Steering, Suspension, & Brakes

tips, technology, tools and techniques related to non-driveline mechanical components

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302GT
Larry Shimp

(195 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

panhard rod alternative?
Posted by: 302GT
Date: April 03, 2012 08:28AM

I have a suggestion for an alternative to a panhard bar for the MGB rear suspension that is especially suited to rubber bumper cars. It is to adapt an Alfa Romeo “triangle”. All Alfas with live rear axles from about 1956 through about 1993 had a rear suspension consisting of trailing arms, coil springs, tube shocks, and a stabilizing “triangle”. The triangle was mounted to the left side of the body through two rubber bushed pivots and attached to the differential case with a ball joint. As such, it provided 100% of the lateral location as well as rotational stability (in the vertical plane). The ball joint ensured that the locating functions occurred without binding, and, unlike a panhard bar, there is no sideways axle movement as the springs compress. There should be many of these triangles left because no matter how bad the car, these do not rust. The rubber bushings seem to last forever, and replacement rubber bushings (in several hardnesses) are available as well as poly bushings. The ball joint itself is massively overbuilt; its diameter is about 1.5 inches, it runs on spring loaded seats, and can be easily taken apart for cleaning and inspection. The reason this modification is well suited to rubber bumper cars is because it goes on the left side where the RB cars have no battery box. If adapted to a chrome bumper car, then the left battery box would have to be removed. It should be very simple to fabricate and weld two (heavy gauge) sheet metal brackets to the body for the rubber bushed pivots. Not quite so simple is providing a tab with a tapered hole for the ball joint on the differential case. Alfa Romeo simply welded the tab on and that should probably be possible on an MGB (or replacement) differential. It terms of the rest of the suspension, I think that this should work with the original leaf springs as well as with a coil spring conversion. Attached are pictures of the triangle itself and in position on an Alfa. (For some reason the lower picture always appears upside down.)
truiangle 2.jpg
triangle 1.jpg


roverman
Art Gertz
Winchester, CA.
(2977 posts)

Registered:
04/24/2009 11:02AM

Main British Car:
74' Jensen Healy, 79 Huff. GT 1, 74 MGB Lotus 907,2L

Re: panhard rod alternative? U-joint angle ?
Posted by: roverman
Date: April 03, 2012 01:57PM

Larry, seems like this arm pivot length should match that of lower trailing arm to avoid excessive pinion angle change ? Thanks, roverman.


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: panhard rod alternative?
Posted by: Moderator
Date: April 03, 2012 03:18PM

Larry, if you locate this device's axle connection off center, doesn't it necessarily move the rear suspension's roll center to the side too?

I've seen a variety of similar devices on a number of vintage race cars. Just for contemplation, here's a snapshot of one of them.

(Jerry Richards' #40 MGB GT V8)
http://www.britishracecar.com/JerryRichards-MG-MGBGTV8-40/JerryRichards-MG-MGBGTV8-40-DD.jpg
(note: the blue rod in the foreground is a Fab-Tek adjustable anti-sway bar. If you look very carefully, you can just see that Jerry also has trailing links outboard, underneath his leafsprings, although the A-shaped device fight's spring wind-up and pinion angle change to some extent.)



Edited 1 time(s). Last edit at 02/02/2017 10:32AM by MGBV8.


MGBV8
Carl Floyd
Kingsport, TN
(3713 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: panhard rod alternative?
Posted by: MGBV8
Date: April 07, 2012 09:12AM

Looks like a micro version of a wishbone locator.


302GT
Larry Shimp

(195 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

Re: panhard rod alternative?
Posted by: 302GT
Date: April 10, 2012 05:39PM

In terms of the length of the upper arms being shorter than the lower arms (or leaf spring): this is common with many 4 bar set ups. Pinion angle changes are minimized by having the upper locator pointing down at normal ride height. As the suspension compresses it moves through an arc that beings it level, then pointing up. This minimizes the horizontal movement of the arm at the axle and is compatible with the longer lower arm which tends to minimize horizontal movement because of its bigger arc radius.

I agree that the roll center will be slightly off-center, but it seems to work well even in Alfas modified for racing.

It is a micro version of a wishbone locator, but the size is very much compatible with the dimensions and loads of the MGB rear suspension.


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