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HS-7954 alternatives

Xpress

Xpress

GSN Sponsor Tier 1
Flyingjon said:
Thanks for the clarification. I was almost sure that I'd seen them in a HV application but figured I must be wrong. @ChickenBalls do you know the HV torque/speed specs in those?
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The HS-7955TG servo was introduced before HV specific servos came about. We ran a lot of extensive tests on it and found that it can handle direct 2S Lipo just fine, but it is the only servo in our pre-HV lineup that will handle HV no problem. I run 6, 7955's in my 35% Yak on HV without issue, they are a little bit noisy at center and get the minimal load jitters we have explained before but once the engine is up and running and airflow is moved across the surfaces they will be rock solid.

We don't have official torque ratings on 7.4v for the 7955 but it will be similar to the 7954. Somewhere around 400oz at 7.4v. All I know is 2 of them is plenty for a 35% that has HUGE oversized ailerons (bigger than any 35% out there now).

Either 7955 or 7954 will be great.
 
ghoffman

ghoffman

70cc twin V2
I would like to see that test data. I have tested about a dozen 7955's and none have pulled more than 300 oz-in even on 8.5V, and 280 oz-in is more typical. Before it is suggested that perhaps my testing method is flawed, this same methodology showed a Futaba BLS-157 at 495 oz-in, and Savox 2270 at 440 oz-in and a Hitec 5685 at 180, all very close to advertised specs. I use a 3S battery through a Castle BC Pro, a 1 inch servo arm at 90 degrees, and calibrated the digital scale on a known 20 pound weight.
 
ghoffman

ghoffman

70cc twin V2
Xpress said:
We can't give out proprietary test data. Like I said, 2 7955's is more than adequate on the ailerons of a 35%. You'd need 3 of them on a 40%.
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They (2x, 7955) had wicked aileron blowback on my 104 AJ Slick on 2S lipo, and 1x on the ailerons on my 91 EF Extra. I took them off and used them on the elevators. It was not even close, so that is when I tested them. Another local friend made his own test and got virtually the same results (280-300). They absolutely do not do the advertised 333 oz-in.
 
Xpress

Xpress

GSN Sponsor Tier 1
There could also be lots of variables. But keep in mind, with 2" 3D arms you're only looking at about 150oz of torque output, maybe less. Lots of variables.

I've never had blowback on mine, even high speed rollers.
 
stangflyer

stangflyer

I like 'em "BIG"!
Flyingjon said:
@mnfatboy I'm sorry. Setting changed...
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I have multiple airframes with the Hitec HS 7954 servos. From 30%, 35 and even one of my 40 centers had 7954's in it. I recently changed them out as I started noticing a little blow back on the elevators. This is only since I have been really pushing the envelope more with the 260. If I were still flying it as I had been for the last year and a half, there was really no need to change them. In short, torque specs or no, the 7954 is an awesome servo that comes through like a mighty champ. JMO.... On my 30% Edge, they are more than I will ever need. Savox makes some great servos. As does MKS. They are all very good servos...You really can't go wrong no matter which way you go.
 
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