either way I don't see the need for a full weld and see no problem using caulk provided it's decent stuff. Sika flex urethane is good stuff and pretty reasonable.
    I don't see a need for a full weld either but the OP does. There are all kinds of sealers that would work. A weld could eventually rust out, what paint or coating would protect it the best etc.??? Like I said, I think the OP is way way over thinking it. Better use 309 or better stainless rod. 7024 works great when you're used to it and will basically burn by itself. Higher deposition rates than 7018 because of all the iron powder in the flux. Burned lots of 3/16"and 1/4" Jet rod back in the day almost 40 years ago. Yikes! can't believe I've been welding that long.

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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by stewbuntu View Post
    I dont want to just "glue" the plate on but rather make the three pieces as one/bond. I'm not sure the structural thickness of the container but it's at least 3/8 inch on the corner/horizontal beams and I'd like to use minimum one quarter inch plate or 3/8.
    I'm a little puzzled by you wanting to use such heavy stuff (and 3/8" is HEAVY, let alone 1/2") for what sounds like it amounts to "keeping the rain off." You could do that with sheet metal. I also suspect you could park a 50-ton tank on top of the conex as-is without fear...this all just sounds like crazy-level overkill to me, but I don't know what you're doing, either...

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  22. #19
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    Re: Off grid 1/4" or 3/8"

    Probably be best to weld enough to structurally join containers, then caulk with a good polyester caulk (Lexel). I agree, if you feel need to use a steel bridge to make weathertightness more permanent, 1/8" is adequate.
    These containers won't fit together tightly enough to weld the gap. A strip of 1/8" steel might bridge the gap. You can weld where it touches, then hammer the gaps for a close fit.
    Last edited by Willie B; 05-10-2021 at 07:12 PM.
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    Re: Off grid 1/4" or 3/8"

    Quote Originally Posted by Willie B View Post
    Probably be best to weld enough to structurally join containers, then caulk with a good polyester caulk (Lexel). I agree, if you feel need to use a steel bridge to make weathertightness more permanent, 1/8" is adequate.
    These containers won't fit together tightly enough to weld the gap. A strip of 1/8" steel might bridge the gap. You can weld where it touches, then hammer the gaps for a close fit.
    If there is a gap, through round bar in it but then it probably needs 2 passes or maybe a weave. I thought Conex boxes are made to get real close together?

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