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W.D.
08-19-2005, 09:55 PM
Hello;

I am contemplating on building a chassis using a 75 Suburban as a sort of pattern. I want to make a few changes to the new chassis and I want to build it out of rectangular tubing. For my design the rec tubing is a must.

I have the basic design figured out but I want to find out what the best tube to use for the frame. The frame will need to be pretty heavy duty as it will see some off road use...not much but some.

I found a site somewheres that they use 2X4 rectangular tubing for a frame...not sure what gage though.

So what size and what gage would be the best to use?

Any help would be appreciated.
W.D.

Marty Comstock
08-20-2005, 03:34 AM
what is the current thickness of the frame? im betting it isnt more than 1/4'' thick, 2x4x1/4 is a common tubing size and using rectangular tubing would give you much more stiffness than your current channel type frame.
post some pics of what youre doing, we love that here :-)

Marty

W.D.
08-20-2005, 07:48 AM
what is the current thickness of the frame? im betting it isnt more than 1/4'' thick, 2x4x1/4 is a common tubing size and using rectangular tubing would give you much more stiffness than your current channel type frame.
post some pics of what youre doing, we love that here :-)

Marty

Sorry, no pictures.....
I am leaning towards 3x4x11 gage....do you think it would be rigid enough since it is tube instead of channel? If not I'll probly use 3/16.

Also, is there any frame charts on the net that anyone knows about showing locations of mounting holes, motor mount locations and such? The only one that I have found is Chucks Chevy Trucks site. I have the suburban chassis to measure from but something easier like a chart would be nice.

Marty Comstock
08-20-2005, 08:09 AM
1/8th wall, i may feel a touch nervous about that, i would definitley opt for the 3/16 minimum, which is probably equal to your existing frame thickness. true, the added side would increase strength, but youre looking for increased strength anyhow. as for dimensions on mounts and such, just level your frame on stands and take measurements to a parallel surface. i dont know of any charts avail on your frame, maybe somebody else can jump in and help here.

Marty

W.D.
08-20-2005, 08:15 AM
1/8th wall, i may feel a touch nervous about that, i would definitley opt for the 3/16 minimum, which is probably equal to your existing frame thickness. true, the added side would increase strength, but youre looking for increased strength anyhow. as for dimensions on mounts and such, just level your frame on stands and take measurements to a parallel surface. i dont know of any charts avail on your frame, maybe somebody else can jump in and help here.

Marty
THANKS Marty
Maybe someone can direct me towards some on line charts. Until then I'll just do it the old fashion way.

rsanter
08-20-2005, 08:22 AM
if you have the room to do it, go with a 2x6 or 3x6
for similar weight you will get much more strenth

Boogiemanz1
08-20-2005, 08:58 AM
Is this a scratch built vehicle or will there be an OEM body on it. It would be helpful to know what you are doing, and what it would be used for to make a valid recommendation........john

W.D.
08-20-2005, 09:24 AM
Is this a scratch built vehicle or will there be an OEM body on it. It would be helpful to know what you are doing, and what it would be used for to make a valid recommendation........john

It will be a scratch built body similar to the HMMWV. I could use the 4x4 GM frame if I wanted to, but I'm trying to design the frame around areas that conform to it. Maybe make it a unibody design maybe or both. Leaning to making a separate frame and body mostly.

FriarTuck
08-20-2005, 07:03 PM
That picture comes from my Baja 1000 days. I think rsanter is pretty close. 2x6x1/8th or maybe 3/16th as Marty suggested, will handle a lot of abuse if crossmembered correctly. Using 1/4" thick is just overkill, or "pound foolish" as we used to say. Many of the really strong unlimited class v8 trucks used modified truck frames that were mostly 3/4 ton PU frames fishplated with 1/8" plate. And it was never the frame that failed. Usually it was the appendages.
Anything fully boxed is inherently stronger.

W.D.
09-20-2005, 10:56 PM
I need some tips as how to calculate ride height so that I can calculate leaf spring hanger mounting points before the body goes on.
I have figured out how to articulate the axle movements using the spring measurement guides that I have found on-line.

As a guide I plan on using a GM 350 engine and transmission,solid front axle, 52 inch leaf springs in the rear and 47 inch leaf springs at the front maintaining a 130 inch wheelbase. The body weight will be about 1500 lbs without the interior components.
I can get close on the rear mounts from the frame that I have ... but the frame that I have has IFS, has 56 inch rear springs and I don't have access to a 4x4 at this time.

Are there any "Rule Of Thumb" methods as to how to go about this?
I have searched many hours on-line trying to find this info.... but have yet to hit upon the right "search words" to find my answer.
Any help would be greatly appreciated.

THANKS
W.D.

gator 1
09-21-2005, 05:34 AM
Ride height is not set by spring mount locations. the mounting points are set to make the spring work correctly. To alter the ride height with springs you will have to place the rear on the top side of the springs to lower and under the spring to raise. After deciding which side of the spring to use you can space with shims or blocks to fine tune. Gator

Bambi
09-21-2005, 02:28 PM
Chevy and GM truck chassis are pretty stout to begin with, plus they did an awful lot of engineering. I can not see why anyone would want to build another chassis.
There are also tons of Hummer type kits that are available for this type of project using the GM chassis. Body wise anyone could build one from scratch, the toughest part would be makin the hood assembly. The best kits have done some redesign homework in which they set back the engine about 10 inches.
This makes a whole world of difference in how the vehicle handles. Apparently using 3/4 or 1 ton axles, big tires etc. These work better than the REAL Hummers at a fraction of the cost.
Using rectangular tubing to replace one of these frames will really gain you nothing. They because of design and materials used are probably much stronger than a rectangular tubed frame. Anyone who has cut or welded on one of these frames will attest to the fact that they are not made from the steel used in rectangular tubing. They are quite tuff. I doubt seriously that you would even need to box one in only in a few places. Mainly in the steering box area.
Also considering that your lookin for prints to put all the mounts and stuff back in the stock location. Even GM chops up old stuff and modifies it till they come up with somethin that works. Cut and grind and do it all over again til its right.
Lets see build me a Hummer. One 3/4 or 1 ton chassis, a pair of Rockwell axles, some 48 inch Mudders, a big diesel, maybe a Duramax with turbo, maybe a turbo CAT an Allison tranny and then have a ball.
Since yours is not mainly for offroad, my idea maybe a bit too extreme.
Some food for thought, Good Luck

Bambi

W.D.
09-22-2005, 09:34 PM
Bambi... the GM frames are fine and the are tuff as nails .... and I'm not trying to improve on them....but some of the people that I have been in communication with have a hard time finding GM Suburban frames. There is one guy in Austrailia that finally had one shipped special so he could do a replica build. I sent him frame specs from a hmmwv and a gm truck with some information on it but it was not enough to fabricate a scratch built frame with.
There are other considerations also that I want to design into the frame as to the shape to allow more inside compartment room for the riders by removing most of the "tunnel" down the middle.
But in the meantime I'll just keep searching and one day I'll find the answers I'm looking for.
Thanks for the imput and all the replys are welcome.
I enjoy reading the many of the forums that are out there and sometimes I manage to learn a few things along the way.

Any imput or ideas are always welcome.

THANKS
W.D.

fordguyfordman
09-29-2005, 03:51 PM
Hey W.D.
If you go to www.hotrodders.com you may be able to find somebody ther that has the dimensions your looking for.
Tom

geoking
09-29-2005, 04:37 PM
This requires an expert to answer...
Please call Brent @ Fatman Fabrications in Charlotte NC.

He builds entire frames as well as front end kits. I had him make a custom crew crew cab chassis for a 1948 Chevy and he chose the guage and size. He is a very smart engineer and will be happy to either give you advice or BUILD it for you. Pending your desire. This link will take you to the phone number: http://www.fatmanfab.com

Nice person, easy to deal with,
George

tdoty
09-29-2005, 05:50 PM
Wow, I must be spending too much time in cars! Even my FWD Grand Prix has more of a tunnel than any GM truck I've ever driven.

Just drop the engine a few inches in the frame, and the tunnel will disappear .................................. or use really tall body mounts :D!

Tim D.