【正文】 1. baseplate, 2. bearing housing with ball joint bearing, 3. main axle, 4. lever arm, 5. beam, for brake caliper fixation, 7. brake caliper, 8. holderupThe lever arm assembly is the main assembly which allows measuring the brake torque. The brake caliper is placed via adapter on the long lever arm (Fig. 5。 mounting construction, 7. hub with mounted brake disc, 8. direction change for the wire rope, 9. brake lever, key, 11. water reservoir to collect splash water, 12. lever arm assemblyThe hand force is produced with a Fluidic Muscle (Festo AG amp。hler GmbH, Weisse Breite 7, 49084 Osnabruck, Germany), an average pulling velocity of the brake lever under resistingforce of the brake system was found to be . Three different subjects were tested with the advice to pull five times as fast and hard as possible. One subject activated the brake with two fingers, two with one. The maximum releasing velocity was between and .3. ConstructionWith the measured values the test bench could be dimensioned. To get an advantage in parison to the outdoor tests, the whole test process has to be precise, guarantee constant conditions, requires a small number of test personnel as well as having a fast throughput. The concept was to use a powerful threephase engine with a worm gear (Fig. 4 , 3 and 4) on whose shaft a hub (Fig. 4, 7) with the brake disc is mounted. The force values are measured with two load cells, one for the hand force and one for the resulting brake force. Controlling is done with a realtime controller system (pactRIO cRIO9073, a real time controller including FPGA) and a LabView2009 application (National Instruments, Austin, TX, USA)Fig. 4 overview of the test bench。heim, Germany) and the camera VDS Vossk252。sseldorf, Germany). These films are indicating applied pressure differences as red color density variations. These films were positioned between the brake pads and the brake disc while applying a force of FH = 100N at the brake lever. The found pressure was about 12Nmm2 The measured pressure multiplied by the pad area, which is pressed against the disc (420mm178。 high values at the beginning and end are from the trigger signal。 additional the wheel radius (rl) is shown.The most important mechanical difference of these two categories (rim and hub brakes) is the acting radius (rr),which is important for the brake torque as shown in Fig. 2. The smaller the acting radius is, the higher the friction force has to be to produce enough brake torque, which decelerates the rider. To get the same brake force, the friction force of a disc brake (rotor diameter 160mm) produced by the friction of the brake pads and the brake disc is about times higher, pared to a rim brake between brake pads and rim to equalize the shorter lever arm. A realistic brake force at the front wheel, when a bicycle rider (80kg) in upright position (it depends on the position and the geometry of the bike) does a rollover, is in the region of about 400N. To produce this brake force, a disc brake with a 160mm rotor needs to produce a friction force of about 1666N. Calculating with a friction coefficient of about , the applied force, which pushes the brake pads against the brake disc must be 3332N. If the rider is heavier and shifts his center of mass backwards, the possible brake forces can rise up to over 700N (measured). This brake force is produced by possible hand forces of about 100150N. Basing on 400N rollover force and an applied hand force of about 80N means, the overall transmission ratio of the brake (mechanical and hydraulic ratio) is about 4045.2. Measurements and results for the dimensioningThe key factors to construct a well designed test bench are the knowledge of the appearing mechanical values, such as the maximum brake torque, the applied hand force and the velocity of the brake lever. To find out these values several measurements took place. To find out the reachable brake torque or brake force, two different approaches were chosen. One was to check the maximum reachable value of the deceleration with the help of a threedimensional acceleration sensor, which was placed on the top tube of the main frame of a mountain bike. The measurement setup was built out of a sensor platform called “Neon” (Spantec GmbH, Gumpendorferstrasse 132/2/5, 1060 Vienna, Austria). This sensor platform does a 10bit a/d conversion and records the data on an SDcard or digitally transmits them via ANT+ wireless munication to a puter. The chosen threedimensional acceleration sensor type was MMA7260Q (Freescale Halbleiter Deutschland GmbH, Schatzbogen 7, D81829 Munich, Germany). Its measurement range was set to +/1,5g.Fig. 3 Acceleration measurement showing a maximal braking when just using the front disc brake (Avid Juicy seven, 203mm rotor) of a mountain bike. Positive values representing deceleration。 a disc brake (hub brake) for mountain bikes mounted by IS2000 standard [2]Brakes for bicycles are categorized by their acting position [3]. This means, if the brake force is applied at the hub of the wheel or at the rim. In Fig. 1 the three most popular brakedesigns are displayed. The left and the middle ones are rim brakes, the right one is a disc brake of the category hub brakes. The one on the left, a single pivot side pull caliper brake, is mostly used for road bikes in a modified version. The brake is mounted by just one canter mounting bolt, which is located directly over the wheel. The Vbrake, shown in the mid picture, is mounted on two bolts, which are fixed on the seat stays or the fork blades left and right from the wheel. On the right hand side, a disc brake is shown, which is mounted by two hex screws on the left fork blade or on the left seat stay, based on the IS2000 [2] standard for bicycle disc brake mounting. Another mon mounting standard is Post mount [2].Fig. 2 parison of the different acting radius (rr) of rim and hub brakes。To get objective