4-links

[tsm1@domain.elided (Tom Mandera)]

Alright alright.. I'm lazy!  I didn't want to think too hard on this one..
it seems the longer I'm out of "real" school, the weaker those years of
Chem, Physics, and Calculus become.. (Note: despite all that stuff, I
haven't used ONE bit of it at work.. I use it more in my hobbies (Scouts)
than anything else..)

Anyhow, I was trying to visualize how this all works.. and I was trying to
determine how/why having a 4-link setup *doesn't* interfere with axle
rotation.. or, one tire higher than the other.

I've examined Jim Weed's setup (online) a good bit, and asked Jim some
questions about it last year (he's been *quite* busy lately, so I haven't
picked his brain any more)..

Jim runs one V from the top of the pumpkin to the inside of the frame rails.

Another V runs from just outside the frame rails down to just under the rear
spring perches.

So, having ONE point on top and ONE point on the bottom of the axle, we
eliminate the axle rotating around it's axis.  Fine, no pinion walk-up.

But isn't part of axle wrap when one tire torques up, and "springs" off the
ground, then slams back again?  You twist the spring a bit..

Is that ONLY because the axle is trying to "walk" the pinion up, or is there
any actual up/down (or rotating) force at work?

I guess it's the "S" twist of the springs that does it.. the pinion tries to
walk up, and the spring turns into an S, then gets angry and forces the axle
back down, causing the all-too-familiar hop-hop-bang-bang.

So by eliminating the pinion walk, I eliminate axle wrap and wheel hop, right?

Then the only issue left to discuss is how the 4-link does or doesn't limit
overall axle articulation.. the axle now must follow the same arc as the
4-link links.

I think that is also why dual shackles were used on Jim's Scout.. to allow
the axle (and springs/shackles) to follow the arc laid out by the 4-link arms.

Jim's photos clearly illustrate how he mounted the links to the frame
(inside ones have new holes in the frame, outside ones have new "perches"
welded under the box frame).

I can't figure out how he mounted the "V" to the top of the differential,
nor exactly how he mounted the outboard links to the wheel hub area.

He's running a rear spring over (which I'm planning), so it's not like he
could just run the Links to the U-bolt / shock plates.

Is this something I would WELD to the axle flange area?

FWIW, Jim told me (a year ago) not to bother with the 4-link, that it was
too hard to do the welding with a body on top of the frame... but now I'm
changing my mind again.. ;)

Oh, BTW.. the next time you think of building a vehicle.. send it off to
live with someone else for 9 months or so while you mull it over... I guess
that's the one good thing that came of all of this.  I've already thought of
and discarded and re-thought of and re-worked the various aspects of my
buildup dozens of times.. and, fortunately, My truck wasn't handy at the
same time a as my thoughts, along with a wrench / torch / welder / saw /
whatever. 

*smile*

Thanks,

-Tom Mandera, Helena MT