Digital vs Ball Bearing Servos- which one?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> RC Airplanes >> Beginners >> Digital vs Ball Bearing Servos- which one?
Page: [1]

Login
Message << Older Topic   Newer Topic >>
Digital vs Ball Bearing Servos- which one? - 6/27/2008 10:15:11 AM   
cappaj1



Posts: 486
Joined: 6/21/2008
From: Rochester, NY, USA
Status: offline 		I'm thinking of getting a Futaba 2.4 GHz as my first radio and there are options to buy it with either two types of ball bearing servos or digital servos, ie:

"Available with 4 S3152 digital high-torque servos (FUTK7000/7001); 4 S3004 ball bearing servos (FUTK7002); or 4 S3001 ball bearing servos (FUTK7003)"

A manufacturer's site states digitals are 10 times faster which much quicker response, and have enormous standing torque, 3 times an analogs but require a larger battery and heavy duty harness (no big woop to me).

Since the servos are relatively inexpensive when purchased with the radio, why wouldn't I just go with the most expensive ones, the digitals? I'm willing to put up with the extra current draw.

And any links to a larger battery and heavy duty harness would be appreciated. Thanks.

< Message edited by cappaj1 -- 6/27/2008 11:56:57 AM >

_____________________________

-Jim-
Keep thy airspeed up, less the earth come from below and smite thee.
       Post #: 1

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 1:11:01 PM   
Fastsky



Posts: 2844
Joined: 12/10/2001
From: Calgary, AB, CANADA
Status: offline 		Since you are new to flying your first plane will be a trainer which has slower responses to stick movments. This is needed to help a new pilot learn to fly his/her plane. The faster digital servos simply aren't needed for a plane like this and in fact you probably wouldn't notice a lot of difference because of the laid back reponse time when compared to a faster flying/reacting sport model. The digital servos will only use up your battery capacity much quicker than standard servos. I would save the exra $$ and get a servo such as the Futaba FUTS3003 Servo - Standard for about $10.00 which will last you for years in a trainer. The $$ would be better spent on fuel and other things that will get you air time. At this stage servos that are more $$ aren't going to make a big enough difference to notice. I have some planes with precision servos because they were all that were available when putting together my plane and I don't see any difference in flying. If the S3001 is one of your choices then I would go with those. They are a good servo. 8D]

< Message edited by Fastsky -- 6/27/2008 1:17:49 PM >

_____________________________

Current favorites: Great Planes Stuka 60, Modeltech P47 60, Seafury 60, Rascal 40, Phoenix Decathlon 40.

(in reply to cappaj1)
       Post #: 2

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 1:17:41 PM   
Missileman



Posts: 2822
Joined: 2/14/2006
From: Algonac, MI, USA
Status: online 		First off lets get the nomenclature right.
Your choices are Analog and Digital. Both can be ball bearing.
Digital servos are overkill on a trainer or most any plane that does not require pinpoint accuracy and will run your battery down faster. Stick with analog servos unless you really need digital.

_____________________________

Comments by author are not to be confused with the truth, past or present.

(in reply to Fastsky)
       Post #: 3

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 2:15:27 PM   
da Rock



Posts: 6650
Joined: 10/11/2005
From: western, NC, USA
Status: offline
quote:

ORIGINAL: cappaj1



A manufacturer's site states digitals are 10 times faster which much quicker response, and have enormous standing torque, 3 times an analogs but require a larger battery and heavy duty harness (no big woop to me).



Digitals aren't normally 10X faster than...... non-digital servos. As for "enormous standing torque" that's another specification that isn't entirely true. And darned if digitals don't automatically require a larger battery. Darned if that mfg's site hasn't produced one of the most misleading interpretations all in one shot, we might ever hope to read.

Go onto the Tower website and look up the specific servos you're wondering about. I picked Tower simply because they almost ALWAYS have detail specifications about everything they list. Bring up the tech info on each servo and note the torque rating and speed rating and weight of each. Also look and see if the number of BBs are the same.

Relying on advertising will screw your enjoyment of this hobby. Getting the details will help you get what you pay for. And some retailers give those details. Servo details tell the story in your case.

(in reply to cappaj1)
       Post #: 4

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 2:27:33 PM   
da Rock



Posts: 6650
Joined: 10/11/2005
From: western, NC, USA
Status: offline 		So taking my own advice, I did the research for ya'

You're actually deciding betwee the S3152, S3004, and S3001 servos
They all have 1 ball bearing.
They are all about 1.6 ounce in weight.

So here is how much each sells for.
And how much torque each puts out.
And how fast they put that out.

S3152 .. S3004 .. S3001
$30ea ... $13ea ... $20ea
69oz ..... 44oz ..... 33 oz
.22sec ... .23sec ... .28sec

(in reply to da Rock)
       Post #: 5

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 2:41:01 PM   
cruzomatic


 

Posts: 1937
Joined: 1/28/2003
From: San Antonio, TX, USA
Status: offline 		I'm thinking S3004's. Save the digi's for something later.

(in reply to da Rock)
       Post #: 6

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 2:58:45 PM   
-pkh-



Posts: 2383
Joined: 5/28/2004
From: Emmaus, PA, USA
Status: online 		The S3004's are great general purpose servos. I have had around 40 of them in various planes, and have never had a problem with one. They are perfect for a trainer. If you do get the package with the S3152's you may want to put them aside for a more advanced plane and buy four S3004's for you trainer.

_____________________________

Paul - Helis: Two Raptor 50V2s, Venture 30CP, Blade CX2
Planes: Twist 150, Twist 60, Tribute 36, GP .40 Mustang

(in reply to cruzomatic)
       Post #: 7

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 4:25:44 PM   
plugin



Posts: 448
Joined: 5/12/2007
From: Bogota, COLOMBIA
Status: offline 		What is the real difference between analog and digital? I presume that the digital servos don't use a potentiometer to determine position like analog servos do, but instead they use other method. Right? If that is correct, how does an analog servo know the desired travel position?

_____________________________

I am the R/C Stig.

(in reply to -pkh-)
       Post #: 8

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 4:34:57 PM   
Jburry



Posts: 560
Joined: 7/12/2006
From: Cape Spencer, NB, CANADA
Status: offline 		An analog servo uses a pot to determine it's position. The farther from the commanded position it is, the harder it tries to get there. In other words, the more a surface is deflected (by windloads or whatever), the harder the servo will try to push back.

A digital servo likely also uses a pot (it would also be possible to build one with a digital position wheel, not unlike a mouse), but the electronics between the pot and the motor are a bit different. If the servo is at anything but the commanded position, the motor will use full power to try to move it back. When we resist an analog servo, it begins to buzz a bit, then tries to move us back harder and harder as we push. A digital servo pushes with all it's got right off the getgo. This leads to a more accurate servo position and higher electrical drain. Digital servos typically sing a strange digital song when powered (a result of the motor power pulsing constantly on and off at extremely rapid rates). "Deeededeeedeee!"

Very few sport planes will benefit from digi servos. Their real payback comes with precision aerobatics. In a typical .40 size sport plane, very, very few pilots could tell you what's in it for servos unless it's close enough to hear that digital song....

J

_____________________________

Revver Bro. #220

(in reply to plugin)
       Post #: 9

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 4:53:21 PM   
cappaj1



Posts: 486
Joined: 6/21/2008
From: Rochester, NY, USA
Status: offline 		Thanks, Guys,

You've convinced me the only difference I'll be aware of in my first plane will be in my wallet, so I'll skip the digitals.

_____________________________

-Jim-
Keep thy airspeed up, less the earth come from below and smite thee.

(in reply to Jburry)
       Post #: 10

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 5:37:06 PM   
PipeMajor



Posts: 592
Joined: 5/5/2003
From: Twin Cities, MN, USA
Status: offline 		Another difference between digital and analog - the analog servos will be nice and quiet. I fly a trainer equipped with Futaba S3004 analog ball bearing servos (they weigh only 1.3 oz) and they work great. You can get them for around $13 each and they won't drain your battery pack nearly as fast as the digital servos will.

My son has an electric powered Mini UltraStick which has JR digital micro servos. When we turn on the radio power they sit there and rattle. The noise "rattled" us initially but were told that's standard behavior with digital servos.

(in reply to cappaj1)
       Post #: 11

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 5:42:53 PM   
Jburry



Posts: 560
Joined: 7/12/2006
From: Cape Spencer, NB, CANADA
Status: offline 		I'm using S3004's in several planes, from trainers to my 100+mph .46 mustang. Great servos for the money.

J

_____________________________

Revver Bro. #220

(in reply to PipeMajor)
       Post #: 12

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 6:05:51 PM   
brett65



Posts: 1069
Joined: 12/21/2007
From: Oklahoma City, OK, USA
Status: online 		I use a digital in my 1/8 scale savage to steer the giant wheels, and its even a little overkill. My trainer has the cheap JR st47 servos and can do anything I tell it. I will even knife edge, but trainers don't look cool in a knife edge.

_____________________________

Truckzilla w/LRP28,Firestorm,Spek DX3.0,Micro-T,uglystik,SkyRaider Mach 1 TTpro 46,Phoenix Extra 300S OS 55AX Futaba 2.4 6EX

(in reply to Jburry)
       Post #: 13

RE: Digital vs Ball Bearing Servos- which one? - 6/27/2008 6:06:39 PM   
Campgems


 

Posts: 1911
Joined: 2/18/2006
From: Arroyo Grande, CA, USA
Status: offline 		I'll throw this out. When I first started, I picked up a 9CAP supper which came with S3151 digitals. My first plane required six servos and I found some new ones on Ebay at a very reasonable price. I ended up with a dozen or so of them. My first plane got set aside and I then bought a trainer and comenced to learn to fly. The trainer, with five 3151 digitals and a 600mah battery was good for five 15 minute flights a day. Battery life was never an issue.

The fact that you are running digitals doesn't automaticly mean that you have to have a monster battery and 12 gage wiring. Current draw depends a lot on the load you are putting on servo.

THere was a post about a year or so back the the author had done extensive current draw vs load graphs for several servos. There just wasn't that big of difference in current draw.

If you notice, none of the spec's in Tower's adds, or on the Futaba site will list current draw of the servos. It is to variable depending on the load it is moving.

I pickup my servos from Ebay dealers and usuall pay less thatn $12 each including shipping. I only fly the digitals. I couldn't tell the difference in performance between the analogs and digitals, and price being equal, why not go with the more presice servos.

Don


(in reply to cappaj1)
       Post #: 14

Page:   [1]
All Forums >> RC Airplanes >> Beginners >> Digital vs Ball Bearing Servos- which one?
Page: [1]