How much can you gear up a TT-02? Turns out the answer is quite a lot.
I had already geared my car up to the maximum level on the standard 0.6 mod gears. The most you can go on it as previously shown is a 64t spur and a 28t pinion.
This gives a motor-prop ratio of 2.285 (prop is turning 2.285 times slower than the motor. I found that you can gear it up much further by using 48 pitch gears.
On the Max10 3300kv 0.6 mod gears were good enough for 50 mph. I believe though that the car can do much more if I can keep it stable. The motor was perfectly cool and I upgraded it to a HPI Flux Vektor 4800kv. This motor runs a very similar speed on 2s as the Max10 does on 3s due to the higher kv rating. On 3s I haven’t managed to get a good speed run yet due to weather conditions. My best is 53 mph (going partially sideways).
I am trying to get a setup in my stock TT-02 that will run at a really good speed on 2s as the 4800kv motor is still cool even when run on 11.1v.
The stock TT-02 with its brushed setup is going to be my guinea pig for this, and any successful setup will get transferred to the brushless Type-S.
Now with speed testing it is not as simple as just putting in an expensive setup and gearing it to the moon. You have to keep a close eye on the temperatures of the motor and the ESC as they may be under a lot more strain.
So I decided to go straight in with a much lower ratio and just closely monitor it. I was using an E-Tronix 15t modified brushed motor that was stone cold on the 64t/28t setup and a 2s lipo. I used the following parts:
Spur - CRW48060
Pinion - SCH-CR4832
This is a 60t spur and 37t pinion giving a rather more extreme ratio of 1.621.
To put it in perspective, the previous ratio of 2.285 means that the car in theory should be going 1.4 times quicker now on this ratio (2.285 / 1.621 = 1.40). Obviously it never works out exactly like that due to other factors such as air resistance, motor stress, etc).
The ironic thing is I was sure that I would need a custom gear cover for these ratios, but forgot to factor in that these 48 pitch gears are physically smaller than the 0.6 mod ones. So they actually have more clearance than before and the stock gear cover is absolutely fine!
Please note that a lot of the 48 pitch gears will only bolt into two of the holes on the speed gear adapter. I found this was perfectly fine when using it in the car.
Unneeded 3d printed gear cover off Ebay.
I am not speed testing the cars just yet, as I am trying to find the correct ratio first. I can tell you that the 1.621 ratio nearly fried the brushed motor!
So I went with a bit of a calmer ratio with a 32t pinion and a 64t spur - so a ratio of 2.0. This works really well on the brushed motor (just gets a bit warm) so will be very interesting to transfer to the brushless car.
I have the gears to also try the 37t pinion with the 64t spur that will provide a 1.729 ratio. Nicely in between the 2.0 and the 1.6 ratios already tried.
The next step is to basically try all of the gear ratios I have available and speed test each one in both cars until I find the best ones.
Speed testing is not easy! You need to experiment with setups, ratios etc so I will do all of these in one day as the TT-02 is an easy car to change the gears on (10 minute job). Speed/heat test results coming soon!
