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  • Lonnie-S
    started a topic Welding Tubes on Chassis - Need Strategy

    Welding Tubes on Chassis - Need Strategy

    I'm building a sports car chassis out of RHS and tubes in mild steel. I am a relatively new welder and using a Millermatic 140 (MIG) for the project.

    I've gotten to the point where I need to weld some 0.75" x 16 gauge tubular cross braces into a larger structure of 1.5" x 1.0" 14 gauge RHS (photo below).

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    While this is my first real need to do this, I will be doing it many times over the project and I'd like to produce high quality welds I'll be proud of. I'm not worried about them being strong enough. I've got the penetration, etc. down and my practice welds are plenty strong. However, I'd like some help on getting the weld to look good and flow together. Intuitively, my approach is to do 4 welds where each one is 1/4 of the perimeter of the joint. I don't know if that's right or wrong. It's just what came to mind.

    Also, the 4 segments don't overlap well and you can see each of the 4 welds clearly (examples below). I've seen much better on professional race cars, so I'm looking for some help and suggestions on how to make mine look good while remaining strong.

    Also, while my samples below are at 90 and 15 degrees, there are quite a few that will be at 45 degrees too. How does one handle the narrow (tight) part of those 45 degree welds? Do you let the filler wire get long and close to the join or do you just try to build up a fillet and don't worry about getting in deep between the pieces?

    Thanks,

    Lonnie

    PRACTICE EXAMPLES:

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    Last edited by Lonnie-S; 04-23-2012, 06:13 PM.

  • H80N
    replied
    Lonnie

    any news, progress and/or pics??...

    Leave a comment:


  • H80N
    replied
    Australian Miata Based Build

    Here is an Australian build with a tremendous amount of good quality detail photos that you might find of interest.. lots and lots of good detail stuff..

    http://www.locost.ozcarnut.com/html/chassis_photos.html

    they also pay a lot more attention to crash protection and torsional ridgidity..

    so they add a fair amount of additional bracing...
    Last edited by H80N; 01-31-2014, 06:09 PM.

    Leave a comment:


  • H80N
    replied
    That's funny.... it says "Motorsports"....

    like the old "AskAndy" forum back years ago..... before it got split into 3 different...


    BTW Lonnie pls keep us posted on your progress....

    Leave a comment:


  • traumajunkie
    replied
    Welding Tubes on Chassis - Need Strategy

    I agree it is very nice work. I would also like to see how your welds have progressed (considering this is a welding forum not a car forum). Overall looking good.

    Leave a comment:


  • elvis
    replied
    Nice work. I applaud you for keeping at it and ignoring the critics. It seems you are doing nice work. And I am sure you have learned a lot over the last year or so. Are you following a set of plans or working from your own design?

    Leave a comment:


  • H80N
    replied
    Lonnie

    your Locost/Haynes chassis is looking GOOD..!!

    what is your plan for engine and suspension donor..??

    Leave a comment:


  • Lonnie-S
    replied
    Originally posted by Vegas Racer View Post
    . . . <SNIP> . . .

    Most of these projects never see th light of day anyway. The builders lose interest or get to the point they are over their head and it get abandoned. Don't get me wrong, I'd like to see your project succeed but at this point you still have more learning to do.

    Good luck!
    Yup, I appreciate what a challenging task it is for sure because I've now just about done it. I'm closing in on a finish in the very near future. All the major structures are complete, but there is still some work to do.

    I've just proceeded slowly and done lots and lots of test coupons as I've encountered new welding situations. The chassis is a custom version of a sports car based on the Lotus 7 roadster. I built a rotisserie to rotate the chassis as I did the final welding, which allowed me to turn almost all the welds into flat and horizontal welds. It's primarily RHS in 16 and 14 gauge.

    Cheers,

    Lonnie
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  • Vegas Racer
    replied
    The deal Lonnie is that you haven't yet mastered out of position welds on round tubing. Your first question is enough in and of itself to see you don't yet have the experience for a chassis. You won't believe it but here are many, many others that came before you trying to do the same thing. You say you can't go more than 90* on piece of tubing. That, you will need to practice. Your teacher may have had that experience but at this point you don't. Not yet, anyway.

    The couple of guys like Sundown (who certainly knows what he's doing) and Old Skool make good points, not on assumptions but on what you've actually posted to the thread. You asked the question in the first place when before starting this project, you should have known. Your choice of machine is a bit suspect as well. It's a fine machine, but this sort of work is usually done with a minimum of a 180 amp class machine. That's not to say you can't do it with the MM140 but it's not the best tool for the job. An MM211 or a 252 would be a better choice. Then you state you can't do out of position rounds very long. Nothing wrong with learning, but those three things alone make others with more experience question the wisdom of tackling such a project at this point.

    Most of these projects never see th light of day anyway. The builders lose interest or get to the point they are over their head and it get abandoned. Don't get me wrong, I'd like to see your project succeed but at this point you still have more learning to do.

    Good luck!

    Leave a comment:


  • Lonnie-S
    replied
    Originally posted by Old Skool View Post
    Everyone learning a new skill has to start somewhere but you have to learn how to walk before you can run and from your photos you're just beginning to crawl. Chassis work at your level of experience is dangerous and irresponsible.
    Nonsense!

    I'm relatively new to welding, but up to this task. You're making assumptions that are not based on fact or personal knowledge. I took two, 1-semester classes in welding at my local community college given by a man with 40 years of experience, 20 years of which was welding at nucular plants here on the west coast. He knows welding and did a good job of teaching us the basics of the four fundamental processes. I don't fool myself into thinking I'm an expert. However, I do know the basic requirements for a sound weld.

    I've practiced on numerous small sample coupons of the chassis material, carefully examining how well my welds penetrated and adjusting the voltage and feed speed to produce a good, basic weld. I purchased some good welding reference books and have read the sections relevant to the type of welding I'm doing.

    My fit-up is excellent. I make a point of it. Every joint is tight and there is no slop or big gaps to fill. I prepare and clean every joint before welding and bevel the edges of the members when appropriate to make sure I get good penetration. My welds may not be the prettiest around, but they are sound and strong.

    I'm never too proud to ask for help if I don't feel confident in my knowledge. Ninety percent of producing good work is having the right attitude and mastering the basics. I'm confident I have those things covered.

    Thanks again to all those who responded positively.

    Leave a comment:


  • Old Skool
    replied
    Everyone learning a new skill has to start somewhere but you have to learn how to walk before you can run and from your photos you're just beginning to crawl. Chassis work at your level of experience is dangerous and irresponsible.

    Leave a comment:


  • jontheturboguy
    replied
    Originally posted by SundownIII View Post
    Let us know where this "sports car" will be operating so we can avoid the area.
    Ok???

    Explain?

    Leave a comment:


  • SundownIII
    replied
    Let us know where this "sports car" will be operating so we can avoid the area.

    Leave a comment:


  • Lonnie-S
    replied
    Thanks!

    Thank you to all who replied. I'll start following the thread mentioned.

    And, thank you Spence for the very specific suggestions. I can see where 180s make sense. I do think I'll need some practice with the wrist action for 180s. I'm right handed and tend to feel welding from right to left (push) is most natural for me - at least currently. So far, using a push technique, I haven't been able to weld further than the 90 degrees or so of my current samples without the tip twisting out of position. I think this is a case of practice, practice, practice.

    Also, I think I'm going to the local steel supplier and see if I can get some larger, scrap tubing to practice on. It just occurred to me that this would give me more of a chance to train my wrist to the task if I spread the process out over a larger geography while learning.

    Cheers,

    Lonnie

    Leave a comment:


  • spence648
    replied
    I would do those in 180 degree welds, ( 2 welds) Remember to never start or end on a tack. when tieing in to the next weld start in front of it to pre heat and burn back into the end of previous weld then proceed, i do almost like a half circle, burn into one toe then circle out to other toe then proceed welding, if you practice this too you can get it to burn in without the excessive build up. Practice doing 180's cause you will need to get used to rotating your wrist to keep up with proper work angles, remeber to plan ahead on where your tie ins will be so they will be the least visable(is what i do) as far as the sharper angle tubes i do a little of both, long arc and fill in the gap, i want to get in as deep as possible so i will let wire long arc a little but not enough to lose gas coverage and cause excessive splatter, another thing that helps me is i always start in the toughest, or hardest to view spot so it just gets more comftorable, hope this helps,

    ps. welds look pretty darn good for a beginner!

    Leave a comment:

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