HV Servos or not?
 

I am about to purchase some servos for a new project - SM Large Hawk.

I am wondering from those who have used them - if HV servos ( I happen to be a JR user) have been perfect or if there is any issue with them?

I will be running 2S lipo and would use a 1222 receiver.

Plan B is what I usually use - Weatronic receiver, same batteries and standard voltage servos.

Thanks in advance,
Dave

RE: HV Servos or not?
 

Dave,

I have been using the 8911 HV's in my BVM F-100 for two years now and i have not had 1 single issue with them at all. I'm running a Spectrum 12120 power safe receiver and two 5000 mh lipo's none regulated and it's a great set-up. I also have all the other surfaces and controls on HV servos. ABSOLUTLY NO ISSUES!!!!!!!!!!

RE: HV Servos or not?
 

I agree with Greg. Have been running them for years with no issues. Love them.

RE: HV Servos or not?
 

thanks Greg.

I hope to catch up with you sometime. I have family in Naperville and used to get to Winamac.

Thanks again for the info. I am planing on 8911s as well.

Dave

RE: HV Servos or not?
 

That is what I have for a winter project. All JR 8911 HV. Also trying electric retracts and a E brake. I have used 8911 HV in a couple of projects and have not had any trouble. Just got my Hawk and looking forward to the build. What are you using for a turbine.

RE: HV Servos or not?
 

I have a Jetcat 160Sx for the hawk. Goshawk for me. Where are you getting your electric-SM retracts?

Thanks
Dave

RE: HV Servos or not?
 

I am having Down and Locked do them. I was going to but a JC 160 in but used it on another project. So I guess it will be a JC 180.
I have a Tutor with a 160 and it could yse a little more power, maybe i'll change it with the 180. I have a new BAE display color scheme that the Brits cam out with this year.

RE: HV Servos or not?
 

Thanks - is the cost for conversion 1,2 or 3 times the cost of the valve and servo? I didnt know they where doing gear this big?

I am sticking with the 160Sx from what I have heard, read etc.

Dave

RE: HV Servos or not?
 

I am not sure of the cost I think it is in range of $600.

RE: HV Servos or not?
 

Dave I've got that set up in my Hawk and it works perfect except if your elevator swings over center and you turn on. It will instantly break a control arm. Not sure if anyone else has experienced this but it sucks. Super strong servos and nice not to have regulators. Your going to love the Hawk!!! Scott

RE: HV Servos or not?
 

Thanks Scott!

RE: HV Servos or not?
 

I've got 8 of the 8911HV on my UB, Dave, and one 8711HV on the N/G.....over 50 flights....no probs....JR also makes digital micro servos now with HV for retract and brake valves as well......

Originally I was running dual 7.4/4000 LiPo's into a 1222, but switched over to dual 2300/A123 for the last 20 or so flights.....IMO safer when charging, and field charging with a CellPro 10S dual output A123 charger at 4 amps re-loads them to 100% in the time it takes to refuel and pre-flight.

TA

RE: HV Servos or not?
 

Tom, And a lots cheaper too!!! Lipos don't forgive if you leave plugged up to the 1222 for 45 days! :( A123's don't care :) Scott
Expensive mistake!!

RE: HV Servos or not?
 

Tom,
With the a123 and 6.6 volts, do the HV servos care about the lower voltage?
DD

RE: HV Servos or not?
 

Not very much. They dont care that much but a little sad im sure. :)

RE: HV Servos or not?
 

I noticed no change in speed with the 123's(they are very fast), but there is some loss of power from the 470 oz at 7.4 down to 200 oz at 4.8v. according to the spec page. So at 6.6v, presuming a linear drop, you still should have about 390 oz +/-

Spec page does mention A123/LiFe as suitable......

TA

RE: HV Servos or not?
 

Seems like SM Large Hawks with JR 8911's are all the rage Dave! Considering you are GIVING AWAY your UB (why ARE you selling her BTW???)

Anyways, my SM Hawk 100 was supposed to be here by now:eek:, and lo and behold, I of course have EIGHT 8911's coming with her along with A123 receiver packs from Electrodynamics and Andy Low.

Dave we should do our build together!!! Are you going to use the BVM manual?
Anyways, now that I crashed your HV servo thread (sorry), I would agree with Tom Antlfinger's extremely knowledgeable and well written post above. 8911 + A123's = winner combo!

Shaz
:D

RE: HV Servos or not?
 

Not to change the subject of the thead but who are you getting your e-brake from. Also the down n locked retract conversions work great. I have them in my gramunia me-262 and Tomahawk L-39. They work extremely well.
George

RE: HV Servos or not?
 

Hi Tom
Just a question here but if you are powering the 8911's with only A 123's why would you go to the extra expense of the 8911's over an 8711 when you can get 406oz. at 6 volts. Just curious are they quicker or for some other reason. One thing that Horizon is starting to show on their website though, is that the 8711 and 8411 are on the discountnued list, which I am not too happy about. I hope this is not true.
Thanks for your comments.

RE: HV Servos or not?
 

I am going to try a modified BVM E-Brake. I will use 2 cylinders on one mount with a large servo in the center. One cylinder pointed each way to operate one brake each. Mounted on the bottom under the intake

RE: HV Servos or not?
 

THE
The 8711HV is a better servo, and more expensive than an 8911HV. the 8911 is a plastic case, where the 8711 is an all aluminum case. Toms UB has the better 8711HV servos from tip to tail.

RE: HV Servos or not?
 

Geeeez! Senility is really setting in......just passed #70 couple of weeks ago......Guess it is time to sell my jets and stick to my 1oz indoor heli's...[:o]

Kirk knows what is in the UB as Kirk built the plane and I bought it RTF.......I remembered the 8711 HV on the N/G, but somehow got locked on to the 8911's. Just had the flap servo and aileron covers off last week, looking straight at 8711 HV's...:)

In any case, the presumed linear drop in 8711HV motor power should be the same as the 8911HV.....as power is near identical to 8911, they may be using the same motor?

Thanks Kirk......

Good question AKB......I bought the UB RTF with the 8711HV servos installed with 2 Lipo Bats.......

RE: HV Servos or not?
 

If you guys want some serious servo power take a look at the JR 6301, metal cased servos, the HV version, the 6311, take upto 8 .4 v but are rated at 7.4 V for 36.5kg/cm , 40% up on 8911s. A reduction to 6v drops the torque about 10% .
Using those on the stabs and flaps on my SG Hawk. MP80Ts, brushless, on ailerons, very active with a gyro in operation.

With a Weatronics system one can select the voltage to groups of servos, perfect.

See www.rcjapan.net

Don't give up because you're 70 Tom you're ahead of me, my pathfinder !

Regards,

David G.

RE: HV Servos or not?
 

Double post....

RE: HV Servos or not?
 

RE: HV Servos or not?
 

Hi Shaz,


Yes I am building per BVM with upgrades. I dont think I will have mine for 6 weeks ++. I think I might go LiFePo.

Will let you know when I get it. I have to get some servos on the way soon, was waiting to see if my UB or A10 would sell first.

Hope all is well out there!

Dave

RE: HV Servos or not?
 

Make sure that your whole system is HV compatible (or you have different voltage power supplies available) if you want to use HV servos. I had a delta and bought 2 HV servos for the elevons but then couldn't get a suitable servo for nosewheel steering so had to abandon the idea. This was a while back when HV servos were new and the availability is much better now. However, I would make sure that everything (electric gear, all servos, switches, valves, sequencers etc) all work at the required voltage or it becomes a pain to sort out.

RE: HV Servos or not?
 

Tom,

The Product Description says they are OK:

JR’s HV servos are designed with motors and electronics that operate off the direct voltage of a 2-cell LiPo, LiIon, or LiFe receiver battery pack (6.6V to 7.4V nominal voltage).

In any case, a brilliant marketing move by JR to convince everybody they need to spend $200 for HV servos when the previous, non-HV ones have worked fine for years.

RE: HV Servos or not?
 

The usual cure for the servo's going over to one side when switching on is to rebind after setting everything up, this usually cures it.

Mike

RE: HV Servos or not?
 

Craig, I think you are missing the point. JR's marketing states that HV servos were introduced because of the change in battery technology, with widespread use of Lithiums, so that HV servos can be used without regulation, seems a sound logic to me, particularly as HV servos can still be used at standard voltage with only a small torque reduction. It was customer/ technology driven. Your servo voltage spec. is YOUR choice dependant on your battery/ regulator configuration. That said, some HV servos offer really amazing torque.

As for price, many HV servos are little different in cost (some are the same, 6310 and 6311HV for example) as standard voltage servos. Many JR HV servos are priced at way way, below $200 !

It is also unsafe to assume ALL servos of the same spec. will work on unregulated A123s. I replaced some JR 9411 servos after almost 300 flights on the elevators of a Bobcat, fitted with A123s, originals worked fine BUT replacement, new, 9411s simply could not cope, became very jittery until regulated to 5.9v.

regards,

David.

RE: HV Servos or not?
 

sorry finger trouble.

RE: HV Servos or not?
 

Thanks everyone.

I just have to decide if I am using the weatronic receiver or the 1222. The idea was if I use the 1222 and the HV, I dont need regulators, otherwise I am with Craig. All of my other regular JR servos have been great.

Thinking HV/1222/ LiFePo at the moment.

Dave

RE: HV Servos or not?
 

So in other words, they reduced the quality of their "old" product so we have to buy the new one? 300 flights seems like a pretty good endorsement for a servo/battery combination. I'm not disagreeing with the logic behind HV servos but what worked in the past should not change just because something "better" comes along.

Craig

RE: HV Servos or not?
 

Please be aware that if the servo number doesn't exist in the Horizon Hobby inventory, if it ever needs service, Horizon will not work on it. Already know by trying to get service work done on 8511's. They told me if it is not sold in the Americas they will not touch it.

FYI
Alan

RE: HV Servos or not?
 

Craig,

I think your statement is totally unjustified and very wide of the mark. I do not believe for one second that JR has reduced the quality of their standard servos just to force us to buy HV, they are simply giving us the choice, now the use of lithiums is widespread. In the case of my 9411 servos JR may actually have IMPROVED the servo in the 8 years since the old ones were installed. The new ones may well have better, stronger motors and enhanced electronics to extract the best performance at the design voltage and operating them at a higher value, unregulated 123s, caused the overshooting and slight hunting at end points and neutrals. Operating at design voltage they seem to be faster and more powerful than the old ones., they certainly work beautifully. I changed the servos for new ones only because I had need for two 9411s on rudders of other models and it seemed logical to put the NEW servos on critical flight controls. *

Using your logic we would still be flying around using VORs and ADFs when FMCs, IRS and GPS with digital autopilots are available, in fact the norm !!

I rest my case m'lud.

Regards,

David.

* Some may remember I rejected BVs recommended BobCat rudder servo spec. (as did JR) 11 years ago and instead installed 9411s (and on elevators). Those original 9411s are still installed on the Bobcat rudders. As the rudders have a gyro on them and hence are VERY active, moving continuously, I will leave those servos in use till (if) one fails to see just how much life there is an a servo ! At the moment those servos still work beautifully with very little gear slop and are still very accurate.

RE: HV Servos or not?
 

David,

Using your logic, VOR's and ADF's would have quit working when they were IMPROVED following the introduction of newer FMC/IRS/GPS technology, but of course, that didn't happen. My comment about JR reducing the quality on "old" servos was facetious and I stick by my assertion that what has worked in the past should not quit working with the advent of newer technology.....a justified opinion, in my opinion and very much on the mark.

I'll buy the "better", "stronger", "enhanced", products when I have the need and feel they match the proven reliability of my current equipment.

Regards,

Craig

RE: HV Servos or not?
 

Those original rudder servos were only a problem when a gyro was installed. And.....I still stand by my original comments from 10 years ago the only problem with the elevator servos was poor rigging on the part of the builder. My Bobcat STILL has the original elevator servos in it, and it's 11 years old with a bazillion flights on it.

DR

FWIW I like the new HV servos but then again I like LiPO batteries as my receiver packs as well.