TOY: Re: Double Shackles

[Thom Singer <ntsqd@xxxxxxxxx>]

--- Evan Mills <mudyota@hotmail.com> wrote:
> >Perhaps somebody can explain this to me because it looks like some
> work
> >for no gain to me. I don't see the point of drooping the tire past
> the
> >point where the spring is unloaded. If there is no spring pressure
> on
> >the tire then the only weight on the tire is that of the axle itself
> >and the wheel/tire combo. Keeping the tire in contact with the
> ground
> >is good if there is some vehicle weight on it. Beyond that point I
> >don't see the need. Am I missing something ?
> 
> Sure. Leverage.
> 
> The whole reason that solid axle flex better than IFS is that they
> aren't  
> isolated from one end to the other - sothey can act as a lever. 

Can't go there. As I see it, the only detraction to IFS in principle
and not specific execution, is the reduction of ground clearence during
suspension compression. An IFS tire is more likely to be flat to the
ground than a LA tire which is due to the way the geometry of each
works. This would lead to a bigger contact patch for the IFS.

> The
> two 
> springs act collectively as a fulcrum, when one side is up on a rock,
> the 
> axle pivots downward on the other end, and is actually forced into
> the 
> ground by the high-side tire. As on tire is forced up into it's wheel
> well 
> the springspush the other one into the ground, so it's not just
> gravity 
> doing it's thing.

All of that makes sense, except for one thing. The lever arm of the
tire doing the work is far shorter than the lever arm of the tire being
worked on. Make that two things; no matter what you do short of
stuffing the cab under a rock you only have the vehicle weight to work
against. The weight of the vehicle and all the forces opposing it have
to zero out or the rig is in verticle motion.

> Furthermore, the spring on the high-side is doing all of the pushing 
> downward - because it is compressed beyond it's static position,
> which is 
> where it will return if given the chance. The spring on the low side
> is 
> pulling upward some amount - because of these same forces. The double
> 
> shackles work just like normal when comressing - one is mashed
> against the 
> frame - but when drooping, the shackle unfolds, preventing that
> side's 
> spring from fighting the articulation.

That is what I expected it would do. I just don't see the point of
doing it.
 
> Even if you don't buy this, next time your truck is on an RTI ramp,
> try to 
> lift the tire opposite the one all the way up the ramp. Good luck.

I haven't done this on an RTI ramp, but I have had one tire in the air
and it is very easy to lift it up. At least until you start to load the
spring much, then it gets tougher.
 

=====
TS
Ventura, CA

"Teach you all I know and you're still stupid."
-- Howdy Lee

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