Something really impressed at work these past few days, and again it has to do with the same GT3 RS that we took a look at in my first post. I talked briefly about how this certain costumer opted for an after market flywheel and a multi-plate clutch on his car. These two words, flywheel and clutch, which are so mundane within the automotive vernacular literally made me change the way I look at race car engineering. Yet, the two things I'm about to discuss are relatively simple in design, however, make huge leaps and bounds to increase the performance of the vehicle. So let's again dive into things.
The flywheel is typically a steel or chromoly disc with a ring of holes at the center which allow it to be bolted to the crankshaft and an outer gear profile that allows the starter to crank the engine over (not always for some race cars). Steel and chromoly are strong materials and are great for chassis, roll cages, anti-swaybars, and wheel hubs but are quite dense. Freeing up weight at the flywheel allows for a more instantaneous throttle response and quicker acceleration as rotating mass is reduced. The guys at AASCO have taken this truth to the extreme by creating an aluminum based flywheel. Now this may sound weird seeing that aluminum is soft and quick to deform under heat, which is what friction creates. The flyweel takes a good amount of bashing, especially from bad drivers, as it comes in direct contact with the friction discs of the clutch. Having a purely aluminum flywheel would be extremely detrimental as it would mostly likely contort, expand, or shear the surface of it. So as seen in the picture above, the center portion of this specific flywheel has a concentric black ring. This ring is not some anodized aluminum piece, but rather a thin chromoly disc which is attached to the aluminum flywheel using flat socket head cap screws. This allows for a widely lighter flywheel yet still allows for normative grip when compared to typical clutch discs and conventional chromoly flywheels. Another cool thing about this specific piece is that if the chromoly wears down, you simply unfasten the flat head screws and install another chromoly ring.
Next is the Tilton multi-place clutch. The theory behind multiplate clutches is the more discs, the more faces of contact which allows for a higher torque capacity before the clutch slips. Traditional clutches rely on the face which comes into contact with the flywheel. That's why most single disc after market clutches which say they have higher torque capacities have a very stiff clutch-pedal feel. They simply increase the torque capacity by using a pressure plate with more static tension which applies more pressure on the disc. Multi-plates don't have to use this stiff pressure plate method to gain higher torque capacity numbers because your using both sides of several friction discs. Just think of it as sliding two sheets of sand paper on each other versus trying to slide stacks of sand paper upon one another. I have a feeling that the stack is going to be harder...
Lastly, probably the coolest thing that caught my eye about the Tilton setup is the use of a hydraulic release bearing. See typically, the clutch master cylinder moves fluid when the driver depresses the clutch pedal. Since, the fluid has nowhere to go but to the slave cylinder (kinda derogatory calling one cylinder the master and the other the slave, IMO), the fluid from the master cylinder extends a rod which protrudes out of the slave cylinder. This rod on the slave cylinder actuates a hinged fork (kinda like a see-saw) which pushes a ball-bearing. The ball-bearing moves with the motion of the slave cylinder rod and is pushed against the pressure plate, engaging or disengaging the clutch. This specific system eliminates the fork and slave cylinder as the clutch pedal pushes the nearly incompressible fluid into a sleeved cylinder. The pressure causes a volume change and so the height of the hydraulic release bearing rises in the same fashion as a brake piston when the you slam on the brakes. This motion is directly applied to the pressure plate which again engages or disengages the clutch. So essentially the hydraulic release bearing is: 1) the slave cylinder, 2) hinged fork, and 3) release bearing all in one which you have to admit is pretty bad ass. As you can see in the picture above, steel braided line is used to transfer clutch fluid into the hydraulic release bearing. The other line is used as a line for bleeding (removing fluid or air pockets in the clutch system). The bleed line is attached to an external bracket on the side of the transmission case. This bleed line is not necessary but prevents "sailor-mouth" syndrome in mechanics who won't have to remove the transmission every time the clutch system has to be bled.
Well I know there has been a decent pause between this post and the one prior, but I'll try to be a bit more consistent. Till I find something else interesting to write about, I'm over and out.
-Josh
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