JPOR: Snip? Yea Right....

["S. Perkio" <sperkio@xxxxxxxxxxx>]

> ----------------------------------------------------------------------
> 
> Date: Mon, 12 Mar 2001 11:33:39 -0700
> From: "Brett Davis" <bdavis@enviropax.com>
> Subject: Re: JPOR: Ladder bar forces (warning)
> 
> Also noted, there is a much higher chance that if something breaks related to the ladder bar,
> it will probably be where it attaches to the axle since the forces are much larger there, but
> since this would not be catastrophic it wasn't really worth mentioning.
> 
> Brett Davis wrote:
> 
> > ****************Please Remember to snip your replies***************
> > You make a good point except that when the ladder bar is employed the springs are taken out
> of the axle wrap business for the most part.  (sometimes the ladder and the springs actually do
> battle)
> >
> > When/if the shackle breaks, the axle will rotate a certain amount until the springs take up
> the force, and since this will be sudden, the axle will rotate more than usual.  The axle will
> rotate at least as much as it would normally without the ladder bar.
> >
> > Say the axle rotates, without the ladder bar, approx 10 degrees (fairly common).  At the end
> of a 3' ladder this is 6.25 inches.  Say that under shock loading when the shackle broke that
> the axle housing rotated 20 or 30 degrees (possible), that's up to 20" of movement, enough to
> do some damage.
> >
> > I am continually amazed at the under-engineered ladder bars and especially locating arms that
> I see on rigs, but not when I see them broken on the trails.  Maybe I am too conservative in my
> assumptions, but even using "traction limited" values the numbers are huge.
> >
> > Brett
> >
> > ssmith@ai.com wrote:
> >
> > > ****************Please Remember to snip your replies***************
> > > I think that something that you guys aren't thinking about &#8211;
> > >
> > > First, I would guess that racecars are probably using coil springs.  This would cause the
> ladder bar to manage all the forces on the axle.  The leaf springs on 'most' Jeeps (CJ/YJ/etc)
> will limit the force/distance of the moving ladder bar.  It will also limit the stresses on the
> ladder bar itself.  When working, the springs and the ladder bar will be working together to
> limit axle wrap.  If the ladder bar should break, it won't be a free moving object - the leafs
> will limit its movement.
> > >
> > > I have mine made out of 1"x1" square tubing.  It is, I think, 3/16" thick (maybe 1/8, but I
> think 3/16).  I'm running a total of around 110:1 crawl (T18/4:1 D300/4.27) with a Ford 5.0 V8.
> It has never bent.  I have run Die Trying, Patriot, Rusty Nail, Helldurado, etc...  I have had
> the weight of the Jeep on the ladder bar.  It is very strong.  I copied the design from someone
> else running a similar hp/torque setup.  Theirs has not bent/broken either.
> > >
> > > For the connection at the front, I used two category 2 tractor heims that I welded together
> to form a shackle that will rotate in all directions.  I welded a bracket to the original skid
> plate and reinforced the skid plate with angle iron.  Everything is holding up fine.  Also -
> the longer the ladder bar, the less stress on the actual shackle/heims/etc on the non-axle end.
> > >
> > > That being said - I'm not an engineer.  Just going by what I have seen and what I use.
> And, it is always better to over engineer then to under engineer..
> > >
> > > Steve
> > >
> > > >
> > > >From: JpCj74x4@aol.com
> > > >Date: Mon, 12 Mar 2001 09:29:01 EST
> > > >To: jeepoffroad@4x4wire.com
> > > >Subject: Re: JPOR: Ladder bar forces (warning)
> > > >
> > > >****************Please Remember to snip your replies***************
> > > >Brett,
> > > > You make a very good point to safety here. I race cars on dirt and have seen
> > > >a ladder bar break causing some serious damage. On this car the bar was
> > > >located on the chassis near the driver, above the drive shaft. Between the
> > > >driver and the bar was, oh, about .045" aluminum forming the cockpit. I guess
> > > >the bar slammed down first breaking the driveshaft (which got into the
> > > >cockpit a little) but when the ladder bar bounced back up it almost ripped
> > > >thru 1 3/4" x .090 chassis.
> > > >  I can just imagine what it would do to a rusted out tub and the back seat.
> > > >
> > > >Greg
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> > --
> > Brett Davis
> >
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> - --
> Brett Davis
> 
> ------------------------------