overhead welding

[uninformed]

any tips on overheads, i,m welding some 4mm plate to the underside of my chassis, along the center line about 250mm in length. the chassis should be about 4mm thick at this point. i'm using a mig. and preperation is the key
cheers, serg

[ISUZUROVER]

Overhead welding with a mig is pretty easy - just make sure you don't stay on one spot for too long.

[Pinball]

Roll the rig over....

or cover up lots... rolling slag down the shirt HURTS!!!



Spock

[Geoffsa]

If the vehicle is road registered I think it is illegal to weld or drill the chassis.
I could be wrong, but someone will confirm.

Geoff.

[BOGAN V8]

If the vehicle is road registered I think it is illegal to weld or drill the chassis.
I could be wrong, but someone will confirm.

Geoff.

As far as i know if you weld or drill the chassis you will have to get it engineered again withe mods the olny thing you cant do ( or they dont like) is welding to the top of the chassis...

[Major60]

[quote="rolling slag down the shirt HURTS!!!



My MIG doesn't make much slag..... I must have an old one....

[up2nogood]

Perhaps he meant spatter?

[Bush65]

Welds across the top or bottom flange of the chassis can greatly reduce its fatigue life.

[ISUZUROVER]

Welds across the top or bottom flange of the chassis can greatly reduce its fatigue life.

I think uninformed is talking about welding to a defender chassis at the point where the factory weld is (where the 2 c-sections join). If properly designed this wouldn't affect fatigue life would it? Series LR gearbox crossmembers were welded from bottom rail-bottom rail of the chassis.

[Bush65]

NSW RTA put out a document on vehicle mods. If I recall correctly, this said welding to the top and bottom of the chassis is prohibited. This is more or less what Geoff said.

My statement in previous post was based on various design codes for fatigue. The Australian standard which deals with this AS 4100 (steel structures code) section 11.

The "bible" is Bristish Standard BS 7608, Fatigue design and assessment of steel structures.

Any welding on the flanges will greatly reduce the fatigue strength. To assess this you need to find the matching class in BS 7604 (detail category in AS 4100). Each class or category has a corresponding SN (stress vs number of cycles) curve. The class (detail category in AS 4100) depends on geometrical details, direction of fluctuating stress and location of possible crack development.

The most difficult factor to determine is the fluctuating stress in the area where the weld is.

[uninformed]

well its to late to worry now as one side is done and the other will be finished next weekend. the area is at the rear outrigger (D110 tray back) on the bottom rail running front to back 250mm in the center where the two chassis sections overlap and become 4mm thick. basicly i'm strengthing the outrigger to handle the mounting of my slidders. if you look at the outrigger the top of it overlaps and is welded to the top of the chassis rail. this outrigger is designed to take the weight of the body ie: downward pressure. now a slider whants to lft it up. and rip it of the vertical face of the chassis. so i cut and bent up some 4mm plate to cap the underside of the outrigger, i also made it wider at the base/chassis to act as bracing to resist twisting. i also welded into the outrigger some 15mm nominal bore pipe to act as squish tubes. when im done ill try posting some pics up in the rover section.
cheers serg

[uninformed]

heres a pic of the underside of the chassis rail
serg