lov2flyrc

My Feedback: (24)

Ok....
So I'm just trying to do the finishing touches on this customers F-15 that I did a Gut and Reinstall on. Plane was bought built but never flown. I sit down with the radio to begin the programing. One flap is dead centered, the other is off by about 1/2".... So, I pull the linkage off and adjust the flap to center. Turn the system off since the phone rang. Fire it back up.... Flap is off agian by about 1/8" same direction [sm=confused.gif]. I touch the flap and it jumps.... [X(]. I then begin to apply slight pressure to the flap and well...... see for yourself on [link=http://www.dreamworksrc.com/Video/Hitec.wmv]THIS[/link] video. I open up the covers to see whats installed....... HITEC 225MG
Both flaps do the same thing. Fully charged 4000 mah duralite pack on a 5.1 regulator. These are supposed to be roughly 60 oz/in at this voltage.... Just for kicks, I thought I would check to see what servos are installed on the ailerons.... JR DS168...Roughly the same torque and As you can see from the video, same pressure and they dont budge.
Time to rip out the Hitecs
Todd

wojtek

My Feedback: (73)

same servo, and same problem i had .... eventually it will die all together .. I replaced mine with the non digital equivalents, and not problems from there ..


Wojtek

unknown

It seems you are pushing more than 60 oz of pressure on the flap VS ailerons .

seanreit

My Feedback: (60)

LOL, point well made Todd, however, that scares the crap out of me cause I thought based on some 40 size planes I used to fly with 225's in them that the 225 was a bulletproof servo.

In fact my big stick had 1 225 on the elevator and never saw what you just showed me.

Thank goodness I've been out of planes where a 225 seemed like a good solution for over a year.

That is CRAZY!!

seanreit

My Feedback: (60)

The 225 isn't a digital servo so far as I know.

seanreit

My Feedback: (60)

Maybe we get an answer to this post:

http://www.rcuniverse.com/forum/m_20...tm.htm#2017495

UK Flier

Hope this wasn't a case of cruelty to servos, the manufactureres spec recommends this small servo for planes up to 10 pounds.

http://www.hitecrcd.com/Servos/HS225MG.pdf

unknown

"Yep" for fast electric boat and electric car steering .

This is the appropriate servo to use

Chris True

My Feedback: (14)

Hate to pop your bubble but the JR DS-168 IS a Hitec servo.

Made for JR by Hitec, same as the Hitec 5125MG digital wing servo.

Spartan Missile

not my quote but:
"buy cheap, buy twice"

The Ghost

lov2flyrc,
Looks like there is a dead feed back pot or control board in the servo. Happens. You did not say if the servo is new or S/H. Ditch the servo and fit a new one.

Cheers.

lov2flyrc

My Feedback: (24)

I'm fully aware of this....my point was the comparison in torque since they are both rated closely spec wise.

Didn't choose the servo nor would I have used this servo ever in a jet..... This is what the plane was delivered with. Regardless...it is obviously just another crappy servo from Hitec.

Both flap servos do the same thing..... I would venture to guess they are new servos but have no idea. Customer bought the plane with them installed.

Will be installing JR Digi's ..... Hitec [sm=stupid.gif]

mglavin

My Feedback: (31)

It's unlikely both servos are defective (but possible), and as you note they both exhibit the same behavior. What is common in the installation of these servos? I have use the 225 extensively with fun-flys and small race planes and have had very good results. Your problem appears to be an installation problem, BUT I've been wrong before.

In any event this is NOT the right servo for the job, IMO...

You didn't mention anything of the specific of 225MG servo installation.

Can you observe the servo arm deflecting?

How are the servos powered up through a wye, extensions, multiple connectors or? Electrical losses or resistance can contribute to a servo exhibiting similar behavior. Can we assume the power source is also used on the aileron servos which are working fine? Cycling the servo connections sometimes reveals a problematic component.

What length arms are employed and are the control arms at least equal length to the servo arms?

Change out the wye, extension or what have you if the arms are of reasonable lengths and all else checks out.

All things being equal a Digital servo has at least three times the holding power of a standard analog cored motor servo. What may work in less than ideal conditions (specific mechanical setup and or the lack of mechanical advantage) in some applications with a digital may simply be to much to ask of a standard servo.

Shaun Evans

Yikes...

I'd be curious to see if it does the same thing with a different servo in the same location. Do you know the history (use) of those two particular servos? I'm wondering, because over the years, that servo (Hitec 225) has been a VERY reliable servo for me. I've used it in lots of applications, including the rudder servo on a turbine-powered Starfire (I did have a huge mechanical advantage, though; with a very long control horn and a short servo arm...). In that application, the servo centered beautifully, and could knife-edge the bird all day.

EddieWeeks

Seems to me the flap can move ~3 inches total travel while
the aileron only move like +- 0.75 inches... or half the travel..

If your ATV is not set to maxium on the flap you will loose power also..

Hope this helps

Eddie Weeks

Shaun Evans

Hi,

I'd be very intersted to see the linkage on that flap setup.

lov2flyrc

My Feedback: (24)

Sorry shaun,
Should have taken a shot of it but it was typical linkage setup, 1" from servo center and about 3/4" from flap surface. I ripped out the Hitecs, installed JR3421's with the exact same setup and the flaps works perfectly.....
Todd

BirdofpraY

My Feedback: (31)

Todd, Here is a Hitec digital that I was going to use for a airbrake that failed on the Tango thus the reason I decided not to go with the Air brake setup. I have lost total confidents in Hitec this will make my Third incident with Hitec servos. Now they are off the list for alternatives. For those that need real data here is a picture. Servo was bought new and failed. I burn in all my Hitec servos with the programmer. Also Servo is a HS-5645MG digital. Hitec if you are reading all this, you are in the need to up you QA and inspections process because there are allot of escapes getting out.

J. Campbell

My Feedback: (31)

I would like to just pose the question of WHY now everyone thinks they must have or have to have digitals?? Digitals have a lot of torque, ungodly amounts of it. Jets really dont need it In my opinion. Digitals are great for HUGE 33% to 40% areobatic planes that you MUST have alot of tourque to move a huge surface.

The day before digitals came out everyone was running 4.8volt Coreless servos, jr 4131's, 4721's and futaba stuff too and we were all satisfied that we had PLENTY of tourque and perfect centering with the coreless.

The digitals may be better on centering but i think you would be hard pressed to SEE the difference. They definatley have more ounces of tourque but do we really need it to move a surface 1 inch or less???? They definatley suck more juice and do have programming issues. Im not sure on the weight vs regular coreless .

I mean there are guys putting 4 8411 digitals with 100+ ounces of tourque on the elevons of a Kangaroo! I for one wont use digitals and continue to use the coreless because of the above reasons. NOT trying to piss anyone off or belittle there thinking, just wondering why! Russ

LGM Graphix

My Feedback: (22)

Well, I personally use digitals because unlike coreless you are getting the majority of your torque right away. The digital servo's power comes in much earlier than the coreless.
on a 40% scale plane you're right, you need the torque to move the huge surface, but it's moving a lot all the time, the airplanes aren't that fast. At 200mph in a jet I want to know my servo isn't going to stall at the smallest movement due to the power curve not being high enough there. Just my opinion though, and really, the digitals aren't that much more money than the coreless servo's. Oh, also, the digitals are less current drain than coreless for teh power. Remember the original JR Super Servo's, I used to run those in my pattern planes, when digitals came out I was amazed at how much LESS drain they had vs the super servo's.

J. Campbell

My Feedback: (31)

When i said they suck more juice i was refering to the fact that most people who use digitals use a 6 volt system in leu of a 4.8. I dont have much experience with digitals other than what i have witnessed at the field and read on the net. They probably have their positives along with thier negatives. I guess to each his own. Russ

unknown

Any test videos of the (installed JR3421) [sm=thumbup.gif]

wojtek

My Feedback: (73)

Russ, for one, i have read a thread here a while ago, where someone has 1 8411 per wing on a roo, and at high speed , was stalling the servo as it did not have enough torque. So 2 8411 or equivelant torque servos are actually appropriate in somehting like a roo .... as for more torque over less ??? well, to most people alreayd dumping a few gran into a jet, the diference between a $70 and a $112 servo is inconsequential ... On my skymaster grippen, i used 3 8611 servos, where probably a futaba 9202 would have probably sufficed on the wings at around $55 a piece .. but the extra $100 i paid for the 8611s is not big deal when you add up the rest of the plane, turbine , etc at $5K+ ....on the other hand, on some 40 size sport planes, I'll use a 3003 for $12 - $15 .. ... now what i don't get is when people use $100 digital servos to do things like operate their brake or retract valves



Wojtek

J. Campbell

My Feedback: (31)

Good point, although i dont use 112 jr servos anyway. If i were to use a digital i would use the hitec at 70. But i think i will just stick to the old standard of 70 to 100 oz coreless for now. It is not a price issue for me as the coreless cost as much as the digital. It is just an issue of current drain, programming problems and of course overkill, real or imagined. Russ

Skymac

My Feedback: (8)

Yep.............