My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

"mark" wrote in message
...
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

I don't think a frame made of that tiny tubing would be very good.

Steve g

In article ,
mark wrote:

My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

Aluminum is far less stiff than steel, and doubling thickness may yield a
too-floppy frame. I would stick with steel unless you reengineer the frame.

Joe Gwinn

"mark" wrote in message
...
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

This looks familiar, Mark. Didn't you post this same question here three or
four years ago? Someone posted something similar.

Anyway, as Joe Gwinn says, aluminum has 1/3 the stiffness of steel, roughly
1/3 the strength for low alloys of each, and weighs 1/3 as much. A box
section tube doesn't take advantage of aluminum's low density, so there is
no weight advantage in using aluminum in this way. To get equal strength in
the same section (2 x 4), the aluminum tube will have to have walls that are
3X as thick as the steel one.

I don't know Jeep frames but if the frame isn't boxed (in other words, if
it's a U-channel or top-hat section rather than a rectangular tube), and if
you use box-section aluminum to replace it, it will be a great deal stiffer
and stronger. But that's because the tube is stiffer and stronger, not
because it's aluminum.

All in all, aluminum sounds like it's a lot more trouble than it's worth.
Welding that thick section and producing a *strong* weld with it will be no
picnic, unless you're an expert. It will cost a lot more for the material. I
can't speak for the galvanizing but I thought that hot-dipping a frame was
supposed to be a reasonable cost proposition.

I'm sure you'll get other opinions.

--
Ed Huntress

"Ed Huntress" wrote in message
...

"mark" wrote in message
...
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

This looks familiar, Mark. Didn't you post this same question here three
or four years ago? Someone posted something similar.

Anyway, as Joe Gwinn says, aluminum has 1/3 the stiffness of steel,
roughly 1/3 the strength for low alloys of each, and weighs 1/3 as much. A
box section tube doesn't take advantage of aluminum's low density, so
there is no weight advantage in using aluminum in this way. To get equal
strength in the same section (2 x 4), the aluminum tube will have to have
walls that are 3X as thick as the steel one.

I don't know Jeep frames but if the frame isn't boxed (in other words, if
it's a U-channel or top-hat section rather than a rectangular tube), and
if you use box-section aluminum to replace it, it will be a great deal
stiffer and stronger. But that's because the tube is stiffer and stronger,
not because it's aluminum.

All in all, aluminum sounds like it's a lot more trouble than it's worth.
Welding that thick section and producing a *strong* weld with it will be
no picnic, unless you're an expert. It will cost a lot more for the
material. I can't speak for the galvanizing but I thought that hot-dipping
a frame was supposed to be a reasonable cost proposition.

I'm sure you'll get other opinions.

--
Ed Huntress

During our 8 year tour in the Marshall Islands where you can corrode a glass
thermometer, we saw jeeps made of Stainless Steel that were made in the
Phillipines. No rust.. People that owned them were not excessively rich.
Don't know what they cost, but looking back we should have bought and
shipped a couple of them to the US .

Stu Fields

On Sun, 28 Feb 2010 06:52:53 -0800 (PST), mark
wrote:

My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

You do NOT ewant an aluminum frame. Perhaps stainless steel.
Aluminum frames on a jeep WILL flex. Particularly a 2X4 x1/4 tube.
ANY time aluminum flexes it is a stress, and all stresses are
cumulative. Frame life would likely be measured in months.

Steel is different. It has an elastic limit, and as long as that
loimit is not exceeded, no cumulative stress occurs.

I'd build a stainless steel TUBE frame if I was going to the trouble -
but Iron Horse (I believe that is still the name of the company)
supplies ready made replacement frames at a very reasonable price.

I have the full dimensions for the CJ frames, they have a LOT of bends,
brackets, and quirks to make a fabrication job pretty messy. There are
several companies that do these from 2x4" tube to replace the double
channel original. Under $2000. A quick google came up with
http://www.throttledownkustoms.com/framesCJ7.html
http://www.acmejeepparts.com/product...cessories&c=38
The galvanized versions run around $800 more IIRC

You do not want to use aluminum: flex, fatigue, and strength all work
against you.

mark wrote:
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

On Feb 28, 2:18*pm, RoyJ wrote:
I have the full dimensions for the CJ frames, they have a LOT of bends,
brackets, and quirks to make a fabrication job pretty messy. There are
several companies that do these from 2x4" tube to replace the double
channel original. Under $2000. A quick google came up withhttp://www.throttledownkustoms.com/framesCJ7.htmlhttp://www.acmejeepparts.com/products/product_search.php?cn=Frames+%2...
The galvanized versions run around $800 more IIRC

You do not want to use aluminum: flex, fatigue, and strength all work
against you.



mark wrote:
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 *wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.- Hide quoted text -

- Show quoted text -

Roy, as for the bends, I am going to eliminate the arches for the leaf
springs, I have a 4" suspension lift so straight frame rails will be
fine although I will have to bring them in narrower at the front.
Around here we use 4X4 1/4 aluminum box tube to build cranes for
aquaculture boats that are constantly lifting 1500+ lbs 8'-10' out
from the hydraulic lift cylinder and I see many aluminum boat trailers
made form I beam, box tubing should be stronger. Also i have a
fiberglass body which is much lighter. Each frame rail will have the
load spread out to 4 points due to the leaf springs. Maybe if I use 4
X 4 instead, a 20' length is only ~$200.00

mark wrote:
My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.


Aluminum is a VERY poor choice for a frame of a Jeep. The frame in them
is engineered to flex and allow the suspension to operate well. That
flex in aluminum will work harden the frame in a short time and cause
failures. The welds will be the first failures and then the rails
themselves.
Even if you doubled the thickness the frame will be the weak point.

Now if you have access to stainless and a way to work with it that would
be a MUCH better choice. It would flex like the steel and retain it's
strength. The alloy of the stainless would be a BIG factor though.

Personally if I wanted a long lasting rig I would start with a custom
tube frame and a fiberglass or stainless body. One of the locals has a
set up like that.


--
Steve W.

wrote:
On Sun, 28 Feb 2010 06:52:53 -0800 (PST), mark
wrote:

My original jeep CJ-7 frame has rusted out and I was thinking of
building a new one from aluminum. Would 2 X 4 X 1/4 wall (if that is
even available) box tubing have the equivalent strength of the stock
1/8" wall steel frame? I would like aluminum because it will last
forever, no need of any paints etc..., very easy to work with and
cheaper than building a steel one and having it galvanized. My second
choice would be stainless 1/8" box tubing.

You do NOT ewant an aluminum frame. Perhaps stainless steel.
Aluminum frames on a jeep WILL flex. Particularly a 2X4 x1/4 tube.
ANY time aluminum flexes it is a stress, and all stresses are
cumulative. Frame life would likely be measured in months.

Steel is different. It has an elastic limit, and as long as that
loimit is not exceeded, no cumulative stress occurs.

I'd build a stainless steel TUBE frame if I was going to the trouble -
but Iron Horse (I believe that is still the name of the company)
supplies ready made replacement frames at a very reasonable price.

Oh boy, if you can buy a frame that's the way to go. Unless you're just
determined to build your own frame for the sake of it, and have a well
equipped shop at your disposal, you'll spend less time and probably less
money buying one.

Aluminum works differently than steel, and is not corrosion proof --
particularly when you bold a bunch of steel parts to it.

Stainless is hard to weld, and fatigues far more readily than steel.

Steel can be painted or galvanized to not rust, and works pretty darn
well for frames. Very few cars have aluminum frames for a very good reason.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com