Hitec fans what do you think about this?

[caurimare]

I just received this in Troybuiltmodels monthly newsletter, I am a die hard fan of HITEC servos spacially 5955 TG reading this numbers makes me wonder.
what do you guys think? also check out the servo test it is also interesting.
TBM SERVO AND SERVO EXTENSION TESTING
** TBM SERVO TESTING: TBM conducted its own servo torque testing using the pictured equipment. We monitored the voltage at the Rx, the voltage at the battery, the amp draw at the battery, and the torque of the servo. We used a TBM 2-cell LiIon battery with a MPI Miracle switch (which has a built in 6v regulator). We tested other batteries and other regulators from Fromeco and Smart-Fly and there was no difference in the performance of the 1 servo. We were concerned with moving torque, not holding torque. We are interested in the power available to move a control surface into position. The most powerful servo, and the most power hungry was the JR-8711. It drew as high as 5 amps initially though the load dropped to 4.2 amps in less than a second. Having 13 of these on a very large plane like a 50% plane leads you to conclude that there could be a momentary current draw of 65 amps if all the servos were stalled. To put this in perspective, most of the circuit breakers in your home are 15 amps, and the best 4-cell LiIon has a burst output capacity of 18 amps. IN REALITY a plane with 13 JR-8711 servos will never require 65 amps. We estimate based on some testing that 50% planes will typically pull a peak of 40 amps, 40% planes pull a peak of 20 amps, 35% planes pull a peak of 10 amps, 33% planes pull a peak of 8 amps and 30% planes pull a peak of 5 amps on a routine basis. NOTE: I am not concerned too much about the torque values I obtained being lower than the stated torque values of the manufacturers because they are publishing holding torque, not moving torque, and their testing methods are different. I do feel very confident that the relative amount of torque difference from servo to servo is accurate and should be used to determine the servo you should use in your aircraft.

TBM SERVO ENDURANCE TESTING: TBM conducted its own servo endurance testing using the equipment shown above. We found that the first 1/10 of a second that the servo is used that the torque is at its maximum. The performance then degraded substantially over the next 60 seconds (of intermittent use), and stayed at that lower value for the duration of the testing. For instance the JR-8711 has an initial torque of 358 oz-in, and after 60 seconds (of intermittent use) the case heats up to 120 deg F and the torque drops off to only 280 oz-in! This is a decrease of over 20%. I regret to report that the Hitec HS-5955 lost 40% of its torque by dropping from 248 oz-in to just 152 oz-in in about 60 seconds (of intermittent use). To define intermittent use: I did not simply stall the servo for 60 seconds to see what would happen. I operated the servo as if I was performing knife edge passes along the flightline and knife edge loops, so the servo was cycled on an off and was stalled for no more than 8 seconds at a time

TBM SERVO EXTENSION TESTING: TBM conducted its own servo extension testing using the equipment shown above. We found that adding a single servo extension (22 gauge with universal connectors) between the Rx and the servo will cost you 1.5% - 5% of your power to that one servo. Adding another extension will cost you another 1.5% - 5% and so on. In one of the many tests run, I put ten 6"extensions in series and measured a total drop of 15% of the maximum torque that a single JR-8711 could put out. In another test, I put ten 48" extensions in series (40' of extensions) and found the drop in power to be 55%. Therefore losses due to servo extensions is a combination of plug losses and wire resistance losses. POWER LOSSES IN SERVO EXTENSIONS
SERVO EXTENSION LENGTHEXPECTED TORQUE LOSS6"1.5%12"2%18"2.5%24"3%36"4%48"5%

[XJet]

I use Hitec servos (almost exclusively) and love them (especially the 5955TG) but it's been my experience that Hitec's torque claims are more often than not, just the fantasy of some marketing droid.

They are not alone in hyping their servo torque/speed ratings but they have sometimes taken this "embelishment" to a new level, almost an art-form.

The product is good -- just not as good as they claim.

I'm not surprised at the *real world* figures uncovered by TBM's testing. It's *really* hard to get a lot of torque out of a standard-sized servo and not always a good idea to do so. Larger motors and gearsets can do the job with far less stress and greater efficiency -- albeit at the cost of a *little* weight increase.

[Freddy Warbird]

well, if these test are in any way accurate, the JR servo isn't delivery either. It cost more, and doesn't have titatium gear set. How are servos tested at the factory in the first place. Is there a different standard of testing , and rating to claim what the companies claim? In other words, is throwing a pull scale at the thing, a legit ament assessment to a particular servo standard?

[Vic3D]

I fly JR radios, but I will keep sticking with my Hitec 5955's. Only ones with titanium gear. 130 flights later 0 slop on mine. And I abuse them.

[crhammond]

I have a 35% Panzl with 4 x 5955 and 4 x 5985 servos. My Weatronic Rx has recorded AMP draws of 20A. 10 to 11 A occurs even in gentle flight like IMAC Sportsman. But those loads are VERY short lived. I have never seen a sustained load of more than 1/3 of a second. Average loads are still around 1.5 A for IMAC flying.

I like the HiTec servos - I never liked them in cars but in airplanes they work well. I am sure the torque numbers are exaggerated a bit but I have not noticed them fading in flight.

I don't doubt the 8711 numbers. I have seen those suckers suck batteries like mad in other airplanes.

A lot of it depends on how hard you fly too - los of 3D stalled flight with full throw and prop wash is going to pull a lot of amps.

I have noticed that in hot temperatures servos and engines and basically everything with an engine or motor in it loses performance.

It would be interesting to see how some older servos drop off like the 5945/5985/8411/8611 ... maybe the big motors in the new ones cause more heat and result in greater fade than the older ones?

[Freddy Warbird]

	Quote: Originally Posted by Vic3D
	I fly JR radios, but I will keep sticking with my Hitec 5955's. Only ones with titanium gear. 130 flights later 0 slop on mine. And I abuse them.

I sail the same boat.

[forgues research]

	Quote: Originally Posted by Vic3D
	I fly JR radios, but I will keep sticking with my Hitec 5955's. Only ones with titanium gear. 130 flights later 0 slop on mine. And I abuse them.

Actually , Hitec has a few servos with titanium gears, and the 5995 which are the most powerfull of the bunch and even beating the JR 8711.

That's what I have on my 52% Edge, but none goes through the receiver/s
They have there own batteries.

Roger

[Freddy Warbird]

When was the last time anyone seen a servo reach 120*F?

Do those servos come with Pull Start?

[GremlinX]

I love my 5955's... just wait until they answer back with a 6625 or something... whatever their answer to the 8711 is...

[Vic3D]

	Quote: Originally Posted by forgues research
	Actually , Hitec has a few servos with titanium gears, and the 5995 which are the most powerfull of the bunch and even beating the JR 8711. That's what I have on my 52% Edge, but none goes through the receiver/s They have there own batteries. Roger

Yeah, that's true! Hitec is the only brand with titanium gear servos.

[Edge 540]

Directly off Hitecs newest flyer:
6v specs speed torque
7965 .10 138
7985 .13 172
7966 .08! 111
7975 .11 144
7955 .15 333

Plus 2x resolution.

[exeter_acres]

Ummm..this thread is 5 months old

[airborneSGT]

OH snap we got some new servos. No wonder why the 5955's were being discontinued.

[50%plane]

Thanks for bumping this thread!

Good stuff

[MattyMatt]

Well.. it seems that the aluminum case on the 8711 is a very large heat sink, which will allow it to take on more and disapate the heat faster. I will be using these in my new Dalton 300.

The big change to come in servo tech will be the brushless servos... speed, tq, less heat, and hopefully can take a Lipo/Lion voltage.