July 20, 2017

In February 2017 ROAR formally began a process of updating rules for brushless electric motors by asking for input from Affiliate Members who manufacture and/or import these motors. At that time ROAR stated that the objectives for the update included but were not limited to: stabilizing the performance level in classes using spec wind motors, improving availability, clarifying maximum price requirements, clarifying what changes were permitted to motors by members and clarifying when motors had to be resubmitted for approval.

Following a comment period using the private Affiliate Forum on, ROAR then published notice of a number of specific proposed changes to the brushless motor rules to our Affiliates on May 1, 2017.  Our policy is to allow a minimum of 30 days for comment from our Affiliate Members (manufacturers) on those specific changes. This comment period has now expired.

The result of this process of consultation with manufacturers and industry experts is a complete re-write of Section 8.4 of the ROAR Rule Book. A complete re-write made it easier to lay out the changes in a manner where they could be more easily understood. These changes will take effect on October 1, 2017 unless otherwise specified in the rules themselves.

The key changes in this re-write include:

1 – Establishing a minimum resistance for approval purposes for each spec wind listed in the rules. These minimums are to be based on the best motor of each wind submitted and approved prior to September 1, 2017. Following that date, motors below the final published minimums will not be approved. Consideration was given to selecting a resistance for each motor which was higher than the best motors already approved in order to “roll back” performance levels to an earlier level. This would have resulted in motors already in the possession of members becoming illegal. Trying to turn back the clock is often appealing but seldom works well. In the end, we accepted that the minimum resistance would have to be a moving target to accommodate motors already in the manufacturing pipeline. Once the final numbers are established on September 1st we expect that future motor submissions will quickly converge on those numbers.

2 – Establishing a policy of publishing the minimum resistance obtained for each brand and model of motor during the approval process. These published numbers will then become the basis for inspection at events. Each brand / model motor will be compared to the resistance results for that brand /model motor obtained during the approval process. Consideration was given to simply using the minimum resistance number for a particular wind for event inspection. However, this would have allowed for the possibility of modifications to motors submitted with a relatively high resistance number to bring them to the minimum and would have created the possibility of running a motor modified to have 16.5 turns and a legal resistance against 17.5 turn motors for instance.

3 – The rule revisions make it clear that the maximum allowable price for approved motors applies to all variants sold by the original manufacturer / importer including tuned or select motors. The revisions also make it clear that the penalty for exceeding the maximum price will be removal of the motor from the list of approved motors.

4 – Changes have been made to “availability requirements” and motors may be submitted for approval prior to having the volume available to comply with the availability requirements. These changes are being made in order to increase the likelihood that an approved motor is readily available to all members.

5 – A number of provisions were made to permit easier inspection and identification of motors during the approval process and at events.

6 – Allowable “modifications” and substitutions to approved motors have been specified.

7- A list of changes by the manufacturer which require re-submission for approval has been included.

8 – Due to a rule change originally made in 2009, 540 modified motors have been implicitly allowed to have 4 pole rotors since that time. Several such motors were approved following that change and remain on the approval list. At some point a practice of listing these motors as “4X4 SCT” motors was adopted although no such classification exists in the actual rules. This rule revision explicitly allows 4 pole 540 motors as modified motors for classes other than 4x4 SCT and includes specifications for these motors.

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