Ok, Im confused. What makes a good servo ?

[Helder22]

I have been reading a bunch of threads about servos for the Lepton and some come up constantly:

HS-85MG
L: 29mm x W: 13mm x H: 30mm (1.14" x 0.51" x 1.18")
Transit: 0.16sec/60 deg (4.8V) 0.14sec/60 deg (6.0V)
Torque @ 4.8V: 3.0 kg-cm, (41.66 oz-in)
@ 6.0V: 3.5 kg-cm, (48.6 oz-in)
Weight: 21.9g (0.77oz.)

94761Z
Operating Speed (4.8V): 0.15sec
Operating Speed (6.0V): 0.12sec
Stall Torque (4.8V/6.0V): 55/66 oz.in.
Motor Type: Std 3 Pole
Bearing Type: Dual Ball Bearings
Dimensions: 1.06 x 0.47 x 1.18
Weight: 0.80 oz.

S9650
SPEED: .14 sec @ 4.8V
.11 sec@ 6.0V
TORQUE: 3.6 kg-cm @ 4.8V (50 oz-in @ 4.8V)
4.5 kg-cm @ 6.0V (62.5 oz-in @ 6.0V
Weight: 0.9oz (26g)

S3150
Speed: 0.25 sec @ 4.8V
Torque: 51.4 oz-in @ 4.8V
Dimensions: 1.1x0.5x0.8 in (28x13x19.7mm)
Weight: 0.80 oz (23g)
Power Supply: 4.8V (Futaba does NOT recommend using 6V)


S3102
Speed: 0.25 sec @ 4.8V - .20 sec@ 6V
Torque: 51 oz-in @ 4.8V - 64 oz-in @ 6V
3.7 kg-cm @ 4.8V - 4.6 kg-cm @ 6V
Length: 1.1" (28mm)
Width: 0.5" (13mm)
Height: 1.2" (30mm)
Weight: 0.7 oz (21g)

From what I see the best servos if comparing the speed and torque would be:

94761Z
HS-85MG
S9650

The most affordable is the HS-85MG

Yet from what Im reading lots and lots of people are choosing the s3250 and s3102 over the HS-85MG even though they are slower and have comparable torque.

So, what makes some of these servos a better choice than the others ?

[TMoore]

The 761's fit the space, they are fast and they work on 6 volts.

I like them.

TM

[Finless]

Yep... the 94761Z is a awesome little servo for the Lepton. You wont go wrong with this servo :thumbup:

Bob

[toyturbo]

the 3102's are what is recommendedf by Hirobo and are readily affordable.

[eheliflyer]

Stick with a digi servo. The 94761s have already been proven to work perfectly on the Lepton. You already spent the money for a Lepton don't go cheap on the rest of the electronics. This is already the top of the line heli in the Mini class so get good electronics and you won't have any worries except when you have a brain fart and crash it! :lol:

[Blik]

I agree with eheliflyer, and the 94761's fit perfectly and very fast. The only problem was no available gear sets. I contacted Heliproz about stocking these and stock is now available along with the cases.

Cheers
Blik

[spork]

So, what makes some of these servos a better choice than the others ?

That's a good question. People have been telling you which ones work for them, which is useful info; but it would be interesting to reduce this to specs. I'm guessing the critical parameters are:

cost
weight
size
transit speed
torque
bandwidth
input voltage
efficiency

I imagine you could have a very fast analog servo, but it will inherently have lower bandwidth because it's updating its position command far less often. I think the only place we really need high bandwidth on our helis is on the tail during fast backward flight.

I think input voltage is kind of a matter of convenience. Whichever servo matches your systems voltage is better. Efficiency seems like a secondary parameter as well to me.

Maybe someone more in the know can give us better info.

[Two Left Thumbs]

Do you have to shim the 94761Z, or do they mount right out of the box?

On mine, it seemed the horns were too close to the frame, by 2-3mm.

[CRAZYKEV]

I used the supplied servo shims and flip them opposite of how they should be used to shim out the servos. I'll try to get a pic.

[Two Left Thumbs]

That's a good idea. I ended up using double shims. One in the double servo holes as intended, and a second between it and the mount. I was concerned the Hirobo supplied screws would be too short, so I used the Airtronics screws instead.