ramcfarland

My Feedback: (44)

Hello all-
Do you think the new JR 8611 digital will provide enough torque to handle pull/pull on rudder on my Wagstaff Great Planes Extra fitted with the new ZDZ 50 NG.?

Thanks all,
Richard McFarland Ama 52920

Chris Moon

My Feedback: (8)

That should be plenty. I have an 8411 on the rudder of my Patty with BME50 power and have no problems with it holding the rudder. I have also used an 8411SA as well with excellent results. I have the servo in the tail. You will love the way your Patty flies. Just small pitch to belly in knife edge, but not too bad. It's an excellent flying plane.

Geistware

My Feedback: (16)

Yes, that will be plenty.
I used two 9202 with excellent results
If you decided to use a 6 volt system, you will have more available power from the digitals.

RickP

My Feedback: (2)

Should be more then enough. I think 1 8411 would be enough. I've seen one 8611 on a 2.3 composite ARF working fine.
RickP

jongurley

My Feedback: (29)

It will have more than enough I have 1 8411 on my CA 27%er extra and it will be a plenty..

GoeKeli

My Feedback: (18)

Is it true that the 8411 or 8611 develops gear slop rather quickly? I would really like to use some of these servos but am not sure. Thanks for bringing this up. I am having a hard time with a hitec 645 on my H9 CAP rudder and it seems to not or hold it's center well and at 4.8 volts gives up when really really stressed.

JOe

jongurley

My Feedback: (29)

It depends on the the maneuvers etc. IF you have a 8411 on the rudder and only use it for taking off or a knife edge once in awhile then no it will take for ever to get any type of slop at all. On the other hand if you have the 8411 on your patty and use the rudder alot it is still not going to wear out because it has more than enough power for the size rudder surface you have. [8D]

barryb-RCU

Don't know about the 8611. My experience with 30 or so 8411's is :

o airframe vibration is what wears them out
o a big, heavy, foam wing airframe with a very smooth twin (like the brison 6.4) wears them out more slowly
o most wear happens around idle settings
o 8411's last a lot longer on vertical surfaces (rudder) than horizontal ones (elevator, aileron)


The life cycle of my horizontal surface 8411's (I've been through 30 or so) has been :

initial install : great
20-50 flights : slop is greater. Can't feel it flying but can with my fingers and can see it in greater surface vibrations
80-150 flights : pots start to wear out from all the small oscillations (whether you've replaced the gears or not).
At this point your surfaces may begin oscillating on their own on the ground.
150+ : By now you've pulled the servos, sent them to horizon, and they've sent you replacements. Excellent
service, usually replace rather than repair.

My experience has been exactly the same with metal (8411) and plastic (8411sa) gears.

ramcfarland

My Feedback: (44)

Very informative thread,aside from having pots go south sounds like an extra gear set would be the ticket for ER field maintance-

rmh

IF---one takes the time to really lighten and balance the ailerons and elevators -- this wear problem is greatly reduced .

John Murdoch

My Feedback: (11)

Hummmm.... I've been thinking. I've had an 8611, running 6V, on my Patty and I thought it was awfully weak. Knife Edge loops lost surface control. Point rolls wouldn't hold either with that cheap 8611 servo. I think you aught to buy 3 of them and gang them together to get the maxium torque needed for these kind of maneuvers. Then, after you've found out that three of them is way overkill, you can sell two of them to me, cheap.

Just kidding. The 8611 would be an excellent choice for the pull-pull rudder on a Patty.

Cincinnati Joe

I've got one 8611 on pull pull rudder on a hangar 9 sukhoi with BME 105 and it does the job nicely. With a big wheel, though, the play in the output shaft bearings is readily apparent. The big blue hitec has just about the same torque on 6 volts with almost ZERO bearing slop. I may change it out - will have to wait to see what happens as the flying season goes on...

ramcfarland

My Feedback: (44)

HUMMMMMMMMMMMMMM Very interesting........[sm=cool.gif]

FastFredd

The 8611 has much less play in the gears initially. They are also designed differently than the 8411, with different materials so that the wear (slop) is minimized. Should last much longer with regards to developing gear wear and slop. The 8611 is a "mighty" servo. You will like it.
Fred

ramcfarland

My Feedback: (44)

Thanks fred- I'm an Airtronics flyer but the numbers on the JR's 8611 are about twice the power of the Airtronic's 58Z Digital(which I like) but couldn't resist the #'s on the 8611 and put one on rudder- you know. Now a dilemma: I put Airtronic's and JR "logos on my latest project . I like this servo compatibility thing,sooo when is Futaba going to (join the club)[sm=lol.gif]

Doug Cronkhite

My Feedback: (34)

If you get slop in the 8611 I'll be impressed. Mine are all running tight after some 60 flights in my 46% Ultimate with a ZDZ-210 for power.

ramcfarland

My Feedback: (44)

I thought so- was reading another thread.. developing infro. on "core-less high end type's." did not take a lot of researh to grab an 8611 for my application, in which I hooked the Kevlar pull /pull to it early A.M. and it is nice indeed.

rmh

For those who are actually going to use the 8611 or similar servos.
The performance of these is seriously influenced by the power available to them.
It is a MUST, to have a battery setup which will not "droop" when the servos are operating under flight loads.
Use a 6 V high amperage potential, set of batteries - multiple power inputs, power distributors, dual switches, etc., which are designed to transport the current needed for these servos.
There is a BIG difference in performance .
Just adding the high performance servo is of little or no added performance value.

ramcfarland

My Feedback: (44)

Hello Dick,
Would appreciate your suggestions specifically for a Great Planes Wagstaff Extra thus far powered up with A nickle metal 1500 4.8 V equippted W/ ZDZ 50 NG, Airtronics 58Z's, one on each elevator half,one on each aileron and of course the brand new 8611 which is on pull pull rudder. Let me know Dick just call me at RCSC and I'll get paid to listen.. [sm=lol.gif]

blkbird68

My Feedback: (19)

Dick has pointed out the one thing everyone tends to overlook. I have done alot of static testing with servos under load testing current draw and voltage losses when I built my power buss and you would be amazed at how much less current a given servo will draw and how much cooler the servo will be when it actually receives full voltage when under load. battery choice and the # and type of connections in the system play a major roll in robbing voltage before it gets to the servo. Alot of planes have servos in them that have far more "rated" torque than the planes would actually need. However you have to remember that the "rated" #'s are based on tests done with no extensions and the servo actually receiving "full" voltage. In actual use these super strong servos sometimes come up short because they are being choked to death.

Scott Claboe

My Feedback: (9)

blkbird68,is right thats why I would like to use a lit-ion 7.4 volt with regulator.Always at 6 volts,ALWAYS.My patty has a 8411 on a pull-pull system.works killer!!

ScottC

Shortman

My Feedback: (21)

I think this is where Lithium Polymer batteries will shine. A 2100 2C Thunderpower pack is capable of handling 20 amps continuos and 40amps in bursts. Now thats much much much better then any Lithium Ion and NiMH/Nicad could ever get and the servos couldn't possibly eat that much juice.

Where do you buy a power buss?

blkbird68

My Feedback: (19)

You can do like I did and build your own... or you can spend a ton of money and buy one of the commercially available units.

There are several, the I4C isolator is closest in function to the one I made and then of course there are the the Emcotech and Powerbuss Pro http://www.rcuniverse.com/forum/Emco...1635038/tm.htm and several other that I can't think of right off the top of my head.

This thread has a pic of the buss I made...

http://www.rcuniverse.com/forum/m_13...tm.htm#1362193

Shortman

My Feedback: (21)

Do you have any graphs or hard data comparing a normal rc set-up and one utilizing the power buss system?

blkbird68

My Feedback: (19)

...all I have is my observations using a DMM's here at home and an ocilloscope a few times at work. At the time I did all this I wasn't really looking to right a paper on the subject.... I tested servos direct off the RX buss (which showed pretty good actually) and through extensions of 24,36, and 60 inches repeating the same test with the same servos with the connectors changed out and using the buss. I used a 6 cell 3000mah NiMH pack through 2 powerflite adjustable regs for all tests and the battery to switch connector was a deans for all tests. I never pulled the battery down to dropout of the regs which I had set to 6.2V under a 1 amp load. Although at the higher loads the regs output did droop some due to internal losses. I used JR heavy switches for the "stock" tests and powerflite switches on the buss. Losses though the two brands of switches were similar. A couple tests powering straight of the RX buss (using no switches therefore no extra connections) showed little loss until total buss load was over 4 amps and even then the losses were less than a volt. Adding extensions and switches to the mix (extra connections)is when the real drops occurred. All the extensions showed the same loss at currents below 4 amps showing that the 22awg wire was plenty. The main losses appeared across the connections. So you can make a significant difference in the systems performance just by changing out connectors. If nothing else, changing the connector between the battery and the switch should show a difference in performance in a large plane. My buss is overkill for most applications (IMO) just common sense stuff like keeping the # of connections beyond the RX buss to a minimum or changing those connections to something better, at least 22awg wire for you extensions and on large applications switches and battery packs with 18awg wire, and changing the battery to switch connector would go a long way. Another advantage to using a buss like mine is that if you use matchboxes, gyros , etc. they can be put between the rx and the buss isolating them from any servo loads and giving them a nice constant 5V power source. While the servos can enjoy whatever voltage you want to run on them. So were does all this get us?? Well, obviously, you can fly without doing all this, but doing it will make a difference. Just my 2 cents. If you want graphs well, I guess you'll have to do them yourself...not trying to be a smart**s but I did what I needed to prove to myself what was going on. And I'll be happy to share that info. but I am not going to re-do everything just to make graphs or "proper documentation".