[Cortina-list] Odd ball rear axle
peter.pentz at gmail.com
Sun Feb 28 16:34:43 UTC 2016
You are so very right about the forces on a Panhard Rod.
Geoff Pile had one on his Escort before going to a Watts linkage. It sheared
the entire bracket off the chassis rail going through the RH turn at the
bottom of Mid O's Madness turns, slinging the car into the tire wall.
When we looked closely we discovered it had actually ripped the chassis rail
spot welds away from the trunk floor.
The problem with a Panhard Rod is that it actually causes the axle to move
around horizontally as the axle loads up in the corner, unlike the Watts
linkage, which locates the axle perfectly irrespective of wheel loading. On
my car with a Watts linkage the tire is around a 1/4" from the inner wheel
arch when the wheel is fully compressed, but it has never touched the inner
wing. It also spreads the loading to 2 different post points on the chassis
Peter.pentz at gmail.com
Saint Charles, IL, USA
From: Cortina-list [mailto:cortina-list-bounces at lotus-cortina.com] On Behalf
Of Gerald Elliott via Cortina-list
Sent: Sunday, February 28, 2016 8:16 AM
To: cortina-list at lotus-cortina.com
Cc: Gerald Elliott <gelliott at eastlink.ca>
Subject: Re: [Cortina-list] Odd ball rear axle
I designed , fabricated and installed such a system in my racing MK2, using
a 3 link system with a Panhard Rod and coil over shocks.
The adjustable lower links bolt into the original leaf spring mounting
holes, the adjustable center link goes from the top of the Quick Change rear
to a custom bracket tied into the roll cage system.
The height adjustable Panhard is tied into a vertical post that extends
from a roll cage bar in the trunk (left side) just behind the axle. The rod
extends to the right hand axle tube and is bolted to a special bracket which
is in turn clamped to the axle tube. Except for the vertical post , all the
parts for the Panhard Rod came from the Bicknell's catalogue.
There is a support rod I fabricated which extends from the vertical post
to the roll cage on the right side, at about a 30* upwards angle.
To give you some idea of the forces involved, the original vertical post
snapped off above the Panhard Rod during a warm up lap and one of the crew
spotted it just as we were getting gridded for a race. I got a 2" x 3/8's
steel tube,drove it up into the existing post , welded it into place.
installed this system almost 14 years ago and except for the above mentioned
problem, it has worked perfectly.
Sent from my iPad
On 2016-02-28, at 1:20 AM, John McCoy via Cortina-list
<cortina-list at lotus-cortina.com> wrote:
> There have been many designs and ideas dealing with the forces a flat
> differential housing negotiates. My current favorite is a floating
> rear roll center using a chassis mounted watts.
> As rear wheel drive transitions thru a turn, roll energy pivots thru
> the roll center. Without getting into a long discription of how this
> energy relates to the traction of a flat axle, its easist said,
> lowering the roll center is better, and fixing and controling that center
> Hence the early A arm was a design to lower the roll center. The
> problem is, the Cortina having a relitivly high CG & body roll a
> result of lower roll stiffness in the rear of the car, i.e. the famous
> three wheel turn, this would twist the best of mounts and bend the
> housing of A frame roll center mount.
> So, you see some pretty optimistic attempts, like seen here,
> unfortunately, often left out is a solid system to locate the housing
> longitudly like a panrod, utilized, reduces side loads on the A frame
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