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Old Nov 17, 2005, 06:21 AM
Heli-addicted
Melbourne, Australia
Joined May 2005
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Tower Pro MG995 Servo any good?

These servos appear to have good specs at a cheap price:

Digital, metal gears, double ball bearings, coreless motor, .17s/60 degrees @ 4.8v, 13 kg/cm torque (208 oz/in) and around $24! Are these things any good or not? I've heard their 9g servos are pretty dodgy quality, do these follow suit?

Cheers

James
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Old Dec 07, 2005, 04:18 AM
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Just bumping this thread to get an answer from anyone! Someone must have used them! I've heard the usual "at that price they can't be any good" and this might be true but I'd like to hear from some users as to why. Anyone???
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Old Jan 02, 2006, 05:19 PM
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TowerPro MG995 Servo

FYI, on 11-22-2005 XJet posted the following on the RCUniverse RC Radio Forum:

"I've been checking these servos out and can report the following:

1. they are very torquey -- I haven't measured the torque yet but it may well be the amount claimed.

2. they are quite fast, perhaps as fast as claimed -- again, I've yet to actually measure them.

3. they are all metal geared -- even the gear driven from the motor shaft appears to be metal, unlike most other MG servos which use a nylon gear at this point in the train.

4. they do appear to operate with a higher motor drive frequency than a regular non-digital servo so may well be digital.

5. the servo-amp is not well matched to the motor/geartrain/feedback pot. In essence, this mismatch manifests itself as significant overshoot when the servo is repositioning. This is to say that if you command the servo to move clockwise to a position, it will actually move past that position (by 3 degrees or so) then move back to the correct position.

Even more strangely, if the servo is at rest and you try to move the arm, it actually moves *towards* the pressure being applied.

6. resolution is "okay" but not as good as most other brands of digital servos and there are even some good non-digitals that are better.

7. without a servo -arm, the weight is 2oz exactly, not the 1.78oz advertised.

8. these servos adhere to Futaba standards (spline and direction) but come with a JR/Hitec connector.

9. physically, the assembly leaves a little to be desired. The PCB on all the units I inspected was incorrectly inserted into the case so that it was sitting on an angle rather than square to the bottom (not a biggie but perhaps indicative of a lower QC standards?). The feedback pot and motor are connected to the PCB by wires and dabs of glue support these wires only where they mount on the pot. The wires to the motor are unsupported and will almost certainly break through fatigue over time if the servo is exposed to moderate or high levels of vibration.

So is this servo a bargain or a bust?

I guess it depends on your expectations.

If you're looking at it as a sub $20 budget servo then it's not bad at all. You get what would appear to be a bullet-proof metal gearset, a supposedly coreless motor, a digital amp and plenty of torque at a faster than average speed.

However, if you're planning to compare this servo to something like the Hitec HS5945 (digital, coreless, metal-gears which sells for around $90) then you'll be disappointed. Its' when put alongside a "quality" coreless digital that the MG995 shows that it really is a low-cost servo. The quality servos have a markedly better resolution, are rock-steady when repositioning and don't even budge when subjected to load -- all areas where the MG995 suffers.

The ultimate test however, is how do they fly?

I threw one on the rudder of my Katana 3D plane (replacing an HS5925) and I did immediately notice the slower speed. The plane also felt less "solid" in rudder response during knife-edge and in a hover -- but the Hitec certainly wasn't over four times better (as the price might suggest it should be).

If you fly iMAC or turbine-powered models (where precision and reliability is of paramount importance) then I strongly suggest you stick to the more expensive options. However, if you just want a bullet-proof servo that has a snot-load of torque and costs little more than a standard servo then these are worth a look.

I would strongly recommend however, that people take a moment to drop a dab of hot-glue or acid-free silicon glue on the motor leads -- just to pre-empt the inevitable."

Hope is is some help.

Cheers
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Old Apr 06, 2006, 12:11 PM
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Sander,

I received the MG995 yesterday. After plug it in my receiver, I noticed that the servo was overshooting. Then I run to the web to find some review for this servo, and found yours. You review seems to be very complete (as impressions ) and I agree with everything. I did not have the chance to mount in my airplane yet, but I will do in the weekend.

For me, this servo is good for the budget, but it's not acceptable a servo that has overshoot. This overshoot is so big that you can see without put in the airplane. If you look to the servo arm you can see. When you link it to any surface, your will multiply by 5x this effect.

I wont recomend this servo for any serious application too. For me, I would only use in some car or a big foot steering. (due to the overshoot)

5. the servo-amp is not well matched to the motor/geartrain/feedback pot. In essence, this mismatch manifests itself as significant overshoot when the servo is repositioning. This is to say that if you command the servo to move clockwise to a position, it will actually move past that position (by 3 degrees or so) then move back to the correct position.
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Old Apr 06, 2006, 11:12 PM
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Tokoroa
Joined Mar 2004
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The digital amps in these servos are actually pretty good.

What I've done with several of my MG995 servos is pull the servo amp out and put it in a standard Hitec servo. The result is a *very* nice digital without any of the overshoot problems originally experienced with the MG995.

The feedback pots and motors are compatible with those used by Hitec's 3-pole standard-sized servos and the PCB is a nice fit in the case so the swap is *very* simple.

On the HS425BB, fitting the 995's digital amp produces noticeably more torque and speed with infinitely better holding power. Likewise the HS475 and I suspect the HS625/645 servos would respond similarly.

The reason I pulled the amps out was that after a lot of hard hucking, the metal gearsets in some of my 995s developed so much slop that they started hunting really bad at neutral -- something that was exacerbated by the almost completely worn out feedback pots. To be fair however, they'd had about 60 flights on a couple of my 3D ships that get thrown about *real* hard.

I've made enquiries and may be able to source just the servo amps (with leads) for around US$8 each. That'd mean I could convert all my HS425/475s and end up with what amounts to $21 digital servos that work *really* well.

By the way, I stripped the motor down on one of the 995s and they most definitely are *not* coreless either :-)
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Old Apr 07, 2006, 05:59 AM
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Xjet,

Can you post this convertion pictures and a simple tutorial how to do that?

Can I use Futaba's S148 to convert this also?

I have no ideia what is the servo amp.
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Old Sep 23, 2006, 12:18 AM
wac
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Old Oct 23, 2006, 02:14 AM
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tower pro servo amps

has anyone else managed to get hold of just the amp circuit from these servos?
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Old Mar 16, 2007, 12:41 PM
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I have just got two on an eBay auction so if and when they arrive (forever the pessimist) I will post my evaluation.
I was doubtful at first if they are truly digital as everything these days gets called "digital" so it wouldn;t have suprised me. I am going to sling them on the rudder and see what the results are. To be honest, the rudder doesn't need huge degrees of cenering acuracy but it does need alot of torque.
It was said elsewhere here that when pressure was applied it moved against the movement. That sounds as though the high torque was simply higher than that being applied and may not perhaps be justified as a real fault.
I remain open minded until I have tried them. As they (Who are "they") say. The proof of the pudding is in the eating!

Nigel Smith
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Old Mar 23, 2007, 06:31 PM
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Well. they arrived today. Noise from them is about normal for all metal gears. speed looks good and torque is also. All results are subjective and have not measured anything. Next test is to put one on a rudder and see the difference.
There is a marked overshoot but this is off load and may improve when loaded up. I personally am quite happy - so far - and expect they will do as they say.
IE fast and with lots of torque. I do think that if we are honest it would be difficult to notice any REAL effect on the plane with the overshoot.
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Old Mar 24, 2007, 07:04 AM
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Quote:
Originally Posted by Satkunas
Sander,

I received the MG995 yesterday. After plug it in my receiver, I noticed that the servo was overshooting. Then I run to the web to find some review for this servo, and found yours. You review seems to be very complete (as impressions ) and I agree with everything. I did not have the chance to mount in my airplane yet, but I will do in the weekend.

For me, this servo is good for the budget, but it's not acceptable a servo that has overshoot. This overshoot is so big that you can see without put in the airplane. If you look to the servo arm you can see. When you link it to any surface, your will multiply by 5x this effect.

I wont recomend this servo for any serious application too. For me, I would only use in some car or a big foot steering. (due to the overshoot)

5. the servo-amp is not well matched to the motor/geartrain/feedback pot. In essence, this mismatch manifests itself as significant overshoot when the servo is repositioning. This is to say that if you command the servo to move clockwise to a position, it will actually move past that position (by 3 degrees or so) then move back to the correct position.
I recommend not to consider this in heli at all. The overshoot problem will result in the servo NOT MOVING at all at fast cyclic/ pitch movement.
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Old Mar 26, 2007, 10:09 AM
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I ran the plane up for the first time today. Judging by the whine when no input I would guess the servo amp IS digital.
I also suspect that the overshoot will not really be a problem but I have noticed that it is not all that fast which may be a problem even for the rudder.
so whats best Strong, powerfull and slowish or
Weak, low power and fast?
Thats todays dilema
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Old Mar 27, 2007, 03:07 AM
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Tokoroa
Joined Mar 2004
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Quote:
Originally Posted by ntsmith
so whats best Strong, powerfull and slowish or
Weak, low power and fast?
Thats todays dilema
This depends entirely on your flying style.

If you like flying on the ragged 3D edge then fast is really important (I use Hitec HS5925s on 6V in the tail of my 3D Mojo60 and they're *wicked* fast).

If you're more into IMAC stuff or sport flying then accuracy and holding power may be more important than speed.

And, I've used a TowerPro MG995 on the rudder of my Katana P. The overshoot made it much less fun to hover than when I used a standard servo, even though the standard was slower and had less torque.

The KatP with the MG995 was almost impossible to keep still in a hover, the tail would be swinging like a pendulum with every control input. With a standard HS425BB I could hold it rock-steady, just like my Mojo and GBee profiles.

Let the truck and buggy boys waste their time with these servos, they're not for planes -- especially when their (lack of) reliability becomes an issue.
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Old Apr 30, 2007, 08:20 AM
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Joined Dec 2006
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I tried a handfull of these servos and found none of them to work correctly. All overshoot center and overshoot stop. They are not digital ! They also jitter and jump unexpectedly. Can't fly em. Anyone else have these problems?
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Old Sep 15, 2007, 10:32 AM
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i purchased finally tower pro MG 946R. double ball bearing, metal geared. there is no problem with over shooting or centering unlike MG995 and MG945 bla bla....
worked fine with my Extra 330L.. nice responce. price is cool $ 22.99
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