Re: How much torque do you need? - RC Groups
Dec 30, 2005, 11:11 AM
Ted Campanelli
Ted Campanelli
Guest

# Re: How much torque do you need?

Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:

Here is a link to a servo torque calculator.

> How do you know if you've got enough torque in the servos you're
> using? I can see one (very complex) way of doing it would be to have a
> (recording) ammeter in-line with each servo and see how much power they
> draw as you put the plane through it's paces. Other than that, or the
> plane falling out of the sky, how can you tell if your servos are
> struggling?
>
> Thanks,
> Steve
>

Dec 30, 2005, 11:11 AM
Steve
Steve
Guest

# How much torque do you need?

How do you know if you've got enough torque in the servos you're
using? I can see one (very complex) way of doing it would be to have a
(recording) ammeter in-line with each servo and see how much power they
draw as you put the plane through it's paces. Other than that, or the
plane falling out of the sky, how can you tell if your servos are
struggling?

Thanks,
Steve

Dec 30, 2005, 03:11 PM
JJVB
JJVB
Guest

# Re: How much torque do you need?

There are a couple of servo torque calculators out there. Do a google
search for them. They will give you an idea of how much servo you
need. They can be a little complicated to use. In general, most
people probably use more servo than is really required.

John VB

Dec 30, 2005, 11:11 PM
The Raven
The Raven
Guest

# Re: How much torque do you need?

> How do you know if you've got enough torque in the servos you're
> using? I can see one (very complex) way of doing it would be to have a
> (recording) ammeter in-line with each servo and see how much power they
> draw as you put the plane through it's paces. Other than that, or the
> plane falling out of the sky, how can you tell if your servos are
> struggling?
>
> Thanks,
> Steve

As suggested do a search for some torque calculators. They are rather basic
but will give you a good idea.

One I tried required control surface width and chord, max deflection angle,
and max speed. From that I assured myself that my servo choice was OK. Input
the max deflection and speed higher than what you realistically expect, it
will give you a good safety margin particularly if you up the throws etc
later on.

--
The Raven
http://www.80scartoons.co.uk/batfinkquote.mp3
** Now I will bring chaos to the world!

Dec 31, 2005, 03:11 PM
Eye Indo
Eye Indo
Guest

# Re: How much torque do you need?

Quick, normal reaction static, but slow reaction in flight.
We all tend to overpower anything we can get our hands on .......

>> One I tried required control surface width and chord, max deflection
>> angle,
>> and max speed. From that I assured myself that my servo choice was OK.
>> Input
>> the max deflection and speed higher than what you realistically expect,
>> it
>> will give you a good safety margin particularly if you up the throws etc
>> later on.

>
> I tried that with the one provided earlier and came up with some
> really low numbers (along the lines of 10-13 oz-in for the elevator and
> 4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
> that either the calculator is a bit off or we way overpower our servos
> (along with our engines....).
>
> What would the symptoms of an underpowered servo be in flight?
>
> Steve
>

Dec 31, 2005, 05:11 PM
Steve
Steve
Guest

# Re: How much torque do you need?

> One I tried required control surface width and chord, max deflection angle,
> and max speed. From that I assured myself that my servo choice was OK. Input
> the max deflection and speed higher than what you realistically expect, it
> will give you a good safety margin particularly if you up the throws etc
> later on.

I tried that with the one provided earlier and came up with some
really low numbers (along the lines of 10-13 oz-in for the elevator and
4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
that either the calculator is a bit off or we way overpower our servos
(along with our engines....).

What would the symptoms of an underpowered servo be in flight?

Steve

Dec 31, 2005, 07:11 PM
Ed Cregger
Ed Cregger
Guest

# Re: How much torque do you need?

"Eye Indo" <amerindo@worldnet.att.net> wrote in message
news:ZGAtf.387641\$zb5.71253@bgtnsc04-news.ops.worldnet.att.net...
> Quick, normal reaction static, but slow reaction in flight.
> We all tend to overpower anything we can get our hands on .......
>
> "Steve" <scasko@aol.com> wrote in message
>>> One I tried required control surface width and chord, max deflection
>>> angle,
>>> and max speed. From that I assured myself that my servo choice was OK.
>>> Input
>>> the max deflection and speed higher than what you realistically expect,
>>> it
>>> will give you a good safety margin particularly if you up the throws etc
>>> later on.

>>
>> I tried that with the one provided earlier and came up with some
>> really low numbers (along the lines of 10-13 oz-in for the elevator and
>> 4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
>> that either the calculator is a bit off or we way overpower our servos
>> (along with our engines....).
>>
>> What would the symptoms of an underpowered servo be in flight?
>>
>> Steve
>>

>
>

I have never had too powerful a servo crash a plane. I have had underpowered
servos come perilously close to crashing a plane. Watts are cheap. Planes
are not.

Ed Cregger

Dec 31, 2005, 07:11 PM
Jim Slaughter
Jim Slaughter
Guest

# Re: How much torque do you need?

At the price of our Hurricane servos, why not go HIGH torque? Check 'em out
at www.flyhurricane.com.
Our standard size 92oz servo is only \$15 with DIGITAL 152 and 191oz metal
gear servos going for only \$40 and \$45. We have all the spare parts too.
Gears, cases, arms, etc.

"Ed Cregger" <edcregger@yahu.com (replace the u with oo)> wrote in message
news:dp6th402fh7@enews3.newsguy.com...
>
> "Eye Indo" <amerindo@worldnet.att.net> wrote in message
> news:ZGAtf.387641\$zb5.71253@bgtnsc04-news.ops.worldnet.att.net...
>> Quick, normal reaction static, but slow reaction in flight.
>> We all tend to overpower anything we can get our hands on .......
>>
>> "Steve" <scasko@aol.com> wrote in message
>>>> One I tried required control surface width and chord, max deflection
>>>> angle,
>>>> and max speed. From that I assured myself that my servo choice was OK.
>>>> Input
>>>> the max deflection and speed higher than what you realistically expect,
>>>> it
>>>> will give you a good safety margin particularly if you up the throws
>>>> etc
>>>> later on.
>>>
>>> I tried that with the one provided earlier and came up with some
>>> really low numbers (along the lines of 10-13 oz-in for the elevator and
>>> 4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
>>> that either the calculator is a bit off or we way overpower our servos
>>> (along with our engines....).
>>>
>>> What would the symptoms of an underpowered servo be in flight?
>>>
>>> Steve
>>>

>>
>>

>
> I have never had too powerful a servo crash a plane. I have had
> underpowered servos come perilously close to crashing a plane. Watts are
> cheap. Planes are not.
>
> Ed Cregger
>

Dec 31, 2005, 07:11 PM
Eye Indo
Eye Indo
Guest

# Re: How much torque do you need?

I just purchase the highest torque capacity units for what my money can buy.
Never think of IF I really need it. What I want .... that is another story
.....

"Jim Slaughter" <jim@slaughter.org> wrote in message
news:xeEtf.2395\$zJ3.290@trnddc04...
> At the price of our Hurricane servos, why not go HIGH torque? Check 'em
> out at www.flyhurricane.com.
> Our standard size 92oz servo is only \$15 with DIGITAL 152 and 191oz metal
> gear servos going for only \$40 and \$45. We have all the spare parts too.
> Gears, cases, arms, etc.
>
>
> "Ed Cregger" <edcregger@yahu.com (replace the u with oo)> wrote in message
> news:dp6th402fh7@enews3.newsguy.com...
>>
>> "Eye Indo" <amerindo@worldnet.att.net> wrote in message
>> news:ZGAtf.387641\$zb5.71253@bgtnsc04-news.ops.worldnet.att.net...
>>> Quick, normal reaction static, but slow reaction in flight.
>>> We all tend to overpower anything we can get our hands on .......
>>>
>>> "Steve" <scasko@aol.com> wrote in message
>>>>> One I tried required control surface width and chord, max deflection
>>>>> angle,
>>>>> and max speed. From that I assured myself that my servo choice was OK.
>>>>> Input
>>>>> the max deflection and speed higher than what you realistically
>>>>> expect, it
>>>>> will give you a good safety margin particularly if you up the throws
>>>>> etc
>>>>> later on.
>>>>
>>>> I tried that with the one provided earlier and came up with some
>>>> really low numbers (along the lines of 10-13 oz-in for the elevator and
>>>> 4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
>>>> that either the calculator is a bit off or we way overpower our servos
>>>> (along with our engines....).
>>>>
>>>> What would the symptoms of an underpowered servo be in flight?
>>>>
>>>> Steve
>>>>
>>>
>>>

>>
>> I have never had too powerful a servo crash a plane. I have had
>> underpowered servos come perilously close to crashing a plane. Watts are
>> cheap. Planes are not.
>>
>> Ed Cregger
>>

>
>

Dec 31, 2005, 09:11 PM
Bob Cowell
Bob Cowell
Guest

# Re: How much torque do you need?

On 31 Dec 2005 10:59:47 -0800, "Steve" <scasko@aol.com> wrote:

> I tried that with the one provided earlier and came up with some
>really low numbers (along the lines of 10-13 oz-in for the elevator and
>4-8 oz-in for the rudder on my 40 size trainer). I am led to believe
>that either the calculator is a bit off or we way overpower our servos
>(along with our engines....).
>
> What would the symptoms of an underpowered servo be in flight?
>
>Steve

When the surface "blows back" at speed, you don't have enough servo attached to
it.
In general, a .40 size trainer doesn't have very large surfaces or very much
deflection, so assuming you set the servo up to move the surface the required
amount WITHOUT limiting the servo travel, you get a mechanical advantage.

On "fun-fly" types with huge control surfaces and 45 degree deflections, the
servo requirements go up REAL fast as the speed rises.

Aileron blowback on one of these makes your heart rate rise REAL fast.