emilsanto

My Feedback: (39)

i am thinking of upgrading some of my older hitec 605 metal gear servos. on my cap232 and a giles 202

Are the any brands that are totaly metal geared.? not like hitec's metal gear set with the plastic drive gear. thats were the problem is on
my hitec sevos' the plastic gear wears real fast and then the servo will fail. i thought about the hitech karbolite sevos but i here problems about them on 1/4 scale planes. i am worried about servo gear strenth on the bigger planes but dont like the slop of metal gears.
also i dont ant to spend 100 buck on 1 dam servo if you know what i mean
thanks

_____________________________

www.flyingaeros.com

Hide Signatures

JCINTEXAS

I've been asking myself this same question. What's the best "all-around" MG servo for 30% and larger planes?
JC

rcairflr

My Feedback: (44)

Why trust your airplane to anything less than a Hitec titanium geared servo. The gears will have no slop on the first flight and still have no slop on the 500th flight.

Campgems

Ijust ordered a set of 6 digital, metal gear, 180inoz servos on ebay for $50 including shipping from China. I'm not expecting much from them, but for the price, I just had to see how they turn out.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150500095931

One of our new glider guys was grumbling about the lash in the metal gear servos he has. We were talking about using a heavy grease. For a glider, it might be OK, but the current draw and the response time both have to go up with the heaver grease. The lash is still there but there is a bit of cushion before the metal to metal contact.

Humm. I wonder how a thousands or so of coper, then nickleplating would help. Imay try that with one of the Cheapos I'm getting. I wouldn't try it on a hundred dollar servo, but for an 8 buck one, you don't have much to loose. My concern though would be the plating separating and binding things up.

I"m guessingIhavea month or so to wait for them. I'll print this on tack it up for a reminder.

Don

ADDED: I did a bit of Google and found these guys have been around since 2006 or so. Really mixed reviews on then, most not very good. I didn't expect much at $8 each. Looks like that about what I'm going to get, not much.

Don

LesUyeda

"One of our new glider guys was grumbling about the lash in the metal gear servos he has. "

It is in the nature of the beast, regardless of manufacturer. The tolerances necessary for "minimum" backlash cannot be held my the manufacuting processes used, and in the sizes used. A "zero" backlash gear train requires gears with a tooth shape that is very special to the application, and in most cases, a gear that is actually two gears, 1/'2 the necessary thickness, and spring loaded such that it's gear teeth try to move away from each other, and into the mating gear teeth.

Les

Texastbird

the MG995s I have sit there and twitch and shudder for no particular reason. Check where the wires go into the circuit board. Some of them are prone to vibrating the solder joint apart. You might need to put some kind of sealant to stop that from happening. Who knows, maybe they have improved them somewhat since I bought some. Good luck.

Zeeb

My Feedback: (41)

AFAIK, all MG gear servos have something other than metal for the primary drive gear material. Forgive my memory because it seems like it was explained to me why that is the case, but I've forgotten.

You are correct on the Karbonite geared servos from Hitec; they are not recommended for gas powered models nor I believe models weighing over 12lbs. Not sure on that weight limit exactly, but they don't want you using them in gassers due to the vibration vs. glow or electric power. Some guys will claim they use 'em in gassers or bigger models, but you won't find any of 'em in my gassers.

$100.00 each for servos? well you can go up to $150.00 each if you want.....

It's just part of the price of going bigger....

Campgems

One could probably make a near zero back lash servo, but not for the prices we would pay. The Zero back lash gears are usually for a really low torque application, IEdriving a linear pot or position sensing device. The spring in the ones I have don't supply much more that an ounce of pressure. Much more the that gear will wear out the one driving it, and the smoothness of the drive train will suffer.

The guy with the MG servos in his glider though had issues other the gear wink. The output shaft was rocking back and forth, not rotating. Isuggested he use a pull/pull with a slight amount of tension on the cables to take that movement out of the equation.

Don

Campgems

An update on the six MG995 servos I ordered. They arrived today. My first observations follows.

1. My first thoughts were that the quality of the plastic castings, both the cases and the horns is not very good. Little strings of plastic in the zip-lock packaging, and flashing in holes and around some edges

2. Ipulled one horn out of a parts package and tried it on all six servos. I discovered it didn't fit all six the same, and easy push on some and on others it was going to require the screw to pull it down.

3. While I had the horn on each servo, I did a couple swipes stop to stop. Four of the servos felt rough in the gears, and turned in one direction easier and smoother than the other direction. One had a couple lumpy area beyond the roughness. The last turns very smooth in both directions

4. The servo that has the smooth gear feel also has a different case casting and wire lead. The case on this one is a matte finish while the other five are a glossy finish. The wire on the mat finish case are glossy and the other five are mat finish. The case casting on the mat case also has a trashcan with an Xover it on the bottom, while the other five do not. The case on this one is a much better casting, no flashing and sharp crisp lines. In my last inspection, I discovered the output shaft is a different design and height, the "good" servo being about 1.5 to 2mm taller.

5. As I was getting the photos ready, I discovered that the cable stress relief on the "good" servo is longer than the other five.

I'm out to the shop to do some testing and dismantling. More to follow

flytreetimes

Check out the PowerHD servo line, paricularly the DS9150 at around$36, and the DS090M, around $34. They have been tested with very good results against he best Hitec has to offer. The DS9150 matches the HS7985 and the DS090M has tested far stronger than the Hitec 5625.
FWIW you can find these tests on Youtube. flytreetimes

Campgems

Well, I got in some bench testing. I started with my Futaba 10C and a R139DP PCMreceiver. Iplugged the six servos in and a volt watch.When I powered things on. it was anticlimactic, the servos centered and just sat there, non of the center jitters I read about. Istarted the servo cycle on the 10C and the first thing I noticed was the voltage was dropping. Now, my battery is a .4.8VFutaba 1000MAH that only tested to 675 MAHtwo day ago, When setting at an idle, the full charge LED on the Volt watch is on solid. Once all servos started moving, the First LED was faint, the second more solid and the third faint. The first yellow was flickering on once in a while. Ipicked each servo up and held it to my ear. The Good servo from my other post today was smooth and you would hear a little whine when it changed directions. The other five were not a quite, A couple of them made more noise in one direction than the other. I kind of expected this as that is the way the gear train felt when I moved it by hand.

Next, I went to a 167 PPM receiver. Things were a little quieter with this RX, but no real difference. Voltage indicators looked like there was a little less load, but not much. The next test was with an Orange 2.4 Fasst receiver from Hobby King. I just got this yesterday. I first set it up with the 10C in 10 ch mode. When I turned the RX on, the servos about jumped off the bench five of the six were chattering and the volt watch was down to a flashing red and both yellow going. Wiggling sticks and cycling settled them down a little bit, but the voltage draw was still extreme. Ithen changed the TXto 7 ch mode and rebound the Orange RX. Now, there were just two servos going nuts. Iswapped these two servos to different channels and the bad behavior followed one servo. The other two swaps were quite. Iplayed with both the servo cycler and stick movement. The red light on the volt-watch was glowing stronger. Then I noticed that the two servos that were chattering the most were getting hot. I unplugged them and the volt watch went back to second and third greens lit. Just to show the problems were with the servos, and not the RX, I loaded the Orange RX with Futaba S3151 digitals. They were fine. Inotice that the stepping noise from the was a much higher pitch than from the MG995's

I took theservo that was thenosiest and took it apart. Nothing obvious in the gears, but when Istarted cleaning the grease off, i found there were twoburrs of brass on the output gear that easily broke off when I touched them withan Xacto knife. At thatpoint, I took all the gears and cleaned them with paint thinner and inspected them with a loupe. Icouldn't really see anything wrong. Ilooked in at the electronics. The motor looks like a standard brushed motor, Two wires to it. The servo leads and the motor leads didn't have the best soldering I've seen, but they were solid. I put things back together, lubing things with white lithium grease.Before I cleaned the case top, I took a look at thegrease with a loupe. There were fine brassdust particles in the grease.Icleaned it all out before I put things back together. Once I put it back together, and went back to the most troubling mode on the Orange RX, this servo was quite a bit quieter and smoother operating.

Isaid I wasn't expecting much when I ordered them at the price they were, and I didn't get much. I'll clean the gear trains on the rest of them and see how they go. I'm not sure I'll use any of them in my P-61 though. Even if they worked OK, the current draw may be a killer.

Iattached a closeup of the contaminated grease. I'm wondering if I would have noticed the metal in it if it had been my Lithium grease or the white grease that Futaba uses.

rcairflr

My Feedback: (44)

You state here that "they have been tested with very good results against the best Hitec has to offer" and then mention the HS7985 and the HS-5625. These two servos aren't even
close to the best Hitec has to offer. You obviously have no idea what you are talking about.

Campgems

Well, I found out something else with the help of RCU. The Orange RX has two modes. A high speed mode and standard speed. It was recomended to me in another fourum that I should try the standard speed so Idid. The wild chatters completely went away. The current draw was down to normal compaired to other digital servos. I'm going to clean and re-grease the other five and fly them for a while. What looked like a bag of sour apples may turn into a good pie after all.

Don

flhyr

I also thought Power HD was good, until recently.

I have a Pwer HD 9110MG servo on the rudder of my 90 size extra. Worked great for almost a year, but now its starting to jitter around nuetral, usually for about 3 or 4 seconds after a quick small bump off center. So I assume the POT is worn... already!

shame, because it was a reasonable price, quick and strong, and precise. Wish they would have use more durable pots....

StevL

I have several 30% and 35% planes, use HiTec 7955 on all of them with "No Problems". I can get them for between $85 and $90 each to my door.

Cheers,
Steve

Jetdesign

My Feedback: (8)

Airtronics makes some nice servos at lower cost than some of the competition; Savox is supposedly remarkably similar JR and is less expensive. Futaba and JR make nice servos.

Don, those MG servos are listed as having a 10us dead band, which is very big (ie very imprecise). From Hitec's website:
There is a noticeable difference (centering) between 1us and 3us, let alone 10.

Campgems

Joe, you bring up a good point. It has raised my curiosity as to what that actually translates to in the real world, IEwhat is the angular accuracy of the servos. Given that the only true accurate points to measure is at the extreme TX stick movements, against the stops, and for the self centering stick, at the center. I'm going to set up an experiment and see what the variances are. I'm going to be limited to the comparisons as I only have a few digital servo types, at least types that I own more than one of so I can rule out servo to servo differences due to wear. Give me a day or twoto get some results back. I at first thought of using a length of rod attached to a servo wheel, but decided to use the laser pointer from my incidence gage. Ihave to make a mount for it and setup a test stand. While I'm at it, I'm going to test a couple RX's and Tx's in the mix. I don't own a servo tester. I'm also going to use both new and used servos of the same type if I have them, IEI have some new and some well used Futaba S3151's S148's, and maybe a couple other types. Iwill also take some readings with the servos in a horizontal plane and vertical plane, with a weight in this mode to eliminate gear back lash. Should be interesting, but I'm not sure it will give any really useful information.

Don

Jetdesign

My Feedback: (8)

Sounds like fun Don, let us know what you find

Campgems

Well, I cobbled together a test bed. I took a big servo wheel for a Futaba Servo and made some wood mounts to hold the GP incidence gage Laser pointer. The pointer doesn't give a very precise dot, but rather a large oval. All the tick marks were on the same point on the oval. The transmitter used is a Futaba 10C modular with the 2.4ghz module and the receiver is a Hobby King Orange set on standard speed. A 4.8V battery was used. I didn’t do any end point testing as that would require a different setup.

The first photo is the pointer and servo wheel

Iused a piece of ply on end held between four 7 AH starter batteries to steady the setup. The target was 10 ft 6 in from the center of the servo wheels, =/- an inch. Photos 2 and 3

My first test was with the servos in a horizontal arrangement. Isoon discovered that the gear lash was screwing things up a bit, so Irotated the setup so the sweep of the laser was up and down. It looked like the gear lash was still entering into things a bit so I took a 5/8" nut and hooked it to the nose of the laser so there was a preload on the gears.

I tested the following servos, a mix of old and new, but only one servo of a type. All were Futaba servos with the exception of the Tower Pro 995MG which has a Futaba spine on the output. The Futabasfollow. S133 mini, S148, S3001, S3004, S3151 Digital and a S9254 high speed digital. Then the 995MG

Some interesting things popped up. As my setup wasn't rock solid,changing servos usually required I sub trimthe servo toget the dot back in the work area. Ifound that the servos all reacted to the sub trim differently (which would leave me to believe thatthey would react in a similar way to stick movement) Istarted counting the clicks of sub trim before the servo started to move in a new direction. The responses varied from each click moved the 9254to 6 to 8 clicks for the 995MG. the 133 was 6-7 clicks. 148 was 5 clicks, 3001 was 4, 3004 was 3 and the 3151 was 2.

All servos showed a range of home positions. And in all, that range shifted depending on the direction you were approaching home. I also found that a slow release of the stick gave more consistent results vs letting the stick snap to center. It was quite common for the movement to stop then bump ahead a click.<o></o>

<o></o>

The 995MG though showed some really strange behavior. The range of center when lifting the weight always seemed to stop at the same point then drift on to about the same end point range the other servos had. This stop and drift was near 2 degrees of rotation. The endpoint range in the opposite rotation was more like the other servos but some what wider. After seeing this test, my hopes of the sour apples tuning into a pie were dashed. <o></o>

<o></o>

I have a few Hitech servos along with some JR and Airtronic servos that are not mounted in planes at this time, so if anyone is interested, I make another wheel and test those also. <o></o>

<o></o>

The last photo shows the actual tick marks for each servo<o></o>

Jetdesign

My Feedback: (8)

Pretty neat. It was my understanding that the dead band relates to the amount of travel a servo can have before it sees a signal to move. A higher dead band setting means that the servo can drift around at a given position (say neutral) and not be told to return until it gets pretty far away. A narrow dead band means the servo is constantly being told to stay put.

Hitecs have adjustable dead band; having a higher dead band (as in 1 or 2 or 3) is good for surfaces that have multiple servos. If you have 2 servos on an aileron with 0 dead band, they will fight and wear each other out.

I assumed your Futaba digitals would be the most accurate, and as you said, they responded the least amount of trim clicks (although I don't know how this compares to analog servos.)

The last bit about the China servos getting close to center, then kind of wandering in, may also be related to all this. Don't really want to harp on the 'dead band train' but it seems to fit.

Science is fun