Rewinding via Splicing Brushless motors

Hey chiefdelphi.com. I was looking at how motors are made and had a super silly idea.

As those familiar with the topic may know, the windings of a brushless motor are directly connected to the output wires. It’s actually pretty difficult to tell the two apart sometimes. If there’s no distinction, would rewinding a motor fall under

“The electrical leads may be trimmed to length as necessary and connectors or splices to
additional wiring may be added”

found in R28?

If there’s no standard on when a wire “ends” and a winding “begins” are we safe to “trim and splice” magnet wire in to out shiny new falcons?

If someone Q&A’s this it WILL be ruled illegal, so please don’t try it.

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If you already know Q&A will rule it illegal, doesn’t that answer your question already?

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But like why

I will also point out that FIRST has definitely done things based on CD discussions in the past. By posting this thread, it’s probably already too late.

To answer the OP’s question, I don’t think it’s legal anyway since R28 does not cover modifying the way a motor is wound or the way the wires inside connect to each other. I also think it’s safe to assume that the motor windings aren’t “leads” as the case would reasonably define that boundary. Technically, the Falcon 500 doesn’t even have any motor leads at all either, the only exposed leads come from the integrated controller.

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For the brushless motors where the output wires are directly connected to the motor windings, it should be pretty easy to distinguish the output wires from the motor windings. The motor windings are very typically some sort of solid, single conductor with a thin enamel coating, usually brownish in colour. The output wires will be some sort of multi-strand conductor with some sort of coloured PVC or silicone insulation extruded over the conductor. The solder joint between the output wire and the motor winding would also be pretty obvious if the motor is disassembled.

If one changes the motor windings without having done the appropriate calculations, it is likely that the motor performance will be lower than the original.

I think the distinction is a little bit more subtle than you think. I’ve seen several hobby motors where the tails of the winding. Without actually tearing down a NEO, there’s no way to determine the actual makeup of the lead ((although I suspect they would be soldered, it’s still very possible that it is not). I am however very certain that any motor in FRC would have more than “solid, single conductor”. NEOs are 12 slot motors, and will have at least three winding wires per phase lead.

Reasonably, but a literal interpretation of the rules would make this legal.

Touché. Although (more) legally questionable, a simple retermination from a delta winding to wye winding would allow for use in different cases without affecting power.

With any FRC legal motor it will be very apparent where the external lead wire ends and where the magnet wire starts. All the motors I have ever seen opened up use magnet wire in the windings, regardless of the number of windings. This includes brushed and brushless DC motors (including NEO’s and Falcons) as well as AC motors at a previous employer where they were designed and manufactured. Magnet wire is typically a single conductor with the thin enamel insulation since it allows one to pack more copper into a smaller space. Motors with external leads, like the NEO, use stranded wire for the external leads since magnet wire is too stiff and the insulation on it is too easily damaged.

Please note that when I referred to multi-strand wire, it means multiple strands twisted together. The 12 windings in a NEO are each a separate, single wire and would not be considered a multi-strand wire when a number of them are twisted together.

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