Digital or Normal (is it analog?) servos in Pattern Plane
 

OK, for anybody that has a clue or opinion. What is better in a 2M pattern plane and why - digital or regular servos. I need to get two wing servos and they will either be Hitec 925's (reg) or 5925's (digis) Both about the same torque, speed and cost. Hitec was no help at all (thanks Hitec). When I posed this question to them I got the wishy-washyest answer you ever heard. So come guys go for it. Thanks.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

Never used Hitec but as a generic answer digitals are the preferred servo in pattern.
Just use good ones. They usually have more torque, more precise centering, better holding
power and near zero deadband. Only downside is cost and a little more battery consumption.
Don't use cheap servos , digital or analog.

tommy s

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

Also, I recently learned that when using digitals you have to be sure to have the right batteries. The way it was explained to me was that going up in mA isnt a problem but digitals will "burn up" if they are say designed to run on a 4 cell pack and you go up to a 5 or 6 cell pack. Maybe someone can clear this up, but Im pretty sure its a consideration.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

My 2cents', Steve. Go digitals, given your options. Superior holding, greater accuracy to return to same point, given same stick movement, MUCH better centering. Now, my comment is based on YOUR constraint of choosing between the two Hitec's you listed.

WRT batteries - digitals consume more mah per movement, basically, so you'll draw more out of a pack in a given flight. When I ran Hitec's, it was fashionable to run them on 4 cell packs; I cannot address the current digitals, but 5 cells with regulators is VERY commonplace.

I believe you WILL notice a very significant improvement in performance in a pattern airplane between conventional servos and digitals.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

4.8v or 6v is not an issue as both servos are rated to handle both. I believe the issue here may be "holding power". I understand the digital theory of cycle rate, power drain, etc (sort of). The thing I don't understand is: WHY, if the two kinds of servos (1) cost the same, (2) have the same torque & speed specs, (3) are the same size, (4) are both coreless; do they even have the regular servos if the digitals have better holding power. I have no idea how their centering compares. What is the reason for getting the standards instead of the digis in this situation. Why does Hitec even make the 925 anymore.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

None
[8D]

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

One of the advantages to the Hitec is the programmer for the digitals, I don't use the Hitec but have friends that do and use the progrmmer to match them one thing you can't do with other manufactures, little difference inprice for the digitals so go with them.

Steve Maxwell

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

splais,
I had the same questions you have when I was deciding on servos for my pattern plane. From what I can tell. I think the cost of the coreless motor is what keeps the price up on the coreless analog servos. I would go with the digital servo. The centering and "Holding Power" will be much better. Just be sure you have a battery pack with the capacity to run the digitals. Airframe vibration will make a big difference in how long your battery will last (especially with digital servos). The digital servo has so little dead band that it pulls a lot more current from the battery while trying to center a vibrating control surface. An unbalanced prop will drain your batteries fast.

Hope this helps
Joe Dunnaway

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

It does. I guess my question is why does Hitec even carry the analog anymore. I have three planes with digis, including an 11 servo giant P-51. Power drain has not been a problem on any of them. It's interesting that Hitec could not give any reason at all for why they carry both. Considering that the analog is something like $84 and the digi is $89, I was planning on going with the digi. I guess we will never really know why they have both other than just personnal preference. I'm still waiting for someone to say "I use the standard because....:. There is another factor I had not thought of. These servos are also used in boats and cars. Maybe there is something in that aplication that dictates use of an anolog servo vice digi.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

They could be still selling them just trying to get rid of stock....

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

Analog vs digital... Hmm..... depends on YOU.

For me, the digitals would be a waste of money. My flying skill just isn't there to support the need for the digital servo. *I* would see no difference in how my airplane performed when I am flying it.

Someone with better skill (at least half the guys in the local club of appx 45 members...) would definitely see the diference. 4 of the local club members NEED the digitals to be competitive at the level they fly in Pattern competition.

They are better. But are your skills good enough to see the difference?

MAYBE in 3 more years my skill will be good enough that digitals would do me some good. (at my current rate of improvement. 3 years ago, I'd have said I'd NEVER be good enough to see it. THANKS B.W. and Todd! {Chip knows them...})

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

Splais,

The Holding power of the digitals is better because the way the servo samples its pot position and the way it applies power to hold that position. I don't have actual numbers but have heard that the position gets read 5 times more often with the digital servos. So they become more accurate....instead of for example 10X a second its 50X a second. So the servo makes small adjustments all the time to go to the required position. This means as flight loads are applied the servo does not have a chance to get as far off commanded position before the servo gets power to bring it back. Also The digitals give more power sooner to the servo as it gets pushed off the required position.

So turn your radio on and grab the servo wheel. You can turn it a small amount before the servo starts to really apply power to go back to the commanded position. Well the amount of error (off command) before the servo applies full power or enough power to get it back is smaller with the digitals. This is the advantage of digital servos. They digital might apply full power at 1/2 deg error...But the anaolg servo comes in with 10% power at 1/2 deg...then if it deflects to 1 degree of error the servo steps it up to 40%...2 degs it says hey we are getting really out of whack here give me 80% and then it steps it up to 100%....But the digital already applied its power and brought the surface back with less error tot he commanded position.

So when you use them on your ailerons in a model, it helps hold the ailerons in the right position as you pull and push through corners. This is the best place for a digital servo....When you are matching surfaces like ailerons or dual elevators....This is where you will see the biggest difference. Now a single servo like the rudder or a single elevator servo you can change the feel via the expo and rates and if setup properly its tough to tell the analog coreless from the digital coreless servo.....

Overall the digitals will give you better performance. It comes a slight increase in power usage but in the course of a day its less than 1 flights worth. If your setup is poor, has any binding or slop the digital servos will fight trying to hold center and will also hunt all the time...This means that current usage will go way up.

Regardless of your servos the linkages and connections are just as important.

I hope this clears it up a little for you.

Troy Newman
Team JR

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

[quote]ORIGINAL: FHHuber

Analog vs digital... Hmm..... depends on YOU.

For me, the digitals would be a waste of money. My flying skill just isn't there to support the need for the digital servo. *I* would see no difference in how my airplane performed when I am flying it.


Without trying to sound smart A**, this is a pattern flying forum. When comparing digital to analog servos, even FH Huber would notice the difference in accuracy, speed and holding power, if he were trying to fly precision aerobatics. Sorry, Just mho. :eek:

I was given some good advice by a senior member of our national F3A team: "Use the best servos you can afford". This has proven to be good advice, for me anyway. I started with digitals in my wings, and went from there. I was also told that at the early stages digitals would be a waste, but when I fitted them, I couldn't believe the difference.

Hope this helps.

Cheers

Chunkylad

PS: The best advice is to listen to those who know. Please read again the post by Troy Newman. Cheers

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

Direct, but WELL STATED, ChunkyLad......when given an opportunity, I always give the same advice...if you have ANY money to "invest" buy good servos and radio gear FIRST, *then* all the other trinkets, "necessities", etc.

Wayyy back, I remember clearly going from 5 pole to Coreless....then Coreless to Digital...each step, for me, was a noticeable improvement in the "feel" of the airplane. Each step gave me one less thing to be trying to fly around.

Similar learnings for me came with control arms, control take-offs, clevises, etc. As Troy and others have stated, control surfaces with sealed hinge lines, tight, slop-free linkages, and solidly-mounted digital servos just make the precision part of this game a little easier to attain.

I think it's helpful to remember that we ALL will only fly as good as the mechanical resolution and response time of the airborne control system.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

The thing nobody has answered yet. IF the digitals are better, and most seem to say they are; why does Hitec even carry the analogs IF they are the same price. Why would anyone buy the analogs.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

I see several posible reasons for selling both

1) Even though you are equilibrating $84 to $89, there are people that will say the analog is cheaper. Look how many people have bought an ASP engine to save a few bucks from an OS, only to mostly regret not spending the extra $5-10(not taking shots here, just my personal experience) Also, 5 servos $5 difference equals saving $25, and more for other brands differing prices between dig and analog.

2) They may still have stock to reduce and sell, but not manufacturing anymore. Can't just throw them away as a viable business.

3) To give builders and pilots the choice. It looks good to have a number of different servos available.

4) Some people just don't want to switch or upgrade and why change what has worked, including the battery mah.

5) Lastly, we just bought a pair of converse court shoes for my daughter that look exactly like they did 30 years ago, just cost a lot more now.

Ed

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

splais - one reason - perhaps - analogs are still out there with coreless and conventional motors. For most users, nearly all that I know, converting to digitals required pretty significant changes in the exponential of the system to make the airplane "feel" normal. Primarily because full torque is immediately available the first beep off center.

Analog servos sort of "wind up" to get to full speed and torque, thus, on many configurations, it feels more "normal" and less "twitchy" than digitals. My experience confirms this need to alter expo on my competition AND "fun" airplanes.

Unless you want to tweak with Tx programming, assuming you have one with adjustable expo in the first place, analogs may be better. Since roughly 94% or more of RC'ers aren't "high end" buyers for systems, there are MANY 10's of thousands of "simple" radios out there without expo as a feature, or with users who just don't want to screw with it for their Sunday fun. Why make their hobby more complicated?

I have no clue; this is just speculation.

RE: Digital or Normal (is it analog?) servos in Pattern Plane
 

After speaking with many members of our club, I think Aerobob's observations hit the nail on the head.

I think a majority of flyers like to keep things "simple". Why invest in servos that are more expensive, and more complex without any percieved need? It's when you start getting a little more serious about your flying, and in particular, more critical in, and demanding of, your set-up, that good quality servos and slop-free control linkages come into their own. Pattern flying demands that our control movements are precise and accurate. I see digital servos as great tools to aid in the search for such precision and accuracy.

I know of a pattern flyer who does not like digitals, because they are "twitchy and jittery". This same fellow hasn't much of an idea about programming his radio for expo or dual rates either!

Cheers

Chunkylad