Project G4 AKA QuasiGhetto

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Turboyota

Senior Member
Mar 29, 2017
2,563
443
83
Yucaipa
FasterNPOO,

Looking at your ugly trailing arms and your proposed “Johnny 5” side overlays got me feelin’ like doing some some calculations!!!

Assumption:
Trailing arm cross section at the lower shock eyelet is approximately a 4”x4” C-channel. I see the additional vertical ribs in the trailing arm that the shock bosses attach to, but I chose to ignore them for sake of simplifying the exercise.


Approximation for 2X vertical overlays:
———
If you add 1/8” x 4” “Johnny 5” vertically-oriented overlay plates to both sides of the trailing arm, the bending strength will increase by 36%


Approximation for 1X bottom overlay:
———
If you add a SINGLE 1/8” x 4” horizontally-oriented bash plate to the bottom of the trailing arm, the bending strength will increase by 57%. (!!!)



For the geeks:
4x4” x 3/16 wall c-channel moment of inertia=3.7in^4 (area= 2.18in^2)

4x4” x 3/16” wall c-channel with 2X side overlays moment of inertia=5.03in^4 (area = 3.18in^2)

4x4” x 3/16” wall c-channel with bash plate single overlay moment of inertia=5.83in^4 (area = 2.68in^2)

***Bottom line: more strength is added with less material and less weight if the bottom of the trailing arm is plated.***

Caveat: If trailing arms fail due to buckling of the sidewalls/webs, design of the trailing arms could be improved(i.e. internal side-to-side webbing or “beauty” overlays at the shock bolt locations).
 

GahnRacing

Bonsai Trimmer
Oct 5, 2012
385
70
28
28
Clovis, CA
FasterNPOO,

Looking at your ugly trailing arms and your proposed “Johnny 5” side overlays got me feelin’ like doing some some calculations!!!

Assumption:
Trailing arm cross section at the lower shock eyelet is approximately a 4”x4” C-channel. I see the additional vertical ribs in the trailing arm that the shock bosses attach to, but I chose to ignore them for sake of simplifying the exercise.


Approximation for 2X vertical overlays:
———
If you add 1/8” x 4” “Johnny 5” vertically-oriented overlay plates to both sides of the trailing arm, the bending strength will increase by 36%


Approximation for 1X bottom overlay:
———
If you add a SINGLE 1/8” x 4” horizontally-oriented bash plate to the bottom of the trailing arm, the bending strength will increase by 57%. (!!!)



For the geeks:
4x4” x 3/16 wall c-channel moment of inertia=3.7in^4 (area= 2.18in^2)

4x4” x 3/16” wall c-channel with 2X side overlays moment of inertia=5.03in^4 (area = 3.18in^2)

4x4” x 3/16” wall c-channel with bash plate single overlay moment of inertia=5.83in^4 (area = 2.68in^2)

***Bottom line: more strength is added with less material and less weight if the bottom of the trailing arm is plated.***

Caveat: If trailing arms fail due to buckling of the sidewalls/webs, design of the trailing arms could be improved(i.e. internal side-to-side webbing or “beauty” overlays at the shock bolt locations).
IMG_1181.JPG
 
Likes: Turboyota

partybarge_pilot

Uno mas Cervesa!
May 14, 2004
9,644
460
83
Easton, KS
your proposed “Johnny 5” side overlays got me feelin’ like doing some some calculations!!!
Nerd alert^^^^^^^^^^

My preferred method of building trailing arms currently is 3/16" bottom plate,1/8'' internal ribs, .090 outer skins, .060 overlays and .060 top plate. Also, double wall bottom under the shocks with 1.5" drain tubes under each one.

Like deez.

88
by Scott Mosteller, on Flickr

86
by Scott Mosteller, on Flickr

The breaks in the sides really help stiffen things up.

With the addition of the TW axle, you have lost all ghetto cred.
 

oorracing

<span style="color: orange;">DR Mod</span>
Jan 15, 2006
10,520
46
48
Long Beach Ca
Nerd alert^^^^^^^^^^

My preferred method of building trailing arms currently is 3/16" bottom plate,1/8'' internal ribs, .090 outer skins, .060 overlays and .060 top plate. Also, double wall bottom under the shocks with 1.5" drain tubes under each one.

Like deez.

88
by Scott Mosteller, on Flickr

86
by Scott Mosteller, on Flickr

The breaks in the sides really help stiffen things up.

With the addition of the TW axle, you have lost all ghetto cred.
What’s the motion ratio on those guys? The shocks look to be forward of 50% on the lowers. Those things are pretty nice looking


Sent from my iPhone using Tapatalk
 

yltaco05

Senior Member
Jan 18, 2006
1,033
78
48
Fullerton, CA
i was wondering the same. Almost like the helm is supposed to be on the frame side. Also looks like the bypass would be 50/50, if the unibazl is on the frame side. putting the coilover forward of that.
 

Turboyota

Senior Member
Mar 29, 2017
2,563
443
83
Yucaipa
If the heim is on the frame side, there wouldn’t be such a stark cross-sectional transition from the trailing arm to the threads of the heim at a highly stressed part of the trailing arm. Bending loads in threads are bad.

The pinch bungs appear to be Light Racing. I really like the design of those trailing arms.
 
Likes: smokeysevin

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