North East Area Group Meet - October 09

That time again, weather was not too bad and a good turnout - 5 cobs all 2 up:

In the foreground above is Ian H's recently aquired AK. Next to my car is Jimmy's MkII Sumo - nearly 20 years old and having had a fair bit of development including a 5 litre Rover Engine and bespoke fully adjustable suspension by magnum engineering. Here's some gratuitous photo's of the GD courtesy of Ian C who turned up to have a gander being on the verge of starting his Pilgrim Sumo build:

Ian's camera produces a nice red! Here we are departing from the Manor House Inn:

And here we are on the approach to Langley Castle:

Here's another classic action shot by Tommy - rding shotgun in John's Sumo - on the climb up to Hartside Summit:

When we arrived at the summit we ended up in the clouds - well it is 1904ft above sea level in October:

Thats Geoff's Dax in the foreground, and a particulalry rubbish view of Cumbria in the background.

As you can see below it was a bit dreary, and after a quick bite to eat it started to rain. Discretion being the better part of valour we promptly rany away back down to Alston and the Sunshine.

All in all a good 100 mile run out with pleny of interesting roads. As usual the map of the route is below which you can click on and be taken to the details on google maps.

The ride with the tweaked suspension and anti-roll bar was a marked improvement. I had Dave as a passenger (currently building a GD in Darlingotn) who had the misfortune(?) of a previous ride in the car when I was running it far too stiffly damped at the front. He felt that both the quality of ride and cornering was much improved.

I had also treated the windscreen to a coating of Rain-X both inside and out and am pleased to report that it did make seeing through the screen much easier than before and appeared to increase the effectiveness of the wipers by around 500%!

So, here's hoping for some decent weather in November....... might be pushing our luck this time.

Bump Steer Measurements Again

Worked on this Last night and all of Today - 14 Hours in Total!! - It's a pain with the body on!

As before - time to break out the mirror, laser and graph paper:

Firstly I removed the spring and damper (and disconnecting the anti-roll bar). I then swapped some shims over on the top balljoint / wishbone to remove a bit of caster - this as you might expect made a mess of the bump steer effect.

To cut a very long story short - I moved the steering rack around in small increments (not easy with the body on and an accusump in the way) - moved the suspension through it's range and plotted the results. I then input these into the laptop to provide a record of the changes and try to figure out the next step:

I ended up with lots of results:

Conscious that Christmas was not that far way I settled on the best I could manage, repeated the exercise for the other side, then checked the first side. Here's an averaged set for both sides - (both sides were with a couple of minutes of each other):Despite my best efforts I could not reduce the effects to any less than this - nor could I achieve the ideal of some toe-in under bump). On my first graph when I first measured the bump steer - when i got confused with minutes and seconds! - I also got confused with toe-in and toe-out! - the slight toe-in under bump was in reality toe-out. All in all then not a good effort as it turns out. Ignoring the extremes of travel (where things tend to get excessive no matter what you do) the bump steer effects are generally less than 5 minutes - less than the 13 I had before!

Having adjusted the caster and rack height I nipped off down the local tyre centre to get the tracking re-set. On the way back I sought out some bumpy bits of road. I still noticed a slight effect on large bumps but it was much reduced from that previously not requiring any steering correction. On generally uneven / bumpy roads the car felt quite settled. Plotting graphs is one thing - it is how it feels when driving that is important. All in all a good improvement over the previous set up. The reduction in caster (2 x 1.0mm shims swapped) has reduced the steering effort a bit without affecting straight line stability.

I am now however - intrigued with the whole concept of steering geometry and bump steer. Over the winter I am going to see if it would be possible to eliminate it completely - probably not notice that much difference on the road - but that's not the point now!

Bumpsteer Revisited

So.... I have a small bumpsteer issue to resolve. On the 180 mile drive back from GD I paid particular attention to the characteristics that were being exhibited.

When encountering a "bump" the very slight pull on the steering feel wheel seemed to be associated with the extension phase of the damper as opposed to the compression phase. It is not really a significant effect - but you know what it's like once someone points something out to you and you can't help but keep noticing it!

I looked back at the graph I posted when I did the original measurements:

I also measured the "ride height"damper length and found it to be 12 inches. So if you look at the green line and assume a normal damper range of +/- 1 inch you can see I should be expecting a range of around 13 arc seconds change in toe per wheel - Now 13 arc seconds is pretty small - in fact t is 13 /3600's of a degree - so why do I appear to be getting some bumpsteer effect.

I'll tell you why.... 'cos after racking my brains I discovered I had cocked up my calculations - the scale for the green line should read arc minutes not arc seconds!!!

Now I ignored the effect because I thought 13 seconds was negligible - which it is. 13 minutes is not!! especially when you consider that I am running 10 minutes of total toe-in on the front!!

Bugger!

I was kind of led down this path of ignoring the effect as it was small due to the fact that I ran out of adjustment on the steering rack mounts. To get rid of the toe-out bumpsteer effect I needed to raise the rack - but I was at the end of the slotted holes - "it's only 13 seconds so I'll leave it"

Andy had recommended that I reduce the castor angle - this will also have the effect of lowering the front of the steering arm (i.e the same effect as raising the steering rack). So this should give me back the adjustment I had lost.

So the plan will be to "swap" one /some of the castor shims over from the front to the back and then get the mirror and laser out to re-check the bumpsteer effect and take it from there.

To avoid further cock-ups I have drawn out the laser and mirror method of measuring bumpsteer on AutoCad and have confirmed that it is a valid and accurate method.

Changing Castor angle and rack height will of course necessitate re-setting the front toe-in.

All in all a bit of an annoyance - but at least everything makes sense - the theory now matches up with the practical experience.

So if you end up running a lot of castor to get the steering to self centre for SVA/IVA don't be surprised if you can't get the adjustment to elliminate all the bumpsteer. You'll have to change it afterwards.

Trip to GD for Suspension Tweaks

The time had come to return to the GD Mothership and have the ant-roll bar fitted and the suspension tweaked. It was dark and 2 degrees C when I left at 7am! 120 miles later it was time for a coffee and some fried slices of pig in a bun to warm up:The journey was reasonably uneventful ending up at GD in the warm winter sunshine: After a bit of a chat with Andy we set to work fitting the anti-roll bar:It is a bit of a Chinese Puzzle fitting the anti-roll bar with the body on and necessitated removing the alternator to get it in. My advice would be to fit it before the body goes on. I originally didn't think I would need one - but once you get used to the levels of grip available you can't help but corner that bit faster and you'll soon find yourself needing one. And here's the man himself Andy Burrows hard at it:You can see the anti-roll bar in the following photo - it's the black bar running just aft of the chassis top brace:

It is held in place by two clamp blocks - one each side - which allow the bar to rotate but hold it in position as shown below - this also shows the retaining ring which butts against the inside of each block to fix the bar transversely:The anti-roll bar is connected to the lower shock mount by a rose jointed drop link:I knew I should have painted the track rod ends!! The lower end of the drop link is connected to the lower shock mounting bolt by a threaded extension:The extension piece is of a much larger diameter to provide a large bearing area onto the shock mounting bracket to accommodate the leverage forces. At the top the drop link is bolted directly to the arm of the anti-roll bar:At the moment the outer hole is being used. If the inner hole is used then this will increase the effective stiffness of the anti-roll bar by around 15%. You will need to grind away the return on the inner wing to provide clearance for the connecting bolt - you can just make this out in the photo.

After everything was put back together it was time for a test drive. After some rudimentary checks of wheel cambers Andy set the dampers to mid range and off we went. It was quite strange sitting on the "wrong" side of my car whilst someone else drove it.

What happened next can only really be described as astonishing. Andy drove the car much faster than I ever had (and probably ever will) although it never felt out of control. After a brief stop to twiddle with the dampers following slight front o/s lock up we continued at an increased pace. I am ashamed to admit that on more than one occasion I felt my right leg twitching for the "ghost" brake pedal on my side of the car!!

It certainly was an eye opener to see how fast a skilled driver could drive the car relying on the feedback he gained from the car. It was also comforting to be shown what the limits of your car are as it then gives you a yardstick to measure how close you are to (or far away from!!) them with your own driving.

The verdict upon our return was that it was now probably "95% there". Having had a quick blast myself I had noticed an improvement, particularly with respect to roll. Andy did say that I probably wouldn't notice a marked improvement as it wasn't "a million miles out" to start with.

Andy left me with a small list of things to do when I got back:

1. Increase tyre pressures to 23 psi front and 22 psi rear - I had reduced the tyre pressures as a result of having overdamped the car - the overdamping was due to trying to control roll by damping as I did not have an anti-roll bar fitted.
2. Check the bumpsteer as there was slight effect noticeable - You will remember from previous posts that I could not eliminate all the bumpsteer as I had run out of adjustment on the steering rack mounts.
3. Reduce the Castor angle - this will reduce steering effort and will drop the height of the front of the steering arm - this should bring the steering rack back into the range of adjustment to eliminate all the bump steer. I had deliberately set a high castor angle to ensure self centering at SVA which can be a problem with new (stiff) steering components.
4. Slightly increase the negative camber of the rear wheels to improve corner entry - a bit of a faff to do this one but Andy reckoned it wasn't desperate and would make a nice "winter job". I had set the rear cambers as per the build manual - but the final setting depends upon actual ride height/damping plus the feedback Andy got from driving the car.

All in all a good day and a fantastic experience having the man behind the car actually drive the one you've built. I was also quite pleased to hear that I had "screwed it together properly".

The drive back highlighted a car with a different character - It felt more compliant than before. It is interesting to note how drastically I had overdamped it. Originally I had the rear dampers on 9 clicks - they were now on 8 and I had the front dampers on 7 they were now on 4!! The car felt much more planted and less skittish - as you might expect from reducing the front damping. I also noticed the slight bumpsteer effect which I hadn't really noticed before - probably as I had artificially limited the front suspension travel by running too much damping.

So a few jobs to do. They will have to wait to next week as I'm away this weekend.

Oh...... and my new rocker cover gaskets did the job!

New Rocker Cover Gaskets

Hats off to Real Steel.... New Gaskets turned up today - Guaranteed not to leak, blow out or suck in:

So, out with the old ones:

Hmmmmm.... doesn't look good - Looks like it has slipped over the edge of the head and then got crushed when tightening (possibly even over tightening?). Interesting how the entire cork gasket is impregnated with oil.

The new ones are rubber bonded onto a steel frame - so they keep their shape and fit where they are supposed to with no slipping out:

Piece of cake to fit compared to the cork variety - no flopping about etc. I'm feeling confident so fingers crossed.

Just need a few more routine checks and we are ready for the journey back to the mothership.

Return to the Mothership

New (proper) gaskets ordered and I'm booked in at GD on Thursday for an anti-roll bar and suspension tweaks.

Thursday looks good for a 400 mile round trip:

Just hope me gaskets turn up before Wednesday night!

Another Day Another Suspension Tweak

Here we go again.........

At the last meet I found my recent suspension tweaks had resulted in a marginal deterioration. So I retraced my steps and then made some more tweaks with a few more short test drives along the same stretch of twisty road.

I am now at:

Front Dampers - 7 out of 12 clicks

Rear Dampers - 9 out of 12 clicks

Front Tyre Pressures - 21 psi

Rear Tyre Pressures - 20 psi

End result? an improvement over where it was before I had made it temporarily worse. Feels reasonably planted now.

There was however a little downside..... spotted a drop of oil on the floor! Turns out to be nothing more than the rocker gasket (again!).

After I changed them last time - looks like it was slightly displaced beyond the front of the head and has been pinched and ultimately broken.

Oh well - I'll get it right one day! It is a little tricky as the cork gaskets are smaller than the outer rim on the rocker covers so you sort of have to guess where they go - they also fall off / slide out of position if you don't silicone them to the covers.

North East Area Group Meet - September 09

Another month and time for another Area Group Meet. Unfortunately all the regular die-hards had other commitments. Fortunately two new proud owners turned up. We had Chris with his Cheetah 427 and Mike with his Southern Roadcraft: Chris unfortunately had a prior commitment and couldn't make the drive out. So that left myself and Mike to take advantage of the lovely summers day. The route I had planned was a figure 8 with the lunch stop at Rothbury taking in some nice driving roads - Click on the map for more details:
And here we both are at the lunch stop at Beggars Rig - after all the crappy weather recently it was nice to eat lunch sat in the sun:

Beggars Rig overlooks the River Coquet towards Simonside - time for another photo opportunity - this has turned out to be one of my favourite photos of the cob so far:

Having fiddled with my suspension and tyres pressures again... the end result unfortunately was not as good as I had previously. The time to go down and see Andy at GD is rapidly approaching I think!

A good day of 100+ miles of driving in the sunshine on country roads with beautiful scenery - exactly what Cobra ownership is all about.

Shame about the odd tractor.......... but they were quickly dispatched!

First Scrape! and other stuff

It's not as bad as it sounds...... caught the bottom of the oil cooler scoop on a road hump on the way into a friends estate - no real damage other than some scrape marks underneath out of sight.

On a similar vein - I had the front wheels off this weekend to get them balanced again (long story) and noticed that there was an area of underseal underneath each arch that had been rubbed off by the tyres. So as a consequence of this, and the scrape, I've raised the front ride height slightly. I may revise this after fitting the front anti-roll bar. I've tentatively arranged with Andy to go down to GD end of September and get them to fit the anti-roll bar there and then and get Andy to finish tweaking the suspension.

Going back to the wheel balancing issue - I was getting a slight tremor at 75ish that you could drive through and would be gone by 90. Nothing too drastic but it was starting to annoy me - particularly as I had been and had them balanced on two previous occasions but it had never quite solved the problem. So this time I carefully checked wheel rim and tyre run out (both in line and laterally) and also checked the wheel bearings. Everything checked out within acceptable limits so it was off to a different tyre place that didn't employ "yoofs"!

I stood over the the guy this time and watched the process - as the wheels are quite wide it was explained that I would need two sets of weights on each wheel to get the dynamic balance right - one set on the back edge of the rim the other set towards the front edge but just behind the wheel face so they are not visible. So 10 minutes and 25 quid later job done. It turned out to be a marked improvement and has cured the issue.

It was also time for another clean and polish after spending 4 hours driving in the rain at the last monthly meet. This time I had a change of heart and instead of using Auto Gylm products I used One Grand Omega Glaze followed by One Grand Blitz Wax (Carnauba). In all the whole process took about 8 hours but I was quite pleased with the results:

Finally, after a discussion with my Engine Builder, Jez, we have concluded that I can turn up my rev-limiter from a conservative 5200rpm to 6000rpm - this will give me an approximate increase of 15% in road speed for each gear. This will come in handy as the thing accelarates so quickly I was not spending much time in the lower gears! I just need to psyche myself up for another upside down in the footwell episode first - perhaps in hindsight I should have put the Mallory Hy-Fire unit somewhere more accessible? where though I'm not sure.

Update and August Meet

Well, that's a month gone by. And to be honest it was a month of not driving. This was mainly due to allowing my partially severed finger to heal!

The next thing I knew it was the third Sunday of the Month and time for our North East Area Group Meet. This time I had selected a route that covered most of the Historic Lead Mining Areas of the North East. The route is shown below, click on the image for more details:

Having been promised a decent forecast by the Met office, on Sunday the weather turned out to be poor. As a result only myself and John with his sumo turned out. We then proceeded to get wet for a few hours! In hindsight visiting the highest market town in England (Alston) when the weather was bad was probably not a good idea. However, I did discover that you could open the boot, sit inside and eat your sandwiches in relatively dry comfort!

Here is the only photo of the day taken in Alston, we only stopped 'cos I was desperate for the toilet!

Have a close look at the Estate Agents sign..... somewhat appropriate.... even if it was a fluke. The route was definitely a good one, but was spoilt by the weather.

My finger troubles have also kept me out of the garage. I still have some more work to do on fine tuning the suspension. I know GD will do it for free, but at the moment I still want to try and get to grips with it myself, thereby getting a better understanding of "cause and effect" and ultimately (hopefully) reaching a better understanding of how my car handles.

At the moment I'm thinking of adding an anti-roll bar to the front. I omitted this in the build as the consensus was that it would not be needed for mainly road driving. However the more I get used to the car the more I seem to chuck it around - my only way of controlling body roll at the moment is by increasing the effect of the dampers, but this in itself has some drawbacks to overall ride quality. The levels of grip available on tight corners have been resulting in some contact between the tyres and front arches. I also think that the front springs have settled a bit more and need to be adjusted.

Hopefully I can fit in some tinkering time in the garage in the not too distant future.

Watch this space.........

North East Area Group Meet (July 09)

After a couple of days of torrential rain with some associated flooding we got 5 cobs together and we chased the sun round all day! Went for a drive up to Keilder reservoir and back through Otterburn and Stamfordham. Click on the map to see the details: It was a cracking day out:In the last photo you'll notice my left index finger is bandaged up - had an accident at work on Wednesday - sliced it down to the bone, severed some nerves and damaged a tendon and had to have it stitched back on. 160 miles later....... it's now bloody agony and gone a lovely shade of black - still - too good a day to miss.

Thanks to Tommy for Navigation and Photography duties.

A Miscellany of Distractions

It's been a while since I've posted any updates........ kind of been distracted by other things.

Got s few more miles in, been to another hot-rod meet at the Gateshead Metro Centre - forgot my camera which was a shame as there were 5 cobs there this time!

Now that the build has finished I've still felt the need to tinker. Fixed the mother-in-laws lawn mower (and her TV!) and found a junked treadmill motor on eBay for a few quid..... so with some plastic drainage pipe cut up and shaped for blades I made one of these using other bits and pieces in my garage:

Produces 18v in not much wind and was up to 30v (with no load) in the video. The idea is to charge marine batteries (identified a free source for some) and to then power my garage through a voltage inverter. Just need to acquire a 10foot scaffold pole as a mast now.

Most of my spare time at the minute has been taken up with helping my neighbour plan a somewhat extreme project.......... The plan is to build a twin engined 32 foot offshore powerboat along these lines:

The budget is limited so the plan will be to build the hull in ply (Dave is good with wood) and then overlay it inside and out with fibreglass. Motive power is planned to come from two Lexus V8's liberated from a couple of MOT failure LS400's which we will marinise and "chip" to give us 650-700 BHP. So far I've been getting to grips with some 3D hull design software - still got a way to go with this before it gets the chance to pass the feasibility test!!

Back to Cobras, this Sunday is the next North East Area Group Meet, I've planned a drive out to Keilder Reservoir so here's hoping for a) some not too wet weather and b) some other cobs to turn up.

I'll attempt to remember my camera this time!

What's going on?

You'll have noticed that the pictures in the blog title have changed......... one day it will become clear what was going on.

North East Area Group Meet (June 09)

Well today was the Inaugural Monthly Meet for the Cobra Club North East Area Group. I got there first and began to wonder if I was going to be on my own......However, I was shortly joined by Bob with his AK and Howard with his Unique Autocraft Python.......... and if that wasn't good enough...... then Geoff arrived in his Dax......So there we are.... the largest number of Cobra Replicas in one place in the North East to Date!

The weather was superb, sat outside in the blazing sun eating our Sunday Roasts. As this was the first meet I hadn't organised anything in the way of drive outs as I wasn't sure on turn out. Next Month I'll get a trip out organised.

Interestingly, of the four cars, one was 12 years old, another 15 and the third 20. Two were automatic, 3 had underslungs, 3 had chevy power with the fourth being rover powered.

So that's just over 1000 miles up now..... time to start thinking about rolling road tuning and returning to the mothership for final suspension tweaks. I've tried my best, but it still gets slightly interesting once you are over the ton.... on private roads obviously.