Thursday, August 13, 2009
New BWA Motor and Pinions
BWA has developed an FC-130 style motor intended for low-power racing, with performance similar to the Ninco NC1. Two sample motors are above, the plastic endbell showing on the left, and the metal can end showing on the right. Holes are tapped in the can end for 2mm screws, to provide a secure mount. Shafts are long on both ends to allow mounting in a variety of existing chassis.
Brass pinions have also been added to the BWA line, bored for the standard 2mm shafts, and 1.5mm shafts of the slim can (FF-050) which BWA also makes for lower-power racing. Tooth counts are 8, 9, and 10 for both shaft sizes. The diameter of the pinions increases as tooth count goes up, so smooth mesh may be achieved with standard 50 module pitch crown gears (such as Slot.It) by adjusting the mesh with spacers on the axle. Pinion diameters are 5mm (8 tooth), 5.4mm (9 tooth) and 6mm (10 tooth). These pinions are precisely bored to be a slip fit on the shafts. BWA advises fixing them with Loctite Red 262, with a drop applied to the inside of the pinion first.
Bench testing the new motors was done to determine RPM, torque, and maximum power capability. Five samples were tested, with no-load RPM at 12 volts, reading from 13,832 to 14,275 RPM. The motors were closely grouped in this narrow range, with an average of 14,103 RPM.
Torque was assessed at stall for two motors, showing 110 gcm for one and 115 gcm for the other. Each motor was measured nine times around a single armature revolution, using a 1 cm lever arm pushing on a gram scale at 4 volts; the readings were then averaged, and multiplied by 3 to derive 12 volt stall torque estimates.
Based on maximum RPM and maximum torque measurements, maximum motor output power was computed using the formula described on the Slot Car News Motor List. 3.9 Watts was obtained for the motor which had measured 13,832 RPM and 115 gcm; 4.0 Watts was obtained for the motor which had recorded 14,240 RPM and 110 gcm.
Comparison to the Ninco NC1 shows the BWA ahead by a nose. We have tested the NC1 in the range of 12,858 to 14,237 RPM/12v (about 12 motors) with stall torque at 77gcm/12v (one motor). Approximately 35 more gcm of torque at the bottom end should make the BWA motor feel a bit more snappy off the line, but not so much that the venerable NC1 won't be competitive. At mid and high end RPM, the BWA motors should provide the same driving feel as the NC1.
Big thanks to Al of BWA for sending Slot Car News the sample motors and pinions. There has long been a need for a reasonably priced, lower-power motor in standard FC-130 configuration, and at $4.00 per motor, the price is not just reasonable but great. The earlier BWA FF-050 slim can remains in stock (tested by SCN at 14,145-14,702 RPM/12v, and 63-71 gcm/12v).
At $1.00 each for the pinions, which can be had to fit FF-050 slim-can motors, as well as standard-can FC-130 motors, slot car builders now have the parts they need to complete their vintage and other low-power slot cars.
BWA parts are sold through the BWA web site only, at: www.bwaslotcars.com