# Servos



## Kammo (Aug 2, 2008)

Hey guys, just ran across this little gem...
I figure for anyone wanting to do 3 axis skull and what nots...
check this out

Combo Deal! 4pcs Tower Pro MG995 Metal Gear High Speed & Torque Digi Servo IP ($11 Ea + Free Shipping)


----------



## SpectreTTM (Jul 7, 2004)

Kammo said:


> Hey guys, just ran across this little gem...
> I figure for anyone wanting to do 3 axis skull and what nots...
> check this out
> 
> Combo Deal! 4pcs Tower Pro MG995 Metal Gear High Speed & Torque Digi Servo IP ($11 Ea + Free Shipping)


These look like a great deal. They look more powerful & Faster than the 425BB that I bought a while ago.

Has anyone ever bought anything from this vender?

It says they are Digital. What is the difference? 

Can I use any normal Servo Driver?


----------



## SpectreTTM (Jul 7, 2004)

I think I found my answer

Tower Pro MG995 Servo any good? - RC Groups

Too bad. Looked like a good deal


----------



## Kammo (Aug 2, 2008)

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


----------



## Kammo (Aug 2, 2008)

Well, I wont be putting these in my airplanes, but I think they might work for the 3 axis skulls or maybe something else. I will go ahead and get a pack and see how well they work, Ill let you know how it turns out.....


----------



## SpectreTTM (Jul 7, 2004)

Yeah That is what I was thinking about using them for.
I bought a bunch from Servo City last time they had their 20% off sale.

Yes I'd be curious how they work. 

Thanks for the post.


----------

