Cracking disks and cracking times

Race cars can be as simple or complex as you make them. 

Generally the way things work is that you start off with a nice small, simple car and a firm intention of keeping things that way. 

Where it all started. Simplicity personified.

However, within a handful of races, the red mist descends on the brain and the urge to go faster begins its insidious corruption of your most determined plans for simplicity.

Drivers will know it well, but for the uninitiated, "Red Mist" is a term used to describe what happens when a driver (usually a race car driver) looses all sense of reason and "MUST WIN AT ALL COST". This is usually associated with an on-track event, like being overtaken by a competitor, but can relate to the degree of self convincing that happens when unjustifiable sums of money need to be spent for dubious return on a race car. 

Personally, I managed to hold out for almost half a season before I started to fiddle with my perfectly functional Lotus 7. By the end of my first season of racing I had already justified building a bigger, faster car, with the firm intention of that being the end of the story. I reasoned, quite logically, that once I had a good strong platform to work off, I could focus on improving my skill rather than my equipment.

That lasted a whole season, which, looking back, was not a bad achievement actually. 

What followed, I firmly blame my fellow racers for. 

You see, I had managed to knock a whole 3 seconds off my Lotus 7 laps times with my new car. However, everyone else seemingly suffers from the same affliction and, by the end of the season, my 200kw V8 powered rocket ship was one of the slowest cars in the field, and, for once, this did not have all that much to do with my rather mediocre skill. Even in skilled hands, my car was barely tickling the middle of Class D. Success during my second season came more from the misfortune of my fellow racers, rather then me beating their pants off.

Thus, the following season saw work start on making the Type 6 a little more ferocious. This process involved a number of upgrades on the car, all culminating in the fitting of a big fat turbo at the end of last year. 

Hair dryer attached.

This is where the complexity thing comes in. Once you start changing things on an already built car, the knock on effect is hard to quantify up front. Seemingly small issues tend to have gloriously profound effects later on down the line.

Test driving the car on the road seemed to indicate that we had got everything right, and the 2014 season should be a "good one". The emergence of smoke from the exhaust a few weeks after the install was a cause for some concern, but race day was looming and we decided to adopt a typically "racing driver" strategy of "lets race and see what breaks".

The first race of the season started well with me clocking a sub 1:24 time on the third lap of the race. This was the fastest I had ever gone, so I could be forgiven for being a little bullish.

However, things rapidly turned sour as the car started cutting out under full throttle. I finished the race and, suspecting a low fuel level, topped up the tank for race two. The addition of the turbo has severely dented the fuel economy of the Type 6!

Needless to say, this was not the problem, and I pull off after the second lap, sneaking home quietly to avoid ridicule.

The following weeks involved a number of fault finding sessions, culminating in the replacement of all the fuel lines and the high pressure fuel pump, none of which solved the problem. 

New AeroQuip all around and a beefy Bosch "044" pump

Eventually a trip to Herman and the dyno revealed a waste gate that was stuck partially open. The earlier smoking issue, which had been due to a incorrectly routed turbo oil drain pipe, had caused a carbon build up on the waste gate plunger shaft. Once the car was used in real anger for the first time, this build up burnt hard and caused the plunger to seize solid. 

The cutting out was the ECU desperately trying to save the engine from becoming a shrapnel generator behind me. On the up side, we now know the engine can handle 0.7 bar of boost for short periods.

Dyno-side waste gate repairs

Some spanners, sand paper and a couple of hours later the waste gate was, well, wasting as it should again. Herman did a few dyno runs just to ensure all was well, and the figures were stable at 260kw and 500Nm. 

Just in time for the second race day of the season.

April is not normally known for it's heat down here in Cape Town. That honour usually falls to February. But, this year, clearly Feb was on leave and April was standing in. I knew it was hot when I keyed the ignition of my car for the second race, after it had been standing for around 4 hours, and the temperature gauge still read over 60 degrees. Track temperatures where measured at deep into the 40's, and the day was a real test of man and machine. Many did not survive and I was glad to have an open top car to cool me down during the action. I noted many a Porsche driver emerge red faced and slightly wobbly from their rear engined ovens after the racing.

The heat did allow for some seriously sticky tyres and I was revelling in, what was essentially, a new car to me. Race one was extra special as I managed to out drag Cyril's GT3RS coming out of turn 5, clocking a 23.3 lap time in the process. The fastest time ever recorded by the Type 6. I took second place overall in Class D for the day and was happy that the car had performed flawlessly the whole day, despite the searing heat and close racing.

Well, almost, that was. On the way home that evening I detected a bit of a ticking noise coming from the front brakes. This seemed to be coupled to a pulsing feeling from the pedal. 

All had not survived the day, it seemed.

Closer inspection yielded, not one, not two, but three of the four disks had cracked from edge to centre. We would later discover that the fourth would also have cracked had the calliper for that wheel not have been sticking. 

This crack is not an attempt to increase braking efficiency!

To be honest, we had sort of created the problem for ourselves. 

Soon after the car had been finished, it showed a rather alarming propensity to warp the off-the-shelf 250mm Toyota RunX disks we were using. After some consultation with "those who know" it was recommended that we get slotted disks. The logic was that we were overheating the disks by using race spec pads. The gas build-up under the pad was not being allowed to escape and this was causing the "high spots" on the disks often mistaken for physical warping. Rather than spending copious amounts of cash on custom race spec disks, we opted to have the off-the-shelf items slotted. This was duly done and the consumption of disks immediately ceased.

Fast forward to the present, where we had replaced the 250mm disks with 282mm items. Thinking to avert the same issues as before, we dutifully slotted these disks as well. Of course, the forces at play now were all a little bigger. I was arriving at the corners much faster and braking effort was much increased with the extra downforce. Add this to fact that we slotted our disks right to the edge, and the result was somewhat predictable. All the disks had cracked down one of our slots.

This proved to be the perfect time to finish off the brake upgrade we had started the year before. The long term idea was to use standard 305mm disks off the Toyota Rav4 SUV, but at the time we could not get the correct calliper brackets made up in time, so instead we using some existing brackets and cut the 305 disks down to 282.

Craig designed some nice brackets which were made up by a local CNC shop and, hey presto, we had 305mm disks all round. 

Race car porn, right there!

We again slotted the disks, but this time we stopped short of the edge of the disk. Hopefully this will maintain the structural integrity of the disk under load. Sometimes I think I should attach my GoPro to a chassis member and film the underneath workings of the car. One can't help feeling this might well be more exciting to watch than the racing sometimes.

Anyway, at the recent race day the new brakes worked exceptionally well, although I suspect some extra cooling ducts might be next on the never ending list of "stuff to do".

Fetching blue tint to the new brake disks

The racing for the day was once again fast and furious, with the added excitement of the inclement weather. Clearly Feb was back from leave and April could once again revert to it's usual character. I arrived good and early having neatly dodged a rather determined rain cloud, only to have it catch up with me during qualifying. This created a situation more suited to creatures with gills, than cars with slightly ageing semi slick tyres.

Storm clouds gathering...

After attempting to drift (like a race driver, not a boat captain) through turn 2, and failing dismally, I decided it was safer to just start at the back of Class D. 


Thankfully the weather cleared up for our races and both were action packed events. Unfortunately, in Class D, competition is fierce, and starting at the back will mean finishing at the back if everyone brings their A game. 

It was an A game day for all except me and I finished the day fourth over all. Not exactly stellar, but a great day of good, clean racing none the less.

Class D is now looking like "the" place to be. The class times have been realigned due to the ever decreasing lap times, putting around 9 cars in D, with just over a second separating them. This provides for some good, close racing.

All told, the season is shaping up better than it started. Now, if I can just keep the effects of the red mist at bay.