Personal hitec 5955 test!!!

[jonkoppisch]

Alright, I knew that there had to be an easier way to explain leverage and the right way to test.

Grab a weight, 12 pack out of your fridge, gallon of milk or...

Hold it straight down to your side, that's no resistance,

now, keep your arm straight and start raising your arm until it's straight out, that's where knife edge would be and that's where you should measure your torque..

Anything less is inaccurate...

If I'm right the way that your test is setup it's giving a semi false reading..

[Kiwi]

Mike,

I like your curiosity and despite any of the negative comments you likely now have more idea of what you have installed in your plane than those who just go with the manufacturers specifications. Mate never give up testing and fiddling with things to see what really makes em tick. It will provide you with a life time of enjoyment and enthusiasm.

As for the torque of servo A versus servo B its pretty much all baloney. Unless your really taking every possible step to make a plane ultra light most people have more servo power on surfaces that they can ever use. The proof of the pudding there is the voltage and current capability of the flight system they have installed.

As an example the 8711 is quoted by the manufacturer as having a maximum current consumption of 4 amps. Now that will not be holding the famous 400 in oz of torque. A servo draws most current when it is moving. Not when its holding. The holding current is extremely low and often in the area of 30% of the maximum rated capacity of the servo.

Now assume pilot A has four 8711 servos on the ailerons. If the load required to rotate that airplane maximizes the capacity of the servo then he needs 16 amps to roll it. Thats just the ailerons, nothing else moving. That mate very rarely if ever happens and countless data loggers have shown flight loads on 40% aircraft are more in the 5 to 6 amp range. That tells me you could run with servos with 70% less torque and likely never know the difference. Well for someone like me I promise you I will never know it.

Of course if you roll like Mark Earl then that power and speed sure helps but I dont see to many capable of repeating what he does.

Your Hitec's will do what ever you need from them. The 8711 will likely out torque them and out hold them but the bottom line is I bet you never ever reach the limits of the servo before you reach the limits of the pilot.

Keep on testing, finding out what makes em tick and likely you will even be lucky enough to melt a few things as well. Its all in the name of acquiring knowledge.

[Kiwi]

Wrong.

The servo arm is at 90 degrees with the rudder in neutral. As it rotates the arm (moment) gets shorter so the effect of that is an increase in torque as the servo turns.

Plus in a knife edge the rudder is actually holding he tail down, not trying to lift it. Its a balancing act but there is little load at all on the servos. The fuselage and vertical stab are being held into an angle of attack and thats all the rudder servos are doing. See my post above regards on board power data logging.

Now if you want to Max out your rudder servos do a knife edge loop or a flat turn. Both would load the servo much more than a good straight knife edge.

Snaps, blenders or any high speed maneuver that requires full deflection of the flight surface are the only time servos see extreme loads. And agin its moving the servo that consumes energy, not holding it in one place.

	Quote: Originally Posted by jonkoppisch
	Alright, I knew that there had to be an easier way to explain leverage and the right way to test. Grab a weight, 12 pack out of your fridge, gallon of milk or... Hold it straight down to your side, that's no resistance, now, keep your arm straight and start raising your arm until it's straight out, that's where knife edge would be and that's where you should measure your torque.. Anything less is inaccurate... If I'm right the way that your test is setup it's giving a semi false reading..

[randy racer]

just a few short years ago the best servos we had to use didn't have the torque of the 5955tg's and had sloppy gear trains . now we have the 5955's and great no slop gears that hold up under the loads we put them through .but some people would rather use the other brand that has even higher torque servos with sloppy gear trains that have issues with motor burn out due to over powering them for higher torque. i think a servos that does it's job well and holds up for the long haul is the smarter one to use. bragging rights about my brand is stronger won't keep your plane in the air if it locks up.

rr

[jonkoppisch]

I think that there will be a big difference, whether you realize it or not??? This was taken from anther thread (I'm going to snip a little as it's quite long)

"I have set up (5) 40%ers last winter all with 5955s....that they where not sufficient enough for a 40% plane...I held the plane and throttle up.I then hit full up 3d elevator and it only went up 1 inch.I let off the throttle and it went up the rest of the way (5 inches).Can you say major blow back? Yes I only have one 5955 on each elevator half with a 1.5 ''with a 1:1 geometry .As Hitec advertises 333tq.oz. this should be enough power assuming that the loss of torque under load was with in acceptable tolerances like 20%loss .BUT after TMB did there testing on them I understand why I get so much blowback now.I am only getting 153 tq.oz. under load....
2 5955 on each aileron also gave me lots of blow back in the air.
In my 40% Carden Edge I have (3) 5955s on Rudder pull pull. I would do a Knife Edge circle and found my self add ing more and more rudder stick throw on 3D rates until the stick bottomed out.AS the plane came around the last 3/4 of the circle I looked at the rudder and it was almost FLAT and the plane was sinking.I had to role out.I did this over and over with the same result.... MAJOR BLOW BACK! I tried a forth servo on the rudder and it was just enough to power the rudder through that simple maneuver....
I will slowly change out all of my 5955s with JR 8711s."

First hand experience with the 5955

corrected post link to http://www.flyinggiants.com/forums/346434-post21.html

PS, if you want to see this guy fly and if he has a clue what he's talking about click here

http://www.flyinggiants.com/forums/345745-post33.html

[jonkoppisch]

	Quote: Originally Posted by Kiwi
	Wrong. The servo arm is at 90 degrees with the rudder in neutral. As it rotates the arm (moment) gets shorter so the effect of that is an increase in torque as the servo turns. ...

Isn't that what I said? I was applying it to the test. At neutral, or as in your first sentence, there is no load. On his test, the neutral position is under full load, then lifting from there.. if it takes less torque or power to do a knife edge then why do people have to put more than 1 servo on the rudder to be able to do just that?

[mikedannielle]

[Kiwi]

John,

I would bet my bottom dollar his problem is not Servos but VOLTS!!!!!!!

I have a 40% Pitts with a 212 3W that will pull the roof off your house. It has two 5955 on the each elevator and you cannot get those to blow back no way. Those elevators are barn doors by the way, I mean big!! But the power system is enormous by model standards and I will be tossing it soon to go with direct 3000 MaH A123 cells rated at 40C.

The ailerons on that Pitts only have 5945's. Fast as light but not high torque and you get no blow back from them.

There is absolutely no god given reason for a servo or servos to require more stick as you go unless your maximizing the voltage and current capability of the system feeding power to the servo(s). Again thats because the servo once it is holding the position does not draw huge amounts of current.

A good way to prove that is look at the test carried out by Mike. Did you see his servo slowly loosing ground. No way.

There's a whole lot more to getting your servos to perform that reading the manufacturers specifications and blindly accepting them. The secret to good servo performance is power (Volts) Pressure (Amps) and keeping them cool.

In fact my next 40% will be built using the new Ace Hobbies 200 in\oz servos. They are super strong, no gear slop, fast as they come and they have an alloy finned case to keep them cool. I can assure you even with those setup on a 40 % model correctly there will be no blowback.

[jonkoppisch]

Well, here's what he's using volt wise... Don't think it's that

I got some new 5600mha fromco packs switched out SM power expanders and regulators,checked for any binding at any point in the range of motion and STILL THE SAME RESULTS

I will say that unless your flying hard, you may not even realize that you don't have the torque.. Here's what Joe Hunt said..

"In my experience/opinion the 5955 is a great all around servo, but if you can afford the 8711 it is ALOT better servo. Much more power moving off center, much smoother and better centering. Big, big difference in the way the two feel on the wings of the same model plane (the Aeroworks 122" Extra 260 QB). The 8711s just kill the 5955s on the wings of that plane."

Located at http://www.team flying circus.com/Forums/tabid/54/forumid/7/tpage/1/view/Topic/postid/7082/Default.aspx

You have to remove the spaces between team flying circus

[Kiwi]

	Quote: Originally Posted by jonkoppisch
	if it takes less torque or power to do a knife edge then why do people have to put more than 1 servo on the rudder to be able to do just that?

Mainly because there's enough space to fit them in but not because it needs it. I can assure you I have seen a lot of guys 3D the buggery out of 30% and 35% planes with single servos on the flying surfaces.

The rudder is a real good example as to why it can be done as well. That bit at the top that hangs forward actually balances the load required so you have a sort of power assisted rudder if you like.

Many 40% sized models have the same balance horns on elevators. If you take the time to set them up right and dynamically balance them then the servo does very little work at all.

You know Chip Hyde's big Ultimate is some ten plus years old. He won the TOC with that and if my memory serves me right you were lucky to find a servo with 150 oz of torque back then, but they still done it.

Its all about setup, linkages, powerful battery systems etc. Sure Super duper high torque servos are great but only if your taking two out and replacing it with one.

You can have all the servo power in the world available but if your setup is not right then it dont matter a darn. Look at the 8711 incidents for a good example. They are great servos but they are not a cure all on their own.

Its the entire system that counts. Not just the black plastic box at the end of the wire.

[XJet]

To properly measure the servo torque you need to use a drum, not an arm.

A drum with a 2" diameter (1" radius) to which a line (kevlar is good) carrying the weight is attached will ensure that the load remains constant regardless of the angular position of the servo output itself.

It seems to me that we have as much "religion" in servos as we do in engines, RC gear, batteries, oils, etc.

My philosophy is that everyone ought to use whatever *they* think works best for them.

I've got TG5955s in my gaser -- but it's only a 50cc and I'm pretty sure I could get away with some 5945s -- in fact another guy at our club does have 5945s fitted to the exact same airframe and it flies just fine.

The sole reason I went the 5955 way was because I don't see the point in changing gearsets every season (or more often) simply to save $20 on the purchase price of a servo. That's right, the 5955 is only about $20 more than the 5945 (if you wait for the good specials from Servo City) and that's only about the cost of one gearset.

That the 5955TG has more torque is just a small bonus (for me). That the gears seem to last forever is the real point of distinction.

Now, I also design and manufacture UAVs, some of them weighing over 120lbs and having a 12 foot wingspan. When we really need torque on such big birds, we don't toy around with silly little standard-sized servos, we just throw some Seikos in there and get all the torque we could ever want.

If/when I decide to build a 40% bird for 3D, I'll look closely at what represents the best value for money at the time and go that way. It might be JR, it might be Hitec, it might be Futaba. I'm so agnostic that it's not funny because I let my wallet do the decision-making. Mind you, I buy on *value* not on price so that means I don't always go for the "cheapest".

[Pale Rider]

	Quote: Originally Posted by mikedannielle