Faster servo comparable to 8611s ???

[ConRadical]

Oh guys.. I've decided i need a servo that's a bit hotter than the 8611s on my AM 33% yak...
isn't an issue with me.. Any ideas?

CG

[ConRadical]

also thinking about using the following horns: let me knwo what you think..

[Toro]

new futaba I think they're the 9152 or something like that... not sure on specs, and they are a bit larger so you may have to modify a tad. Why not 8611 ??? Thats all I have ever flown on the big stuff, and have never had a problem with em yet. plenty hot for a 33. Those horns are not to bad. I havent used them, and changed out all of em from a CHP that I got to rocket city. I bet though you shouldnt have a problem with a little 30 minute in the screw hole with the screw and your good to go.

T

[Toro]

here u go\\

Control System: +Pulse Width Control 1520usec Neutral
Required Pulse: 3-5 Volt Peak to Peak Square Wave
Operating Voltage: 6 Volts Only
Operating Temperature Range: -20 to +60 Degree C
Operating Speed (6.0V): 0.19sec/60 degrees at no load
Stall Torque (6.0V): 278 oz/in. (20kg.cm)
Operating Angle: 45 Deg. one side pulse traveling 400usec
360 Modifiable: No
Direction: Counter Clockwise/Pulse Traveling 1520-1900usec
Motor Type: Coreless Motor
Potentiometer Drive: Indirect Drive
Bearing Type: Dual Ball Bearings
Gear Type: All Metal Gears
Connector Wire Length: 12"
Dimensions: 1.91" x 0.99"x 1.56" (48.6 x 25.2 x 39.7mm)
Weight: 3.0oz. (85g)
Control System: +Pulse Width Control 1520usec Neutral
Required Pulse: 3-5 Volt Peak to Peak Square Wave
Operating Voltage: 6 Volts Only
Operating Temperature Range: -20 to +60 Degree C
Operating Speed (6.0V): 0.19sec/60 degrees at no load
Stall Torque (6.0V): 278 oz/in. (20kg.cm)
Operating Angle: 45 Deg. one side pulse traveling 400usec
360 Modifiable: No
Direction: Counter Clockwise/Pulse Traveling 1520-1900usec
Motor Type: Coreless Motor
Potentiometer Drive: Indirect Drive
Bearing Type: Dual Ball Bearings
Gear Type: All Metal Gears
Connector Wire Length: 12"
Dimensions: 1.91" x 0.99"x 1.56" (48.6 x 25.2 x 39.7mm)
Weight: 3.0oz. (85g)

[ConRadical]

I just want some fasters servos always felt like my 8611s aren't super fast... I'm using 8611's because that's what i'll have with my trade from Jim.. Why not use 8611s.. they're the same price and speed.. but more torque. Is the weight on it that much of a difference?

[Toro]

I Imagine your probably gaining a couple of OZ on each Servo. Probably a total increase of about 1/2 Pound or so. All metal gears, and I know they are bigger than the 8611's

[ConRadical]

Toro.. what are those specs for? whatever it is it's slower than 8611s which is .18 @ 4.8... I'm really hoping to get something around .1 but still have the torque.

[Toro]

9152's.... a tad slower, but look at that MONSTER TORQUE !!!

[ConRadical]

But the 8611 has 320oz @ 6v seems the 8611 beats the 9152.

[Shortman]

Torque ratings are torque ratings. Once you fly them, that's where you tell the difference. I would be willing to bet those 9152s outfly the 8611s in precision and holding power. The 9255s they make are absolutely the shiz when it comes to helicopter servos.

[ConRadical]

I might have to give the 9152's a chance then.. That's why i'm posting... trying to get everyones opinions.

[luke3dreturns]

I would very much doubt that. Ive experimented a fair amount and the 8611(or 8511 as its known over here) is still the best servo ive ever used. Futaba specs on their servos (and their prices too) are ambitious to say the least. A while ago one of the leading flyers here in the UK, after suspecting this for ages hooked up a 15kg futaba digital to an 11kg 8411, to see which was stronger. Guess which one won!!

[notorious_benny]

The only way to solve this is to do a back to back comparison. Buy one of each servo that you want to use, then set up a test stand so you can hang specific weights off each servo at 1cm or an inch (whatever suits you just kkep it exactly the same for each servo) then also make a pointer off the arm as well, that way you can test the ability of the servo to hold and move the given weight hanging off of it as well as being able to see if the servo centres to the same point every time.

To test the servos speed you would probably need a high speed camera, so you had better call the myth busters!



I also run JR 8511's and dont have a problem with them, though I would be interested too see a true comparison done scientifically, however holding power is one thing and speed is another. You could put a different gear train in the servos that we run, they would move slower but have a higher tourque rating or vice versa.

[KrisW]

Here's the question. . Why do you need more speed?

The 8611's. . heck, ANY servo with .15 transit at 6v, move just as fast as your thumb, unless you TRY to outrun them. so, why faster?

Secondly, this is a 33% plane, meaning smaller control surfaces, which require less torque to move. I don't know how many servos you have on ailerons, but by merely going to a longer arm on the servo, the perceived speed of the control surface movement will increase. For instance, if you have a 1:1 ratio between servo and control surface, moving the servo arm 45 degrees in 1/10 second means the control surface deflects 45 degrees in the same amount of time. . 1/10 second. If you are underdriving the servo. . say a 1:1.5 ratio, you servo has to move over 65 degrees for the control surface to move 45 degrees, so it takes 50% longer, and now you are up to .15 seconds for the control surface to move.

Conversely, if you run a 1:.8 ratio, the servo moving a mere 40 degrees will net a control surface movement of 50 degrees. . in .08 seconds. . .making it TWICE as fast as the 1:1.5 ratio.

So, if you are running 2 servos per aileron, and want more "speed", just go to longer arms on the servos, and dial up the Expo on the transmitter to make things less sensitive on center. Your resolution will suffer, but you will have the speed you need (want) without having to swap in new servos. The same principle applies for your elevators and rudder.

One thing to remember. . at higher speeds, massive surface deflection does little more than stall the control surface, because the air cannot "turn the corner" at higher speeds. So, the only place you need 45-50 degrees of deflection each direction is at LOW speeds, where it takes less servo torque to move the control surface against the airstream in the first place. Remember, to double the throw of a control surface requires FOUR times the torque . .and at low speeds it takes a lot less torque large deflections. For 3D, in this case, even with only one servo per aileron, longer arms on the servos would work fine, and you could go to a lower rate for high speed flight. I really can't see anyone being silly enough to want 50 degrees of transit on every surface at 90 mph. First you'd have to install more servos to get the necessary torque . .secondly within a second of throwing the sticks one of two things is gonna happen. . Either you are going to slow the plane down tremendously due to the massive drag induced by using "air brakes". . or the plane is going to disintegrate due to the forces involved. Either way, things are going to slow down very quickly. The "Hey guys, watch this" aspect of massive throws at 90 mph loses its appeal when the plane leaves a 100 yard debris field on the ground.

So, if you want more speed, go to 25% longer arms, and dial up the expo and change your low rates. Be CAREFUL not to overload the servos with too much speed. . they'll either stall due to blowback, make the plane turn inside out, or literally stop the plane in midair due to the drag induced. none of the three is really desireable.

One last thing. .If you MUST change servos, the 5955 HiTec digitals have several advantages over the 8611A's. . MORE torque. .Same Speed. . Titanium Geartrain, 3-4 times the geartrain life, Same Weight . .Programmable. . LESS COST ($85-90 per servo from some sources). Specs are 333 ounces of torque, .18 seconds on 4.8v. . .15 on 6v weight 2.1 ounces. They can be programmed for Center, End points, direction, bandwidth, on board failsafe, and speed, and you can perfectly match 3-4 of them together by adjusting the programming until the servo arms move exactly the same.

http://www.servocity.com/html/hs-5955tg.html

Servo City, Chief Aircraft and other vendors give bulk sales discounts on some servos. . including the 5955's

I really don't know why you are even considering the Futaba's. They are slower, heavier, and have less torque. The HiTec 5955 is THE standard case servo right now .JR even UPgraded their 8611's to 8611a's by using the same coreless motor HiTec started out with in the 5955's.

Sounds like a PLAN to me. . . .

[notorious_benny]

Dont forget also Kris that if you use longer servo arms (or conversely shorter control horns) you need more tourque to hold the surface at any given deflection, not just maximum, because you are mechanically diasdvataging the servo.

One of the other aussie guy's here on the giants has a 2.6 comp arf ak he uses for precision Imac only, the linkages are set up with shorter servo arms and maybe longer control horns? to maximise the resolution out of his servos. This gives the servo a mechanical advantage meaning more force can be applied to the control surface before the servo will 'give' than if long servo arms and shorter control horns are used.

He also has a 2.6 extra that is set up for maximum throws I am only guessing that he has used the same servos in the extrra as for the Yak, if he comes across this forum he may hopefully enlighten us if there is any difference in 'feel' and control 'speed' between the two models.