To:               LandCruisers@tlca.org
Send reply to:    LandCruisers@tlca.org
From:             Willem-Jan Markerink 
Date sent:        Sun, 7 Jun 1998 20:48:55 +0000
Subject:          Re: Is Shackle Reversal Really Better?

On  5 Jun 98 at 23:36, Edwin C. Gilbert wrote:

> I know there has been much discussion on the list concerning
> shackle reversal. If this is such a good idea, then why have
> the auto makers been building their vehicles with the
> shackle in front all this time? Does reversal only benefit
> offroad use? I understand the mechanics of the reversal and
> the reason for getting the axle to move rearward. Enlighten
> me as to why it has not been used in production!

Many many moons ago we had a long & tedious thread about SR's on the 
ORML. One of the lesser known disadvantages is the fact that you 
won't have the 'self-steering' effect from the suspension when 
cornering.

Just try to imagine what the axle does in forward-backward motion
when lifted on one side, and lowered on the other. The
axle-side/spring that goes down (inside) will move to the center of
the vehicle (this applies to both front and rear axle btw), the side
that goes up (outside) will move outwards; thus creating a
self-steering effect, that helps you steer into the corner.

With a SR, this effect is removed....the rear still steers you into 
the corner, but the front goes the other way.
On coil spring vehicles the linkage is identical to the factory leaf 
spring setup....the fixed pivots are in the center.

Other reasons are more straight-forward, like the simple fact that 
the ends of the frame are bend upwards, thus creating the most space 
for a shackle. A related argument is the fact that the frame horns 
are inherently less rigid than further inwards on the frame....makes 
more sense to create the fixed pivot on the strongest & most rigid 
point, and leave the shackle pivot (which is only stressed in 
left/right motion on impact) on the least strong and most flexible 
part of the frame.

One last mechanical argument is compression of the slip-joint in case 
of SR, in contrast to extension on the factory setup. No matter how 
ugly the jump, you will never come close to over-compressing the 
slip-joint to the point of crashing the T-case. Dismembering a 
slip-joint in the same scenario on the factory setup seems a mild 
pennance for getting airborn....


-- 
Bye,

Willem-Jan Markerink


      The desire to understand 
is sometimes far less intelligent than
     the inability to understand



[note: 'a-one' & 'en-el'!]

To:               LandCruisers@tlca.org
Send reply to:    LandCruisers@tlca.org
Date sent:        Sat, 13 Jun 1998 00:49:18 -0700
From:             cruiser@akcache.com (Whatley,Mark)
Subject:          Re: Is Shackle Reversal Really Better?

Will Byars wrote:

> >Some time ago, there was a technicle post
> >someone found on another list and  posted
> >it here that discussed the benefits of having
> >the rear of the springs anchored to the frame
> >under severe braking conditions.  That discussion
> >did not go far as I remember, and I did not
> >see it mentioned in this round of discussions.
>
> Hmmm.  Never saw that post, or at least I don't remember it. Anyone got an
> idea which digest to look in? This would be some interesting information to
> see. It would help me figure out the chassis dynamics. (I'm going to buy a
> suspension design book one of these days...)

  It's actually pretty simple in this concern. As the stock front suspention
compresses under braking, the caster of the axle increases, and the steering
becomes more stable, and less likley to dart and wander. With the shackle reversal
the axle looses caster unde suspension compression. This makes the vehicle less
stable directionally, andmore likely to dart and wander. Combined with the extra
loading due to the weight shift, it *theoretically* leads to less steering control
under heavy braking.

  I have NOT ever tried to compare the characteristics of two otherwise identical
rigs. On paper it makes sense anyway.


Mark...

Date sent:        Wed, 19 Jan 2000 15:32:16 -0800
To:               landcruisers@tlca.org
From:             Rob Mullen 
Subject:          Re: Shackle Reversal - years (trying again)
Send reply to:    landcruisers@tlca.org

At 05:16 PM 1/19/00 -0500, Tim Bridges wrote:
>I have a brand new one sitting in the garage - still in the box. I
>bought it for my 1976 FJ40, but decided against putting it in my trail
>rig - I am going to go coil-over asap. Anyway, I now have a 1982 BJ42
>and was wondering if the same kit would work (newer spring model)? This
>will be a daily driver rig, so the reversal could be just the ticket.

It won't work properly--you'd have to switch to all small-eye bushings, 
shackles and fixed pins.

It's not a good idea to butcher the 42 frame for the hokey bolt-on reversal
anyway.  If you follow their directions and use the stock slip joint, it'll only
last a year before it's totally blown out.  If you then get a brand new Spicer
long-travel slip joint, it'll only last a year before it's totally shot.  Both
myself (custom reversal) and Chad Koehn (LCAH reversal) put similar Spicer slip
joints in our trucks at the same time.  Exactly one year later, they were both
totally destroyed.

BJs are a lot harder on front drive shafts than FJs.  I think it's due to 
the combination of the vibration of the engine/drivetrain and the fact that the
blow-by tube vents right near the slip joint.

I'm now working on designing MY OWN slip joint that should stand up a 
little better.

If I could wave a magic wand and undo any mod to my 40/2, it'd be the 
shackle reversal.  They create way more problems than they solve.
--
Rob Mullen RAMullen@wimsey.com       North Vancouver, B.C., Canada
TLC FAQ & TT Story Editor            TLCA #3036, Coastal Cruisers
'80 Toyota BJ40/2 Land Cruiser       Why walk?...When you can CRAWL!

From:             Andrew Farmer 
To:               LandCruisers@tlca.org
Subject:          [LCML] Revolver higed shackles...
Send reply to:    landcruisers@tlca.org
Date sent:        Tue, 30 Apr 2002 13:27:26 +1200

Is anyone using these on an FJ40?
Are they any good?
Is there a similar product available in Australia?

Thanks
Andrew Farmer
FJ40
Wellington, New Zealand.

To:               landcruisers@tlca.org
From:             gbrown@ihug.co.nz
Subject:          Re: [LCML] Revolver higed shackles...
Send reply to:    landcruisers@tlca.org
Date sent:        Tue, 30 Apr 2002 01:48:45 GMT

Andrew Farmer wrote:
> Is anyone using these on an FJ40?
> Are they any good?
> Is there a similar product available in Australia?

Hi Andrew, there is also a folding shackle sold by one of the guys on the
www.pirate4x4.com board.  I believe he goes by the login fc187.  You should be
able to find them if you do a few searches. Part of the design allows you to put
a bolt through the two halves of the shackle and lock it together for on road
driving.

Having said all of that I decided against using folding shackles as most people
who have tried them didn't recommend them.  The general opinion appeared to be
that they could unfold on you at the wrong moment (getting on or off the gas
during hill climbs) which is rather unsettling to say the least.

Guy
1985 FJ40,
Christchurch, NZ

PS Are you also on the NZ 4wd Forum?

From:             "James Henry" 
To:               
Subject:          Re: [LCML] Revolver higed shackles...
Send reply to:    landcruisers@tlca.org
Date sent:        Mon, 29 Apr 2002 20:20:40 -0600

----- Original Message -----
From: 
Sent: Monday, April 29, 2002 7:48 PM

> Hi Andrew, there is also a folding shackle sold by one of the guys on the
> www.pirate4x4.com board.  I believe he goes by the login fc187.  You should be
> able to find them if you do a few searches. Part of the design allows you to
> put a bolt through the two halves of the shackle and lock it together for on
> road driving.
>
> Having said all of that I decided against using folding shackles as most people
> who have tried them didn't recommend them.  The general opinion appeared to be
> that they could unfold on you at the wrong moment (getting on or off the gas
> during hill climbs) which is rather unsettling to say the least.

I considered these shackles (well, the revolvers, and the hypershackle), and
decided against it for the following reasons. Cost: They were nearly 3x more
expensive than the nearest high-quality anti-inversion counterpart. Not that
they cost 3x more to make. Traction: The shackle is only going to hinge/unfold
when there is little or no weight on the spring, ie at full droop, while this
will allow the tire to travel a little more, what is the net gain? The tire
travels more. For my specific application, my truck will have rolled onto it's
side long before any benefit to the extended shackle would be noticed.

Just my 1/50 of a dollar.

James H.
SLC, Utah.
76 FJ40 'Blood Sucker'
Wasatch Cruisers
TLCA #11233
FJ40OMERS900035InchMTR's Non-USADistJimCCarbStock otherwise.

From:             "Willem-Jan Markerink" 
To:               landcruisers@tlca.org
Subject:          Re: [LCML] Revolver higed shackles...
Priority:         normal
Send reply to:    landcruisers@tlca.org
Date sent:        Wed, 1 May 2002 15:44:26 +0100

On 29 Apr 02 at 20:20, James Henry wrote:

> I considered these shackles (well, the revolvers, and the hypershackle), and
> decided against it for the following reasons. Cost: They were nearly 3x more
> expensive than the nearest high-quality anti-inversion counterpart. Not that
> they cost 3x more to make. Traction: The shackle is only going to hinge/unfold
> when there is little or no weight on the spring, ie at full droop, while this
> will allow the tire to travel a little more, what is the net gain?

Pondered about that lately....*if* there is still a tiny bit of droop
left (after flipping), you only gained the traction of the weight of
that tire+1/2axle....at least on a hard surface....you might gain a
bit more digging effect on a soft surface however....like an airborn
peddle, or like those crazy Icelandic (and Aussie?) mud
floaters....:))

> The tire travels more. For my
> specific application, my truck will have rolled onto it's side long before any
> benefit to the extended shackle would be noticed.

In the rolling aspect, my above argument works opposite....the
weight of tire+1/2axle would have kept the vehicle down by that
amount in that case (with normal shackles).

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]










From: "William Larman" 
To: 
Subject: reversed shackles,
Date: Tue, 22 Jul 2003 23:40:37 +1000

Hi , My name is Bill, I have been a LandRover fan for many years. These 
vehicles are built standard with the shackles at the back of the spring. 
While this system may provide a slightly smoother ride and reduce the 
likelihood of spring breakage in fast off road travel. it actually 
reduces the vehicles cross country abilities and increases the 
likelihood of transmission and front spring breakage by creating severe 
front axle tramp. eg, when a leaf sprung LandRovers front axle is 
pushing forward via the spring
The arch in the spring is increased which tends to extend the wheelbase 
and jack the front up on climbs, reducing traction. also, the stored 
energy in the spring due to the increased arch reaches a critical point, 
then fires the axle back again.causing axle tramp. I have seen a Rover 
wind its front springs up to such an extent on a rocky climb that when 
they let go, the whole vehicle jumped sideways 3feet and smashed the 
shocks against the axle housing and broke both front springs. all at 
very low speeds in crawler gear (127:1)
A standard Toyota under the same conditions would do this. The front 
axle will push forward half an inch until the spring is flat and 
straight. it is then effectively a solid traction bar. also the front of 
the vehicle doesn't jack up, so front end traction is not reduced. if 
trail conditions are such that traction is lost, it does so in a much 
smoother manner, where a Rover will leap up and down until something 
breaks.
Another reason I would not recommend a shackle reversal on a Toyota is 
that their driveshaft slip joints are so good that they" hydraulic" in 
compression. The alloy transfercase housings are not designed to cope 
with the hammering than an effectively incompressable driveshaft would 
subject it to.
                                                                       
Regards   Bill.

If you have any question, remark, comment, want to share some philosophy or just want to express your opinion about these pages, feel free to send email to: w.j.markerink @ a1.nl