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HomeAircraftHelicopterMain Discussion › DS821 airworthyness
03-07-2008 01:46 AM  10 years agoPost 1
eggmcmuffinplz

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Los Angeles, CA

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Are these servos good enough to put into a Hurricane 550? Can I do 3d on them?

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03-07-2008 01:48 AM  10 years agoPost 2
Eury

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Dover NH

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Go to Horizon's site and read the tech note on them. They are fine on electrics up to 50 sized, and 30 size glow helis.

Nick Crego

Citizen #0168

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03-07-2008 01:52 AM  10 years agoPost 3
eggmcmuffinplz

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Los Angeles, CA

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Ok

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03-07-2008 04:08 AM  10 years agoPost 4
David Blain

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Mt. Dora, Florida (USA)

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I like the term "airworthyness"---DS 821's failed in my 30, I have some if you need them... Like Eury said, check the site, I am sure they are readily available... They may be reasonably priced but just one cost me $175.00 on a Raptor 30 w/ OS 37!

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03-07-2008 04:11 AM  10 years agoPost 5
RAK402

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Alhambra, CA

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Sean,

I would not do it. I have read reports of the output shaft breaking on throttle.

I still have four brand new ones I do not know what to do with. They are not going in any helicopter, now matter how small or if electric.

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03-07-2008 04:35 AM  10 years agoPost 6
michael88997

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Lewisville,Tx

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a guy at my field has them in the 550 and does 3d and their fine, two guys at my field have them as their cycle servos in 600ns, and two others have them as throttle servos on 600ns... all been flyin alot since beginning of last year with no failures yet.. i wouldn't recommend them on 50 size nitro collective but a 550 doesnt vibrate much at all if you set it up right so you should be fine

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03-07-2008 05:17 AM  10 years agoPost 7
bstock

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Easton, MD.

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I know I am the one that got you started in thinking about these servos... so I am sure you are going to take this with a grain of salt

The known fix for the output shaft breaking every once in a while... is to put in a slightly longer screw. It strengthens it. It has also been on nitros (the vibration) that this seems to happen once in a while.

I didn't bother on my Hurri... because if you do the oz/in torque math on the cyclic needs of this heli... it is so light, and with 500 blades... I didn't see the need for it.

I am not a 3D pilot... but I do bang on this heli. It is fun for that... it just gets it! (much better than a 6S T600e)

I have let 3D pilots fly it... and they wring it out... and it does great.

There is a very active Hurri section on HF... and allot of guys are using 821s. In the last 6 months I have been active in it... I have yet to hear of a 821 failure.

Hope this helps - Brent

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03-07-2008 05:34 AM  10 years agoPost 8
eggmcmuffinplz

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Los Angeles, CA

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Maybe they used loctite on the output shaft to secure the servo arm?

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03-07-2008 05:49 AM  10 years agoPost 9
bstock

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Easton, MD.

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Hard to say... I hope they knew better than that.

Even with the longer screws... they are screwed if they made that mistake

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03-07-2008 07:26 AM  10 years agoPost 10
Blax1

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Sydney Australia

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eggmcmuffinplz,
Hi, here is a cut and shut from the Spektrum site
I sold mine that came with the my DX7, and replaced them with DS8231's for my Caliber 5, I sleep now
"QUOTE"
New Guidelines for DS821 Servo Use
Tuesday, February 20, 2007

The DS821 servo is a powerful, accurate sport digital servo recommended for RC airplane applications up to 1.20-size. For helicopters, the DS821 operates best with 30-size glow models, and up to 50-size electric. Loads and vibration in larger models may cause premature failure of the servo resulting in damage or injury to property and persons.

Important: Do not use liquid thread lock with the DS821 servo!

Do not use any form of liquid thread lock to secure the servo arm screw to the output shaft of the DS821 servo. Chemicals in these liquids react with the polycarbonate gear set causing the plastic to become brittle, fracturing the final output gear. "UNQUOTE"

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03-07-2008 12:42 PM  10 years agoPost 11
kevntri

rrNovice

Rockford, IL

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I have one on my throttle. on my R50
I am going to switch out a Futaba 3151 from the cyclic.
I think I will put the 3151 on the throttle and ge rid of the 821 all together.

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03-07-2008 01:37 PM  10 years agoPost 12
michael88997

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Lewisville,Tx

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Maybe they used loctite on the output shaft to secure the servo arm?
DO NOT USE loctite on these servos... it causes the gears to become weak and they will fail... just put some longer screws in there if you worried and go fly them, they are ment for 50 size electrics and a 550 is a little smaller so your good to go

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03-08-2008 10:57 PM  10 years agoPost 13
LJS

rrKey Veteran

Minnesota, USA

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Hi All,

I put an 821 on the throttle of my 600N and it failed hard over in less than two gallons.

That being said, I have 380 flights on my Swift with 821s on cyclic.

I probably should switch them out, but they seem to be working pretty well in the Swift. Go figure...

Keep 'em flying.
LJS

Logo 600 VBar, 10S
TRex 600E VBar, 8S
Logo 500 VBar, 6S
TRex 600ESP, 6S

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03-09-2008 12:23 AM  10 years agoPost 14
eggmcmuffinplz

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Los Angeles, CA

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So should I trust them in my hurricane?

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03-09-2008 03:23 AM  10 years agoPost 15
bstock

rrKey Veteran

Easton, MD.

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Yes

I do... and I am pretty picky about what I will run in all of my helis.

I have a T600n - and No... I would not trust them in that (9252s in that)... but they will work good in a Hurricane (they really do work great in mine).

They are rated up to a 50 electric... and the Hurricane is slightly smaller than a 30... and a lot lighter than any 30 I know of. The cyclic load on them in a Hurri... is way less than they are rated for.

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03-09-2008 09:40 PM  10 years agoPost 16
dialarotor

rrElite Veteran

Traverse City, Michigan

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DS821's good for plank friends
Not in my heli or my friends. Buddy bought 4 and 1 amp failed and twisted the output shaft on another in 2 flights of a scale set of mechanics. Give them to a plank flier.

RapRexSynLog Pilot

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