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HelicopterMain Discussion › Actual Servo Speed Under Load
09-12-2007 07:50 PM  10 years agoPost 41
AirWolfRCrrProfessor - 42½ N, 83½ W - My Posts: All  Forum  Topic

Try this chart. Print it out and plot your servos.

The chart has been moved 5 posts down in this thread to conserve bandwidth.

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09-12-2007 09:14 PM  10 years agoPost 42
AceBird

rrElite Veteran

Utica, NY USA

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Just how many years of experience does it take on a given servo? We have been using some of these servos for quite some time now.
Years don’t matter John, hours of use matters and I can’t answer your question directly. I don’t have the experience. But if you queried the list and someone reported that they consumed 10 gal. of gas using a particular servo you would know that it would be good for at least 35 run hours. It is a pretty safe bet that the servos that last the longest are probably the best choice. It is highly unlikely that someone would use a servo for 10 gal. worth of fuel if they weren’t satisfied with the performance.

Quite a lot of technical confusion going on in that other thread, ey.
BUT, real world numbers are still needed, as many as can be had.
. . . . to see where on the chart we fall.
I don’t think you would ever finish the chart before it became obsolete.

Ace
What could be more fun?

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09-14-2007 03:59 AM  10 years agoPost 43
The Dude II

rrVeteran

IN - USA

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Just saw this...

I was wondering about this very subject...and back in the spring I started down the avenue.

I’m a plane guy and on my 5th season of helis…so no extreme 3D yet…but I have goals!

My #1 bird was complete/flying and decided to build a "clone".

I now have two nearly-identical Pantera 50s (#1 has 9252s on the cyclic and #2 9155s and then…well…you know about landing inverted…so #2 now has 600mm TFT vBlades)

Otherwise they are equipped as follows:
Audacity Pantera 50 kits
OS 50 Hypers
Audacity Pro Mufflers
Fromeco Arizona Regulators @ 6VDC
Fromeco ReLion 2cell Li-Ions (2600mAh)
GV-1s
GY-611s
V2 vBlades 600mm #1 heli (139gram)
TFT vBlades 600mm #2 heli (128gram)
9252s on Throttle
PCM 8Ch Futaba receivers driven by a 9zWCII.

Total dry weight on #1 is 8lb 0oz.

Total dry Weight on #2 is 8lb 1oz.

CCPM setup is:
+/-12 on the collective
10 degrees on cyclic
Hover 1750rpm
Idle 1 2000rpm
Idle 2 2100rpm

My alternate blades for comparison are SWE Carbon Fiber 600mm and 620mm.

The #2 heli, with any blade set is far “crisper”.

As I log more flights (#1 has somewhere near 80 flights, #2 is near 20) I’m finding that I don’t bog the head as badly on the #2 vs. the #1 bird.

Rolls are more axial on #2 than #1.

Tic-tocs…large difference…#2 heli is on the money…very little correction is needed…#1 is a bit trickier to make the move look as good.

The difference is small between the two…but rest assured, my next servo purchase will either be for more 9155s or should I stray from the futaba camp, the JR 8717.

lotta ins, lotta outs

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09-14-2007 03:00 PM  10 years agoPost 44
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Were you going to tell us what the specs on the 9155 and the 8717 are ?

Are the 9155's supposed to be different from the 9351's ?

Assuming that your 9155's and the 9351's are the same performance, your observations are saying that torque requirements for cyclic and collective are well above about 25 in oz which is where the 9252 and 9351 cross on the chart.

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09-14-2007 03:51 PM  10 years agoPost 45
The Dude II

rrVeteran

IN - USA

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From Futaba's site:

http://www.futaba-rc.com/servos/servo-select.php

Servos that match your request:
6.0V; Digital; Standard size; 100 oz-in or greater torque; .2 sec/60° or faster; Air;
Stock Number Name Type Size Torque Speed Weight (oz) Use
FUTM0212 S9152 Digital Standard 278 0.19 3 Air
FUTM0213 S9153 Digital Standard 208 0.15 3 Air
FUTM0215 S9155 Digital Standard 192 0.13 2 Air
FUTM0235 S9350 Digital Standard 138.8 0.12 2.1 Air / Surface
FUTM0241 S9451 Digital Standard 120.8 0.1 2 Air / Surface

Looks that the 9351 is a "Surface" servo...what I've seen of these "surface" servos (friends 9451s) is that they have a shorter lead. As far as centering or "other" spec's that Futaba makes between "surface" and "air"...I do not know. Maybe I'll call today.

Otherwise, 9155 & 9351 are the same...even the asking price of ~ $109.

The JR 8717:
http://www.jrradios.com/Products/Te...ProdID=JRPS8717

$109 as well for the 8717.

Hmmm...after looking, the JR spec does boast a bit quicker...but also at a small weight penalty (2.36oz vs, 2; that'd be ~1 oz heavier with 3).

Have a fiend building a second 600N Sport...he's looking to go to the 8717 over the 9451(his #1 ship)...I'll let him build it and report back when he's complete.

lotta ins, lotta outs

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09-14-2007 04:07 PM  10 years agoPost 46
AirWolfRCrrProfessor - 42½ N, 83½ W - My Posts: All  Forum  Topic

You might want to re-think those 9155's - - - - I just added the JR 8717 to the chart.

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09-14-2007 04:07 PM  10 years agoPost 47
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

My Posts: All  Forum  Topic

My only question is, where did that formula come from? Not that I doubt it, just curious...
I finally found out where I got the formula from! I got it from ChristianM here on RR.

I was going through some paperwork here in my office, and I ran across some servo info that had the formula written down on. I thought maybe I got it from RC Heli, but I couldn't find it anywhere. Then I Googled it and still couldn't find it anywhere. Anyway, I found out it was from ChristianM.

Kudos to ChristianM for getting us this formula!

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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09-14-2007 04:18 PM  10 years agoPost 48
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

Hate to rain on anyone's parade but that formula is what you get when you start with,
1) zero speed at maximum torque
2) rated speed at zero torque

And that's what the chart shows.

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09-14-2007 04:24 PM  10 years agoPost 49
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

My Posts: All  Forum  Topic

Hate to rain on anyone's parade but that formula is what you get when you start with,
1) zero speed at maximum torque
2) rated speed at zero torque

And that's what the chart shows.
That is correct. The stall torque means the servo has stalled - zero speed. And of course the rated speed is done without a load - zero torque.

What is your point?

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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09-14-2007 04:29 PM  10 years agoPost 50
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

My point is the formula is not any mystery and a chart is a lot more informative.

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09-14-2007 05:07 PM  10 years agoPost 51
SSN Pru

rrElite Veteran

Taxachusetts

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My point is the formula is not any mystery and a chart is a lot more informative.
His way is better than yours, that is always his point, in every post

Stupidity can be cured. Ignorance is for life!

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09-14-2007 05:42 PM  10 years agoPost 52
AceBird

rrElite Veteran

Utica, NY USA

My Posts: All  Forum  Topic

The stall torque means the servo has stalled - zero speed. And of course the rated speed is done without a load - zero torque.
Why is it assumed that it is a straight line. I don't think it is and I would also think that there is a greater variation with analogue servos.

Ace
What could be more fun?

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09-14-2007 05:49 PM  10 years agoPost 53
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

I doubt that it is a straight line. The link to that French site earlier in this thread seems to indicate that.

BUT I am confident that, whatever it is, the curve will be charisteristic for all servos and a simple straight line comparison will be adequate for evaluation of one servo against another.

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09-14-2007 05:53 PM  10 years agoPost 54
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

My Posts: All  Forum  Topic

That is correct. Servo response is not linear. However, as stated earlier, it is close enough that we can use this formula and this chart to make valid comparisons.

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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09-14-2007 07:06 PM  10 years agoPost 55
damaen

rrVeteran

Umeå, Sweden

My Posts: All  Forum  Topic

I wouldn't put too much trust into this considering everything is theoretical using manufacturers (ideal) ratings and extrapolating those numbers using simplified formulas...

Henrik

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09-14-2007 08:06 PM  10 years agoPost 56
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

You work with what you have, a heck a lot better than having no info at all.

I'm not prepared to dismiss everything because I don't have all the details.

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09-14-2007 08:26 PM  10 years agoPost 57
gullie667

rrVeteran

Brooklyn, NY

My Posts: All  Forum  Topic

A servo stalls at its rated speed? I never realized that.

Helicopters - 1000 parts flying in formation.

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09-14-2007 08:39 PM  10 years agoPost 58
AirWolfRC

rrProfessor

42½ N, 83½ W

My Posts: All  Forum  Topic

HU ? ?

If it's running at speed - - - - it's not stalled - - - - is it ! ?

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09-14-2007 08:45 PM  10 years agoPost 59
gullie667

rrVeteran

Brooklyn, NY

My Posts: All  Forum  Topic

Eh... I mean a servo stalls at its rated torque? I never realized that.

Helicopters - 1000 parts flying in formation.

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09-14-2007 08:57 PM  10 years agoPost 60
Rockohaulic

rrElite Veteran

Canyon Country, CA, USA, 3rd Rock from the Sun

My Posts: All  Forum  Topic

I mean a servo stalls at its rated torque? I never realized that.
Yup - That's why it is refered to as the stall torque. It's the torque at which the servo no longer operates and stalls.

It's confusing, because to look at the specs, you would think that it can operate at the rated speed at the rated torque. Life would be easy then picking out a servo!

But if you look at the fine print, the speed is at zero load, and the torque is the stall torque.

Saturday morning I flew my helicopter in my pajamas
How it got in my pajamas I'll never know

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HelicopterMain Discussion › Actual Servo Speed Under Load
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