skillet92

Hey guys i have a GP 330s Extra and am putting a gas 45cc engine on it. My question is the choice of servo. I was going to put the Hitec 5645mg because of the price and torque, but after seeing the way that it centers my Super Chipmunks rudder have started to reconsider. I am know considering the 985mg because it is coreless. My question is does a coreless motor center better than a cored one?

Jezmo

The POT and electronic control board (digitals tend to center better) determine center not the motor type. If it doesn't center well the POT may be dirty or bad. They can be replaced if you have basic electronic skills.

HighPlains

My Feedback: (1)

Iron core motors do suffer from an effect known as "cogging". Certain design changes to the motor can limit the effect, but these tend to lower the maximum torque. A motor at rest tends to settle at a point between magnetic poles. What cogging means to the servo designer is that it takes a certain amount of motor current for the motor to climb the hill, and thus for a purely analog servo amplifier, a bit of error is needed before enough currect is generated to offset both cogging and friction.

Coreless motors do not have the cogging effect, so less motor current is need to start movement.

However with digital amplifiers, motor type is less important.

mrbigg

My Feedback: (21)

The 5645 is a cheaper servo, made with cheaper parts. If you want quality, you have to step up to a 5995 or equivelent.

Jezmo

I don't disagree with the "cogging" theory but, when looking at the amount of distance between where the motor will stop between "poles" and then factoring in the gear ratio, the amount of servo arm position change would be so minuscule it wouldn't matter in most applications. If one needs that kind of accuracy then he needs to do like mrbigg says and spend the money to get something like a 5995 or equivalent. Also, let's remember the POT is attached to the output shaft and will request movement from the motor until it centers if the controller (amp) is set up right. In my humble opinion it all boils down to the quality of the whole package, motor, pot, board, etc. A good coreless motor with a junk pot or sloppy gear train/loose output shaft is still going to be a junk servo. Later Gents.