on July 28, 2010, 6:34 am, tyrellracing wrote:

I agree that this setup should meet the rigidity requirements. However due to the overkill its not my style. I am a firm believer in less is more. A well engineered setup with nothing but what is necessary will weigh less than the live axle and leaf springs did. every ounce of extra weight is just that much more to pull up to speed and drag to a stop. That is my only reservation to the tube steel parallel to the frame rails to support the irs by the leaf spring mounts. Its redundant and it creates unnecessary weight. The real harm of this weigh is in the additional polar moment of inertia. For those who have never heard of this phenomena, every ounce added to a vehicle ahead of the front or behind the rear axle will behave like a pendulum. If you drive a car into a corner in a slide and at the apex let off the throttle, the polar moment of inertia is what pulls the rear of the vehicle around in a spin. This is not a characteristic I want in my car. The more weight added the more pronounced the effect. Adding weight to the front ahead of the axle tends to make the vehicle sluggish when turning into a corner

on July 28, 2010, 9:53 am, Daze wrote:

"I am a firm believer in less is more. A well engineered setup with nothing but what is necessary will weigh less than the live axle and leaf springs did. every ounce of extra weight is just that much more to pull up to speed and drag to a stop. "

Great points, two thoughts though, for those of us that do not have the engineering know how, we have no choice but to use common sense, experience, systems already proven to work and then over build to compensate for the lack of engineering knowledge.

as far as the weight, how do you plan on shaving 100#?? The complete Jaguar IRS unit with cage weighs in at about 100# more than its live axle counter part. I have the exact figures some where and can post them if you like.

"That is my only reservation to the tube steel parallel to the frame rails to support the IRS by the leaf spring mounts. Its redundant and it creates unnecessary weight. "

Tyrellracing, you should have spoken up before. I value your opinion and did not realize you were not fond of my leaf spring mount design. There were really only two factors that led me to setting it up this way. The first is I wanted a bolt in, and I still do, so to facilitate that, this design seams like the best solution. The second is I am not convinced that the rear frame rails are strong enough to support the cross bar. The biggest issue I have with the frame rails is the steel thickness. they are so thin that it is hard to get a solid place to weld on mounting tabs.

This is the best part about a forum like this. I love the information and the differences in opinion. I have learned more here in the last few months than I did over the last year of trying to dig up info on my own.