+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 10 of 15

Thread: Question for judges and experienced builder connected with welding

  1. #1

    Question for judges and experienced builder connected with welding

    If such a poor fitting is acceptable? If not, what can be done to prevent disqualification?

    Kind regards

    joint.jpg

  2. #2
    Do you think that this is the best welding that you can do to prepare yourself for a mechanical engineering career? What is your definition of excellence and how far do you think you are from that definition?

    Here is my take: The question is not whether this is acceptable by technical inspection or not but if you are proud of this welding. After all FSAE / FS competition is much more about offering you the chance to get better prepared for your engineering career than the pass / not pass technical inspection.

    By The Way... who are you?
    Claude Rouelle
    OptimumG president
    Vehicle Dynamics & Race Car Engineering
    Training / Consulting / Simulation Software
    FS & FSAE design judge USA / Canada / UK / Germany / Spain / Italy / China / Brazil / Australia
    [url]www.optimumg.com[/u

  3. #3
    To more closely answer your question, there is a stipulation in the rules which requires that all tube joints be welded 360* degrees around their circumference, so you need to join that weld bead all the way around until it meets the weld on the other side of the joint.

    This is true of any tube joint in the required structural portions of the frame, and should be followed for any other tube fabrication on the car.
    _______________________________________

    Northwestern Formula Racing Alum
    Head Engineer, Frame/Suspension 2006-2009

    My '73 Saab 99 Road Race Build

  4. #4
    It looks like you are TIG welding. I am TIG welding our chassis also, but MIG can also be used if you like, which would be faster and easier. If the tubes fit together nice, a good TIG weld will be a bit lighter and more pro looking.

    To get a better weld, it helps to have the tubes fitting together better before you start to weld. But with practice, you can learn to fill the gaps you end up with. We end up with lots of gaps also, but I do fill all the gaps with weld.

    For the corners as in your picture, adjust your tungsten tip out a bit longer, maybe to 10mm, if you normally have it out 7mm. This helps get in the corners. Point the arc towards the full tube, as it can take the heat.
    University of Tasmania (UTAS)

  5. #5
    Keep in mind that any welded joint is a major source of compliance in your chassis. The weld is always weaker than the surrounding tubes, and if you have huge gaps resulting in the tubes being made of weld you're going to end up with a floppy chassis. Which will in turn snowball into a cracked chassis.

  6. #6
    I'd fail that at a tech inspection at a kart track. It only takes a few hours at a grinding wheel to know how to fit tubes together properly.

    Get an air-powered rotary tool with a carbide burr and the thinwall stuff used in FSAE cars will be easy to get right.
    Charles Kaneb
    Magna International
    FSAE Lincoln Design Judge - Frame/Body/Link judging area. Not a professional vehicle dynamicist.

  7. #7
    This may just be me speaking in ignorance, but what why would a weld contribute to compliance?? It isn't like the modulus changes.

  8. #8
    Quote Originally Posted by Alumni View Post
    Keep in mind that any welded joint is a major source of compliance in your chassis. The weld is always weaker than the surrounding tubes, and if you have huge gaps resulting in the tubes being made of weld you're going to end up with a floppy chassis. Which will in turn snowball into a cracked chassis.
    Sorry I can't agree with this. A long unsupported tube is a source of compliance. The welded part is the strong bit (unless you are very very bad at welding).

    If the gaps are properly welded up, it is still strong. The bad thing then is that you have extra weld and the chassis becomes heavier, (bad if you are worried about a 31kg chassis vs 30.5kg).
    University of Tasmania (UTAS)

  9. #9
    Jonny, I think we're playing different games in different stadiums across town here. A long unsupported tube is obviously compliant because of poor triangulation.

    A weld such as the above will be more flexible than one fit and welded and treated properly, which will still be more flexible than the same joint made of billet (if it were possible.)

    If you could get a perfect weld and fitment around the entire tube, then the difference would probably be negligible. From the discussion on the UTAS thread, you probably have more experience than both myself and virtually all members of this forum so you are probably much closer, but will never reach that theoretical perfection.

    If anyone doesn't believe me, it would not be that difficult to test different weld methods and post-treatments and bring the results to design with you!



    Now - for some other random blatherings...

    Did you know that weldments are not allowed in most anything that would be considered "life critical" in the aerospace industry? This is because even done to the best that modern metallurgy and science allows, they are still considered to be major stress concentrations and weak points, to the degree that it is standard to assume that your weldment has as much as 20% less strength than a similar stamping or casting etc. due to the fact that they are always considered to have internal cracks and low fatigue life.

  10. #10
    There is no post treatment. We are just talking about mild steel here. The tube is mild steel, the weld material is mild steel. No heat treatment can be done or is needed.

    The tube is 1.6mm wall. The weld thickness varies, but maybe 2.5mm thick. If the weld material has 20% less strength, then which part is stiffer?
    University of Tasmania (UTAS)

+ Reply to Thread
Page 1 of 2 1 2 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts