Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

What do extreme speed guys use for servos?

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Old 05-20-2007, 10:17 PM
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Tommygun
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Default What do extreme speed guys use for servos?

Hi all, I was hoping you guys could help me select some servos for an old school pattern ship; a Great Planes Tiporare. I know technically it's not a magnum or diamond dust style speed plane, but these are supposed to be pretty quick. Servo selection is proving very difficult, because I was under the impression coreless would be good. I read on this forum that Futaba 9202s, the ones I was considering, were not well liked for extreme speed. I'm not sure if I like digitals though, because of the high amp draw, high cost, and as far as I can tell, little perceived benefits for fixed wing. If I'm wrong, please correct me- I thank you in advance for your inputs!
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Old 05-20-2007, 11:08 PM
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Flyboy Dave
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Default RE: What do extreme speed guys use for servos?

This is all you need for the ailerons and elevator on almost any plane. They have
about twice the torque, and metal gears that will not strip.

http://www.hitecrcd.com/servos/show?name=HS-625MG

FBD.
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Old 05-21-2007, 09:53 AM
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Default RE: What do extreme speed guys use for servos?

I thought you guys didn't like metal geared servos because they wear out quicker. Also, do most of you use coreless? I had standard Futaba bb servos in my Cermark F20; they seemed fine except I did lose an aileron servo.
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Old 05-21-2007, 10:02 AM
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Default RE: What do extreme speed guys use for servos?

For all practical purposes, standard servos work fine in regular sized planes up to
60 size. Now, maybe for a Patriot XL with a Jett .90 in it....one might insist on some
strong servos. I have been using some stronger srevos in the 60 to 70 inch torque
range for years on the faster planes, but the probably weren't really needed.

The key thing is to use a big battery, with plenty of juice for the servos.

FBD.
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Old 05-21-2007, 12:12 PM
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Razor-RCU
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Default RE: What do extreme speed guys use for servos?

SAVE THIS SPOT FOR ME LATER (I am at work)

Hitec 925's are a good fit but let me get home and check my "data"
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Old 05-21-2007, 01:01 PM
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Tommygun
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Default RE: What do extreme speed guys use for servos?

Well what do you recommend for batteries? I see so much conflicting info on these; they now say the high MAH NiMh bats are no good for high amp draw servos, and that more people are using LiPo receiver batteries. But then that opens up a huge can of worms as well. There's almost TOO many options.
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Old 05-21-2007, 03:07 PM
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Default RE: What do extreme speed guys use for servos?

I just use NiCads.....

cheap, easy to work with, relatively safe. And sometimes that extra weight works out to your advantage trying to tweek a CG.

As for servos..... I use and decent servo I have laying around.

The pylon racers have Hitec 225 servos on board..... i also have the 5245 servos as well.

Other speed stuff.... what ever decent BB servo was on the bench at the time.

I rather like the Hitec 425bb servos. Strong, centering is pretty good, and for general use in anything I fly I trust them.
Hitec 605, 615, 625 have served me well too.

When I think back to the servos I flew for pattern, racing, even giant scale sometimes ..... say 10-20 years ago..... JR 501, 517, even Futaba s8, s16, s-18, S-26, s-28, s-130, 131 and 148 servos sometimes were good enough. The JR 4011s were a favorite. I still have a few futaba S-28 and S-16 servos laying around

I think the MRC-40 and 42 servos were in that 30-40 in/oz range too.

I seem to recall my first Curare had 27oz/in sport servos in it (futaba S-16) And, one servo driving both ailerons.

The kraft KPS-14 servos had a whoping 29 oz and the BIG BAD KSP-15 had 38 in/oz !
(I had KPS-15 servos in my first helicopter)
Some folks I knew were flying 8lb 60 size pattern ships with the tiny (then tiny) KPD-12 servos .... whopping 18in/oz each


Folks are spoiled by the variety of good, low cost servos available these days. And are often confused by what servos do, or how they work, and what application they serve best. Not everything people fly is 3D with 40% total area control surfaces deflecting 75deg.

Bob
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Old 05-21-2007, 03:15 PM
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daven
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Default RE: What do extreme speed guys use for servos?

I've been using alot of Futaba 9650's lately in my Q40's. Really seem to be working well.

Jr 3421's are nice also, but on the spendy side.

I've pretty much gone away from the Hitec 225's on surfaces that matter.
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Old 05-21-2007, 03:41 PM
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Default RE: What do extreme speed guys use for servos?

ORIGINAL: daven

I've pretty much gone away from the Hitec 225's on surfaces that matter.
Yeah, no doubt there are some better servos for QM and 428.

But since I have a good handful of them, and the 424 racers and sport planes are happy with them... I'd be happy to buy more. They also work great in the fun-fly planes. Amazing how fast you can get 1/4lb out of an aircraft if you put your mind to it. I also put a handful into the F-14 I am trying to finish.
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Old 05-22-2007, 12:51 AM
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Default RE: What do extreme speed guys use for servos?


ORIGINAL: bob27s


I seem to recall my first Curare had 27oz/in sport servos in it (futaba S-16) And, one servo driving both ailerons.
Well if you were to select servos for that airplane today, what would you use? Would you take advantage of modern technology by going coreless, and is digital important or overated?



Folks are spoiled by the variety of good, low cost servos available these days. And are often confused by what servos do, or how they work, and what application they serve best. Not everything people fly is 3D with 40% total area control surfaces deflecting 75deg.

Bob
Very true, I'm pulling my hair out trying to decide what I want to put in this plane. I could've ordered the stuff and had it here 2 times over by now, but every night I read something else and start the online servo research game all over again...
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Old 05-22-2007, 12:04 PM
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Default RE: What do extreme speed guys use for servos?

I have used Hitec servos with some success. I like their smaller servos more than the big ones, but I've never had an in flight failure. I use 645MGs in my big Westerner, and have used 635s without troubles. 69oz torque on 4.8V and 89oz on 6.0V. They are very strong and are standard servo sized.
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Old 05-22-2007, 12:21 PM
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Default RE: What do extreme speed guys use for servos?

For a Curare today.... probably for a Tipo or Tio 750/825 too......

Id likely rig it with two seperate aileron servos..... HS-225 or the 5242 digitals.... the digitals tend to center a bit better. The ailerons are not large, deflection required is minimal. Less mass outboard on the wing is better. Plus they are shallow enough to easily mount the servo below the wing skin surface, and just allow the servo arm to be explosed.

In fact, to save some weight, the 5242 servos would be good all around. I believe JR ad Futaba have "midi" size servos like this too... worth considering. The lighter the better

No reason I wouldn't populate it with the 425BB or other decent JR 517 type ball bearing sport servos for sport use.

For competition, the centering is more important. That is where a few extra $$ in servos comes in. These days, the digitals are worth while. Coreless motors help with speed, and also help with centering too.

That is the advantage of the digitals.... they are more precise as a stepper motor. They rely on electronics, rather than a potentiometer to detect position.

Of interest, coreless today is much better than in yester-year. Coreless servos were great back then for speed and power, but they had a real bad reputation for durablility in vibration enviroments. I tended to avoid them after losing two aircraft to coreless servo motors giving out.
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Old 05-22-2007, 01:14 PM
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Default RE: What do extreme speed guys use for servos?

in my turbine jet i use JR DS3421s both the SA and the MG and they've worked out great, as Dave previously mentioned they are a bit costly but they are excellent servos. they have the advantage of being smaller then a standard servo with twice the torque and to boot they are lighter, you can save a few ounces over a standard servo on even small planes.

personally after using many Hi-Tec servos over the yrs i will never buy another one and won't use a free one on any control surface nor on any application that is 'critical' I've just had way to many of them fail, even their HS-225s and 85s have failed numerous times for me.

kc
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Old 05-22-2007, 01:42 PM
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Default RE: What do extreme speed guys use for servos?

The only Hi-Tec's Ive really used (6 of them) are the 605's. These were (obsoleted) the
time proven heavy duty servos, in the Std. size that were bullet proof and used foerever.
I only started using them because Cirrus (Hobby People, made by Futaba) servos in the
60-70 0z. range went obsolete.

The Hi-tec 625 and the 635 are now the new HD standard size in the inexpensive
(under $30.) type servos. I've only had two servos go bad on my in 35 years of r/c.
One was a Futaba 148, and one was a Cirrus. They both failed brand new on the bench
before the planes were flown.

I'm not a fan of the small (expensive) servo's, I use the Std. size exclusively now. I did
have one of the tiny servos on a throttle awhile back....guess what ? It stripped the gears.

So much for the small servos.

FBD.
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Old 05-22-2007, 02:46 PM
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Default RE: What do extreme speed guys use for servos?


ORIGINAL: Flyboy Dave

I'm not a fan of the small (expensive) servo's, I use the Std. size exclusively now.
whatever works best for you, but it's less then desirable to have the servos hang out the bottom of the wing or the side of the fin because the servo is thicker then the wing/fin (and yes i do mean thicker, not taller). on my A-4 the only place you can fit a standard sized servo is the flaps, and in there i used DS2721's which are a standard size. i also try to save every oz i can, just part of the 'Go Faster' mentality therefore i use micro servos on retracts/brakes/tail hook/etc......

kc
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Old 05-25-2007, 12:26 AM
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Default RE: What do extreme speed guys use for servos?

What do you guys think about Tower digital servos? They look pretty good for the price...
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Old 05-25-2007, 12:29 AM
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Default RE: What do extreme speed guys use for servos?

you get what you pay for.

kc
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Old 05-25-2007, 02:15 PM
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Default RE: What do extreme speed guys use for servos?


ORIGINAL: Tommygun

Well what do you recommend for batteries? I see so much conflicting info on these; they now say the high MAH NiMh bats are no good for high amp draw servos
I've never heard that, curious what the reasons are for that? The newest breed of high mAh NiMH cells are lower resistance so 4 of today's cells will output more voltage under load (more power) with the mAh to back it up. Lipos are lighter but NiMH are easier to handle all around and perfectly fine for most sport applications.
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Old 05-25-2007, 05:02 PM
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Default RE: What do extreme speed guys use for servos?

not all NiMh have a low internal resistance and will 'Brown Out' your receiver when used with digitals under demanding situations. and IME it's the vast majority of the ones floating around for sale that have the higher internal resistance. they are great for low current draw applications where the weight savings are a bonus.

kc
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Old 05-25-2007, 11:20 PM
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Default RE: What do extreme speed guys use for servos?

I have had no problems with the HS 645 MG,,,i thought the HS 635 (KArbonites)gear WERE good ;;;but they failed on me,,,so now i don' t use anything thats karbonite just MG--metal gear..---
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Old 05-25-2007, 11:21 PM
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Default RE: What do extreme speed guys use for servos?



In my whiplash I usd JR 8417 digital, High speed, metal gears and 80 oz/in torque.

In the Oakdale Phenom I have Hites HS-5645 mg it has a Jett 60LX. lots of torque! for high speed runs

I like the digitals for their holding torque.

I have the programmer from hitec too.
it can reverse set end points ceter point and much MORE. on hitec digitals only.

most of my othe planes have HS-425BB HS-645 mg and HS 225 and even HS-85MG

on my turbine Jet, the Kangaroo's elevons four JR-8411 digital
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