Hitec 6985HB for jets???
 

HI guys:

My local hobby shop (sheldon's in San Jose, CA) is having a huge sale of 20% on everything. So I picked up a few Hitec 6985 digital servos. The spec are very good at 144/172 oz.in at 4.8/6 volts. They are Karbonits gear and are very tight. I ran them on my hitec programmer and they seem very strong. I am planning to use these in conjunction with hitec 5955 and JR 8611A in my next few jets..

Have you had any experience with these servos in jets, such as on ailerons or rudders or flaps???

Please, this is not a hitec vs JR, it just seems like a good deal at about $66 each..

thank you in advance..

RE: Hitec 6985HB for jets???
 

I'm using the Hitec 5645 MG digital servos on my Reaction 54 for ailerons, flaps, elevator, and rudder and have ahd no problems. These have about the same amount of torque and were about $55 each. I have 36 flights so far and they work great.

Bob

RE: Hitec 6985HB for jets???
 

I use Hitec servos in everything. MG for jets, and the HB`s stay in my boats ;)

RE: Hitec 6985HB for jets???
 

SJN
A longer screw is supposed to remedy that problem.
The Karbonite servos aren't recomended for big gassers but the lower vibration levels of jets may allow their use. The safest type is of course metal gears.

RE: Hitec 6985HB for jets???
 

Thiis is my first ever posting and I came to this thread because of my interest in servo reliability. I have used most of the popular makes of servo and last January I fitted 2 Hitech hs5645mg 10.8 kg. digital servos to the tailerons of my Fiber Classics SU 27 Flanker. After about 20 flights I noticed that one of the control surfaces was moving slower than the other. This dissapeared for a short while but then settled into slow servo movement. Thinking that there maybe something binding I diconnected the control surface and discovered that it was the servo. I sent this back to the UK agent who returned it after repair. After several e-mail queries to the agent I was told that the motor had been replaced. I would have preferred a replacement but this was not forthcoming. This was replaced in the model and several more flights were undertaken. I noticed last week that during a preflight check that the other servo was slow. I have packed them off to the UK agents, Amerang. I have requested that they be replaced with new ones but have not had a response yet. Mindfull that with a taileron controlled model, the two servos are all you have. To have suspect servos on these surfaces is very disconcerting. I have no real gripe with Hitech since I have bought many of their servos but this is worrying. Hitech give their torque out at both 4.8 and 6 volts but on these servos there is only a 4.8 value which is 10.8 kg. Has anybody any comment

RE: Hitec 6985HB for jets???
 

the 56XX series have been problem prone from the start , I would not trust there . I would stay away from the karbonite gear trains. The 59xx series and up are all good servos and I have never had nor heard of failure with any of these. I have several 5945 and 5925 servos and they are great. I am thinking of using 5955 servos on most applications where i would have used 8611 servos before. Similar power, and a lot less slop in the gear train... the digital programmability just takes these over the top !


Voy

RE: Hitec 6985HB for jets???
 

Ehab, is 6985 or 5985. I just got 4 HS-5985MG and they are the same specs as yours. 144 oz.in @ 4.8v and 172 oz.in @6v. They said have 3 metal gears and one karbonite, not sure wich gear is the karbonite. I'm planning to use them in my new pst panther for ail, elv. and rudd.

Rgds
Alejandro

RE: Hitec 6985HB for jets???
 

Hitec will n o longer make the 5945 and 5925. They have been replaced by the 5985 and 5965 respectively with improvements.
Even though the 56xx series were recommended for my R-54, I went with 5945 servos on my ailerons and elevator with 5645 on flaps and rudder. I have used the 5645's on on other planes with no problems.

RE: Hitec 6985HB for jets???
 

I like Hitec servos but as others have stated do not use 56XX or any of the Karbonite gear trains on your jets.

My $.02
Happy Flying
Gene

RE: Hitec 6985HB for jets???
 

They are 6985...

So it looks like it will not be a good servo for jets? Only a few years ago we were flying turbine Bandits and other jets with servos with plasic gears...

RE: Hitec 6985HB for jets???
 

What about the 5985? At least have 3 metal gears with only one karbonite. Did they do the job? or is better replace them? I have not install them yet and the guy in my LHS is willing to exchange the servos if they are not save in a jet.

Rgds
Alejandro

RE: Hitec 6985HB for jets???
 

I got this from the sales manager at Hitec. Karbonite gear train servos should NOT be used in aircraft weighing over 12lbs. The longer screw helps but it is not a complete fix. Since turbine jets put even more stress on servos due to the high speeds I would not use them in ANY jet. I recently had a customer lose both aileron servos on takeoff of the maiden flight on a 27% Extra with the longer screws. These were the 6985 servos. The aircraft was thankfully recovered with minimal damage. Hitec replaced the servos with the 5985MG.

I talked with one of my customers who is an engineer dealing with plastics for a local printer manufacturer. He said they have experimented with this type of material and could never achieve consistent strength. It appears that Hitec is experiencing the same problem.

Please don't risk your airplane or injury to those around you. The 5645 servos are a metal gear train and customer feedback has been very positive at my store. If others have had a different experience with this servo I'm sure they'll explain.

This is not a slam on Hitec. About 90% of the servos my store sells are Hitec. They just whiffed on the Karbonite stuff at higher power levels. It seems to be a great material for the smaller servos like the HS-65.

RE: Hitec 6985HB for jets???
 

So is the claim that Karbonite gears were many times tougher than plastic not very accurate? Or is it back to quality control issues with the Karbonite gear?

RE: Hitec 6985HB for jets???
 

This the way to go exactly what I would do.
Regards

RE: Hitec 6985HB for jets???
 

Hey guys,

Karbonite is definatley stronger than nylon (4 times per testing) but we have found that due to the hardness of the material that it can be more brittle causing it to shear in some situations. The 6985HB has actually been discontinued because the power to geartrain strength was not a good match. The 6975HB and 6965HB's are still available and shine in helicopter usage as the Karbonite holds up well there, even in heli's up to .90 size. We feel comfortable using Karbonite in high performacne models up to 12lbs utilizing one servo per control surface.

Note that the metal and titanium geared servos use what we can an M/K (metal, karbonite) gear as the first gear off the motor pinion. Most all other manufacturers use an all nylon gear here. The M/K gears have never stripped under normal conditions so there is no need to worry about its usage here.

My suggestions for high power, high cost jets are to just use the best we offer... the 5955TG. There is no better servo on the market today for performance and reliabilty. It seems there are so many people in this forum that put down Hitec servos but the truth is that when comparing flagship to flagship, we offer a superior product. I'm so confident in that statement that I challenge anyone to make an argument to dispute that.

Mike Mayberry

RE: Hitec 6985HB for jets???
 

Mike; thx for your response. I do think that Hitec, JR and Futabs make exclellent products. I like the programming features in the hitec servos and I wish other mfgs would follow suite...

I bought the 6985 based on the ads in the rc mags and based on the specs. I did not know they were discontinued. Is it possible to ask hitec for an upgrade to 5955 and I'd pay the difference in price? You can pm myself...

RE: Hitec 6985HB for jets???
 

It would seem that my contribution with my slow servos has expanded the discussion. I would value a comment from Mike Mayberry. Comments on the first output gear on metal gear trains being of a non metalic formulation is interesting. To say they never fail can in my opinion be challenged since I had two failures with Multiplex micro 'digi' servos where the motor output gear which appeared to be made of a fiber material just crumbled before the servos were even flown. I couldn't buy spare gear sets for these but the UK agent was prepared to replace these for an exhorbitant fee. I subsequently discovered that they had experienced problems with this gear. These were fitted to a large Peter Nye Grumman Panther. I believe that Multiplex and Hitech are one and the same manufacterer now. Once again I don't wish to knock anybody but merely to pass on my own experiences and try and learn more about servo performance.

RE: Hitec 6985HB for jets???
 

Ron- I'm happy to comment. First of all... you state the output gear crumbled to dispute my claim, but yet I was referring to the first gear next to the motor pinion not the output gear.

I'm not sure what MPX servo you are referring to either as the Titan is the only digital servo with Karbonite gears.

However, it's been my experience that when the Karbonite output shaft crumbles like you describe that loctite had been used on the screw as it will attack the material.

Mike.

RE: Hitec 6985HB for jets???
 

Guys thanks for your sugestions. In that case there is no reason to test the 5985 in my panther. I will go to my LHS and exchange them for 5955T.

Rgds
Alejandro

RE: Hitec 6985HB for jets???
 

Mike I'M SORRY FOR CONFUSING YOU, I'M NOT AS YET FAMILIAR WITH THE BEST JARGON. I WAS QUERYING THE SLOW ACTION OF MY SERVOS. I ADDED THE COMMENT ON GEAR FAILURE SINCE IT WAS INCLUDED IN THE GENERAL COMMENTARY. ONCE AGAIN ALL I SEEK IS ANSWERS RON

RE: Hitec 6985HB for jets???
 

If this thread is still open I can report that I have been given full credit for my hs 5645 servos but I still don't know why they went slow. Ron