impactiq

My Feedback: (57)

Just wanted to see what you guys are using for servos in your birds. I been thinking of going digital for my next "old school" project.

8178

My Feedback: (17)

For very fast 60 size pattern aircraft, I use Futaba S9252 digitals for ailerons and elevator, S3151 digital for rudder and S148s for throttle and retract gear valve. For slower 60size and smaller 40 size aircraft S3001 (or s148 with ball bearing kits) work very well.

impactiq

My Feedback: (57)

I do like Futaba servos. Have had good luck with them. I have a few S3151's laying around from my R/C cars in good working order. I am thinking a micro on throttle. I'll look in to the S9252. Word on the town though is if you are going digital with a 6v Rx pack.... you must use a voltage regulator. Know anything about this?

8178

My Feedback: (17)

The Futaba 9C Super comes with a 1500 ma 4.8v flight pack battery and a heavy duty switch harness for use with the digital servos. The servos have heavy duty wire as well.

8178

My Feedback: (17)

Some of the SPA guys flying digital servos say that they find that more expo is needed because the digitals respond so precisely.

impactiq

My Feedback: (57)

That is what I am looking for..... precision. A servo the moves and centers perfect everytime.

8178

My Feedback: (17)

It does seem odd that they would add more expo when the precision of the digital servos is one of their main advantages.

impactiq

My Feedback: (57)

I would half to say it is stick movement to servo travel (and speed of servo) vs. personal preference for what the plane is doing with the amount of stick input applied. I know when I went digital on my nitro on road cars.... it was a day/night difference. I use expo to get my "linear" feel to what the car should be doing with the amount of input I am putting in on the sticks. Some of these digitals are very fast and a 1/8" movement on the stick is a true 1/8" on the servo.

vintageflyer

My Feedback: (1)

Yeah the expo Really helps out with digitals. You dont get that unwanted aileron input when you pull forward or back on the stick. Well, you do, but you can dail it down. The 14mz has a feature that you can actually choose how far you have to move the stick before you have any input. They claim its for precise flying.

DM

spbyrum

I set the new Curare up using techniques I'd read about to maximize mechanical advantage. I used 3151s throughout. What I found was that by only using 5/16 of the servo arm and 5/8 on the control surface I use very little expo. I'm using none at all on the elevator, 10% on ailerons and 15%of rudder. The expo I do use is basically to keep my nervous thumgs from moving things that don't need it. The 3151s don't eat the batteries like some of the earlier digitals I've used in larger planes, too.

teamvortex

My Feedback: (6)

Steve -

I'm at a loss to understand what difference it makes on expo as long as the ratio is kept the same (2:1 in your case).

True, if you use 5/8" and 5/4" instead of 5/16" and 5/8", the force into the pushrod is only half of what you have, however, the torgue from the servo and into the surface is the same. Unless there's some serious friction in the rotation axis of your linkages or bending in the pushrods, it shouldn't make a difference. Actually, if there's a pushrod bending issue, the shorter arms would make it worse. What am I missing?

Rich
TeamVortex

NM2K

My Feedback: (14)

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You nailed it.

I'd rather fly a model with great linkage and sport servos than a model with great servos and crappy linkage.

I have flown sixty powered competition pattern aircraft with Kraft KPS-15 and 14 servos, only changing out the stock pot wiper to a Giezendanner unit. Those servos provided only a little more than half of the power that modern sport servos provide.

The Futaba FPS-148 with ball bearing kits do a wonderful job with adequate torque for average sixty powered models.

I have gone JR in recent years and I use a variety of their servos. My best servos at the moment are 4721 JRs. I'll upgrade one of these days, but not until I truly need to do so. Spending a lot of money on servos to control old fashioned pattern planes isn't on my agenda. Good servos? Yes. Competition grade, state-of-the-art servos? No. I think the money can be better spent elsewhere in the hobby. But, of course, this is just my opinion.

blw

My Feedback: (3)

Steve,

I have a .40 sized pattern plane with 4 S3151 digital servos. I have a Hitech HS-55 for the throttle. I can fly for several hours one a 1100 mah pack. Yes, the servos are fast and they don't drain the batteries. I have somewhere around 150 flights on the plane and the servos are still doing well.

Deadstik

My Feedback: (8)

I have to agree with Ed that for general "Sport" flying, there is really no need for the expense of the digitals, even flying a vintage pattern bird. A normal Futaba/JR/HiTec ball bearing servo will do a great job for a long time at less than $30 apiece.

For "Competition", meaning you actually are going to fly in competition, your plane deserves only the best, and that would be digitals on all flight surfaces. The key to linkages is that you should set your servos to use all the available "steps" 1024-2048 using your servo arm length and control horn length to where on "High" rates, you use 100% of your stick movement to get the desired manover result. Linkages have to be absolutely slop free and the money spent on the "high priced" hardware is worth every cent. It makes no sense (cents) to spent $50 on a servo and have a steel pin/plastic point of movement. That type is wearing out from the moment you start flying. For competition flying, you really do need the best equipment you can buy, because everyone else is going to.


Deadstik

8178

My Feedback: (17)

Are you saying that with PCM systems it is better to have your servo move the full “normal” distance with the “high rate” set at 100% because you achieve 1024 positions in the “normal” movement of the servo, e.g. the most possible positions in the smallest total movement distance? In contrast to having the high rate set at say 130% and having each 1024 position result in more movement and less granularly. It would seem that with 1024 PCM radios the highest rate setting by default will always have 1024 positions and each lower rate will have something less than 1024, e.g. 50% low rate would only have 512 positions available. The thing I don’t understand is how the receiver knows to decode larger changes in the pulse width to the servo when high rate is set at 130% for a given change in the 1024 possible positions. Somehow the value of each 1024 position must be reestablished when a rate is set more than 100%. I’ve looked around on the Futaba site and other sites and cannot find an explanation.

8178

My Feedback: (17)

After giving this more thought the 0 to 1024 positions must represent the total servo movement not the 100% setting because as I add the higher rate above 100% the change is real time. So 130% or 140% or whatever the total servo movement can be must be 0 to 1024.

I posted a question in the Futaba support forum to see what they have to say about the operation.

Deadstik

My Feedback: (8)

8178,

You ask a very good question. If you set up a plane the way that I do, which is to set up surfaces using 100% of available servo movement, how can you possibly get 130% from the servo? Have to find a tech rep to go into that one... or, I think I'll play with one of my sport planes and see what the 130% setting does if I already am using 100% of the servo movement. I'm certain everyone has their preferences as some people like "soft centers" and others prefer "breathe on" centers. I am one of the latter in that when I touch the stick I immediately want the plane to react. No ramp up, no expo. I used to set up triple rate ailerons for 3 rolls (in 5 seconds), slow roll and maximum for other manuvers. I find now that I can do the slow roll just as well on the 3 roll in 5 second setting. I think it depends on how you practice, and what feels good (and scores well)..... snowing here right now.. so guess it's time to build tomorrow.

Dan

Carolina Custom Aircraft

8178

My Feedback: (17)

The answer from Futaba on PCM steps http://www.rcuniverse.com/forum/m_3898456/tm.htm