Beautiful car! But I think you indeed maxed the motor as well as the battery. If your motor has 26'000 rpm @ 7.2V (making it a ~3600 kV motor and that is about the highest rpm I could find 12T brushed motors for), then with your 6.5 cm diameter wheels and your gearing you make exactly 35 mph. This includes the voltage sag of a fully charged NiMH battery of about 1 V to 7.2 Volts net current to feed your motor. With my TT02, using almost the same gearing as you (32T pinion, 64T spur) but using the Castle MambaX BEC and the 7700kV motor, using 2S LiPo, so far on my initial runs get some 70+ mph, but then drawing some 350 Watts to maintaing top speed (>800 Watts during accelleration). This is enough for even a good LiPo to sag almost 1 V. This means, I get battery limited and I am going now for 180C speedrun packs. Higher discharge rate will help more then going LiHV, as that one will voltage sag more under such load. For your car, it also means that going half that speed, you car needs 1/8th (power required scales to the cube of speed gained) the power, meaning some 44 Watts. At 7.2 V, this represents some 6 Amps. This is what NiMH can give you, but obviously with no further headroom. It seems to me that you are limited at 6 Amps power draw, it makes sense that even with gearing you won't get any faster. As soon as the motor draws more through higher gearing, voltage will sag more, limiting your rpm. Using a LiPo will allow you to gear up. Or when you use the same setting with a LiPo, you go some ~39 mph due to less voltage sag. You still have some headroom on the Amps for your ESC not crapping out on you. But mind you, these predicted 6 Amps are steady state max speed. During initial accelleration, you draw more, esaily the double, but at the cost of a even more pronounced voltage sag. Maybe some 15 Amps in your case during initial accelleration. Thus, my guess is that you are both battery and motor limited and plan accordingly, should you want to venture past 40 mph. So you got from the car what it is supposed to give you in its current form. You can make it a rocket, but that will bring a serious escalation of the power system.
You could have kept the battery in your trouser pocket to try and warm it up a bit, but it probably wouldn't have made much difference. Maybe go lipo and brushless just to get it twice as fast without much more effort, but then you're in a whole different world of upgrades and insane speed. It might be too fast lol
I have enjoyed this series mate👍🏼 i have spent alot on my tt-02 and have put a hobbywing max 10 combo in it, it is quick now. Im not even sure if i have any stock parts on it anymore😂 whats next then?
Definitely Lipo 1st, just to approach, reach 40. Nimh are good for playing, not for speed runs. Brushless, you will enter a new world 😅 Not sure the joggers, bikers, dog-sitters will appreciate 😅 Heat is only needed for the battery, but "cold" is much better for the ESC/motor. 🤝
Solid efforts, sir. Great video series, and good luck on the next.
Thank you kindly!
Beautiful car! But I think you indeed maxed the motor as well as the battery. If your motor has 26'000 rpm @ 7.2V (making it a ~3600 kV motor and that is about the highest rpm I could find 12T brushed motors for), then with your 6.5 cm diameter wheels and your gearing you make exactly 35 mph. This includes the voltage sag of a fully charged NiMH battery of about 1 V to 7.2 Volts net current to feed your motor.
With my TT02, using almost the same gearing as you (32T pinion, 64T spur) but using the Castle MambaX BEC and the 7700kV motor, using 2S LiPo, so far on my initial runs get some 70+ mph, but then drawing some 350 Watts to maintaing top speed (>800 Watts during accelleration). This is enough for even a good LiPo to sag almost 1 V. This means, I get battery limited and I am going now for 180C speedrun packs. Higher discharge rate will help more then going LiHV, as that one will voltage sag more under such load.
For your car, it also means that going half that speed, you car needs 1/8th (power required scales to the cube of speed gained) the power, meaning some 44 Watts. At 7.2 V, this represents some 6 Amps. This is what NiMH can give you, but obviously with no further headroom.
It seems to me that you are limited at 6 Amps power draw, it makes sense that even with gearing you won't get any faster. As soon as the motor draws more through higher gearing, voltage will sag more, limiting your rpm. Using a LiPo will allow you to gear up. Or when you use the same setting with a LiPo, you go some ~39 mph due to less voltage sag.
You still have some headroom on the Amps for your ESC not crapping out on you. But mind you, these predicted 6 Amps are steady state max speed. During initial accelleration, you draw more, esaily the double, but at the cost of a even more pronounced voltage sag. Maybe some 15 Amps in your case during initial accelleration.
Thus, my guess is that you are both battery and motor limited and plan accordingly, should you want to venture past 40 mph. So you got from the car what it is supposed to give you in its current form. You can make it a rocket, but that will bring a serious escalation of the power system.
Thank you so much for this comment. So much detail and information. Thanks for taking the time to watch and pass your knowledge on.
Great to see your Raikiri again. Yeah go for LiPo next year :)
Deal!
You could have kept the battery in your trouser pocket to try and warm it up a bit, but it probably wouldn't have made much difference. Maybe go lipo and brushless just to get it twice as fast without much more effort, but then you're in a whole different world of upgrades and insane speed. It might be too fast lol
Probably be going lipo and brushless for next years runs. Thanks for taking a look and commenting.
I have enjoyed this series mate👍🏼 i have spent alot on my tt-02 and have put a hobbywing max 10 combo in it, it is quick now. Im not even sure if i have any stock parts on it anymore😂 whats next then?
Thank you. Got a M05 and making a mess of doing a mini cooper body shell for it 🤦🏼♂️
Definitely Lipo 1st, just to approach, reach 40. Nimh are good for playing, not for speed runs. Brushless, you will enter a new world 😅 Not sure the joggers, bikers, dog-sitters will appreciate 😅 Heat is only needed for the battery, but "cold" is much better for the ESC/motor. 🤝
Thanks for the tips!