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Frequently Asked Questions |
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Sprockets, gears or drivers? Kart clutches use sprockets. Not gears. Not drivers.
Air Gap? Vortex and Bullet clutches do not have an air gap specification. Air gap adjustments are a "patch" for poor spring design. The torsion spring in the Vortex clutch and compression spring in the Bullet clutch were designed specifically for kart racing. Note that SMC spring dimensions are very different from those used in other clutches. They are not common hardware store springs. Air gap sensitivity has been "engineered out" of SMC clutches.What is the main difference between the SMC Bullet and SMC Vortex? The Vortex spring is attached directly to the lever. There is no pressure plate. The Bullet spring is attached to a pressure plate.Which clutch is faster, SMC Bullet or SMC Vortex? The Vortex clutch is potentially faster but we have intentionally held back on its acceleration to make it equal to the Bullet clutch. Other differences? The Vortex can be adjusted easier and repaired faster. The Bullet works well with a greater variety of engines. Will brake cleaner damage SMC clutch discs? The friction material used in SMC clutch discs is the same material used in high performance brake pads. Brake cleaner will not damage the SMC clutch disc. Use compressed air to help remove dirt and evaporate the brake cleaner. Carburetor cleaner, gasoline, kerosene or similar solvents are not recommended because they leave a harmful residue. What is the recommended sprocket bearing lubricant? Mineral based oil such as common SAE 30 weight motor oil is preferred. Excess oil can find its way to the clutch discs. If the lubricant is mineral based motor oil, it will burn off at approximately 350F degrees which is within the normal operating temperature of the clutch. Greases and oils containing silicone or Teflon have a higher oxidation temperature that prevent burn off. Consequently such lubricants are NOT recommended. How much oil does the sprocket bearing require? Only a few drops of oil will do. The bearing is capable of a 2500 pound dynamic load and 14,000 rpm. It's obviously over-designed for racing. What causes sprocket bearing failure? Dirt, chain misalignment, inadequate lubrication and other problems will cause the rollers to slide rather than roll. This additional friction generates enough heat to damage even steel parts. What causes bearings to "walk out" of the sprocket? There are numerous possible causes including the following:
Why don't SMC drums have lightening/cooling holes? Holes save very little weight but they do admit chain oil and dirt, disrupt air flow and waste horsepower. Why doesn't SMC make steel drums? Aluminum dissipates heat five times faster than steel. That's a much, much bigger advantage than the extra durability of steel. What can I do to make a Vortex clutch hit harder? There's nothing that you can do. A hard hitting clutch is a function of the pressure plate design and a Vortex clutch has no pressure plate. Is there an advantage to a clutch that hits hard? Yes. It causes clutches and tires to wear out quickly thus making manufacturers and kart shop owners very wealthy. It is not faster. See Speed Secrets page for a detailed explanation.Is there an advantage to a clutch that engages smoothly? Yes. It accelerates faster because energy is extracted from the engine at a controlled rate. There are four strokes per cycle in the typical kart racing engine. Three strokes consume energy (exhaust, intake, compression) and one stroke (expansion) produces energy. It is possible for the clutch to extract energy from the engine too quickly (hit hard). The engine has little remaining energy to fully power the exhaust, intake and compression strokes and consequently loses rpm ("bogging" or hesitation). In contrast, a clutch that engages smoothly exacts less energy per cycle but has many more cycles. It multiplies out to more total energy i.e. greater acceleration. What is hysteresis? "His-ta'-ree-sis" is the difference in engine speeds when the clutch engages and disengages. For example, an average clutch on an accelerating engine will engage at 4000 rpm. When slowing down from high speed the same clutch will disengage at 3500 rpm. This clutch has 500 rpm (4000 rpm-3500 rpm) of hysteresis. Why is hysteresis important? A clutch with less hysteresis will accelerate the kart faster. What causes hysteresis in a
disc clutch? There are
several causes. The most serious
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Structure Mechanics Corporation 513- 598-1600 |