Sunday, 21 February 2010

Cleaning the Wheels

It is -2 degrees today and I've just spent the morning outside cleaning the wheels and polishing the rims and spinners - what a ball-ache it was with all the nooks and crannies on the Halibrands. Still it was much easier to do with the wheels off the car.

I went for the clear anodised finish on the rims and whilst it may not give the shiniest of shiny finishes it does seem to have protected them and made them easier to clean. The rims were finished off with the polish supplied by image with the wheels - which interestingly looks like, smells like, applies like and buffs off like Auto Glym Super Resin Polish!

I've put the back wheels back on(after making sure I had not forgotten to grease anything) but left the fronts off as I still need to check the front wheel bearings and callipers.

I'm too cold to be bothered to do anything else today!

Saturday, 20 February 2010

Sat Nav...... In a Cobra????

Over the last few years I have become accustomed to using Sat Nav. And with the desire to travel abroad in the Cob - combined with my Wife's poor navigational skills I had been thinking about how to mount my Sat Nav in the Cobra. I had managed to conclude that the normal windscreen mounting brackets were not going to work and also that the unit needed to mounted low down to cut down on glare with having no roof. I hadn't really come up with a solution until I found a strip of spring steel in my oddments box.

And after a couple of hours here's the end result:
Very neat and discrete and when not in use the arm folds away under the dashboard:
There is a piece of chassis foam stuck to the underside of the arm to prevent the mount securing nut marking the the tunnel leather when it swings back under the dash.
The arm is fixed to the under-dash panel using a nylon washer to create a friction pivot:
The under dash 12v socket is conveniently located for powering the Sat Nav. You can also see a small aluminium bracket that the arm locates into when in the "deployed" position - here's another view:The bracket is just a cut down bit of aluminium box section bolted to the under dash panel. There is also a piece of chassis foam stuck to the top of the arm to space the arm off the bottom of the dash - just gives things a little more stability.

I got a spare powered mount off E-bay and this was simply bolted to a hole drilled in the end of the arm:Job Done.

The wires you keep seeing in the background are the leads from the battery conditioner you'll remember that I included a fly-lead under the dash to make connecting up easier.

Sunday, 14 February 2010

More Winter Jobs

Tme to crack on with my list of things to do. Worked over and under the entire car checking nuts and other fasteners and lubricating / greasing every thing that needed it. All fluids were present and correct:

Whilst I was under the car I noticed some drips of oil underneath the accusump - not enough to drip onto the floor (which is why I had not noticed before) but enough to need attention:

Bit puzzling as the valve was screwd up F.T. when it was all assembled? - managed to nip it up another quarter turn so that should fettle things. Got a few more odds and sods to do but the main outstanding essential job is to fit the Hood and Sidescreens. These should be ready to collect in a couple of weeks - which will clash with going on holiday.

Sunday, 7 February 2010

Adjusting the Rev-Limiter

Following discussions with Jez my engine builder, he had informed me that it was OK to turn the Rev-Limiter up to 6000 rpm ( from the 5250 it is set at now). I was a bit worried that this would turn out to be a bit of a pain as I had hidden Mallory Hy-Fire unit away behind the dashboard - admittedly to put it out of the way of engine bay heat and water.

I needn't have worried - took out the three fixing bolts and it drops down as expected:

It was then a simple matter of unplugging the three harnesses and removing the heater vent pipe and Bob's your Uncle!Took the access panel off - twiddled the dial - and put it all back together - the under-dash panel went back as easily as it had come out.

Job Done.

Saturday, 6 February 2010

Adjusting Wheel Cambers

First things first, a trip to Machine Mart kitted me out with a set of "wobble bars" - socket extensions that will accommodate a +/- 10 degree deviation in line:As you can see below - the 500mm bar is just the job:With the four brake disc retaining nuts removed, 5 minutes of rotating the drive shaft and tapping with a rubber mallet saw the shaft come free allowing the shim pack to be adjusted:With the correct shims fitted new disc retaining nuts were fitted (important not to use the old ones) and tightened to the correct torque. Conveniently you can use the handbrake to prevent the shaft rotating. This becomes a bit of pain when working on the nearside as you keep having to walk round the car to operate the handbrake.

The cambers were measured before and after (at full droop) and the removal of four 20' shims on the offside saw a negative change in camber by 1.05 degrees and the removal of two 20' shims and the addition of a 10' shim on the nearside saw a negative change in camber of 0.35 degrees. This should give me near or damn it -0.5 camber at ride height on both rear wheels.

All in all quite an easy task and nothing to feel daunted by. Next up was adjusting the camber on the front offside wheel. I had calculated that I needed to remove 3/16 of shim - however this was based on the original jag set up. The upper wishbone pick up points are orientated differently on the GD so a little trial and error was required. The original 1/4" shims were removed one at a time by loosening the fixing bolt:The end result was found to be two stainless steel 7/16 washers giving a negative change in camber of 0.8 degree - which give or take 0.05 of a degree should be the same camber as the nearside wheel:
The original 1/4" shim - 250' was replaced with two 7/16" stainless washers at 45' each - so the total reduction in shim was 160' a tad over 4mm and 30' less than the calculated 190'.Quite a productive morning - although I won't be able to check the final settings until the car is back on the ground.... but the indications look good.
If there is a moral to this story then it is not to worry about cambers too much during the build as they are very easily adjusted once the car has been "shaken down" on the road.

Jaguar Suspension Development

Before I get round to adjusting the wheel cambers on the car, it is time for a history lesson with some of the background behnd the Jaguar's development of its suspension systems:

From the early 1960s to the present day virtually all serious racing cars have used the classic double wishbone suspension arrangement, or a close variation on the theme. There are many alternatives that have seen widespread use: beam axle, de Dion, swinging arm, trailing arm (even semi-trailing arm), sliding pillar (Morgan, unbelievably in this day and age), McPherson strut (front) and Chapman strut (same thing at rear), but for precise control of wheel movement and low unsprung weight, double wishbones remain the favourite. The beauty of the arrangement is that by careful design of the pivot points and arm lengths the camber of the wheel can be maintained close to the optimum even while the body rolls during cornering. Not only that but the roll centre - a term for the abstract point around which the car rolls when cornering - can be held consistent thereby helping to confer the vehicle with stable handling characteristics. Then there are ways of further refining the handling characteristics by angling the axes of the wishbones in various ways. For instance wheel toe-in and castor angle can be made to vary with body roll to enhance steering feel, or upward suspension deflection can be made to act against the forward weight transfer under braking to oppose front end dip. This is known as anti-dive and a similar arrangement in reverse, known as anti-squat, can be applied at the rear.

Jaguar's legendary Technical Director, William Heynes, knew that independent front suspension was essential for any car that claimed to be advanced and refined, so had adopted double wishbones at the front on the Mk V saloon just after WW2. However the case for independent rear suspension was not so clear cut and even the outstanding D Type had a live axle at the rear, which helps to explain why its greatest successes were nearly always at race tracks with the smoothest surfaces. Obviously this handicap would only become worse so Bob Knight and his team, with one eye on production applications, devised an independent rear suspension for an experimental successor to the D Type known as E2A. Within a year the E Type was launched (1961) with a productionised version of this same independent rear end, incorporating the now familiar rubber mountings as a vibration barrier and trailing arms to provide fore and aft control. It continued with only minor alterations until the last XJ-S left Browns Lane in 1996.
A notable but less well-known member of Bob Knight's team was Derrick White, highly regarded in club racing circles for creating his effective Impala racing car, later moving from Jaguar to be Chief Designer for the Cooper F1 team and then being credited for the Honda/Lola that enabled John Surtees to snatch a lucky win at the 1967 Italian GP. Talent was not a rare commodity at Jaguar in those days. The point of all this, of course, is to show that Jaguar were near the forefront of vehicle design with suspension systems technically superior to those of most other manufacturers of the time. It may not be obvious but Jaguar's well-known independent rear suspension assembly is geometrically very similar to the double wishbone system preferred by race car designers, in the way wheel camber is controlled. This becomes clearer when the pivot points are highlighted as in the accompanying diagram. Particularly notable is that the driveshaft doubles as the top link so that the under-floor space requirement is kept to the minimum.