quick motor ?'s

[mudrinner4ever]

hey guys,
i dont now how many of you read the Xtreme RC Cars magazine but in the June issue on page # 164 they talk about wiring 2 motors in a series or parallel. i was wondering if i were to run 2 lathe 55 or 45 turn motors(most likly 45, ill explain later)in a series with a LRP speed control would it be able to hold the torque and pull from the motors. i had an idea of what speed control i was gunna run but i forgot. when wired two motors like this it would double the torque and the turns(example 2 55's would be 110 turn and 2 45's would be 90 turns). im looking at running this speed control,
http://www.lrp-electronic.de/e/lis/

its the Quantum Micro Reverse A.I. digital

someone who reads the mag read the section and fill me in! im pretty sure i forgot tons of info so ask if needed! thanks!

Luke

 

[JohnRobHolmes]

To answer your question, you could use that speed control with two motors in series. but....

You dont get power from thin air. I have read so many misquotes and bad comments on series vs parallel it is getting sad.

For simplicity I will assume the motors are both connected to the same spur with the same gearing, and they have the same wind with the same resistance, and that the magnets are the same. Basically identical setups.

Our constant for comparison = X = one motor run by one battery

Two Motors wired in series will see half the voltage, and thus run at half the speed of X. To combat this lack of power two batteries must be run in series. Your voltage doubles, your runtime goes back down to normal, and we have the same performance as 2x. (two motors, two batteries, easy enough to see)

Two motors wired in parallel will see full voltage, and will draw whatever amperage they need, and run at full speed. We now have 2x but at half the runtime. Two motors, but one battery. Your runtime will be halved because you are running two motors. To combat this we run two batteries in parallel, and now we have the same performance as 2X (two motors, two batteries, all is the same)

There is no way to cheat the system and get more torque (power, speed, whatever) while keeping the same runtime without adding weight. Also, there is no way to extend your runtime and keep the same power (without changing a battery setup). I can pull out the formulas, but I dont think anybody wants to be bored by any more 1000 word electrical theory posts.



For most crawlers, you are better off with one battery and one motor. If you really want more power, just add a few cells to the battery pack and drop your pinion a few teeth to compensate for the higher motor rpm. It will give you a better power to weight ratio and put less strain on your parts.

 

[Mad Scientist]

Very good post, johnrobholmes. I totally agree with adjusting cell count and gearing to tweak performance. Proper motor choice for the conditions can also play a big role.

 

[mudrinner4ever]

ok, kool thanks! then i guess ill stick with the one motor and battery!