RC-Monster Forums - brushless questions to prove a point

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- - brushless questions to prove a point (https://www.rc-monster.com/forum/showthread.php?t=9979)

1. What KV is a faster motor. a 3500kv or an 8000kv motor?
2. When an esc is rated for 6S, does this mean two 3 cell batteries, or does it mean two 6 cell batteries?
3. Can you run 2 brushless motors on the same spur gear and gain twice the speed, or is there a slight gain with 2 brushless motors?
4. Are there faster and better RC Brushless electronics than Novak, and LRP?
5. Can Lipo batteries explode with out proper balancing?

1. 3500kv, a lower KV motor will handle more volts before it exceeds its max RPM and the stator explodes.

2. could be either 2x 3cell packs in either series or parallel or 2x 6cell packs in parallel but not in series.

3. no, running 2 motors on the same ger ratio will not increase your top speed at all, you will increase the torque but you need to gear up to use that extra torque to raise the top speed.

4. Yes

5. overcharging a LiPo can make it catch fire whether a balancer is used or not, a balancer means all cells should catch fire at the same time tho.

Torque is not force x distance. It's force x radius, since torque only applies to rotation about an axis.

Work (Joules) is force x distance which is also equal to torque x radians (1 revolution = 2pi radians)

Power (watts) is work / time.

Since velocity = distance / time, velocity x force = watts

Write this down on a piece of paper. It is very simple math.

Also, 1HP = 746 watts = 550 ft-lb/sec
1ft-lb (work) = 1.35 Joules
1lb-ft (torque) = 1.35 Newton-meters
1 Newton = 4.45 lbs
1 Meter = 3.28 ft

Quote:

Originally Posted by myndseye (Post 148846)

Not exactly. Most motors from a given manufacturer, of the same series, but different kv ratings produce equal torque if all else is equal also. The difference comes because of the limits of the motors. For example; Mamba Max motors all have the same max rpm, lets say 60,000. To get a motor to that rpm, a certain amount of voltage would have to be applied. To find out how much voltage you need, take the rpm and divide it by the motor's rating. To get the lower kv rated motor to the same 60,000 rpm, it would take a higher voltage. With current being equal in both systems, the higher voltage system makes more watts of power, since watts are voltage * current. They both will be spinning 60,000 rpm (making neither motor faster), but the higher voltage system will have more horsepower. The higher horsepower system can pull a bigger gear, and thus go faster.

Voltage * Current = Watts
745.6 Watts = 1 HP

So really it comes down to the batteries doesn't it. The fastest is going to be the one that is most efficient on the particular batteries being used.

Or alternatively if you want to pick the the motor first, the most efficient with the highest watt input limit is the most powerful as long as the batteries and gearing are set to reach that efficiency.

When I build my cars, I pick the battery first. I try to find to most voltage and capacity that I can see fitting on the vehicle without unbalancing it, then I pick a motor based on the voltage and current rating of the battery.