13.5 & 10.5 BRUSHLESS MOTORS FOR SPEC RACING B.R.C.A.

BRUSHLESS MOTORS FOR ‘SPEC.’ CLASS RACING.
With the continued development of Brushless motors during the last year, the BRCA Electric Board have recognised that there is a requirement for creating rules to allow Brushless motors to be used for ‘Spec.’ Class racing. As with the rules for ‘Stock’ Brushed motors, the following rules are designed to give motors that have similar power characteristics from the various manufacturers. As the power characteristics of a Brushless motor differs from a Brushed motor, it does not follow that motors complying with the specifications below are equivalents of the current Brushed 27T & 19T motors. The 13.5T Brushless, when used with a sintered rotor is certainly not equivalent to 27T Brushed versions.
The BRCA (EB) has been liaising with various manufacturers that have been working to establish a set of rules that define the ‘Spec’ Classes for Brushless motors. The same basic specifications will cover the various winds and are likely to be adopted by other International organisations. The rules differ from the Modified Brushless Class in that the wire sizes are specified and the size of the magnetic rotor is more specific, to give a volume of magnetic material which is more constant. Only sensored motors are allowed.
It is known that the technology of Brushless motors allows the ESC to give varying timing settings. The following rules only cover the build specification of the motors.
Motors built to the specifications below will share most of the component parts from the current Modified Brushless motors. The Electric Sections within the (EB) agreed that using a motor with a higher ‘build standard’ would be more cost effective. Therefore the price limit is similar.
10. Rules - Spec. Brushless Motors (13.5T and 10.5T ‘wind’ limit)
The following rules have been agreed by various International organisations. Any further amendments/additions that are found necessary will be published by the EB on the BRCA website.
10.1 Only sensored motors are allowed in the Spec. classes.
10.2 The motor has to be rebuildable. Ball bearings are allowed. The motor must be constructed to allow easy replacement of the; rotor, bearings and front End-Bell.
10.3 Sensor connection requirements:-
The motor must use a six-position JST ZH connector model number ZHR-6 or equivalent connector with 6 JST part number SZH-002T-P0.5 26-28 awg. contacts or equivalent. Wire sequence must be as follows: - Pin #1 - Black wire ground potential Pin #2 - Orange wire phase C Pin #3 - White wire phase B Pin #4 - Green wire phase A Pin #5 - Blue wire temp control, 10 k Thermistor referenced to ground potential Pin #6 - Red wire + 5.0 volts d.c. +/- 10%. Compatible speed control must use the 6 position JST header part number X-6B-ZR-SMX-TF (where the X denotes the style of the header), or equivalent. The motor power connectors have to be clearly marked A, B, C. A for phase A. B for phase B. C for phase C
It is not mandatory that sensored Speed Controls have to be used, or that the sensor ‘harness’ has to be connected.
10.4 The Can. (Based on `05` size specifications). The overall dimensions of the assembled motor do not include: - solder tabs, lead wires or the original manufacturer’s logo or name. Overall maximum diameter is 36.02mm measured at whatever point yields the maximum dimension. Overall minimum diameter is 34.0mm measured at whatever point yields the minimum dimension. Maximum length is 53.0mm measured from the mounting face of the motor to the furthest point of the end bell. Minimum length is 50.0mm measured from the mounting face of the motor to the furthest point of the end bell. Motor mounting holes must be on nominal 25.0/25.4mm centres.
10.5 The Stack/Stator: Slot-less stators are not allowed. The stator must be continuous laminations having the same overall shape, being one after the other without anything in between. The laminations must be of one homogeneous material without cut-outs, holes or hollow sections other than for the three slots of copper coil wires and the three grooves for the screws used to hold the entire assembly together. Stator minimum length 19.3mm, maximum 21.0mm. The thickness of the stator laminations is 0.35 +/- 0.05mm. The Inside diameter of the stator must accept a ‘plug gauge’ of 14.50mm +0/-.005 diameter, clearing the stator, plus its windings and the electrical collection ring at any end of the stator.
10.6 The Winding: Only three slot (phase) “Y” (star) wound stators are allowed. No delta wound stators allowed. Only circular (round) pure copper magnet wire permitted. The three slotted stator must be wound with: - 13.5T Class: - 13.5 turns of 2 x 21 awg. (or 0.71mm), & 2 x 23 awg. (or 0.56mm). 10.5T Class: - 10.5 turns of 2 x 20 awg. (or 0.80mm), & 2 x 22 awg. (or 0.65mm)
10.7 The Rotor: Shaft diameter must be 3.175mm where the pinion gear locates. Only one piece, two pole Neodymium bonded or sintered, or Ferrite (ceramic) magnetic rotors are permitted. Magnet length will be 25.00 +/- 1.00mm, not including any non-magnetic balancing aids. Magnet outside diameter will be 12.20/12.51mm (min./max. with no further tolerance) for the entire length of the magnet. The shaft outside diameter where the magnet is mounted will be 7.25mm +/- 0.15mm, with this diameter extending beyond the magnet to facilitate measurement.
10.8 All motors must have the original manufacturer’s logo or name moulded/engraved into the end bell. A unique marking or feature that is difficult to remove must be incorporated into the assembled motor to identify the motor is either a 13.5T or 10.5T Spec. class motor.
10.9 Price limit: The maximum retail price limit for the above motors for 2008 will be £75.00
NOTE: The above rules form the basis for Brushless Spec. motors for the 2008 season. If it is found that variations of these motors from different manufacturers, give large differences in performance, then electrical tests may be adopted.
BRCA Electric Board. 14.02.08 (06.03.08 – 10.3, Sensor requirements clarified).