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Finding the 200 mph motor
Raz over the weekend posted up a video doing 192 mph with the 1721 motor (2400kv).
He was kind enough to send me a screen shot Saturday morning at 4:50am
A little about the 2400 kv..... This motor needs to build up extreme RPMs to run well and requires some gearing torque to help it out. Raz ran over 3000 ft with a long delay on the perfect pass to make this run happen. RPMs are in the 60-65k range. James McCoy on a 2100 ft road hit 180mph and noted the same 60-65k rpms needed.
Looking at gearing calculators you could go over 150mph with the GP5 diffs (2.8 ratio) using a 42t spur and a 25t pinion (assuming your car is up for it and batteries)
I know what you are thinking. That is very different gearing from what I am used to seeing/hearing on these cars! This brings me to the thought of gearing torque and the ideal motor to hit 200mph.
Lower KV has more torque and so do larger diameter motors. Along those lines longer length magnets and windings do the same too.
The question I keep going back to is which is better and where is a good balance between the two.
Taking this estimated Kt value at 500a gives us 530a*0.56Kt =296.8 Inch-Ounces of torque
Take a commonly used motor like a TP 5680 motor in a 1440kv the same 530a * 0.94Kt = 498.2 inch-Ounces of torque.
Clearly the lower KV motor produces a lot more torque but gearing is the equalizer. Which is the greater evil? KV torque loss or gearing torque loss?
If we compare the 2 setups with a goal of 190 mph for both and assume that both can have a voltage sag down to 27 volts (Raz had some custom very large batteries in his setup) .... lets compare the two:
1. Castle 1721 (2400kv)
296 in/oz tq
Geared for 190 mph at 27v and 530a (14.3kW)
Using a gearing calculator and assuming some slip/efficiency loss of around 10%-12% a Spur of 42t and Pinion of 33T would have the potential to net a 190mph pass.
This is a Final drive of 3.56
2. TP5680 motor (1440 kv)
498 in/oz tq
Geared for 190 mph at 27v and 530a (14.3 Kw)
Using a gearing calculator and assuming some slip/efficiency loss around 10%-12% a spur 29T and a Pinion of 38T would have the potential to net a 190 mph pass.
This is a final drive of 2.14
Notice how very different these setups are!?
So what comes next? I see 2 possible next steps....
1. Use a CM version with higher Kv of the TP56 series with a similar 2200-2500kv. Such a setup should net a higher torque from the larger diameter motor AND take advantage of the gearing torque.
2. Find a middle ground of something like 1700-2000kv and see what happens.
*** The problem is that most 56 and 58 series motors are 6-pole and the XLX2 does not handle "higher" KVs with 6-pole motors.
Raz over the weekend posted up a video doing 192 mph with the 1721 motor (2400kv).
He was kind enough to send me a screen shot Saturday morning at 4:50am
A little about the 2400 kv..... This motor needs to build up extreme RPMs to run well and requires some gearing torque to help it out. Raz ran over 3000 ft with a long delay on the perfect pass to make this run happen. RPMs are in the 60-65k range. James McCoy on a 2100 ft road hit 180mph and noted the same 60-65k rpms needed.
Looking at gearing calculators you could go over 150mph with the GP5 diffs (2.8 ratio) using a 42t spur and a 25t pinion (assuming your car is up for it and batteries)
I know what you are thinking. That is very different gearing from what I am used to seeing/hearing on these cars! This brings me to the thought of gearing torque and the ideal motor to hit 200mph.
Lower KV has more torque and so do larger diameter motors. Along those lines longer length magnets and windings do the same too.
The question I keep going back to is which is better and where is a good balance between the two.
Taking this estimated Kt value at 500a gives us 530a*0.56Kt =296.8 Inch-Ounces of torque
Take a commonly used motor like a TP 5680 motor in a 1440kv the same 530a * 0.94Kt = 498.2 inch-Ounces of torque.
Clearly the lower KV motor produces a lot more torque but gearing is the equalizer. Which is the greater evil? KV torque loss or gearing torque loss?
If we compare the 2 setups with a goal of 190 mph for both and assume that both can have a voltage sag down to 27 volts (Raz had some custom very large batteries in his setup) .... lets compare the two:
1. Castle 1721 (2400kv)
296 in/oz tq
Geared for 190 mph at 27v and 530a (14.3kW)
Using a gearing calculator and assuming some slip/efficiency loss of around 10%-12% a Spur of 42t and Pinion of 33T would have the potential to net a 190mph pass.
This is a Final drive of 3.56
2. TP5680 motor (1440 kv)
498 in/oz tq
Geared for 190 mph at 27v and 530a (14.3 Kw)
Using a gearing calculator and assuming some slip/efficiency loss around 10%-12% a spur 29T and a Pinion of 38T would have the potential to net a 190 mph pass.
This is a final drive of 2.14
Notice how very different these setups are!?
So what comes next? I see 2 possible next steps....
1. Use a CM version with higher Kv of the TP56 series with a similar 2200-2500kv. Such a setup should net a higher torque from the larger diameter motor AND take advantage of the gearing torque.
2. Find a middle ground of something like 1700-2000kv and see what happens.
*** The problem is that most 56 and 58 series motors are 6-pole and the XLX2 does not handle "higher" KVs with 6-pole motors.
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