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HelicopterRadio - Servo - Gyro - Gov - Batt › What torque range do you look for in your cyclic​servos?
04-06-2011 03:38 PM  6 years agoPost 1
Rogman88

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West Monroe, LA

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Do you figure the weight of the heli and look for a certain torque criteria to meet your needs? For example, say a 10 lb 600 sized heli, I've seen the average servo torque for the better quality servos to be around 167oz/inch or roughly 10.4 lbs/inch or torque.

So roughly 10 lbs torque times 3 cyclic servos is roughly 3 times the power required to lift the heli. As we know a heli stopping and starting can increase the weight of a heli exponentially due to G force, I would think that it is important to have more than adequate torque on your servos to prevent premature wear and the ability to do the job.

So would one want to keep the cyclic servo power about equal to the weight of the heli?

What say ye?

High Voltage just works better

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04-06-2011 03:50 PM  6 years agoPost 2
heli-cuzz

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Pittston, Pa. USA

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I don't look, but the ones I use have 220oz./.06 @ 8 voltz.

Fury 55 NIB Furion6 CGY750 fbl helicopter-Frenzy CGY750 fbl nitro-Frenzy fbl NOBAR90

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04-06-2011 04:37 PM  6 years agoPost 3
red_z06

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Dumont, NJ

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Torque is not a force unit. T = F x d (or r)
That is why you see oz-in, ft-lb, etc.

160oz-in says that if you have a shaft that is 2" in diameter (1" radius), you can wrap a thread and hang 10lb mass on it and the torque will be able to hold it in position.

If you have a 4" shaft (2" radius), then the force you can hang reduces to 5lb.

So, think of torque as an ability to twist something. You can extract force from it but that value depends on how far away the force is applied from the centerline of the shaft.

We often look at speed rating of a servo for rapid response. Let say you have a 100oz-in servo with 0.06s speed and a 200oz-in servo with same speed rating. Under zero load, both servos will reach the goal in exactly same time. As your load gets near 100oz-in, the first will crawl to a stop while the latter will still run at but at slower rate.

So, sometimes, slightly slower but much higher torque servo will actually run faster than a faster servo with lower torque rating.

www.JustinJee.com

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04-06-2011 04:40 PM  6 years agoPost 4
Santiago P

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South West, Ohio

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Do you figure the weight of the heli and look for a certain torque criteria to meet your needs? For example, say a 10 lb 600 sized heli, I've seen the average servo torque for the better quality servos to be around 167oz/inch or roughly 10.4 lbs/inch or torque.

So roughly 10 lbs torque times 3 cyclic servos is roughly 3 times the power required to lift the heli. As we know a heli stopping and starting can increase the weight of a heli exponentially due to G force
Not a good analogy, You are trying to control the aerodynamic forces in a rotor, not produce lift with the servos.

Rogman

Torque requirements are mainly a byproduct of HOW you fly and linkage geometry. We use to use 54oz servos on 60size helis and put hundreds of aerobatic flights with no issue.
Today is a little different:
With many machines lay out in CCPM and flybarless, the servo has to do the work of the flybar plus move more often. The old mechanical one servo per axis control is much easier on servos. Flybar acts as a control boost as well as a stabilizing, mechanical device.

In 3D applications:
Flybarless 90 or 700 in CCPM I would suggest 150oz-in minimum
90 (700) w flybar in CCPM 94oz-in minimum, 135oz-in preferred
For 600mm or 50 size FBL, 130oz-in, FB: 90minimum.

As Red said, the torque needed has a A LOT to do wiht the linkage geometry. You ALWAYS want to run sevo arms that alow you to use 100% of the travel for your most used flight mode. If you are only 60% total travel adjust, you handicapped the servo to begin with,

For Sport flying you can get away with less torque.
Remember that Torque and precise centering are ALWAYS more important than speed. Anything below .18sec/60degrees is plenty fast.
A fast and torquey but “sloppy” servo makes for a horrible flying machine.

Santiago

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04-06-2011 05:32 PM  6 years agoPost 5
Rogman88

rrElite Veteran

West Monroe, LA

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Good stuff guys. Thanks. The reason I was asking is that I'm seeing that there are some 800 sized helis on the horizon but folks are still using the same servos as the 600 sized helis. I don't know what the weight differences are going to be, but I just wondered how the standard servos of today will hold up with the larger machines.

Also I'd like to change my analog HS 65's for some digitals and am seeing so many choices. I've never weighed my 450, but am seeing that around 2 kg/cm torque is the average of the good servos and sub 13 ms. I see some servos that are sub 10 ms (really fast) but the torque drops to 1.6kg. Benny makes a good point that a 2kg servo running at 13 ms may perform better in harder 3D moves than a 9 ms running at 1.6kg due to slowing down under load.

High Voltage just works better

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04-06-2011 05:48 PM  6 years agoPost 6
Darren Lee

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Woodstock, GA

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A fast and torquey but “sloppy” servo makes for a horrible flying machine.
Amen to that! Best thing I ever did for my N5 was to replace some very old worn out DS610s with BLS253s. Amazing difference!

Team Synergy / Rail Blades / Morgan Fuel

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04-07-2011 03:18 AM  6 years agoPost 7
Santiago P

rrProfessor

South West, Ohio

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Good stuff guys. Thanks. The reason I was asking is that I'm seeing that there are some 800 sized helis on the horizon but folks are still using the same servos as the 600 sized helis. I don't know what the weight differences are going to be, but I just wondered how the standard servos of today will hold up with the larger machines.
Ummm, you are still not quite grasping the concept. Heli Weight does not dictate servo torque requirements. Blade moment around their pivot point and linkage geometry does...

Blade design is the most important player here. To have a good neutral blade, its center of mass and aerodynamic center should be in the same place. Tha blade CG will dictate if the blade is stable or unstable when is pitched, (lead, lag, or neutral to the blade axle)

If the blade is anything but neutral, it introduces a larger moment to the spindle, blade control arm, and consequently to the servo.

So again compadre, is not the weight, but the other whachamafreakingthingies (plurar for a lot of aero bull) that dictate the forces and moments on the rotor head.

Now tell me when you are thoroughly confused so I can stop. lol

Santiago

my mama always said to me, drop that helicopter book or is gonna mess up you head you fool

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04-12-2011 11:35 AM  6 years agoPost 8
Richardmid1

rrProfessor

Leeds, England

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What torque range do you look for in your cyclic servos?
As much as I can afford! You can never have too much torque, its much more important than speed!

60% of the time, it works every time!

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