Custom building your very own chassis from scratch

By Carl Heideman
Oct 21, 2023 | DIY, Fabrication, Chassis, Shop Work, Scratch-Built Solutions | Posted in Shop Work | From the Aug. 2014 issue | Never miss an article

Photography by Carl Heideman

It’s a dream that so many of us have: building our own chassis from scratch. Then reality kicks in. Where does such an endeavor start?

Don’t keep those hopes and dreams bottled up. 

Last time we showed you the starting point for such a project, covering the layout and fabrication of the flat upper and lower sections of our Lotus Seven clone. With …

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kb58 SuperDork
7/14/22 6:03 p.m.
Carl Heideman said:

It’s a dream that so many of us have...

It was for me, for both Kimini and Midlana. I actually enjoy the journey more than the destination.

jmc14 HalfDork
7/14/22 8:48 p.m.
kb58 said:
Carl Heideman said:

It’s a dream that so many of us have...

It was for me, for both Kimini and Midlana. I actually enjoy the journey more than the destination.

It was for me too.  I enjoy the process.  And, the satisfaction of driving my cars after they are built.  It's my passion. I wish that I wasn't getting older!  It's harder for me to build now.  smiley

kb58 SuperDork
7/14/22 9:39 p.m.

I may have one more car in me, but ironically, it's heavy traffic around here that has taken a lot of the enjoyment out of it, which means that no matter what I build, it'll have the same issue. I don't have a desire to build a track-only car, living 99% of its life on a trailer, so that limits things even more.

This reminds me of a cartoon I wanted to make. Two frames side by side, the left being "Rush hour traffic before EVs", and "Rush hour traffic after EVs" on the right, and it's exactly the same.

RonB001 GRM+ Memberand New Reader
7/15/22 5:55 p.m.

Great article series.  I really hope you take it all the way through.

A couple tips:

5.  Many, but not all, framing squares have different scales on different sides.  These can include 1/8, 1/10, 1/12, and 1/16, all on the same square.  Not a problem if you are aware which scale you are looking at.

6.  A way to "prove" that your level hasn't been damaged, and is still giving accurate readings, is to take a reading, then rotate it 180 degrees on the horizontal axis.  If the second reading is the same, your level is good.  If not, beware.  Also, just because the horizontal bubble is good, does not necessarily mean the vertical bubble is also good.

frenchyd MegaDork
7/15/22 6:28 p.m.

In reply to Carl Heideman :

I took advice from Jaguar.  The chassis of the D Type and the later XKE  is insanely light. Plus very fast to make.   
     The used thin tubing square tubing.   No complicated   fish mouths to cut.  Easy to cut and layout. 
   Held a 730 pound cast iron block engine.  ( later the 700 pound aluminum v12 )  suspension was state of the art. 
  Recorded top speed was 182 mph.   
remained in production from 1954 through 1974. 
  The front 1/2 of the chassis frame for the V12 weighed 22 pounds. 
 Passed Federal safety crash test. 
A lot of the newer Trans Am cars have gone in that direction. 

kb58 SuperDork
7/16/22 3:07 p.m.
frenchyd said:

In reply to Carl Heideman :

...The used thin tubing square tubing.   No complicated   fish mouths to cut.  Easy to cut and layout...

Single-plane junctions, I'd agree; two-plane, not so much; three-plane, no.

frenchyd MegaDork
7/17/22 8:54 p.m.

In reply to kb58 :

 Perhaps  you're overthinking  things?    
   For 20 years Jaguar used the same frame design   It's been tested  and meets US  government crash standards. Recently Trans Am cars are adapting it   800+ horsepower and wide sticky slicks ?   

   The remarkable point is how thin the wall thickness is on 1 inch square tubing.   Take a saw and cut through the  frame tube. Then cut through the body skin.  Yep!! It's a lot thinner than body skin!  
       In addition the way the tubes lay on top of each other provide a massively stronger connection than   A fish mouth joint on round tube frames.   Jaguar didn't weld those, they brazed those connections! 
      If you doubt me try it yourself .  
  Braze a tube across another tube forming a triangle   If you tug on it hard enough  the tubes will fail long before the joint gives up.  
  Then connect a tube with the typical fish mouth butt connection.  
     Test that to destruction and it will yield much sooner  than the square tube.   
        While I'll agree round tube is needed for roll bar/cage due to the variety of load directions in a crash. 
     The loads of suspension and torque from from the engine is exactly  predictable. 
  Why add weight and bulk when it's not needed?  



kb58 SuperDork
9/9/22 9:23 a.m.

My comment is entirely about ease of fabrication. To my point, adding a round tube into an existing 3D assembly is very difficult due to prepping the ends at the proper angles. A square tube easier to fabricate in that case. Of course, at the factory, they presumably have all the angles figured out and it makes little difference. Certainly no overthinking.

DaleCarter GRM+ Memberand New Reader
9/23/23 3:46 p.m.

Square tubing seems perfectly fine for my Panoz GTS and my vintage stock car chassis. That said, the application and design dictates tubing, right? 

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