# Aurora Crown Gears



## Grandcheapskate (Jan 5, 2006)

I have a question and maybe you can help. The standard Aurora T-Jet/AFX crown gear has 15 teeth and I know a 19 tooth crown gear was used on the Super II. I have been told Aurora also had a 17 tooth crown gear which came in a hop-up kit. The G-Plus and other Aurora inline chassis use a 20 tooth crown gear. I also understand AW puts 18 tooth crown gears in their chassis.

First of all, does the 17 tooth crown gear exist?

I am trying to determine whether all Aurora T-Jet crown gears have the same outside diameter reguardless of tooth count. The 15 tooth has a O.D. of .310" and the G-Plus is .370". I have no 17 or 19 tooth gears. Does anyone know if the diameters of the T-Jet crown gears are the same? If the O.D. of each gear is the same, then the tooth size must be different.

Thanks...Joe


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## Rich Dumas (Sep 3, 2008)

The Auto World Ultra cars have a neodymium traction magnet and they use the 18 tooth crown gear while the older cars without the traction magnet have 15 tooth crown gears. I measured the ODs of several crown gears. A stock Aurora Thunderjet gear was 0.310", as was the AW Ultra gear. An A/FX gear was 0.309", a regular AW Thunderjet 500 gear was 0.304" and an RT-HO T-Jet crown was 0.304".


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## Grandcheapskate (Jan 5, 2006)

I got a private reply on the size of the Super II 19 tooth crown gear. It measures in at an O.D. of .334", That is quite a bit larger than the stock T-Jet/AFX gear. This leads me to belive that if a 17 tooth gear exists, it's diameter would be somewhere in between, meaning the tooth size stays the same across all the Aurora crown gears.

Now the question is whether a crown gear larger than .309"/.310" installed on a T-Jet/AFX has enough ground clearance.

Joe


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## Fastslots (Jan 28, 2020)

It should clear.. but not by much...


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