can you tell me the advantages of your three-link system over the RRS 3-link or Heidt's 4-link or IRS. I was looking at your site and it's quite impressive, but I have no comparision to what it provides vs others
I guess the best thing to do is compare the generic systems first. So, the RRS is essentially a Watts and Torque Arm, the Heidts system is a 4 link with
Panhard Bar and the IRS is, the IRS. With that said, here are some general talking points.
Watts Link/
Panhard Bar:
WL: Constant Roll Center Height While Cornering
PHB: Roll Center Rises in One Direction and Falls in the Opposite Direction
WL: True Vertical Motion of Axle Thru Jounce/Rebound
PHB: Axle Travels in an Arc defined by the Length of the
Panhard Bar
WL: Lateral Loads Reacted @ Both Frame Rails
PHB: Lateral Load Reacted @ One Frame Rail
Note: The constant rear roll center height, of a Watts Link System, will give the vehicle consistent and equal handling on both left and right turns. The overall benefits to the performance enthusiast include improved steering response, linearity, turn-in and overall cornering response, making the vehicle more predictable and easier to drive on all road at track surfaces.
A Watts Linkage is a lateral control device which consists of (2) horizontal links, (1) vertical link and a structural cradle. The cradle is mounted to the vehicles rear sub-frame (sprung weight) and used as a mounting location for the Watts Linkage. The vertical link or “Crank” is mounted to the center of the cradle which is designed to be at the centerline of the vehicle cross-car. The horizontal links are both mounted to the crank; one at the top and the other at the bottom. The opposite end of each link is mounted to a tower that extends from the rear axle housing. When the vehicle is at ride height, the optimum (rear view) orientation for the links is parallel to ground, with the crank positioned vertically. The optimum (plan view) orientation for the links is parallel to the rear axle tube.
The Watts Link System positively locates the rear axle, preventing it from moving side to side while cornering. With the rear axle essentially fixed in the lateral direction, there is now more real estate for larger rear tires without the worry of tire interference with the inner wheel well while cornering. The rear roll center is also lowered to be approximately equal in height to the center of the crank pivot. The rear roll center is the point where the lateral force is being transferred from the sprung weight to the unsprung weight. Lowering the rear roll center will reduce the portion of lateral weight transfer due to roll center height (a parameter which is not easy to tune) and allow the customer more freedom to tune front and rear roll couple distribution. The geometry of a Watts Link System also produces a constant rear roll center height while cornering unlike a
panhard bar which has varying roll center height depending on whether you turn right or left. The constant rear roll center height, of a Watts Link System, will give the vehicle consistent and equal handling on both left and right turns. The overall benefits to the performance enthusiast include improved steering response, linearity, turn-in and overall cornering response, making the vehicle more predictable and easier to drive on all road at track surfaces.
More Notes:
While a vehicle is cornering and producing lateral force, the axles natural tendency is to move in the cross-car/lateral direction. With a Watts Link installed, as the vehicle builds lateral force, the lateral force is transmitted through the links into the crank, then into both frame rails through the cradle. Since one link is in tension and the other link is in compression, the load in each link is equal and the crank will not rotate. Since there are two links and one crank the lateral load is distributed between each of the two links and both frame rails, unlike a
panhard bar which relies on one link and one frame rail to react all the lateral force. When the vehicle is not cornering, as the
suspension goes into jounce and rebound, the crank travels with the body and will rotate to compensate for the vertical rotation of each link. This geometry will produce true vertical motion without any lateral component, unlike a
panhard bar that will travel on an arc defined by the length of the
panhard bar link.
Ok. Next, the Three link.
THREE LINK BENEFITS OVER A TORQUE ARM
• Less Un-Sprung Weight
• Improved Ground Clearance. Generally Torque Arms have reduced ground clearance below the Differential.
• Dynamic Instant Center (IC) and Side-View-Swing-Arm(SVSA) Geometry is created by the Upper and
Lower Control Arms unlike a fixed SVSA Geomerty of a Torque Arm. The Trilink geometry allows the vehicle to have increased Anti-Squat during acceleration for maximum bite while accelerating and increased Anti-Dive while braking.
Benefit of Three Link over Four Link
• Generally Less Components, therefore, Less Weight
• Less Tendency to Bind While Cornering
• Generally More Linear Through Full Range of
Suspension Articulation
The IRS has its own set of issues as well. In General,
• The IRS is prone to power hop and brake hop.
• The IRS is very sensitive to ride height, relative to half shaft angles.
• Generally, you have issues with torque management as related to the IRS Cradle and Differential Durabilty.
None of the systems you mentioned have a Stabilizer bar, the benefits of a stabilizer bar are….
• Allows you to separate Ride Tuning from Handling Tuning
• Gives you the ability to fine tune the overall vehicle handling balance/response
So, that summarizes some of the differences between the systems. Beyond the kinematics of the systems, considerations need to be made w.r.t material selection, adjustability of the system and the general aesthetics of the system. We are not intimately familiar with any of the specific systems you mentioned, but they may be compromised when adjustability and real world inputs are applied to them. We are from an OEM background, so all of our systems are designed with real world
suspension parameters (i.e
suspension travel).
Hope this helps.
Thanks…Mike