By Mike Garrison
Following the announcement early this morning that the R1 Wurks V21 motors will remain on the approval list (CLICK HERE to read), ROAR has issued a clarification of rules for the stator laminate shape in brushless motors.
Announcement from ROAR Racing:
CLARIFICATION of RULES for STATOR LAMINATE SHAPE in BRUSHLESS MOTORS.
Investigations by BRCA, EFRA and ROAR have determined that after removing the hysol or epoxy coating from the end laminates of various brushless motors, the ‘sharp edge’ on the winding web of the end laminates had been removed to various amounts.
BRCA, EFRA and ROAR have been working closely together during recent weeks to ascertain the degree of deburring/chamfering that exists. It can be a difficult task to find that this procedure has been done, as the end laminates are coated with hysol or epoxy, which can be difficult to remove without affecting the metal edges. We have found that this procedure varies between manufacturers and also between motors of the same type.
Current rules of the above organisations call for all laminations in the stator stack to have the “same overall shape” but provide no guidance on the degree to which sharp edges can be removed. However; normal engineering and manufacturing practices would recognise that ‘removal of sharp edges’ is acceptable.
In order to provide objective, measurable guidance to manufacturers; the organizations have agreed to issue a joint clarification of the rule. This makes it clear that any process to remove sharp edges must be confined to the top and bottom laminate in the stack and cannot affect the thickness of the laminate or the width of the wire winding web. This effectively limits the edge treatment to a thickness or depth of no more than 0.3 – 0.4mm (0.011-0.016in).
The joint clarification states:
"BRCA, EFRA and ROAR hereby jointly announce a clarification in the requirement that the laminations in the stator stack of brushless motors must have the “same overall shape”.
There have been differing interpretations of this rule and confusion with respect to the degree of deburring or chamfering allowed on the end laminations where the wire is wrapped around the stator legs or webs. Recent checks of samples sent for motor approval (current and past) and motors in the field reveal varying degrees of edge treatments from gentle deburring to ground chamfers.
Effective immediately; the top and bottom laminate in the stator stack of brushless motors made to the rules of the respective organisations may be deburred or chamfered only on the wire winding web/leg so long as the overall thickness of these end laminates is the same as other laminates in the stack and so long as the measured width of the wire winding leg or web of these end laminates is the same as other laminates in the stack. This requirement effectively restricts any deburring or chamfering to only the top and bottom laminates in the stack."