Tamiya Motor and Gear Box KitMotor and Gear Box SpecificationsNotes on Assembling the Gear Box from the Tamiya Kit:Design Notes for using the Tamiya Kit:Notes on Using Batteries and Connections:Tamiya Motor and Gear Box Kit Specifications | Assembly Notes | Design Notes | Electrical Notes | Torque Curves Motor and Gear Box Specifications Manufacturer: Mabuchi Motors at http://www.mabuchi-motor.co.jp/english/ Part Number: RC-260RA-18130 Operating Voltage: 6V Mabuchi Motor Torque Speed Curve: (Click for a bigger version) Operating Characteristics of Raw Motor: Current 0.17 A No Load Speed 13,600 rpm Current 0.67 A Speed 10,840 A Torque 1.71 mN-m Max Efficiency Power 1.94 W Stall Torque8.44 mN-mCurrent 2.62 A Operating Characteristics with Gear Box Installed: Gear Ratio RPM at No Load Stall Torque (N-m) 16 1438 0.05 20 1180 0.051 25 1015 0.0813 100 251 0.29 400 62 0.12 Physical Geometry: Number of Mounting Holes - 4 Output Shaft - Circular shaft with 4mm diameter Overall Length - 3.6 inches with all four gears installed. Subtract 5/16 inches for each gear removed. Overall Width: 1.4375 inches Top Notes on Assembling the Gear Box from the Tamiya Kit: 1. Some of the plastic parts come connected on a thin plastic frame. At the points that the parts connect to the framework, little bits of plastic will remain when you remove the parts from the frame. It is important that you carefully trim off whatever plastic remains on the parts when building the motor. If you do not remove these little nubs of plastic, the motor may not assemble properly and may not run. 2. While assembling the gear box, make sure to align the lines on the outside of the gray gear box parts. 3. On the interface between the last arm gear and the output shaft, there is a thin metallic plate. This plate has three flanges which mesh with small notches on the arm gear. The internal gear teeth in the center of the arm gear connecto a small metal cylinder. At high torques, the small flanges and the metal cylinder are not sufficient to transfer the torque and will slip. To stop this slippage, the arm gear surface must be epoxied to the thin metallic plate. It is recommended that you determine your gear ratios before epoxying these parts.4. The three screws that secure the gear box should be tight. However, if the motor doesn’t function properly with tighscrews, then something is wrong in the assembly. Disassemble the unit and reassemble it. 5. Inside each box for the Tamiya kit, there is a little blue tube of lube. It is important that you use this lube inside yougear box. Without the lube, the friction in between the gears will increase, your gear box efficiency will decrease, and your power requirements will increase. Top Design Notes for using the Tamiya Kit: 1. To connect the output shaft of the gear box to a separate rotating shaft, create a new circular shaft with the external diameter of your design and a 4 mm internal diameter. Then add a 2 mm bore to the new shaft and use a key to mesboth shafts. This extra shaft spacer can be used to increase the size of the output shaft to interface the motor with thcoupling to your machine. 2. Do not directly couple the motor or gear box shaft directly to a load. Your design should include a coupling to allowfor misalignment between the shafts and reduce the impact of any loads to the gear box. A piece of Tygon tubing cbe used to make a flexible coupling. The right handed gear box can also be built to provide a coupling between the load and the motor.3. Use ball bearings if needed to reduce friction. They can make a large difference in the required current. In the torqvs. current curves shown below, the use of ball bearings causes a drop in the maximum current use 2.5 amps. Remember - you must justify the use of ball bearings to your section instructor. Top Notes on Using Batteries and Connections: 1. Students must supply their own AA battery cells. Remember to have enough new batteries on hand to run your machine through the final contest. Also, remember that batteries do have a shelf life and will not provide as much power if they have been sitting on your shelf for several months. 2. Use female spade connectors to make electrical connections. Do not solder directly to electrical contacts. 3. If you want to solder a wire to a battery, you have to roughen the battery's surface first. Use a file to do this. 4. Power supplies will be available in lab for testing motors. These supplies can supply more than the recommended 6volts. Be careful that you don't put a large amount of voltage into the motor for a long period of time. Also, the power supplies can provide huge amounts of current compared to what the motors can handle. Again, be careful thathe current going to your motor stays low or you will destroy your motor. There will also be a multimeter in the labto assist in reading the current output of the power supplies. Motors that are destroyed by abuse will not be replaced5. For the competition, the battery holder must be altered to change from 8 AA cells in series into two parallel sets of four AA cells in series. This will provide your machine with 6 Volts. To make this change, the internal connectionthe fourth series cell must by cut.Top NOTE: Torque curves for the Tamiya Kit are available on the Torque Curves