[Ron Sutton]

Originally Posted by Solid LT1

Hello, I'm wondering are the bottom coil over shock mount also being used for Watts Linkage mount on passenger side? Is all this loading on the bolt being mounted in single shear?

I copied this from a previous post on this thread to answer your question.

11. Weight is our enemy, so I design all of my stuff to be as light as it can be & still as strong as it needs to be. Plus I work to multi-purpose things as much as possible … to reduce duplication of items & unnecessary weight.

12. For example the upper Watt’s link crossmember serves as the shock crossmember also. Why run two crossmembers only a few inches apart? That is unnecessary weight. Of course it took me some work to make the packaging all fit well. But there are no wasted tubes, no duplication of mounts or crossmembers & no unnecessary weight.

13. Another example is the Watt’s link housing mounts. I see a lot of heavy, bulky mounts that clamp on. Just adding weight to the rear end. Most have to add two mounts to the housing. My design here dual purposes the right rear shock mount. This not only saves the weight of the bracket & bracing, but bolt hardware too. All of this weight is “unsprung weight”. The lighter we can make the rear end housing … especially out at the ends … the quicker the suspension can respond to irregularities on the track. Lighter unsprung weight in the suspension = more grip.

14. A common question is about the additional load that shock bolt sees with the lower right Watt’s link attached to it. Anyone that knows me very well, knows how safety conscious I am, so you know I did the math. I have a bolt load stress calculation spread sheet I use.

For those that care … calc’s ran as:
* 4000 # Car
* 50% rear weight (2000#)
* 1.5 G load
* 3000# force

No, Ron’s car won’t be that heavy … LOL. I like to do my calcs with more load on stuff than it will actually see. Like a safety factor inside the safety factor.

The bellcrank bolt sees half of the total force going through the Watt’s link.
* 1500# force on ¾” Grade 8 bellcrank bolt @ 1.156” = .0017” deflection (17/10,000)

The four bolts & rod ends each all split the other half of the load four ways, for 375# of force.
For weight savings, I utilize lightweight, tubular chromoly bolts on most mounts that are in double shear. For single shear suspension items, I use special 170,000 PSI 12-point bolts.

The combo shock & Watt’s link bolt sees loads from both the coil over shock & the Watt’s link.
* 1600# force on ½” 160k PSI link bolt @ 0.3125” = .0002” deflection (2/10,000)
* 375# force on ½” 160k PSI link bolt @ 1.1875” = .0022” deflection (22/10,000)
* The forces are from different vectors so the deflection doesn’t really total .0024” … but it doesn’t matter anyway, as anything this small is negligible.

P.S. Shear strength ratings of the hardware is:
* ¾” Grade 8 bellcrank bolt = 39,762#
* ½” 170,000 PSI 12-point bolts = 20,023#
* Chromoly Rod Ends 5/8” shank & ½” hole = 31,390#

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Remember, the coil-over shock applies a max load of 1600# & the Watt's link applies a max load of 375#.