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1934 Plymouth Coupe - Triangulating Quarter-Elliptics - Tech

Jason Grimes' Custom Suspension Mods
By Eric Geisert
1934 Plymouth Coupe Springs
1934 Plymouth Coupe Framerails
With the body of the '34 Plymouth... 
   
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1934 Plymouth Coupe Framerails
With the body of the '34 Plymouth in the background, Jason already created his own custom framerails before the work on the suspension begins. He has also designed and built an X-member for the frame before tack welding the whole setup to his surface table, but then removed the X-member for easy access for other components.
1934 Plymouth Coupe Design
Here's a drawing Jason made... 
   
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1934 Plymouth Coupe Design
Here's a drawing Jason made showing if he keeps the top bars of his triangulated design at 20 degrees from the springs, it will keep the axle centered without any major binding of the bushings (either in the bars or in the springs) when the suspension moves up and down.
1934 Plymouth Coupe Frame
Once the frame was squared... 
   
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1934 Plymouth Coupe Frame
Once the frame was squared and tacked to the surface table, Jason could begin work on the triangulated quarters. The bolt located up top will hold the modified radius rod in place while the holes in the frame are where the POSIES quarter-elliptics will attach.
1934 Plymouth Coupe Bung
Jason begins by fabricating... 
   
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1934 Plymouth Coupe Bung
Jason begins by fabricating a bung (a -inch piece of 0.250-inch tubing, drilled and tapped with -18 threads) that will be used to adjust the quarter-elliptics once they're in place.
1934 Plymouth Coupe Top Rail
A small section of the 3/16-inch-thick... 
   
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1934 Plymouth Coupe Top Rail
A small section of the 3/16-inch-thick top 'rail is fabbed and then drilled to accept the bung.
1934 Plymouth Coupe Weld
With the adjusting bolt in... 
   
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1934 Plymouth Coupe Weld
With the adjusting bolt in place (so the threads don't warp during welding), the bung is welded to the top 'rail piece.
1934 Plymouth Coupe Gramehorn
After the top `rail section... 
   
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1934 Plymouth Coupe Gramehorn
After the top `rail section is welded in place, the "ears" are heated with a torch and hammered down to meet the leading edge of the framehorn.
1934 Plymouth Coupe Grinding
With a little bit of grinding... 
   
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1934 Plymouth Coupe Grinding
With a little bit of grinding to clean up the welds, you should get something that looks like this. After the quarter-elliptics are set in place, it's time to mount them to the axle.
1934 Plymouth Coupe Drawing
Another one of Jason's drawings... 
   
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1934 Plymouth Coupe Drawing
Another one of Jason's drawings shows he'll need to figure in the 7 degrees of caster at the kingpin when there is a load on the spring. He's aware the spring will "grow" under load (a momentary stretch of the wheelbase), but the movement should be minimal.
1934 Plymouth Coupe Leaf Springs

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1934 Plymouth Coupe - Triangulating Quarter-Elliptics - Tech
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