Some welding problems

[Dualsaber]

We are new here,planing to make our own fase car.But we encountered some welding problems.
How can we keep the welding deformation in a tolerable range.

We plan to use a welding platform together with jig and fixture.Postioning these fixture carefully and pre-heat the tubes of farme.So here comes the questions.

1)which type of welding platform is suitable?I mean the type with T-slot or the type have threaded\Unthreaded holes.

2)How about the fixtures?Do we need to design ourselves?Or it's ok to use a flat-nose pliers with V-block.

Do you have some better idea or experience can be shared?Any suggestion would be useful to us.

Thanks~

[Dualsaber]

We are new here,planing to make our own fase car.But we encountered some welding problems.
How can we keep the welding deformation in a tolerable range.

We plan to use a welding platform together with jig and fixture.Postioning these fixture carefully and pre-heat the tubes of farme.So here comes the questions.

1)which type of welding platform is suitable?I mean the type with T-slot or the type have threaded\Unthreaded holes.

2)How about the fixtures?Do we need to design ourselves?Or it's ok to use a flat-nose pliers with V-block.

Do you have some better idea or experience can be shared?Any suggestion would be useful to us.

Thanks~

[Dualsaber]

http://fsae.com/groupee_common/emoticons/icon_smile.gifOne more question:Is the CNC bended tube more likely to have some unwanted deformation after welding?

Forgive my poor english http://fsae.com/groupee_common/emoticons/icon_frown.gif

[exFSAE]

If you're doing TIG welding I wouldn't worry about preheating the tubes. Just have enough practice to the point you aren't using a crazy amount of heat when welding.

And if your welder isn't that good, then do little bits at a time. Do a 1/2" stitch here, then move to another joint, and another joint, and keep moving around rather than really cooking one node.

Set up jigs and platforms don't need to be anything fancy. Don't even need to have T-slots or threaded holes, at least for most of the tube setup. You can make it whatever you'd like so long as it holds tubes in place.

[fixitmattman]

Pre-tack weld evenly in 4 places, check and adjust alignment after each tack. After a few decent tack welds the tube's not going anywhere so it's just a matter of welding evenly, usually in 1/4 sections about the circumerence between the tacks you made.

[Dualsaber]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
If you're doing TIG welding I wouldn't worry about preheating the tubes. Just have enough practice to the point you aren't using a crazy amount of heat when welding.

And if your welder isn't that good, then do little bits at a time. Do a 1/2" stitch here, then move to another joint, and another joint, and keep moving around rather than really cooking one node.

Set up jigs and platforms don't need to be anything fancy. Don't even need to have T-slots or threaded holes, at least for most of the tube setup. You can make it whatever you'd like so long as it holds tubes in place. </div></BLOCKQUOTE>

Then what about the positioning of wishbones joint?I think a the percision of those joints would have tremendous effect on performance of the car.At least these joints need special cares.Is a somekind of positioner needed for the welding work?

Also the percision of tubes contribute the stiffness of the chassis.So I can't agree on that point.

But the welding method you told me is something we never thought of.Thanks~

[Dualsaber]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fixitmattman:
Pre-tack weld evenly in 4 places, check and adjust alignment after each tack. After a few decent tack welds the tube's not going anywhere so it's just a matter of welding evenly, usually in 1/4 sections about the circumerence between the tacks you made. </div></BLOCKQUOTE>

Tacks......It's a good idea but the flatness of the working surface is crucial,right?Adjustion and measurement is important.Even if we were using ruler or gradienter we still useing our naked eyes.So no measurement is precise enough.

Or maybe I was driven myself too much on this question. http://fsae.com/groupee_common/emoticons/icon_frown.gif

Still,thanks for the advise~ http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Hector]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Then what about the positioning of wishbones joint?I think a the percision of those joints would have tremendous effect on performance of the car.At least these joints need special cares.Is a somekind of positioner needed for the welding work?

Also the percision of tubes contribute the stiffness of the chassis.So I can't agree on that point. </div></BLOCKQUOTE>

You can accurately locate your suspension points without any sort of slotted/threaded table. For years our team used a flat steel table and carefully welded our jigs to the table. You can get a very high degree of accuracy this way if you know what you're doing. We were lucky to get a high quality laser table a few years ago so jigging has gotten much easier since then.

As for your second point, you can design your chassis in such as way that only a few tubes (suspension mounting points and rool hoops) have to be jigged. If you bend your roll hoops the right way, your chassis nodes will all intersect at the bends. This way, less jigging is required and you can still achieve a relatively high degree of accuracy.

Lastly, if this is your first car, extreme accuracy in tube placement is the least of your worries. Let me remind you that most "first year" cars become two or three year cars, and that endurance finish rates are typically in the 40% range at most competitions.

If you can build a car in your first year AND finish in every event; you will have done extremely well, and will probably place in the top 25%. Focus more on just building something and less on extreme accuracy or precision for your frame.

/Second and third on posts about welding slowly. 4 tacks per tube; do a quarter section at a time and move to the other end of the frame. They key is to go slow and move around a lot. Our welder (if rushed) could do it in a day; instead he usually took 3 or 4 to make sure it was done slowly and carefully. It's exhausting, tedious work.

[Dualsaber]

I understand.We can still get a tolerable deformation if it's carefully positioned and welded.

You are right,we have more things to concerne about.We made two kart cars before,the first had a very terrible deformation(Up to 5cm).And the second one is using TIG welding.We still have a 2cm deformation in height on the rear track and a 1cm deformation in width on the front track.So I've got headache every time we are about to weld someting together.....

http://fsae.com/groupee_common/emoticons/icon_smile.gif Feels easy now,thanks