flyinrazrback

My Feedback: (69)

I ordered some hitec 5925s for a lanier 30% edge, but just started reading all of the terrible things about them. I also ordered a 5735 giant one for the rudder. My question is, I am thinking on replacing the 5925s with JR 8411s, but dont know what to do for the rudder servo. The hitec giant digital would be used on a pull pull setup on the rudder @268oz torque.

1. Is a single 8411 enough for pull pull on this size aircraft?

2.Or should I just replace all of the 5925s with 8411s and keep the 5735 since I have not heard one bad thing about it.

3. My battery setup is going to be 2x2000 7.2 lithiums, with the voltage regulated at 6v, will this work with the 8411?

Any servo alternatives to 8411s or hitecs? ie airtronics digitals? I know futaba digitals only run at 4.8 volts, and not sure if they are metal gear or not

flyinrazrback

My Feedback: (69)

Or maybe just go back to analogs, never had one of those fail like I head the digitals are.

sfaust

My Feedback: (11)

It all depends on what you plan on doing with the plane. For 3D, you might want more than an 8411 on the rudder, but for aerobatics and IMAC flying, an 8411 would probably be plenty.

Airtronics has a 94358 metal gear analog servo that puts out 200oz at 6v. I use these as 8411 alternatives. You could also go with a Multiplex digital jumbo that puts out 255oz, which is equivalent to the HiTec 5735MG servo. It is a solid and reliable servo from the buzz around the fields. I put two of them in my latest 40% Extra project. I've used the non-digital version in other planes with great success.

flyinrazrback

My Feedback: (69)

good deal, where did you get the airtronics and how much were they?

flyinrazrback

My Feedback: (69)

I fly imac mostly, but a little 3D, just torque rolls and waterfalls, think the 200oz airtronics would be up to the task for the rudder on a pull pull? Cheapest place I found the 94358s was donalds hobby, $99 ea plus 10% off. Think I am going to order 5 of them, one for each surface, which will be complete overkill, and the 1 for the rudder on pull pull

kram-RCU

I'm flying a 33% Extra with a 3W85 power plant. I use 3 ganged 8411's for the rudder. Two would probably be enough, but I lost a similar plane (with less servo power) rather spectacularly to flutter last year, and don't care to repeat THAT.

mt

flyinrazrback

My Feedback: (69)

that bites, do you have to use a matchbox to gang the 8411s on the rudder?

kram-RCU

Don't have to use a matchbox, but it helps with trim and "buzz."

mt

sfaust

My Feedback: (11)

If you can get by with 2 rudder servos, you can avoid the matchbox approach by using two channels on a computer radio and set the programming much like you would with a matchbox. This gains you a few things. One you have a redundant link on the rudder since you have two paths to the servos, and not one with a 'high tech Y' through a matchbox. You will deliver higher voltage at the servo, since you won't suffer the voltage loss of two additional connectors in the path, and the additional loss associated with the resistance of the single servo lead to the matchbox. Finally you avoid having three additional connectors, pins, and contacts with their respective failure points between the receiver and the servos as additional sources of potential problems.

Most 35% planes need somewhere around 340-400oz or torque for 3D, and about 25% less for Imac and sequence work. You can calculate this easily on a spreadsheet that was created by Craig Tenny a while back. It is very complete, and takes into consideration lots of variables from deflection, area, airspeed, control geometry, offsets, differential, etc. It also takes a conservative approach, so the calculated numbers should be more than enough, with no need further padding. Its probably the most accurate estimate of servo torque requirements people like us are going to get. You can copy it from my web site at;

http://www.giantscalerc.com/technical%20main.htm

If you distribute it elsewhere, please give Craig Tenny credit in all links or references.

A 35% Edge, Extra, etc, is well within range with 2 digital 8411's if the linkages and geometry are correct. A 33%, or 30%, should have a very large margin with 360oz of torque, or in the case of two 94358's, 400oz. To max out the servos, you would need to input a full 45 or 50 degrees of rudder at high speed to stall the servos. Something no one does if they like their airframe to come down in one piece

I had a 40% Giles fly for well over 250 flights with only 2 JR8411's, and it handled well even in heavy 3D. Its final demise was dumb thumbs, and not the rudder servos. But, if I built another one, I'd put three in it for that little extra push.

mglavin

My Feedback: (31)

Craig

I use Hitec Digitals on numerous models GS to .60 Warbird pylon racers without any problems. There have been some reported problem with the 56** series servos. Hitec has addressed all known problems with these servos to the best of my knowledge...
That said you mentioned 5925's, there has been very few reported problems with the 59** series. Initially there were some software problems with Hitec Digitals in relation to overdriving the servos past pre-programmed parameters. I have never experienced any problems with Hitec Digitals but am aware of the existence of said problems. Other's have had problems that lead back to extensions, wyes or installation problems, the servo is not always the problem...

I would not hesitate to use the 5925's or the 5735's. Been doing so since they were first introduced without ever looking back... I have over hundred of Hitec's Digitals in service and my flying partners have the same, were all very happy with them...

I'd definitely use a jumbo servo on rudder or possibly two standards. Use a tiller arm/bell-crank, this enables you to take of advantage of short servo arms, mechanical advantage and unloads your servo from loads in tension. One servo will work with a tiller/bell-crank, not the best scenario IMO...

I used to use Multiplex jumbo servo's, then I tried a Hitec 5735, end of story for me and many other's. Multiplex's jumbo hi-speed servos are slow and move with a notable ratcheting motion. Hitec also offers a bullet- proof analog monster [HS-805] which is more powerful than the 5735. But slower and less precise, however they are very popular.

The Airtronics analogs are very good servos. In fact Airtronics has been developing high power, fast analog servos for much longer than other manufacturer's and without the problems other OEM's have encountered.

flyinrazrback

My Feedback: (69)

Thanks everyone for you input, I decided to use the 200oz anolog airtronics servos (94358) on each surface except the rudder, and going to use a hitec 5735 with swbmfg 4.5" arm for pull pull on the rudder. I have searched and searched on the airtronics 94358 and cant find a single complaint, and $99 for a .10 sec coreless metal gear 200oz servo is a good deal in my book. Will report on how I like the airtronics. I have heard good and bad with the hitecs, I am running all hitec analogs in my pattern plane, and they are great. Just dont want to risk my 30% edge due to a servo being stuck at one position.