Pro's & Con's of the DX7 DS821 Servos

[jet22b]

Hi Everyone;

For the past 31+ flight with the T-Rex 600N using the DS821 servos, I have read that these servos are not good to be use in the 600N. Can someone tell me why? I am not doing any hard 3D's with these servo, just sport flying.

Thank you all for your input!!!

jet22b

[mewsikman]

the plastic mountings crack for no reason, change them over to futaba s3152

[jet22b]

the plastic mountings crack for no reason, change them over to futaba s3152

I have the Futaba S3151 servos, will they work??

jet22b

[mewsikman]

ummm i cant really say because they have stopped distributing them in the uk so i cant get any info on them, you might want to get finless advise on this.....

[george0079]

You should really consider using a servo that will withstand the use/abuse of helicopters. The 3151 is better than the 821, but not by much. You should think about maybe getting something like the futaba 9252. They are a small investment for piece of mind.

[aevans692]

I have also been using these servos and have read alot of bad stuff about them and was even looking to change them up coz of what I have read, I have a set of Hitec 625MG super torque.. have been told that these are not much better.

I have had no problems with the 821 I am not into heavy 3d and they have always seemed to worked fine with my flying style , I have spoken to the guy in my local model shop about this and he has told me of a few people who are using the 821 with no prob's who are flying much harder than me..

I guess that I will prob change them as I wouldnt want to wreck my heli coz of a bad servo.

but if I hadnt of searched them up on the net would I still be using them? answer prob yes ,would I have problems with them maybe ,maybe not , I know a few guys who have had problems with very high rated servos..

You can not guarantee that the most expnsive high rated servo will not have a fault or become faulty I guess its horses for courses you pay your money and take your chances....

[stevehonn]

Despite my advice a new flyer at our field is using DS821 servos on his 600N, so far he has had three servo output shafts break, luckily non in flight so yes, they may well do the job but then the failure is without warning. I've been using the DS821's in my Raptor E550 for some months now and have had zero failures so they seem okay on electric helis but can't stand the vibes of nitro.

[aevans692]

Maybe as he is new that there might be another under laying issue , maybe he had mounted them wrong, or maybe he has been over running them with not proper ajusted end points, these are simple things which people over look when starting out, all of the above would wreck any servo..

[Pinecone]

But JR does recommend AGAINST using them on anything bigger than a 30 sized nitro ship. 50 sized electric is OK.

The extra vibration is probably the reason.

But overall, use DS821s on your Trex 600N at YOUR OWN RISK.

[BarracudaHockey]

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.


Straight from JR/Spectrum

[aevans692]

maybe the new guy had been using threed lock.. ooopps..

I have been using them with no probs but am going to change up cause of what I have read, no one wants to drop a heli , even more so coz of a bad servo ... will prob keep it on the throt tho ??