Suspension and Screen
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Suspension Geometry
In my haste to get the chassis rolling I had made no attempt whatsoever to set up the suspension geometry.
Sylva recommend 1.5 degrees negative camber and 1 degree of toe in all round. ACB10s require less camber than radial tyres and figures of 0 to 1/2 degree negative camber for the rear and 3/4 to 1 degree of negative camber for the fronts was advised for an IRS setup. I had also heard of caterhams running 0 degrees rear camber, but this is with a de-dion setup that will not change camber under roll.
My Striker is relatively softly spring with 130lb springs and with no anti-roll bars I expect there to be a fair degree of body roll, which will affect both the front and rear camber angles to the same extent. With this in mind I decided to heed the advice of Sylva, Jeremy after does know a thing or two about how the Striker needs to be set up, but reduce the camber to 1.0 degrees negative to start with and see how the tyres look after a few miles of use.
The rear suspension is fixed on the IRS Striker and adjustment is possible with the insertion of shims between the bearing carrier and upright. Firstly I decided to see what the standard geometry looked like.
With the aid of a pair of 600mm steel rulers, a spirit level, plumb bob and marker pen I set about measuring the rear camber and toe. The chassis was supported with the uprights on axle stands, with the suspension under load representative of the eventual likely ride height. With a 600mm hypotenuse a degree of camber or toe would be 10.5mm, half a degree 5.25mm and 1.5 degrees 15.7mm.
The difference in the distance between the front and back of a pair of rules clamped to the hub, parallel to the ground was 10mm, which meant that each rear wheel was toeing in by 5mm or just under 1/2 a degree. With a single ruler clamped to the hub perpendicular to the ground (see pic above) the camber was 9mm negative or just under 1 degree. This was pretty much ideal. I could increase the toe in a little, but quite frankly as long as the rear is toeing in a little then I think it will be fine and I would rather have less than 1 degree of toe in at the rear than more and I suspect that I would end up chasing my tail with shims to get acceptable toe and camber again.
The front suspension is fully adjustable and I set about getting as near to 1 degree of toe in and 1 degree negative camber as I could. Firstly it was necessary to cut 4 threads off the track rod end onto which the bottom of the upright it mounted. Then by an iterative process I gradually narrowed in on the required toe and camber settings on the front. This was quite lengthy because for example increasing the negative camber will also increase the toe in and vice-versa and so lots of adjustments are needed. I also observed that the camber increased with steering input and so it was necessary to align the front wheels with the centreline of the car after every adjustment of toe. Eventually I settled on 12mm, or just over 1 degree, of toe in and 10.5mm, exactly 1 degree, of negative camber. This was obtained with 14 turns on each track rod end and reducing this the 13 turns on one side or potentially both would set the toe to just under 1 degree and reduce the camber also to just under 1 degree but I decided to stick with just over a degree of toe in which I think will aid self-centering for the SVA test and give slightly greater negative camber at the front compared to the rear. Again I expect to keep an eye on this as the car is used.
In summary my baseline suspension geometry is:
Front: 1.1 degrees toe in. 1.0 degrees negative camber.
Rear: 0.5 degrees toe in. 0.9 degrees negative camber.
Aeroscreen
I wanted to fit the aluminium angle that retains the bonnet in order to get the bonnet on and check the clearance to the engine and also to secure the top of the side panel which was in need of fixing. In order to do this you really need to fit the windscreen supports too so that they abut neatly.
Firstly I fitted the windscreen supports and then used them to mark out the angle of the rear of the bonnet support. The bonnet supports were cut to length and then after a quick rub and polish were riveted in place. I positioned the bonnet supports flush with the outside surface of the side panel to slightly beyond the front of the engine and then bent them inwards to finish with their outer half an inch in from the outside of, or in the middle of, the top chassis rail at the front ready to accept the nosecone. Due to the fact that the scuttle narrows towards the top the bottom of the windscreen surrounds protrude slightly outside surface of the side panel and bonnet support. I thought that this not only looked a bit untidy, but would also cause no end of problems with protruding edges at SVA. Therefore I filed the lower end of the windscreen support to follow the line of the bonnet support and side panel. The centre part of the windscreen support was cut to length and fitted to the scuttle by three M5 cap head screws into rivnuts. The front surface of the surround was positioned flush with the front surface of the side surrounds which also provided adequate space for the return on the removable dash panel. All surrounds were removed given a quick rub down and polish and then re-assembled ready for the aeroscreen. The windscreen rubber was cut to length along the bottom and applied to the three edges of the screen. I then used fairy liquid to push the screen and rubber centrally into the bottom surround and then tightened the side support screws to clamp the screen in place. Finally the side rubbers were cut flush with the end of the side windscreen supports.
Putting the screen on made a huge difference to the appearance of the car and it was too tempting not to see what it would look like with the rest of the bodywork on. The bonnet looks like it is going to need a little trimming to abut the scuttle at the correct angle and also to adjoin the scuttle above the battery tray and the nose seems to need an alarming amount of stretching out to meet outer edges of the chassis, but it is starting to look alarmingly finished...well until you look inside.