Rollbar/ Floorpan work

[Jasontech]

Hi all. I am a novice welder with a Hobart handler 135. I am using gas and solid core wire. I spent several days practicing on relatively thick metal to get a decent bead down. The major problem I am having is welding the thick metal plates that came with my rollbar to the super-thin floorpans.

I am burning holes through the floorpan almost the second I am touching it with the torch!! I have managed to get 1 plate done, but I had to patch several holes I created as well. it was frustrating. I am using the lowest power setting (1 out of 4) and tried various wire speeds.

I am using .030 solid core wire.., is this too heavy?? I did some reading last night and it appears several guys doing VW restores are using .023 or .024 wire. Can this really make such a difference, or are floorpans just very difficult to work with?

Any advice or opinions would be appreciated.

thanks

jason

[Roger]

You are trying to do lap joint between thin floorpan and thick pad of rollbar.
Must be no gap between pad and floorpan so tack weld and as required beat floorpan into close contact.
The thickness difference makes welding more difficult but is done all the time. VW has nice thick sheet metal making it easier unless floorpan is rusty. Rusty metal in floorpan must be replaced.
Direct Torch/heat towards the thicker pad. Pause a little during weave onto thicker pad edge to get better penitration and no pause while on thin floor pan.

There could be too great thickness difference to make the above real practical. Grind edge of pad so it is 60 degree insteed of 90 degree leaving a thin section next to floor pan at original angle. Make the thin section at original 90 degree angle about 2 times the thickness of floor pan. This then becomes much easier weld.

Practice with meal same thickness as your project and do bend tests.

Must be large pad at end of roll bar to spread load onto thin floor pan.

Recommended welding parameters from esabna.com
.023 wire 45-90 Amps 14-16 V 150-380 IPM: 70 amps 15 V 300 IPM optimum
.030 wire 69-140 Amps 14-16 V 150-350 IPM: 100 Amps 15 V 220 IPM optimum

You can see with same settings thinner wire uses less amps so it can weld thinner metal with less burn through problems. Thinner wire at same amps has more concentrated heat getting more penitration.

[Dan]

Jason
Can you define what you mean by thick plates and super thin floor pan? In other words, what are the thicknesses of the materials?

I have a question myself. Would it be acceptable to bolt the plates to the floor board? I was thinking along the lines of sandwiching the floor board with a plate from both sides.

[Guest]

Jason

It sounds like you have to great a difference between the two thicknesses, although it is do-able, that great a difference may /will cause cracking as it receives vibration and flexing. A good work-around would be to place a plate of an intermediate thickness between your rollbar plate and your floorpan. The middle plate shoud be an inch bigger all around to dissapate the stress into the floorpan. As Roger stated keep your arc on the heavier plate, and let the liquid metal sorta drip down onto the thinner plate.

[shortarc]

If this is a Roll Bar for safety purposes and not just for show I sure wouldn't want it welded to a "floor pan" It needs to be welded or otherwise attached to the frame!

[Hobart Expert Rock]

OK MY 2 CENTS WORTH............... IF THIS IS A USEABLE ROLL BAR I WOULD CONSIDER A DIFFERENT MOUNTING SYSTEM........FRAME, STICK WELDED AND BOLTED.............YOUR LIFE OR SOMEONE ELSE'S MIGHT DEPEND ON IT IF YOU SELL THE VEHICLE,..... SORRY I WOULD NOT RECOMMEND THIS JUST BEING SELDED TO THE FLOOR PAN'S............RECONSIDER............ LET'S BE SAFE OUT THERE...............ROCK.........[email protected]

[Four by Girl]

For a rollcage/roll bar to pass inspection at any of our drag strips or any of our pulls they specify they must be bolted to the frame. As Rock stated, safety isn't something you want to mess around with on a vehicle of any sort...truck, car, tractor, motorcycle, atv...
There have been several instances this year where if the guys hadn't had a properly mounted cage, they wouldn't be breathing today (and I do have pics of these).

[Hobart Expert Rock]

JASONTECH.......FOUR BY GIRL..... HAS A POINT......... AND HAS PICTURES AND KNOWLEDGE TO BACK IT UP........ IF YOU WANT I'LL HAVE HER DOWN LOAD ONE OR TWO FOR YOU...... ALSO WE ARE NOT BEING REAL CRITICAL HERE ON A NEW MEMBER. PLEASE DON'T TAKE IT THIS WAY........ WE ARE SIMPLY TRYING TO MAKE IT SAFE FOR ALL CONCERNED, AND I'M GUESSING IT IS A SPECTATOR SPORT ALSO CORRECT...........IF YOU NEED SOME POINTERS TO GO LOOK AT NHRA RULE BOOK, FRAME ROLL CAGE INSPECTION, ETC. I'LL BET SOME OF THESE FOLKS CAN HELP..........THAT SAFETY ISSUE KEEPS CROPPING UP........... WE ONLY OFFER SUGGESTIONS AND SOLUTIONS HERE.........CAN WE HELP YOU MAKE IT BETTER.................ROCK
[email protected]

[Roger]

Last time I checked old VWs had Unibody with no frame. Would be real hard to bolt to frame that isn't there. Still backing plate and bolts would probably be better mounting method.

[Jasontech]

thank you everyone for replying. There is alot of useful information. I am well versed with the NHRA rules of installing a rollcage. I have inspected several cars that have NHRA certified bars installed.

The typical bar install involved welding the thick plates to the floorpan.

I think there are several things that may have been a factory with the burn through. I was trying to weld thick plates with a large edge to a thin pan. I should have grinded the end to a 60 degree radius as suggested. I also may not have had the metal surface properly clean. (any opinions here are appreciated)

In addition, I understand that .030 wire may not have been a good selection for working with such thin metal. I am going to try .024 in a few days on the next plate to see how I fair.

thanks again.