Ackermann Angle and Sierra Uprights

I’d swapped from front mounted Ford Escort MK II rack to a rear mounted Citroen BX rack. I needed to get my Ackerman Angle correct.

see here: http://www.super7thheaven.co.uk/blog/haynes-roadster-steering-rack-2/

To do this I just reversed the uprights and made some new rack extensions.

The next night I looked at what I’d done and thought ‘Oh Balls!’.

For some reason I’d forgotten all about ‘Ackermann Angle– most likely brain damage

I’d reamed out the steering arms so that the track rod ends could mount to the underside of the steering arms. This was to get the ball joint at the correct height to avoid Bump Steer.

Haynes Roadster Rear Mounted Rack
Ford Sierra Upright - reversed
The above shot shows the ‘pink’ reversed upright superimposed over the ‘correct’ grey one.

I knew the steering rack was now far too wide. You can’t just reverse uprights as it screws up the Ackermann Geometry.

As soon as I saw my work, with fresh eyes I knew my mistake.

The front drive shafts on the Sierra Front 4×4 Differential has 23 splines. The Early MK5 Escorts also have 23 splines. When a pair of Escort Uprights (one BNIB) came up for pennies on ebay, I decided to take the chance that my super rare Granada 5 stud 4×4 front hubs would also fit the upright. – They did.

There are 2 types of uprights fitted to the MK5 Escort, 23 and 26 Spline. If I simple wanted 4 stud flanges, then I could use the Escort items. However, I want to use 5 Stud Granada Flanges and the Sierra/Granada flanges, which are a larger diameter and are the same size as the later 26 Spline Escort items. Therefore, I would actaully need 26 spline uprights.

The height of the steering arm also looked pretty spot on. Was I getting lucky again?

Ford Escort MK5 Upright

The next task was to measure them and draw them up in CAD. I wanted to check the Ackermann Angle as accurately possible.

Ford Escort Upright MK5 - CAD

As you can see, although the splines fit, they are useless to me.

To connect them up I would have to shorten the top A arm and extend the bottom. The Steering Axis Inclination would be miles off.

Ford Escort MK5 - upright
Ford Escort MK5 - upright CAD

Finally, although a waste of time, I thought I’d see how close the Ackermann Geometry would be to ‘true’.

Ackerman Angle Geometry

True Ackermann AngleLines drawn from both SAI pivot axis, should pass through the track rod end ball joint, to a central point on the rear axle line.

Ford Escort MK5 - upright CAD

This is how the Ackermann Angle looked.
Ford Escort MK5 - upright CAD

In the above picture, steering pivot on the red super-imposed Escort upright should lie on the white line and not the red one. The red line also has a ‘faked’ bend so it could pass through the steering pivot. Basically, Escort uprights are as bad, if not worse, than the already useless Sierra items.

It looks like I’ll be making my own uprights on my new Milling Machine. 🙂

Custom Ford Sierra Upright - steering arm

Getting the dimensions correct for this custom Ford Sierra Upright hasn't been easy. The reason for making a new upright was the steering arm on the standard upright being wrong for my particular application. Therefore, getting the next stage right, is very important. The next job on the custom front ...

Custom Ford Sierra Upright Part 2

I've been boxing in one of my custom Ford Sierra Front Uprights. So far, I'm quite pleased with how they look. I've also had a trial fitment of the bearings and they slid straight in as if the uprights had just dropped off the production line. When I say 'slid', ...

Custom Sierra 4x4 Uprights Part 2

A while back, I'd bought some super light weight billet Outlaw aluminium callipers (Wilwood copies). At the time I didn't have the front discs to check them against so they were just put under the bench. When the Granada 278mm front discs arrived, I soon saw that these callipers were ...

Custom Sierra 4x4 Uprights

I've started to make my own front uprights. The CAD has taken a while, plus I have had to do some extra research into suspension geometry. A lot of people seem to know about Ackermann Geometry, but the well known image of the two lines intersecting at the rear axle ...

Custom Ford Sierra Upright – steering arm - Part 2

Building a 4x4 Locost Rover V8 Kit Car, means making custom front uprights. Ford Sierra Uprights were used as the starting point. This Haynes Roadster with Custom Ford Sierra Uprights has parts from many makes and models of cars. Ford Sierra 4x4 Cosworth Ford Scorpio Jaguar X type Austin Ambassador ...

Custom Ford Sierra Front Uprights

I had to enrol the skills of the 'brother in law' to TIG weld the new Ford Sierra based front uprights. He's done a cracking job :) The upright has the same bolt spacing for the Mercedes S320 Brembo calipers as the removable steering arm assembly. Therefore uprights can be swapped ...

Haynes Roadster Steering Rack Part 2

I wasn't at all happy with my steering. Because this car is 4x4, the rack was pushed nearly 2" further forward than on a standard Haynes Roadster / Locost. The steering arms were angled backwards about 5 degrees. It didn't look good. Ideally, the steering arms should be in-line with the steering arms / ...

Haynes Roadster Steering Rack

I had neglected to make a jig for the steering rack, but mounting it turned out to be very simple. To do this job, I was armed with a height from the bottom of the chassis rail to the top of the central portion of the steering rack. I had ...

Translate »

Web Design by Go Web Solutions