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Esprit Model . Thunder Power RC . Real Raptors

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Century Hawk - Falcon - Raven - Predator > Hawk Pro servos?
 
 
JustPlaneChris
Heliman
Location: Austin,TX - USA

Okay guys, I need some help. I'm (re)building a used Hawk Pro and have already purchased servos for it. I have a JR ST126MG for collective, and was planning on using JR/Spektrum DS821 for throttle, ail and elev. However, I've been reading horror stories here and elsewhere about the DS821s. I have them in my Swift also (30+ flights so far) but now I feel like I'm flying on borrowed time.

What would be a comparable servo that has a better reputation than the DS821, yet won't cost me an arm and a leg?

-Chris
04-23-2008 04:43 PM
HOMEPAGE  
 
 
Dave M
Senior Heliman
Location: Mi.

If you are just learning.... NO 3d...There will be alot of servos that would work... Futaba 3151 are a low cost digital, but just about everybody has something.

It's OK....It's not your fault !!!
04-23-2008 04:58 PM
 
 
JustPlaneChris
Heliman
Location: Austin,TX - USA

Thanks Dave! I'm not a hardcore 3D guy. I do FFF, loops, rolls, flips, some inverted... just what I call "warbird style" aerobatics. I'll check out the Futaba 3151.

-Chris
04-23-2008 05:40 PM
HOMEPAGE  
 
 
oldfart
Elite Veteran
Location: Vancouver, Canada

I have uses the 3151's on my Pro - and it will do some pretty demanding 3D.

If possible, use a servo with dual ball bearing support of its' output shaft for the aileron. In this type of mCCPM control system, the aileron servo output shaft is the fulcrum point that takes a lot of loading during collective commands. If you use a servo, like the 3151, that uses a bearing at the top and a bushing at the bottom, to support the output shaft (most lower cost servos that advertise that they are bearinged servos are so configured)then you will develop "rocking" play hear in rather short order.

Also use as high a torque servo as you can on Collective.

As any digital servo has more holding power then its' analogue brothers, as long as their motor windings can take the vibes of a nitro heli (the problem with the Spectrum DS821), then they are the better choice.

You may find this article on our site an informative read concerning servos.

http://www.leisuretech.ca/hints_servo.html
04-23-2008 05:42 PM
 
 
SteveH
rrProfessor
Location: Texas

Yep, what Phil said.

I will only add one thing...try to install the servo balls on the underside of the output arms on at least the aileron cyclic servos and the collective servo. Doing that places the output load closer to the top bearing further reducing the mechanical wear in the gear train.

SteveH
Magnum Fuel
AMA76186
04-23-2008 05:59 PM
 
 
JustPlaneChris
Heliman
Location: Austin,TX - USA

Thanks guys! I've been poking around the servo specs at www.servocity.com and it looks like for a few more dollars over the 3151 or 3152 the Futaba 3050 might be a good choice. Dual ball bearings, metal gears, decent torque. Phil, that's a great article! It does make me question the advice I was given to purchase the ST126MG for collective. Oh well, I'm sure it'll fly.

-Chris
04-23-2008 06:10 PM
HOMEPAGE  
 
 
thelane
Senior Heliman
Location: Edmonton, Alberta Canada

I used DS821's all season last year, had three bad crashes and the servo's held up fine. Will be using them again this year as well. I don't fly 3D, just FF, etc.

JR Vibe 50, Hawk Pro w/OS37, T-Rex 450, BCX and DX7
04-23-2008 06:41 PM
 
 
the Wasp
rrProfessor
Location: Vt

the DS811 would work good on the cyclic,, I remember it was only a couple years ago we were paying $54 for them, now they are $19

http://www.heli-world.com/detail.aspx?ID=9234

Jim
the wife wont let me get a Monkey !!,,, damm, can't have anything
04-23-2008 08:16 PM
 
 
Al Austria
Key Veteran
Location: Gainesville, FL

I second Wasp's recommendation. I made a couple hundred HARD 3D flights on my old and beaten Hawk and the DS811's held up amazingly well. Gear train could stay tighter but from a reliability stand point, they were excellent. And for $19, that's quite a deal.

Always remember you're unique, just like everyone else.
04-23-2008 08:23 PM
HOMEPAGE  
 
 
JustPlaneChris
Heliman
Location: Austin,TX - USA

Thanks guys, that's one that nobody else has mentioned. Hard to beat that price too... Hmm.... DS811 or Futaba 3152? Well, I have till next payday to decide.

-Chris
04-23-2008 08:46 PM
HOMEPAGE  
 
 
the Wasp
rrProfessor
Location: Vt

I bought one complete for $29 over a year ago and I thought that was a good price,, for $20 they don't come with rubbers or wheels/horns,, but still a really great price !!

I got horns and I got rubbers LOL

Jim
the wife wont let me get a Monkey !!,,, damm, can't have anything
04-23-2008 08:48 PM
 
 
SteveH
rrProfessor
Location: Texas

It is my "understanding" the DS811 does not have the high failure rate of the newer DS821.

SteveH
Magnum Fuel
AMA76186
04-23-2008 09:01 PM
 
 
Al Austria
Key Veteran
Location: Gainesville, FL

Quote 
It is my "understanding" the DS811 does not have the high failure rate of the newer DS821.

Mine as well. I'm glad to see someone still has them.

Always remember you're unique, just like everyone else.
04-23-2008 09:37 PM
HOMEPAGE  
 
 
Blade_Master1
Veteran
Location: Canada

true or false ?
the collective and throttle servos should be the same speed
but the torque may very between the 2.

you can use a micro servo on the throttle and fuel mixture ?


I'm just curious about what others have tried








JM2C's :)
04-23-2008 09:42 PM
HOMEPAGE  
 
 
the Wasp
rrProfessor
Location: Vt

me-2,,, ee eerrrrr 3..

Jim
the wife wont let me get a Monkey !!,,, damm, can't have anything
04-23-2008 09:45 PM
 
 
the Wasp
rrProfessor
Location: Vt

""true or false ?""


false,, you got curves !!

Jim
the wife wont let me get a Monkey !!,,, damm, can't have anything
04-23-2008 09:45 PM
 
 
SteveH
rrProfessor
Location: Texas

Quote 
the collective and throttle servos should be the same speed
but the torque may very between the 2.

It is my "opinion" that it really doesn't make that much difference unless the throttle servo is extreemly slow.

Quote 
you can use a micro servo on the throttle and fuel mixture ?

Yes, as long as the throttle moves freely.

SteveH
Magnum Fuel
AMA76186
04-23-2008 09:46 PM
 
 
the Wasp
rrProfessor
Location: Vt

OK,, so that's a better answer

Jim
the wife wont let me get a Monkey !!,,, damm, can't have anything
04-23-2008 09:47 PM
 
 
Blade_Master1
Veteran
Location: Canada

Thanks guys
that clears the mud




JM2C's :)
04-23-2008 10:13 PM
HOMEPAGE  
 
 
JustPlaneChris
Heliman
Location: Austin,TX - USA

Speaking of throttle servos, does it have to be anything fancy? I was looking at just a regular Futaba S3004 servo, though the comments on it at Tower Hobbies say "This servo is not designed for use with glow-powered helicopters." I assume that means for cyclic duty...

Any feedback on my choice for the collective servo? (JR ST126MG)

-Chris
04-24-2008 01:02 AM
HOMEPAGE  
 
 
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Century Hawk - Falcon - Raven - Predator > Hawk Pro servos?
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