Top Document: Rec.Bicycles Frequently Asked Questions Posting Part 4/5 Previous Document: 8f.14 Roller Head Bearings Next Document: 8f.16 Brake Squeal See reader questions & answers on this topic! - Help others by sharing your knowledge Date: Fri, 11 Jun 1999 14:53:00 PDT Bicycle brakes have changed greatly since the original wagon wheel brake that pressed a skid pad against the tread, but they have also stayed the same, the skid pad brake still being used. The single pivot caliper brake, commonly called the side pull, came along about 100 years ago and is still the mainstay. This brake was displaced by the centerpull, a derivative of a cantilever brake, to take a large part of the sport market in the 1950s. Meanwhile the cantilever brake with its large tire clearance existed only in a limited way until the advent of the mountain bike that demanded this feature for its large tires and the dirt that sticks to them. Recently, other forms have emerged to meet changing demands of the sports bicycling market. Sidepull Until recently, most brakes had a hand lever ratio (mechanical advantage) of 4:1, with a caliper ratio of 1:1, making most brakes and levers interchangeable. The 4:1 ratio struck a convenient compromise between the reach of the hand, its strength, and brake pad clearance to the rim. At higher ratios too much hand movement is used to bring the pads into contact with the rim, a clearance that is necessary to prevent a dragging brake and to take up pad wear. An important feature of the single pivot is that it has practically no position error through its sweep, the pad remaining centered on the rim throughout its wear life. Its main weakness is poor centering (clearance), caused by sliding contact of its return springs. Exposed to road dirt, the sliding springs change their coefficient of friction unpredictably, causing the pads to retract unequally from the rim. To prevent dragging, liberal clearance is required, preventing the use of the higher mechanical advantage desired by today's avocational bicyclists. Centerpull The centerpull brake of the 1950's, was popular for nearly a decade, in spite of being entirely without merit, being worse in all respects than the side pull brake with which it competed. It had the same hand levers and its caliper the same 1:1 mechanical advantage, but had large position error, moving its pads upward into the tire with wear. Its symmetry may have been its main appeal, an aesthetic that people often admire without functional reason. Its acceptance might also have been from dissatisfaction with flimsy sidepull calipers of the time. It used a straddle cable on which the main cable pulled from a flimsy cable anchor attached to the tab washer under the head bearing locknut. Besides its two levers, it had a connecting bridge that flexed in bending and torsion, making it spongy. Although Mafac was one of the greatest proponents of this design it began to vanish on sport bicycles with the introduction of the Campagnolo sidepull brake. Cantilever The cantilever brake offers clearance that fat tires and mud demand. Its pads pivot from cantilever posts on the fork blades, giving it large tire clearance and a fairly rigid action, there being no significant bending elements in its mechanism. Nevertheless it has its drawbacks. Its reaction force spreads and twists the fork blades, something that became more apparent with suspension forks that require a substantial bridge plate to restrain these forces. Its pads sweep downward at about a 45 degree angle giving them such a large position error that, as they wear, they easily pop under the rim, causing unrecoverable brake failure. Its straddle cable is pulled by a main cable that requires a cable anchor that is difficult to accommodate with rear suspension, while the front straddle cable presents a hazard in the event of a main cable failure, because it can fall onto a knobby tire to cause wheel lockup. The cantilever received a large resurgence in popularity on the mountain bike, along with other innovative designs. One of these concepts was the servo brake that had cantilever posts with a steep helix that converted forward drag of its pads to contact force, a dangerous servo effect that re-emerges from time to time. Servo Brake Servo brakes, ones that use pad reaction force to reinforce braking force, have been designed often and without success, mainly because a small change in friction coefficient causes a large change in braking. The servo effect makes the relationship between application force and brake response unpredictable and difficult to control. The servo effect inherent in drum brakes is what caused automobiles and motorcycles to switch to disks. Brake application pressure being at right angles to the rotating disk, prevents any interaction between reaction and application force. For bicycles, that effectively already have disk brakes, introduction of servo effect is illogical. V-brake The V-brake is currently displacing the cantilever brake because it offers the same advantages while solving two critical problems, those of the brake hanger for suspension bicycles and brake pad dive. The cable hanger seems to have been the main goal because early V-brakes had rigidly mounted pads that traveled in the same arc as those of a cantilever. Newer versions use a parallelogram link that keeps pad motion perpendicular to the rim. As usual, these advantages are not gained without drawbacks, such as brake chatter arising from more complex linkage and clearance required for it to work in dirt, and incompatibility with other brakes by its higher mechanical advantage that requires different hand levers. The difference in mechanical advantage has been bridged by third party hardware, one of which is called the "travel agent", that uses a two diameter wheel to change the mechanical advantage to that of common road brake levers. The device can also be used in a 1:1 ratio to replace the elbow tube of the V-brake to reduce sliding friction. Dual Pivot Greater leverage for the same hand motion requires smaller pad-to-rim clearance, that the dual pivot brake achieves by using two pivot points to define a line of action about which its two arms are constrained to move equally and remain centered. Brake centering was essential in reducing the pad-to-rim clearance needed for a mechanical advantages of about 5.6:1. Higher leverage also required compromise. The offset arm (the short one) sweeps its pad upward into the tire so that this pad must be adjusted as it wears. The brake cannot track a crooked wheel with, for instance, a broken spoke, and because it has a high ratio, it does not work at all when the quick release is accidentally left open. And finally, it runs out of hand lever travel 40% faster with pad wear than the former single pivot brake. Its low pad clearance and narrow flange spacing of current wheels make the brake drag when climbing hills standing, so that racers often ride with the rear quick release open. Part of the light feel of the dual pivot brake arises from the lower (reverse) ratio of the caliper, whose springs now no longer exert as strong a return force on the cable and hand lever. Because this force is lower, a return spring has been added to the hand lever, lowering cable return force, that coincidentally reduces cable drag during free motion of the brake (before making contact with the rim). This makes the brake FEEL even more forceful than it is because it has such a light action in neutral. Delta (Campagnolo) For lack of power brakes that motor vehicles have, brakes with variable ratios have been designed for bicycles, one of which was a major blunder for Campagnolo. Campagnolo introduced the Delta brake (aka Modolo Kronos), whose mechanism is an equilateral parallelogram in which a cable draws two opposite corners of a "diamond" together, such that the other two corners expand. The motion can be visualized by placing the tips of the thumbs and forefingers together to form a diamond. Moving the tips of the diamond together at a constant rate demonstrates the progressive nature of the mechanism and the resulting braking action, the brake pads being connected by links to the knuckles as it were. The motion is a tangent function that goes from zero to infinity. An example of this is the motion of the top of a ladder, leaning steeply against a wall, as the foot of the ladder moves away from the wall at a constant rate. At first the the top of the ladder moves imperceptibly, gradually accelerating until, near the bottom, its speed approaches infinity. Although the Delta does not use the extremes of this range, it has this characteristic in contrast to a sidepull brake that has a constant 1:1 ratio throughout its range. Besides its adverse response curve, its pads moved in an upward arc toward the tire similar to a centerpull, which it essentially is. Hydraulic Hydraulic brakes have their own problems of complexity and reliability that keep them in an almost invisible presence in general bicycling. Their advocates insist that they are superior in all respects in spite of their lack of acceptance by the bicycling public at large. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: Rec.Bicycles Frequently Asked Questions Posting Part 4/5 Previous Document: 8f.14 Roller Head Bearings Next Document: 8f.16 Brake Squeal Part1 - Part2 - Part3 - Part4 - Part5 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: iglesias@draco.acs.uci.edu (Mike Iglesias)
Last Update March 27 2014 @ 02:11 PM
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All throughout time, we can see how we have been carefully conditioned to come to this point where we are on the verge of a cashless society. Did you know that the Bible foretold of this event almost 2,000 years ago?
In the last book of the Bible, Revelation 13:16-18, we read,
"He (the false prophet who deceives many by his miracles--Revelation 19:20) causes all, both small and great, rich and poor, free and slave, to receive a mark on their right hand or on their foreheads, and that no one may buy or sell except one who has the mark or the name of the beast, or the number of his name.
Here is wisdom. Let him who has understanding calculate the number of the beast, for it is the number of a man: His number is 666."
Referring to the last generation, this could only be speaking of a cashless society. Why's that? Revelation 13:17 tells us that we cannot buy or sell unless we receive the mark of the beast. If physical money was still in use, we could buy or sell with one another without receiving the mark. This would contradict scripture that states we need the mark to buy or sell!
These verses could not be referring to something purely spiritual as scripture references two physical locations (our right hand or forehead) stating the mark will be on one "OR" the other. If this mark was purely spiritual, it would indicate both places, or one--not one OR the other!
This is where it really starts to come together. It is incredible how accurate the Bible is concerning the implantable RFID microchip. Here is information from someone named Carl Sanders who worked with a team of engineers to help develop this RFID chip:
"Carl Sanders sat in seventeen New World Order meetings with heads-of-state officials such as Henry Kissinger and Bob Gates of the C.I.A. to discuss plans on how to bring about this one-world system. The government commissioned Carl Sanders to design a microchip for identifying and controlling the peoples of the world—a microchip that could be inserted under the skin with a hypodermic needle (a quick, convenient method that would be gradually accepted by society).
Carl Sanders, with a team of engineers behind him, with U.S. grant monies supplied by tax dollars, took on this project and designed a microchip that is powered by a lithium battery, rechargeable through the temperature changes in our skin. Without the knowledge of the Bible (Brother Sanders was not a Christian at the time), these engineers spent one-and-a-half-million dollars doing research on the best and most convenient place to have the microchip inserted.
Guess what? These researchers found that the forehead and the back of the hand (the two places the Bible says the mark will go) are not just the most convenient places, but are also the only viable places for rapid, consistent temperature changes in the skin to recharge the lithium battery. The microchip is approximately seven millimeters in length, .75 millimeters in diameter, about the size of a grain of rice. It is capable of storing pages upon pages of information about you. All your general history, work history, criminal record, health history, and financial data can be stored on this chip.
Brother Sanders believes that this microchip, which he regretfully helped design, is the “mark” spoken about in Revelation 13:16–18. The original Greek word for “mark” is “charagma,” which means a “scratch or etching.” It is also interesting to note that the number 666 is actually a word in the original Greek. The word is “chi xi stigma,” with the last part, “stigma,” also meaning “to stick or prick.” Carl believes this is referring to a hypodermic needle when they poke into the skin to inject the microchip."
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