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HomeRC & PowerAircraftHelicopterRadio - JR DMSS › JR 821 servos. Why do they suck?????
04-24-2009 12:06 PM  9 years agoPost 1
Eric Giorgianto

rrApprentice

New Jersey

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Hi Guys, can anyone tell me why JR821 servos are no good.I hear people say not to use them for cyclic.or anything else on a 50 size chopper and I am wondering why this is.Also what would be the best mid-priced servos for ccpm cyclic ie: fastest and strongest in the middle of the price range?

Thanks for the info

Regards Eric G.

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04-24-2009 12:18 PM  9 years agoPost 2
BarracudaHockey

rrMaster

Jacksonville FL

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Its isnt so much that they suck, they are being used beyond the manufacuter recommended specs and failing. No surprise there right?

JR says not to use them on anything larger than 30 size nitro or 120 size airplanes.

Do it and the amps die or the output shafts shear off. Do a search you'll find plenty of "i probably should have listened....." threads.

Andy
AMA 77227
http://www.jaxrc.com

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04-24-2009 12:33 PM  9 years agoPost 3
duceduc

rrKey Veteran

Saitama-Ken, Japan

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I have used them on a 50 size heli with no issue. I ended up upgrading my servoes eventually.

I would not recommend using them for a long period of time or avoid them completely as it will possibly fail.

Duc S
Do It! Do It!™
AMA:REVOMIX
RCK:24005615-01

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04-24-2009 12:51 PM  9 years agoPost 4
rotormonkey

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Ottawa, ON - Canada

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My understanding is that the vibration gets 'em eventually. Most recommend not using them on any nitro heli at all.

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04-24-2009 12:58 PM  9 years agoPost 5
BarracudaHockey

rrMaster

Jacksonville FL

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Here's the question you should ask yourself: What is the cost of decent servos versus the cost and time of a wrecked heli due to using a servo beyond its published limitations.

Andy
AMA 77227
http://www.jaxrc.com

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04-24-2009 01:11 PM  9 years agoPost 6
Eric Giorgianto

rrApprentice

New Jersey

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JR 821
Hey guys Thanks for the info. I recently ordered a set of Hitec digitals High speed and 130ozin torque and will be installing them in my chopper.I am by no means a newbee,I have been flying choppers for 15 years and was just wondering what most guys think and use in their choppers.I have never been a fan of 200.00 servos as for me this is overkill for my flying style, I'm am more interested in the middle of the price range for my servos,so any suggestions would be greatly appreciated. I fly mostly FFF with some loops rolls stall turns and some inverted hovering with a couple of "I meant to do that manouvers" thrown in for fun.I don't really do any hard pitch pumping or smackdown kind of stuff,I prefer to fly smoother pattern type moves, so what do you recommend?

Thanks Again Eric G.

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04-24-2009 01:14 PM  9 years agoPost 7
Jonty

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Wellywood

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I quite liked futaba 9252s.

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04-24-2009 01:26 PM  9 years agoPost 8
BarracudaHockey

rrMaster

Jacksonville FL

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Yep

9452s,
5625 hitecs

There's a gaggle of choices in the mid price range

Andy
AMA 77227
http://www.jaxrc.com

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04-24-2009 03:14 PM  9 years agoPost 9
alchemist

rrVeteran

Auckland,New Zealand

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04-24-2009 04:43 PM  9 years agoPost 10
AaronJohnson

rrElite Veteran

mason,MI

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JR DS8231's would be awesome servos for you. They are about 63 bucks a piece from heliproz. These servos are very precise and last forever it seems. Not the fastest but they work perfectly.
They fly a heli very nicely.

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04-24-2009 05:38 PM  9 years agoPost 11
Ravenhyper50

rrKey Veteran

Canada's Capital

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+++++1

I also use these servos and they rock!

I do the kind of flying you do but with some horrible attempts at smack 3Dn They have held up well after many crashes and I never stripped a gear yet. Still rocks with super precision.

DS8231 Digital Ultra Precision Servo
Overview
The 8231 features 5-times the holding power of a analog servo, but only 8% more current drain under load. Its incredible resolution of 5,900 steps per 120-degrees offers unparalleled precision and an almost non-existent dead band. It is the ideal choice for ailerons on an pricession pattern airplane or jet. Heli pilots will find its holding power and resolution to be excellent for rudder or collective on their machines.

Key Features

Outstanding holding torque that's 2-5 times greater than a conventional servo
Current draw is only 8% greater than a conventional servo
Ultra precise 5,900 step resolution for unmatched precision.
New wide-spaced output shaft dual ball bearings for minimal output shaft play
250MHz pulse rate for increased precision
Specs
Size Category: Standard
Type: Digital
Torque: 88 oz/in @ 4.8V, 113 oz/in @ 6V
Speed: .22 sec/60 @ 4.8V, .19 sec/60° @ 6V
Dimensions (WxLxH): 0.75" x 1.54" x 1.36"
Weight: 1.73 oz
Bushing Or Bearing: Bearing
Bearing: Dual
Motor Type: Coreless
Gear Type: Nylon
Application: pricession pattern and jet airplanes, collective and rudder on helicopters

I have had the ds821 FAIL ON ME ! COST ME LOTS $$$ TO LEARN MY LESSION

Raven

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04-24-2009 05:40 PM  9 years agoPost 12
Justin Stuart (RIP)

rrMaster

Plano, Texas

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I sold my 821 servos. Why risk it?

Avant RC
Scorpion Power Systems
Thunder Power RC
Kontronik Drives

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04-24-2009 05:42 PM  9 years agoPost 13
Hellsiege

rrVeteran

Colorado Springs, CO

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+1

Did the same, then later bought some to use in a bigger electric plane w/out issue... It's the vibes that do them in like mentioned above.

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04-24-2009 09:24 PM  9 years agoPost 14
LONEWOLF2440

rrElite Veteran

MYRTLE BEACH S.C

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I wont never use them on a nitro not worth it

MIKADO LOGO 600 TREX 550

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04-24-2009 09:35 PM  9 years agoPost 15
Gearhead

rrMaster

Vt

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JR DS8231's
my friend is in his 3rd year with DS8231's on his Shuttle 30,,keep in mind he is a pattern pilot, the Shuttle being a 30 is not his main heli, he probably doesn't fly the Shuttle weekly,,

a couple years ago there was a clip of a 90 doing very hard 3D, this clip had a torque read-out of the servos, maximum torque used was 80oz,, with that the DS8231 specs sounds good for a 50, but the proof is in the air, there have been some complaints on them,,

as much as I like JR I think it was extremely "extremely" stupid of them to stop making the DS811 !!

Jim
Buzz Buzz Buzz

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04-25-2009 04:34 AM  9 years agoPost 16
Eric Giorgianto

rrApprentice

New Jersey

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JR 821
Hey Guys Thanks for all the input I just swapped out the JR's for a set of Hitec 5625 metal gear servos got a good deal on them and will be flying them tomorrow and will let you know how they perform.
What ever happened to good old JR 4721's those servos were great flew them in my Excell for 5 years and never had a problem and I ran them on 6 volts too!! Ahh the good old days...
Thanks Eric G

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04-25-2009 04:55 AM  9 years agoPost 17
Santiago P

rrProfessor

South West, Ohio

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IF I may, stay away from the HS5625. The do have good speed and torque, but they center HORRIBLY, or should I say they dont center well. Their deadband is 8us which is huge compare to any servo made for helis. Their metal gears develop a bunch on backlash in no time.
In comparison, your old JR 4721's had zero deadband.

I used the 5625s for a month on my XCell and wonder why the heli was all over the place. Switched them for 9252s and it was like a new super precised heli. Night and day.
2 years later I put HS5625 on my Raptor 50 and again it flew like crap. Put other servos in the R50, well, no miracles but the Raptor was much controlable. Hope you get the point.

Santiago

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04-25-2009 05:12 AM  9 years agoPost 18
dkshema

rrMaster

Cedar Rapids, IA

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Why do 821's suck? Dunno, JR dropped the ball and has for whatever reason failed to pick it up and either stop shipping them, or fix them.

Two reasons they suck. Output shafts shear clean off without warning or provocation. Servo amplifier just dies. Either way, it's no goo for your heli. JR and Spektrum published a warning a couple years ago about them, saying don't use in nitro helis larger than a 30 (but they would be OK in an electric 50). Don't use them because the vibration could make them fail. Later on, that warning was toned down a bit, I think now you'll be hard-pressed to find it either on the JR Radios site, the Horizon site, or the Spektrum site. I'd guess that selling a servo while telling people it's prone to failure at the same time would invite the inevitable lawsuit at some point. Make the warning quietly disappear, people forget, and problem is solved.

-----

I used DS8231s in a 70 powered (later 90 powered) Freya for 5 or 6 years. They never gave me a moment's worry. Wasp is right about the DS811. It was a real workhorse, inexpensive, and performed admirably in my now departed EVO 50 for 6 seasons. Still have them, may put them back in something else in the future.

-----

HS6975HB's are pretty decent servos from Hitec. Fast, strong, overall work very well, have a set installed in a 600 Nitro Pro. The Karbonite gears are strong and I believe they outlast the metal ones by far. I like them every bit as much as the S9252s in my other 600 Nitro Pro.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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04-25-2009 05:15 AM  9 years agoPost 19
AltecLansing

rrElite Veteran

North Carolina

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get some align 610 servos, they are 3 fo 180. That's 60 each. Good speed, good torque and great price

Man, I miss the eighties.

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04-25-2009 12:37 PM  9 years agoPost 20
LONEWOLF2440

rrElite Veteran

MYRTLE BEACH S.C

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I got the align 610,s love them

MIKADO LOGO 600 TREX 550

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HomeRC & PowerAircraftHelicopterRadio - JR DMSS › JR 821 servos. Why do they suck?????
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