Welding on vehicle frame

On Mon, 5 Sep 2011 17:21:48 -0700, Tin Lizzie DL


They usually recommend that no welds be made straight across the
frame, but at a slant, to avoid stress risers.

--
John B.

The frame repair section of the shop manual for my Ford gives their rules to
avoid weakening the high stress areas. Can you weld plates to the ends of
the pipes and bolt them to the rails, perhaps copying the pattern and hole
size of the body mounts etc?

jsw

To bolt them on I would have to drill holes in the frame and whatever I
flanged the pipe with. The frame is pretty solid, only a couple of pre-
existing largish (1/2" or better) square and triangular holes spaced too
far apart for what I would like to do.

I would cut the pipes so they fit at a slight down angle off the side of
the frame, then weld them on with a 3/16" or 1/4" fillet around the
pipe.

Which is worse?  Drilling holes in the frame, or making circular welds
on it?

--
Tin Lizzie
"Elephant- A mouse built to government specs." - Lazarus Long

On 9/6/2011 12:29 AM, Tin Lizzie DL wrote:

Welding is worse. Round holes in the center of the web have very little
effect on the structure. If you must weld, diamond shaped patches are
preferred (all sides welded) or rectangular patches welded on the sides
parallel to the frame only (2 sides only).

As for the electronics, I'd take the positive (hot) battery terminal,
hook it to ground to make sure both sides of the electronics are
anchored firmly to the same potential. Put the ground clamp as close to
the weld area as possible to minimize stray fields. Mig or stick, not
tig with HF.

The vertical web of the frame sees much less stress than the upper and lower
flanges, consider a truss. Drilling weakens only the region right around the
hole, welding heat affects a much wider area.

If you weld off the vehicle you can clean and inspect the upper part that
holds the load in tension. At my skill level that includes grind out and
reweld voids. 200 lbs on the step could apply 2000 to the top of the weld.

IIRC I used a sheet metal step bit in a Sioux drill to get into the tight
areas of the frame. Once I machined and hardened a very short piloted
half-round drill bit out of O-1 for a difficult truck mod. Countersinks can
open up holes in tight places too.

jsw

FWIW, I fabbed up and installed to someone else's spec a set of rock
sliders for a buddy's SUV.  They bolted on to the sides of the frame
rails, and you can jack an entire side of the vehicle off the ground
using a hi-lift(farm jack) hooked under one of them. To use a word:
Sturdy.
My preferrence is for something that's removable and improvable.


-m

wrote:


Is the frame of a 2007 Chevy 1 ton van heat treated?   A call to the
local Chevy dealer is in order here.  If you can find a competent
person on the other end of the phone.  Do not speak to a service
writer, try to speak to a lead mechanic if you can.



Remove 333 to reply.
Randy

The clerk at the computer store recently quit to be a dealership service
writer. When I asked him the job qualifications he said they wanted the
ability to write, not to service.

jsw

On Tue, 6 Sep 2011 13:58:46 -0400, "Jim Wilkins"


My piont exactly.

They should be former mechanics, but they are not.

Remove 333 to reply.
Randy

Where I sold cars for two years, he was a former mechanic.  But he was also
the worst mechanic, and had a terrible reputation for finding things that
didn't need to be done, but did them under the warranty program and
backcharged the manufacturer.  He was one of the biggest crooks next to the
owner.  He finally got caught in a state operated sting with invisibly
marked parts supposedly being replaced, and the dealership fired him and a
couple other guys.  Then they moved other incompetents with flowing pens
into their jobs.

Steve

Don't know your exact vehicle as I'm in UK. However, I've welded quite
a few car repairs.
As you say, the eath clamp must be close to the weld. Also try to
strike on the metal that's earthed. It's not to much of a problem when
you're welding a new part on but if you weld 2 existing parts of the
car you can imaging what hapens if the earth is on one and the arc
strikes on the other. All sorts of current paths happen, some of which
may be via the car wiring. Disconnecting the battery won't hurt but
doesn't protect everything.

The steel is probably suseptible to heat changes. Car steels have been
getting tougher for decades now, probably due to cold working and
improved steel specs. Welding can be a problem in high stress areas.
It's not impossible but be careful with your design and check it
routinely afterwards for stress cracking.

John