CB400F Frame Bracing
Common study data
Material - Plain carbon steel Braking Loads - 1200lbs upward on lower bearing race face 8400 lbs opposing on each of the upper and lower bearing race faces, normal to a plane passing axially along the steering axis.
Torsion Loads - 1200lbs upward on lower bearing race face 5000 lbs opposing on each of the upper and lower bearing race faces, normal to a plane passing axially along the centerline of the bike.
Study #1 - Stock CB400F - There is more deflection shown here than in the previous frame study. I re-measured and re-modeled many of the frame components in this study to be more accurate, and changed the material from AISI 1020 to plain carbon steel.
Braking Mode
![](./user/cimage/stock-cb400-braking-disp.jpg)
Torsion Mode
![](./user/cimage/stock-cb400-torsion-fea.jpg)
FEA1 - Side bracing
Braking Mode
![](./user/cimage/cb400-fea1-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea1-torsion-disp.jpg)
FEA 2 - Side Bracing and Shock Mount Bracing
Braking Mode
![](./user/cimage/cb400-fea2-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea2-torsion-disp.jpg)
FEA 3 - Side bracing and Suspension Bracing
Braking Mode
![](./user/cimage/cb400-fea3-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea3-torsion-disp.jpg)
FEA 4 - Side, Swingarm, and Shock Bracing
Braking Mode
![](./user/cimage/cb400-fea4-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea4-torsion-disp.jpg)
FEA 5 - Side, Swingarm, and Shock Bracing
Braking Mode
![](./user/cimage/cb400-fea5-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea5-torsion-disp.jpg)
FEA 6 - "Boxed" spine.
Someone on one of the forums had questioned me about boxing the spine of the frame. Round tube is stiffer torsionally than square, so I looked at adding an extra 2" dia. spine to the frame. The results are a little misleading, because the deflection numbers are worst than for the stock frame. But I also included the stress plots for this version, and the stock frame, below. Have a close look and you can see that the stiffer spine has moved the stresses to other, more flexible areas, resulting in more displacement at the head.
Braking Mode
![](./user/cimage/cb400-fea6-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea6-torsion-disp.jpg)
Stock Frame Stress Plot
![](./user/cimage/stock-cb400-fea-torsion-stress.jpg)
FEA 6 Stress Plot
FEA 7 - Fully Braced.
I threw everything at it. It is the stiffest of all the studies, but would also be the heaviest, adding about 9lbs of extra steel.
Braking Mode
![](./user/cimage/cb400-fea7-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea7-torsion-disp.jpg)
FEA 8 - Side Bracing with extra tubes to steering head.
I really thought that this would make a bigger difference, but I think it needs extra tubes to stabilize the long tube.
Braking Mode
![](./user/cimage/cb400-fea8-braking-disp.jpg)
Torsion Mode
![](./user/cimage/cb400-fea8-torsion-disp.jpg)
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