Sab-a-dab-a-doo! The back-country LJ build has officially started

[Woodrow]

I made a little bit of progress on the build today. I painted the cutting brake levers OD green and the handles coyote tan. I also painted the brake line mounting brackets OD green. I'll post pictures during installation. I also started thinking about anti-roll bars. I already have a SwayLOC for the front, and I've been planning on a custom Anti-rock for the rear. I created a spreadsheet to evaluate the stiffness of the SwayLOC compared to the OEM sway bar for the front. It turns out that the SwayLOC in the locked position is considerably stiffer than the stock anti-roll bar:
View attachment 599612

I mainly created this spreadsheet for putting a solution together for the rear anti-roll bar - when I get to that point. Stay tuned!

Cool. I run a SwayLOC in front at its longest setting and an OEM rear sway bar. When the front is unlocked, this feels like a pretty balanced set up in the rocks. How did you make your measurements? Now I want to measure mine.

 

[sab]

Very interesting, thanks for sharing. It would be more insightful to have another column with torque values comparing the effective torsional stiffness of each. All of the information is there except for the length of the OEM anti-roll bar lever arm.

I'm not sure what you mean by "effective torsional stiffness," but I think that's what I'm showing. The second column is how much force at the end of the lever arm (where the link pushes it up) required to rotate the bar 1°, so it takes into account the lever arm. That's what the values vary for the SwayLOC's four different link mounting holes.

 

[sab]

That is really good testing @sab.

How did you make your measurements?

Those aren't tested or measured values. They are theoretical, based on torsional stiffness and stress calculations. Here's a look at the full spreadsheet for the front SwayLOC:

The biggest factor for error in these calculations is the shear strength. The 150,000 psi used above is likely too high for 4130, which is what RockJock uses for the Anti-rock, and I assume what ORO uses for the SwayLOC. However, that parameter is not used for the stiffness calculations - only the failure calculations.

 

[sab]

Very nice, I wonder how a antirock compares with the unlocked swayloc?

Virtually the same:

I was able to get two of the three parameters needed from RockJock's website. For the other one, I estimated based on the SwayLOC. Here are the parameters, with the estimated one in red:

1. Center section bar diameter = .770"
2. Torque arm length = 14.195", 15.195", or 16.915"
3. Center section bar length = 32"

Assuming the SwayLOC came to market after the Anti-rock, it certainly seems that ORO designed the SwayLOC to match the Anti-rock's stiffness.

 

[jjvw]

Those aren't tested or measured values. They are theoretical, based on torsional stiffness and stress calculations. Here's a look at the full spreadsheet for the front SwayLOC:
View attachment 599643

The biggest factor for error in these calculations is the shear strength. The 150,000 psi used above is likely too high for 4130, which is what RockJock uses for the Anti-rock, and I assume what ORO uses for the SwayLOC. However, that parameter is not used for the stiffness calculations - only the failure calculations.

Another measurement of interest would be the differences in the rate increase of stiffness as the lever arm is lengthened.

 

[sab]

Cool. I run a SwayLOC in front at its longest setting and an OEM rear sway bar. When the front is unlocked, this feels like a pretty balanced set up in the rocks. How did you make your measurements? Now I want to measure mine.

Your setup's stiffnesses are:

For both the SwayLOC and the Anti-rock, the end hole positions don't make huge changes to the stiffness. It's roughly a 10-15% change per hole position. Considering that the SwayLOC at the shortest arm length is about 100% higher than the stock bar, a 10% change is minor.

 

[sab]

Another measurement of interest would be the differences in the rate increase of stiffness as the lever arm is lengthened.

Isn't that in the chart I posted, or am I misunderstanding what you want to see?

Also, the lever arm length is a linear variable in the stiffness equation, meaning that the stiffness difference is a simple ratio calculation:

Stiffness 1 = Stiffness 2 x Lever arm length 2 / Lever arm length 1

 

[jjvw]

Isn't that in the chart I posted, or am I misunderstanding what you want to see?
View attachment 599652

Also, the lever arm length is a linear variable in the stiffness equation, meaning that the stiffness difference is a simple ratio calculation:

Stiffness 1 = Stiffness 2 x Lever arm length 2 / Lever arm length 1

It's more the rate of change from unloaded to loaded. The SwayLoc, while stiffer than stock in it's street mode, ramps up differently due to the added length of the arms. The SL does not feel harsh and jerky the way the factory sway bar does.

 

[Woodrow]

Your setup's stiffnesses are:
View attachment 599651

For both the SwayLOC and the Anti-rock, the end hole positions don't make huge changes to the stiffness. It's roughly a 10-15% change per hole position. Considering that the SwayLOC at the shortest arm length is about 100% higher than the stock bar, a 10% change is minor.

Thanks. That puts some numbers to the balanced feel offroad.

 

[NashvilleTJ]

Dang, Emgineers takes all da fun outta “Dis Swayloc done feels gooder…”

 

[Apparition]

Dang, Emgineers takes all da fun outta “Dis Swayloc done feels gooder…”

I hear you want to leave it in road mode and flex it out to be certain.

 

[NashvilleTJ]

I hear you want to leave it in road mode and flex it out to be certain.

OK - Emgineer I’m not…

 

[B00mb00m]

I hear you want to leave it in road mode and flex it out to be certain.

I did this … bent the axle side mount

 

[jjvw]

Thanks. That puts some numbers to the balanced feel offroad.

A curious disruption to that feel and these numbers is that shocks will shift this sense of balance. For years, I have advocated a stiffer Antirock and SwayLoc setting than the loosest setting precisely because of that sense of balance. As soon as the DSC reservoirs went onto my shocks, I very quickly moved my SwayLoc to it's loosest setting and the entire rig is still far more balanced and stable than it was before the DSCs.

 

[sab]

It's more the rate of change from unloaded to loaded. The SwayLoc, while stiffer than stock in its street mode, ramps up differently due to the added length of the arms. The SL does not feel harsh and jerky the way the factory sway bar does.

The right column is the stiffness, with arm length factored in. The three variables in the equation pertaining to physical measurements are bar diameter, bar length, and arm length. They all work together, but the diameter has a much bigger effect (it’s non-linear.) The underlying equation is the same used to design a coil spring.

 

[sab]

I did this … bent the axle side mount

The main bar for the SwayLOC, as with the stock bar, would break if you literally flexed to the extremes from one side to the other. It’s limited only by vehicle weight.

 

[sab]

A curious disruption to that feel and these numbers is that shocks will shift this sense of balance. For years, I have advocated a stiffer Antirock and SwayLoc setting than the loosest setting precisely because of that sense of balance. As soon as the DSC reservoirs went onto my shocks, I very quickly moved my SwayLoc to it's loosest setting and the entire rig is still far more balanced and stable than it was before the DSCs.

I’m looking forward to playing with the low speed on the DSCs in that respect!

 

[jjvw]

The right column is the stiffness, with arm length factored in. The three variables in the equation pertaining to physical measurements are bar diameter, bar length, and arm length. They all work together, but the diameter has a much bigger effect (it’s non-linear.) The underlying equation is the same used to design a coil spring.

How would an engineer describe the sensation of the SwayLoc in street mode feeling less rough and jarring than the factory anti sway bar despite the SL being a higher rate torsion bar?

 

[sab]

How would an engineer describe the sensation of the SwayLoc in street mode feeling less rough and jarring than the factory anti sway bar despite the SL being a higher rate torsion bar?

An engineer would respond by saying there’s something not accounted for in the analysis and would search for an explanation.

 

[sab]

Thinking about it more, if the angle between the arm and the drop link is considerably different from 90 degrees, that could cause the stiffness to vary. The simplified analysis I did assumes a 90 degree angle. A more complex analysis can be done to factor in that angle.