Walking the Clutch Tightrope Part 1

Click Here to Begin Slideshow When we left you in the last issue, we explained the issues with campaigning a clutch-equipped street-strip car. For anyone who has been there, it can prove to be an excruciating experience. At the least, you’ll end up devoting quality time under the car either adjusting the clutch or fixing drivetrain parts. That’s where the ClutchTamer enters the equation. It’s a device that allows you to use a reliable, conventional clutch in the car without resorting to expensive aftermarket adjustable clutch assemblies. It also allows you to adjust the way a clutch reacts by simply turning a knob from the cockpit of the car. No more climbing under the car to make adjustments. In terms of installation, the ClutchTamer is actually a very simple device. The example we’re illustrating (and also shown the last issue) is a conventional Muscle Car model. ClutchTamers are also available as direct fit applications for a number of cars such as Fox Mustangs, Mazda RX-7’s (ClutchTamer’s Grant Robbins actually developed a Chevy swap kit for those cars), SN 95 Mustangs along with a universal kit. With the universal and Muscle Car kits, a bracket mounts to the base of the dash. With some of the vehicle-specific applications, the bracket fits through a portion of the OEM dash. In either case, the bracket holds the control knob. It looks a lot like a hand choke knob. Another bracket is affixed to the clutch pedal. In between is the special adjustable hydraulic cylinder engineered by Robbins. It’s the secret behind the system. According to Grant: “The small hydraulic cylinder takes much of the inconsistent human element out of precisely controlling your car's clutch pedal. It's adjustable for exactly where in the clutch pedal's travel it becomes active, and adjustable for rate of release from that point on. The cylinder has characteristics similar to those of a 90/10 shock: Pulling the rod out is easy -- only the return stroke of the cylinder is controlled. Because the ClutchTamer attaches to the clutch pedal itself, it works equally well on both hydraulic and mechanical clutch release systems/linkage. “With our ClutchTamer installed, only the final part of clutch pedal's release is slowed down, not the whole release cycle, while the rest of the clutch pedal's travel works like normal. If you are using the clutch pedal during shifts, the slipper will soften drivetrain shock during the gear changes as well. Casual driving is not affected. There is no need to disconnect the ClutchTamer for daily driving. “The ClutchTamer slip controller allows you to select a clutch with more capacity than you would normally choose. Typically that clutch would be too aggressive, but the addition of the first stage of the slip control provides the ability to apply only partial pressure initially, allowing slip. The second stage allows additional pressure to come in over-time to insure lockup farther down the track. “The most surprising thing that you will realize with the ClutchTamer is how much more power you will be able to put down without breaking parts!” Grant goes on to explain the basics of the how the ClutchTamer functions: “As the clutch pedal is depressed, it pulls the rod out of the attached ClutchTamer's cylinder. When the clutch pedal is released the pedal then returns completely unrestricted, until the point that the "initial hit" dial on the cylinder's extended rod contacts the dash bracket. From that point on, the rate of clutch pedal release is controlled by an adjustable orifice inside the cylinder. As the rod slowly retracts back into the cylinder, the rate of retraction is adjusted by simply spinning the cylinder's shaft "inward" (clockwise). We attach a knob to the end of the shaft to make the adjustment quick and easy.” When it comes to basic adjustment, the ClutchTamer makes use of a simple dial type adjustment with an internal detent. The knob is typically located within easy reach of the driver's seat. In most applications, it’s possible to dial in more or less "initial hit" of the clutch without unbuckling from the belts. The dash adjuster dial assembly is designed with a notch milled into the threaded rod, while the inner "Initial Hit" dial incorporates a steel ball detent that is pre-loaded with a simple O-ring. This prevents the dial from free spinning. In the accompanying photos we’ll show you a ClutchTamer mock up in the writer’s Chevy Nova. Installation is similar for most cars. In the next issue, we’ll wrap up the series with some ideas for clutch tuning. You might be surprised at how sophisticated this simple device can really be. ClutchTamer Granny's PO Box 814 Concrete, WA 98237 USA PH: 360-391-1208 Website: www.clutchtamer.com Click Here to Begin Slideshow


Click Here to Begin Slideshow

Running a drag car with a stick shift transmission is like walking a tightrope. Here’s why: In order to make the car work, you have to leave at an RPM suitable for the torque curve the engine produces. Usually that means well above 4,000 RPM. The car can’t dead hook. You need some slippage (tire and clutch) or the thing will start shredding parts. Because of this, it also means you’ll likely be forced to use bias ply tires (and usually with more PSI than you’d first think). The initial solution is to use some form of adjustable slipper clutch. Plenty of folks offer them and there are a number of different examples out there. They all pretty much work the same. In addition to adjustable initial clamping pressure (baseline spring pressures) these clutches all have some form of adjustable counterweight to allow them to remain soft on the bottom end and then progressively lock up by way of centrifugal force during the run (this is really important at the top end). When sorted out they tend to work well. The dialing in process takes some work and it’s coupled with picking the right mix of components. Let’s just say you’ll be spending quality time under the car working out the tuning combination. And this combination can vary from track to track along with other variables such as weather conditions coupled with track altitude.

Fair enough. What if you have a street-strip car? Technically speaking, it is possible to run a car with a soft, adjustable clutch on the street, although the initial designer of these clutches told me a long time ago it wasn’t really good idea. There are various reasons for this, but if you choose to try to use one on a street driven car, be prepared to climb under the car and dial in as much pressure as you can in the adjustable springs. Then you’ll have to ensure there’s sufficient counterweight installed to clamp the clutch at higher RPM. The bottom line here is, slip it too much on the street and you’ll be replacing expensive parts in a hurry. Don’t know about you but I’m not all that fond of bench pressing manual transmissions on a regular basis.

Because of all of the above, plenty of folks with high horsepower street driven cars have resorted to using relatively small diameter, dual disc clutch setups. Most of these have a modified diaphragm pressure plate and for street use, most use some form of organic rag disc or a combination of an organic disc and a metallic puck style disc arrangement. They work great and usually they offer great durability. But there’s a hitch: Dump the clutch at the torque peak or higher and the car will usually go up in tire smoke. Bang the gears in high horsepower, relatively heavy street car and you’ll most likely start tearing up drivetrain parts.

Case-in-Point: Drag Week veteran racer Andy Starr was experiencing similar pain with his huge-by-large power, heavyweight ’56 Chevy. In fact, his stick shift combination pretty much destroyed brute force Dana 60’s on a regular basis. His solution? Andy added a ClutchTamer to the car. Wait a minute. What’s a “ClutchTamer”?

The ClutchTamer is the brainchild of Grant Robbins. A long time ago, Grant was attempting to pump some power through a Saginaw four speed transmission. As we all know, those things weren’t exactly renowned for their brute strength. Grant was going them on a monthly basis. The solution was to soften the initial hit of the clutch. But how? Sure Grant could have tried to modulate the clutch pedal and try to slip the car out of the gate, but in the real world, that’s really a hit and miss arrangement. And miss is more common than hit! But I digress: While wandering through the aisles of a local hardware store, Grant spied a common hydraulic door closer. Boing! The light bulbs went off in his head! What if it was adapted to slow down the clutch pedal return? That’s exactly what happened. Essentially, Robbins devised a way to hook the door closer to the clutch pedal in his car. It certainly modulated the pedal return. And on the track, it worked fabulously. His street car saw 60-foot times in the 1.45-second range, and he no longer left a trail of broken Saginaw four speeds behind him.

The first prototype examples were rudimentary, but over time, the ClutchTamer evolved into a rather sophisticated, well developed and tested component. Before long, it morphed into a custom fabricated, fully adjustable device that sees use in all sorts of street and race applications (actually there are more out there than you can imagine, but some folks are, understandably, not talking!). In the next issue, we’ll dig into the details. Watch for it! And in the meantime, check out the accompanying photos of a new ClutchTamer:


Source: ClutchTamer
PO Box 814
Concrete, WA 98237 USA
PH: 360-391-1208
Website: https://www.clutchtamer.com/

Click Here to Begin Slideshow

Walking the Clutch Tightrope Part 1 - Slide 2

There are several different versions of the ClutchTamer. Some are designed as direct fit jobs. Others, such as this “musclecar” version are a bit more universal.

Walking the Clutch Tightrope Part 1 - Slide 3

The heart of the ClutchTamer is this hydraulic cylinder. What it does is to effectively slow down the rate at which the clutch pedal releases. Essentially, it slips the clutch in a controlled way.

Walking the Clutch Tightrope Part 1 - Slide 4

When you have a really stout clutch setup like this high quality dual disc arrangement from Tilton, you’ll find the key to making it work (and simultaneously, not break drivetrain parts) in a drag race environment is to modulate the clutch.

Walking the Clutch Tightrope Part 1 - Slide 5

There two fundamental adjustments available within the system. One adjusts the hydraulic cylinder and the other sets the “free play in the clutch. We’ll get into the adjustments in an upcoming issue.

Walking the Clutch Tightrope Part 1 - Slide 6

Essentially, the ClutchTamer bolts between a solid piece of dash structure and the clutch pedal. Next issue, we’ll dig into the setup.

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