Clutch 12

To read the earlier parts of this series, go HERE:
Part I
Part II
Part III

In the third part of this series, we began our look at modern dual disc high performance clutch assemblies. If you recall, we started our examination of McLeod’s small diameter RST clutch package.  In this part, we’ll conclude the series. There’s something applicable here for just about any racer (at least those with three pedals on the floor).

McLeod Racing’s RST package effectively reduces the package diameter and at the same time, lowers the overall mass.  So now, instead of using a large, relatively heavy 11.00-inch or larger Borg & Beck or Long style pressure plate, a small, light 9-11/16-inch Diaphragm pressure plate can be used. Instead of using a big 11.00-inch or larger clutch disc, the system makes use of two small, lightweight 9-11/16-inch organic discs.  Obviously, the pair of discs increases the clamping power of the clutch (nearly doubling it over a standard single disc system).  Because the clamping power has increased almost exponentially, then the demands placed upon the pressure plate springs are lowered.  Just as importantly, the reduction in the clutch moment of inertia allows the use of a very lightweight pressure plate spring(s).  That means your left leg is much happier – actually close to the same pressure as you’ll find in a modern FWD econo-box.

Mcleod’s testing has show that the RST can handle up to 800 horsepower. The RXT is the same clutch kit but with upgraded Miba puck configuration discs (a “Miba” puck consists of a bronze segmented disc facing), capable of containing 1,000 horsepower.  There are some options too:  With the RS series of clutch packages, you can also specify an RST II (or RXT II) model.  The “II” means the solid hub is replaced with a sprung hub.  This setup is available in applications where there is sufficient space available in the bellhousing.  Another option is the “Plus” series, available on RST, RXT, RST II and RXT II models. With this option, the clutch package includes a dedicated flywheel.  Because of the developments, it’s easy to see that something like the RST series (along with the variants) just might be the ticket in a dual-purpose street machine.

In the end, if you’re a “three pedal” stick shift guy (or gal) you can name your poison! It’s great to have good clutch choices. 

 

We mentioned before that the pressure plate used in the RST clutch setup is an itsy-bitsy 9-11/16-inch diaphragm job.  Since the job  of clamping is now handled by the pair of discs, it’s possible to reduce the size, weight and course spring pressure in the pressure plate (just like a contemporary drag race clutch).

We mentioned before that the pressure plate used in the RST clutch setup is an itsy-bitsy 9-11/16-inch diaphragm job. Since the job of clamping is now handled by the pair of discs, it’s possible to reduce the size, weight and course spring pressure in the pressure plate (just like a contemporary drag race clutch).

 

Due to the reduced moment of inertia (and coupled with modern pressure plate design), the chance of the pedal getting stuck on the floor at high engine RPM is gone too. And that’s good news!

Due to the reduced moment of inertia (and coupled with modern pressure plate design), the chance of the pedal getting stuck on the floor at high engine RPM is gone too. And that’s good news!

 

Although not a part of the RST clutch package (we pointed out previously the setup is designed to work with stock OEM flywheel assemblies or available with a steel flywheel), you can use an optional aluminum flywheel. McLeod have successfully mated aluminum flywheels to dual-purpose street-strip machines.   Keep in mind this particular application for the aluminum flywheel on the street was a light car with a 572-cubic inch big block.

Although not a part of the RST clutch package (we pointed out previously the setup is designed to work with stock OEM flywheel assemblies or available with a steel flywheel), you can use an optional aluminum flywheel. McLeod have successfully mated aluminum flywheels to dual-purpose street-strip machines. Keep in mind this particular application for the aluminum flywheel on the street was a light car with a 572-cubic inch big block.

 

Since aluminum reduces the overall mass of the flywheel, it helps the engine to reach maximum RPM in a significantly quicker fashion.  Naturally, aluminum wouldn't survive alone in this oft-hostile environment.  That's why McLeod uses this steel heat shield that is fitted inside the flywheel.  Note too that the flywheel carries an SFI tag.  We touched on this in the second part of the series. You need this peace of mind, even with an aluminum flywheel.

Since aluminum reduces the overall mass of the flywheel, it helps the engine to reach maximum RPM in a significantly quicker fashion. Naturally, aluminum wouldn’t survive alone in this oft-hostile environment. That’s why McLeod uses this steel heat shield that is fitted inside the flywheel. Note too that the flywheel carries an SFI tag. We touched on this in the second part of the series. You need this peace of mind, even with an aluminum flywheel.

 

Because aluminum isn't particularly strong (when directly compared to steel of the same size), McLeod searched for ways to improve the structural integrity of flywheels manufactured from aluminum. McLeod decided to forgo the use of excessive milling on the backside of the flywheel.  Many other lightweight flywheels are full of scallops, cut-aways and other weight reducing tricks.  Unfortunately, this process unnecessarily weakens the flywheel.

Because aluminum isn’t particularly strong (when directly compared to steel of the same size), McLeod searched for ways to improve the structural integrity of flywheels manufactured from aluminum. McLeod decided to forgo the use of excessive milling on the backside of the flywheel. Many other lightweight flywheels are full of scallops, cut-aways and other weight reducing tricks. Unfortunately, this process unnecessarily weakens the flywheel.

 

A steel ring gear assembly is mandatory on an aluminum flywheel, but you have to come up with a way to fasten the ring gear to the flywheel to insure it won’t work its way loose.  Here, the ring gear is pinned in place on the flywheel.

A steel ring gear assembly is mandatory on an aluminum flywheel, but you have to come up with a way to fasten the ring gear to the flywheel to insure it won’t work its way loose. Here, the ring gear is pinned in place on the flywheel.

 

Here, you can see how the ring gear pins effectively "sandwich" the flywheel.

Here, you can see how the ring gear pins effectively “sandwich” the flywheel.