Tough NMRA classes beg the question: What is a good clutch?

Tough NMRA classes beg the question: What is a good clutch?

By Fergus Ogilvy:   There are several schools of thought on the question of what constitutes a good clutch. But first there are two separate strands to this narrative that need to be addressed: street or track. It’s key to distinguish whether the car will be used mostly for high-performance street-travel or for track use and its purpose needs to be decided. In either case the clutch has to transmit the car’s horsepower and torque and a stock clutch assembly will flounder in thermal shock and abuse, even in a slightly modified car.   Let’s focus our attention for a moment on selecting a good clutch for a high-performance street car that visits the drag strip occasionally. In this pursuit, the first consideration is usually vehicle weight. Accurate information about the vehicle’s poundage not only guides to the proper selection of an adequate clutch but also has relevance in the selection of the most effective flywheel. Another necessary statistic is the amount of power being transmitted through the clutch. And third, let’s not overlook the gearing. Lastly, pay attention to the size and type of tire conveying the rotational energy to the road or track.   Flywheels and a simple gearing formula Lighter flywheels provoke engine speeds to accelerate and decelerate quicker while the opposite is true of heavier flywheels. Heavier street cars usually benefit from a heavier flywheel, which maintains its advantageous momentum—it inhibits engine speeds from descending too quickly. However, shedding 10 to 15lbs of mass from the rotating assembly of a properly geared vehicle has a pronounced effect on its responses. Hence, lightweight, high-revving race cars...
You may not think it will kill your clutch but it will

You may not think it will kill your clutch but it will

Written by Moore Good Ink: Why precipitate the loss of a perfectly good clutch when it can be avoided? Ram Clutches offers two valuable tips: On chassis dynamometers Probably the greatest threat to the longevity of a clutch system is imposed by the chassis dynamometer. Because there is no tire slippage during the run, any hint of engine lugging can cause the clutch to slip. Consequently chassis dyno time is much more strenuous and abusive on your clutch system than racing passes at the drag strip. At the drag strip On the burnout make certain the tires are wet but not operating in the water. As they begin to gain traction with the pavement, depress the clutch pedal. Do not attempt to extend the burnout toward the tree. When the tires hook they exact a heavy load on the clutch, especially in 3rd or 4th gears. To extend the burnout further exposes the clutch system to a tremendous and unnecessary load. Though this may sound elementary, make certain your car is in first gear before you leave the starting line. Leaving the line in 3rd gear will almost certainly destroy your clutch system. So, prior to pre-staging always ensure you select 1st gear. Lastly, ‘hot lapping’ can transmit severe heat to the clutch. Though some events require consecutive runs always try to provide sufficient time for the clutch to cool. Focus on making quality runs rather than quantity. To understand the basics of Ram’s billet drag racing clutch systems click here. Source: RAM Automotive Company 201 Business Park Blvd. Columbia, SC 29203 Telephone (803) 788-6034 www.ramclutches.com...
Tips on inspecting the multi-disc oval track racing clutch

Tips on inspecting the multi-disc oval track racing clutch

By Jim Mozart, Photos by Moore Good Ink: Commonly, multi-disc racing clutches vary from 4.25in to 7.25in. Racers often favor the smallest diameter clutches available because they believe an advantage can be found in its lighter rotating mass. Yet experience demonstrates that smallness rarely makes an appreciable difference—except in diminishing the clutch’s durability. Some clutch makers fervently believe that the slightly larger diameter clutch with thicker friction materials can withstand much more abuse than its smaller counterpart. Constant racing starts, for example, on a small unit can result in severe wear. Such doctrine is firmly held by Ram, the Columbia, SC long-time racing clutch maker. Monitoring the condition of the multi-plate racing clutch is an essential yet simple operation. When replacing the friction discs during servicing, renew the full pack and ensure the pads are in vertical alignment to apply the clamp load evenly down though the pack. Also, oils and grease cause slippage and damage to clutch components. Always check the oil pan and main seals. Here is how Ram checks their 6.25in Assault Weapon.  Source RAM Clutches 201 Business Park Blvd. Columbia, SC 29203 Telephone (803) 788-6034...
Of five major threats to a clutch system, what would you consider the most forbidding?

Of five major threats to a clutch system, what would you consider the most forbidding?

Archie Bosman: As you sit quietly reading these lines, a whirl of activity is taking place in the bell housing. Let’s imagine for a moment the clutch assembly could express its greatest anxiety, what might it be? Might it be the use of excessively harsh friction compounds on the clutch discs or inadequate clamping forces causing slippage? Perhaps, extremely sticky tires are the main threat? Enumerating the cardinal sins: Apparently ‘no’, according to Ram Clutches none of these represent its greatest fear…its principal concern would be mass—that is the weight of the car carried into motion by the clutch. A heavier vehicle imposes a greater load on the clutch system than a lighter one. Further perils include poor gearing, improper flywheel mass and, indeed, sticky tires. A high performance car with an inadvisably high rear-gear requires more manipulating of the clutch pedal to prevent it from slipping than one with a lower gear. A higher first gear (lower numerically) is also problematic as it, too, imposes a greater load on takeoff and, furthermore, can be detrimental to the clutch even when it is fully engaged. Linked closely with high first-gear ratio deficiencies is the flywheel. The purpose of the flywheel is to create inertia, which refers to preserving a state of uniform motion that helps to get the car moving. A heavier flywheel generates more inertia and thus makes it easier to accelerate from standstill. It also reduces clutch slipping on takeoff. On the other hand, with a properly geared vehicle, that is one with an appropriately low gear that invites the use of a light flywheel, it will...
2015 Mustang upgrade: the trouble with supercharging

2015 Mustang upgrade: the trouble with supercharging

By Sam Logan: Adrian Gomez, an industrious 27-year old who manages Mak Performance, a Miami specialty shop established in 1995, bought a 2015 Mustang 5.0 and with fewer than 7,000 miles on the clock installed a Pro Charger centrifugal supercharger. It extended the Mustang’s power output at the rear wheels from 376hp to 600hp, an impressive 60 percent improvement. With one of the two vital ingredients in place—225 additional horsepower—he decided that instead of fulfilling the role as a drag race spectator at the NMRA season opener at Bradenton, he would present himself as an entrant in the True Street class. This leads us to the second vital ingredient—the clutch. Doubtless it was tempting to ascertain just how long the original factory clutch might support the additional horsepower…and it didn’t take long to find out. The car slipped the clutch on the first pass, running an Elapsed Time of 11.97 seconds over the quarter-mile distance and by the third pass it had overheated and was on the road to ruin. Undaunted the intrepid young Gomez limped back to Miami where he would replace the failed clutch system with a twin-disc clutch-flywheel set-up. His objectives were to acquire better friction materials, 2,400psi of clamping force and an easy clutch pedal feel for stop-start traffic conditions. For all of that, there is no intrinsic weakness in the original equipment Mustang’s clutch arrangement. It is just that it was neither designed to transmit 60 percent additional horsepower nor to transmit it via twenty-nine-inch diameter Mickey Thompson Drag Radials. Nonetheless, its street-driving capacity contrasts starkly with Ram’s Force 10.5 dual-disc clutch-flywheel arrangement, which...
Cure for uncomfortably high clutch pedal on late-model street cars

Cure for uncomfortably high clutch pedal on late-model street cars

By Sam Logan: Most late-model street vehicles use an internal hydraulic clutch release bearing, sometimes called a concentric slave cylinder (CSC). Yet, unfathomably, many of them suffer from clutch engagement high on the pedal travel. For most drivers, this is not comfortable. Conveniently, Ram Clutches has introduced a pedal-height adjuster, which is situated inline between the hydraulic master cylinder and the slave cylinder. It is in effect, an accumulator in which a piston and spring are housed. When the adjustment screw is turned in to its fullest extent, the piston cannot move and the adjuster is bypassed. In fact, this is the condition in which the system should be re-bled. As the adjustment screw is turned out and the pedal depressed, the fluid flows into the adjuster and pushes the piston back. Once the cylinder is full, the remaining fluid is routed to the hydraulic bearing. This essentially introduces free-play to the pedal travel and lowers the point where the clutch engages, allowing the driver to adjust the pedal to the most comfortable driving position. A lower pedal also quickens clutch response. A bonus feature of this adjuster is its ability to control the travel distance of the release bearing. This prevents over-travel of the clutch fingers, which can lead to clutch malfunction at higher engine RPM. Applying the pedal-height adjuster’s resourcefulness to the competition clutch Also worth noting, original equipment manufacturers use pre-loaded release bearings that are in constant contact with the clutch’s diaphragm fingers while competition-style bearing makers do not. By contrast they seek maximum clutch clamping force and, therefore, require some free-play between the clutch release...
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