Banned, then indispensable: Yokomo's gyro rule, 2012 to 2017

The earliest firm evidence in this material is Yokomo's technical rules for the Special Round held 15–16 December 2012, captured on 22 January 2013.

Rule 7 prohibits "drift assist systems, gyros, or any other electronic device that can be used as an automatic driving aid". The same rule set is tight elsewhere too: it requires the Zero One R2 (ZR-DR04) tyre and Yokomo drift motors only. This is a spec-controlled class, and the gyro is written into the same paragraph of control as everything else.

The wording matters for how the part was understood in 2012. "Automatic driving aid" is not how the scene describes a gyro now — a gyro measures yaw and applies counter-steer correction to the servo while the driver still initiates, picks the line and holds proximity — but it is the language Yokomo's own rule used at the time.

Two years later the position is unchanged and, if anything, more specific. Yokomo's entry form for the 15 February 2015 meeting, dated 26 December 2014 and captured 19 March 2015, bans gyros and also bans receivers with a built-in gyro. Which receivers were meant is not stated on the form.

Yokomo was not alone. Red RC's 18 June 2014 item on Sanwa's SGS-01C drift gyro — a product sold for drift, from a radio maker the scene still buys from — carries a caution to buyers about where it can be used.

A note on what is not evidence: D1-10's published rules, captured on 28 March 2012 and again on 24 May 2016, do not mention gyros either way. Silence is silence. It does not show permission, and it should not be read as a second scene running a different rule.

The turn appears in two Yokomo documents from early 2016, and it appears attached to a class rather than to a change of heart about the whole meeting.

The entry form for the 12 March 2016 meeting is dated 22 January 2016. In it, gyros are permitted in the RWD class and described as recommended for beginners. They remain banned in the 4WD classes. Both rules sit on the same sheet.

A notice dated 29 February 2016 on the same meeting's page sets out what the new class is: a RWD (2WD) class with open regulations that admit cars from other makers. For a series that had been specifying its own tyre and its own motors four years earlier, that is the larger structural change, and the gyro permission arrives inside it.

What the documents do not contain is a reason. Yokomo published the rule, not an explanation of it.

Five months after the RWD class was announced, Yokomo's own dealer order sheet dated 24 June 2016 (captured 15 November 2016) launches two gyros: the YG-302 at ¥4,300 and the RPG-302 at ¥5,200, both listed before tax on that sheet.

The copy is where the reversal is plainest. The sheet calls a steering gyro 欠かせない存在 — indispensable — for the RWD class, states that the gyros were developed for 2WD RC drift, and says the YD-2s at the June 2016 D1-10 world championship ran the RPG-302. Within four years, the same company's paperwork moves the gyro from a banned automatic driving aid to a part it describes as indispensable and sells to its dealers.

Those prices are what the June 2016 order sheet lists. They are not a guide to what anything costs now.

The last document in this sequence is Yokomo's entry form dated 25 January 2017, captured that June. The Entry class rule reads "gyros: permitted (any maker)".

That phrasing closes the loop in two ways. The part is allowed, and the open-regulation logic of the 2016 RWD class has reached the wording: Yokomo is no longer specifying whose gyro, in the same way it had once specified whose tyre and whose motor.

• 15–16 December 2012 — Special Round technical rules. Rule 7 bans gyros and drift assist systems; Zero One R2 (ZR-DR04) tyre and Yokomo drift motors required.
• 18 June 2014 — Red RC reports Sanwa's SGS-01C drift gyro and warns buyers that many tracks and series ban gyros.
• 26 December 2014 — entry form for the 15 February 2015 meeting bans gyros and receivers with a built-in gyro.
• 22 January 2016 — entry form for the 12 March 2016 meeting permits gyros in the RWD class, recommended for beginners; still banned in the 4WD classes.
• 29 February 2016 — notice establishing the RWD (2WD) class with open regulations admitting non-Yokomo cars.
• 24 June 2016 — order sheet launches the YG-302 (¥4,300) and RPG-302 (¥5,200), before tax, calling a steering gyro indispensable for the RWD class.
• 25 January 2017 — entry form; Entry class rule reads "gyros: permitted (any maker)".

Three things stay open, and they should be left open.

Which gyro was first used or sold for RC drift is not established by any document here, and no product in this story can be called the first. Why Yokomo changed the rule is not in the paperwork — the documents record that it changed, in what order, and in which class. Which receivers with a built-in gyro the December 2014 entry form meant is not named on the form.

A date circulates in secondhand accounts that gyros taken from model aircraft were in use in RC drift from around 2012. No primary source supports it in this material, so treat it as unverified rather than as the start of the story.

Two things from this sequence are still visible in a 1/10 RWD car on a P-tile or carpet layout.

The first is the pairing. In Yokomo's paperwork, the open RWD class and the permitted gyro arrive together, five months before the company's own units were on the dealer sheet. The 4WD classes kept the ban in the same season. Whatever the reasoning was, the rule moved as RWD moved, not before it.

The second is the vocabulary. The 2012 rule's phrase, "automatic driving aid", did not survive; the 2016 order sheet's word for the same part, indispensable, effectively did. That is the shift worth holding onto — not that a device was legalised, but that a spec-controlled AWD-era rule book had to write a new class before it had anywhere to put it.