Why do you use HV and / or why don't you?

[stangflyer]

Question. Why do coreless motors seem to have better torque values over brushless motors? I guess brushless advantage is only "longevity" in the motor?

Also polling responses.....What do you guys think is a better motor for HV set ups....Coreless or brushless?

The torque value of a coreless may seem significantly higher, but in reality it is a true myth. I say true, because they are rated higher, but the myth is really not a myth in reality. A coreless starts running up to operating speed at the instant it gets a signal from the transmitted input. It uses power to "ramp" up...then becomes constant until it reaches the end of its travel. So in essence, "example", a 486 oz. HS 7950 is only 486 oz. after it ramps up to it. But does retain the torque while input is being fed. However they are comparatively more economical. A brushless on the other hand is almost instantly constant speed and torque from the time it gets the signal until it reaches its e.o.t. The holding force never changes and remains as such until the signal is relaxed. So...a 350 oz. servo is 350 oz. throughout its entire range of motion. In retrospect, they are a little hungrier than a coreless, but because they ramp so quickly, the amount of mah useage is about the same.

As for your second question Kelly, I only own coreless. I have not had the pleasure of owning any brushless as of yet. However I would like @Xpress to send me some so I can try them out. From the people that have used the brushless, they seem to get awesome reviews. However, they are considerably more expensive than a coreless servo. Example: HS7980, 611 oz. @ 7.4 volt. ($145.00) HS9380 472 oz. @ 7.4 volts. ($180.00)

 

[Xpress]

In retrospect, they are a little hungrier than a coreless, but because they ramp so quickly, the amount of mah useage is about the same.

Don't know about other brands, but this is not the case with Hitec brushless servos- the motor inside is so overpowered that it barely sweats to make its full torque value. And when it gets to its holding point, the power needed to move drops significantly as it is only using what it needs to hold its position. The servos were built with a governor on the motor basically.

A LOT more efficient than any brushed motor.

Regarding the differences between a standard brushed motor and a coreless, a Coreless motor does not have a traditional Rotor on the inside and fixed magnets on the outside (all housed in a steel can of course) like brushed motors have had for decades. In a brushed motor, you have an iron core with copper windings wrapped around it with brushed contacts on one end. The brushes energize that core and cause it to spin. There is a lot of rotational mass with the iron core Rotor and as such it can diminish the motors spool up time.

Standard iron core motor:

A Coreless motor does not have a rotating core- instead it has a fixed magnetic core with a copper mesh that rotates around it. Brushes make contact at one end which energizes this copper mesh, which then causes it to rotate around the magnet in the center. This has a big advantage over a standard brushed motor because the copper mesh takes very little energy to spool up, which makes the servo more efficient. It also gets rid of that 'cogging' you might get when you turn a regular brushed motor- it's more prevalent in those high powered brushed RC car motors of yesterdays, where you could only turn it so little before the magnets would grab hold of the iron core.

Coreless motor:

Most digital servos are coreless nowadays because it's a more efficient design, with a lot more precision in moving the servo arm.

 

[49dimes]

Since I went from Futaba 9157's (coreless) to Blue Bird 3114's and 2209's (brushless) the only difference I can tell is price (not a complaint just sayin). Now I also went from A123's with the Futaba's to 2S Lipo's with the Blue Birds and seem to have a lot more battery capacity left over at the end of a flying session. I am also starting to see jitter in one of the 2209's due to gear play/wear after 3 years of use at my pace of going flying (average 1.5 times a month in a 12 month period). The Futaba 9157's @6volts had 472oz torque at $140ea. The Blue Bird 3114's @7.4 volts had 493oz torque at $100ea. And the 2209's 367oz @7.4 at $60ea.

These new 200 dollar servos.....If the gear train lasts longer (motors obviously superior) I will be willing to try them. From the type and number of times I fly I saw no difference really going to HV but the biggest plane I fly is 35%. And my comparison from 6 volts to HV was mainly done with a light 30% airframe.

 

[stangflyer]

Don't know about other brands, but this is not the case with Hitec brushless servos- the motor inside is so overpowered that it barely sweats to make its full torque value. And when it gets to its holding point, the power needed to move drops significantly as it is only using what it needs to hold its position. The servos were built with a governor on the motor basically.

A LOT more efficient than any brushed motor.

Regarding the differences between a standard brushed motor and a coreless, a Coreless motor does not have a traditional Rotor on the inside and fixed magnets on the outside (all housed in a steel can of course) like brushed motors have had for decades. In a brushed motor, you have an iron core with copper windings wrapped around it with brushed contacts on one end. The brushes energize that core and cause it to spin. There is a lot of rotational mass with the iron core Rotor and as such it can diminish the motors spool up time.

Standard iron core motor:

A Coreless motor does not have a rotating core- instead it has a fixed magnetic core with a copper mesh that rotates around it. Brushes make contact at one end which energizes this copper mesh, which then causes it to rotate around the magnet in the center. This has a big advantage over a standard brushed motor because the copper mesh takes very little energy to spool up, which makes the servo more efficient. It also gets rid of that 'cogging' you might get when you turn a regular brushed motor- it's more prevalent in those high powered brushed RC car motors of yesterdays, where you could only turn it so little before the magnets would grab hold of the iron core.

Coreless motor:

Most digital servos are coreless nowadays because it's a more efficient design, with a lot more precision in moving the servo arm.

Wow... that sucks. Guess I was informed incorrectly. I wanted the 9380's for the Sukhoi but chose the 7950's because one; I was informed by two reps. of the mah useage. Spent a lot of time researching before I purchased. And the other was cost. I just couldn't swing a buck eighty per servo. My apologies to anyone that I may have mislead. Good damn thing we got someone watchin' our "six"!

 

[jamesrxx951]

I purchased a bunch of JRMP83T servo's and their amp draw is considerably lower than the previous 8911's. This was all measured with an amp meter. Could not believe the difference. Many users are claiming up to 50% less MAH usage for the same flight/sequence over the standard HV coreless servo's like 8911's.