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rototiller
10-27-2007, 05:21 PM
I just checked the specs on the hs-625mg. Looks good. Same tork as the 821 and a touch faster. But there not digi so you will lose some of the crispness and locked in feel that the digi servos give you. Other than that they look fine. Probly wouldnt feel any diffrents throwing it around. If you start doing pattern type flying you will notice though.

DK

aevans692
10-27-2007, 05:29 PM
I just checked the specs on the hs-625mg. Looks good. Same tork as the 821 and a touch faster. But there not digi so you will lose some of the crispness and locked in feel that the digi servos give you. Other than that they look fine. Probly wouldnt feel any diffrents throwing it around. If you start doing pattern type flying you will notice though.

DK


Are you still using the 821 ? as you have them listed.. I only changed them out as I was worried about them braking on me, I never had any problems with them.

I am not throwing it around to much am just starting flips and rolls but only taking it slow and easy. so I hope the 625mg should be ok for a bit , will get something better as and when I feel I need a bit more..

rototiller
10-27-2007, 07:06 PM
Yes i am still using them. I have done flips and rolls from the moment they went in. I am now up on 6V and REALLY like them. I only have a few flights on the higher voltage but have 9 gallons of fuel on them total at 5V.

Once I heard about the too short screws for the arm i put longer ones in. That was when they went into the Rex witch now has 60 flights.

It does seem like a lot of people are having problems with these. With that said.....I had a set of $100 hi-tech digi's freak out on me, one went full left and locked up. Another just stopped working and this was all on setup. Yes I pulled these out of the box. I have also had $100+ Futaba servos break case's, lose center, all kinds of stuff. Just goes to show that any servo can have problems.

In .40+ planks my fav servo was the 3004 on 6V. I think I found a digi version of that for helis. If they give me problems then I will probly put some better Fut's in there place.

DK

Edit: Its not much but this is a vid of it on 5V.
http://www.youtube.com/watch?v=GgEDsDOyqyg

theLane
10-27-2007, 11:40 PM
I set one of mine down on the table and went to get a coffee... when i came back, i SAW it get up, walk over to the edge of the table and JUMP... broke the output shaft and was DEAD! I believe it was suicide... sad sight I tell you.

Just kidding man... couldn't resist - LOL.

Yes, I guess some do have trouble, but I have been using them for a while and many others are using them as well, with no trouble. Due to the manufacturer warning, I probably would not attempt 3D with them, but a little sport flying I truly believe they are fine. My buddy crashed his 600N and blew out two of those million dollar 9254's (?). I had three crashes and the 821's survived all three times. That's gotta mean something other than "luck".

I think they are getting a bad rap myself.

~Lane

A friend of mine was setting up his helicopter with 3 brand new 821s. One of them died on the bench, just quit working. The other one sheared the output shaft clean off when he bumped the flybar putting it up on a shelf.

I saw another one in a 40 size airplane, with one servo on each aileron, shear off in flight, had the load not be split between the two servos he would have likely lost the airplane.

Its just not worth it, get some decent servos.

Forced_Induction
10-28-2007, 02:17 AM
so what would the experienced pilots reccomend. I dont want to shell out $150 per servo. Im an intermediate pilot, so i dont need a .08 speed servo. What would be a good choice?

aevans692
10-28-2007, 03:52 AM
Thats where I am at , I am just intermediate pilot and dont need the best. I was happy using the 821 and they served me well and seemed to suit my flying style, I am just getting in to flips and rolls but mainly FF..

I became more concerned after what I read on the spektrum web site , think it listed under FAQ.. But they do state that their not good for anything above 30 Ic due to the increased vibrations, I thought on that note if there is a recognised problem and not just hear say, I would change them out , made sense as I had 625MG at hand..

For you guys who are still using them I understand where you are coming from as I prob wouldn't of changed mine out unless I read the statement form spektrum , after which I couldnt trust them even tho I had no probs, I think you should make sure that you have maximum dampening as poss to try and reduce vibration,

just a thought can the out put shaft be changed over, with somthing better ? instead of replacing the whole servo as it seems its the out put shaft which goes first...

BarracudaHockey
10-28-2007, 11:07 AM
so what would the experienced pilots reccomend. I dont want to shell out $150 per servo. Im an intermediate pilot, so i dont need a .08 speed servo. What would be a good choice?

9252s, or 9451s

aevans692
10-28-2007, 12:30 PM
Today I spent a bit of time opening up my 821's and inspecting them, there was no sign of ware and every thing was fine in all of them I did pay close attention to the out put shafts, which seems to be largely the problem, but again nothing there was no gear fragments, no teeth missing, no cracks, no signs of grinding nothing...

As I found no signs of ware this makes me think that any failure is instant , this being the case it then makes it impossible to predict..

Is their a replacement gear set that would fit any metal gears from Jr ?

Forced_Induction
10-28-2007, 01:28 PM
what about the hitec HS-5625MG? metal gear, digital, 130 oz-in TQ, .14 s, for $30 less. Looks like its close to the same specs as the 9252, just a bit slower

aevans692
10-28-2007, 04:28 PM
I just found this old post..

http://www.helifreak.com/showthread.php?t=47026

aevans692
10-31-2007, 05:05 PM
Hi all

I sent an email off to spektrum with regards to the issue with the 821's ( I have since swapped them out as I cant trust them) This is a copy of the email which I have just received back, this is from spektrum direct..





Andrew,

The 821 servos should be fine in this heli. In fact, the DX7 with 821 servos is one of the suggested radio systems for use with the T-Rex 600.

I hope you find this information useful. If you should have any further questions, please reply to this email or give us a call at 1-877-504-0233.

Thanks,
Craig
Product Support Team Member
Horizon Hobby Distributors
4105 Fieldstone Road
Champaign, IL 61822
877-504-0233
productsupport@horizonhobby.com


-----Original Message-----
From: aevans692@btinternet.com [mailto:aevans692@btinternet.com]
Sent: Friday, October 26, 2007 12:51 PM
To: Horizon Hobby Sales
Subject: Contact from Spektrum RC.com

Comments: Hi

I have and been using the Dx7 with no problems and I am very impressed with it since changing from futaba..

When I purchased my Dx7 it came with the DS821 servo as advertised, I am using this servo in mt Trex 600n pro which is a 50 size heli, my concern is that I have heard of many people using the 821 and claiming that they have a tendency to brake, I have read on many fourms that the 821 is not suitable for 50 size nitro helis.

Can you please clarify for me if I should be using the 821 in a nitro heli , and is it safe for me to continue using them..

I am very happy with the spektrum products that I have purchased and will continue using these products, my only concern is with the DS821

Thank you for your time.

Andrew Evans

Name: Andrew Evans
Email: aevans692@btinternet.com

*The customer explicitly requested a response.

==================================

Time Sent: Friday, October 26, 2007 12:50:38 PM

IP Address: 82.45.92.39

User Agent Info: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-GB; rv:1.8.1.8) Gecko/20071008 Firefox/2.0.0.8

ghtracey
10-31-2007, 05:31 PM
They said recommended for a T-Rex 600, not 600n. That's the difference, they say not to use them on a .50 size nitro. I think maybe someone at JR misread what you were using.

theLane
11-01-2007, 08:36 AM
I think to sum it all up, the 821's are fine for sport flying or beginner-type flying, lot's of people are using them in the 600N and they are no more unreliable than the rest.

Once you hit the hard-3D stage, you will want different servos anyways.

~Lane

ghtracey
11-01-2007, 12:14 PM
Are you sure? if that's the case and they are fine for sport flying, why are some people using them as throttle servos in nitro birds having them fail. Spektrum says its the vibration, not the loads that is causing the failures.

vteknical
11-01-2007, 05:48 PM
HS-69695' cyclic and throttle for me. Avg Ebay price from Tom's RC 55.00.
I closed once on a brand new 6965 auction for 42.00. I was buying my stuff a little bit at a time.
You can buy them now for 70.00. Buy from a US authorized dealer in the event you need to have them repaired under warranty.

So far really like them. Shop around and get yourself a good deal on an upgrade to the 821.

rototiller
11-05-2007, 06:42 AM
I have recorded 70 flights on my rex600N with the 821's. They were in a rappy when i got them new and had about 40 flights on that bird. Soo thats over 100 flights on 821's in a 50 nitro.........yesterday my throttle servo lost center. Thank god it went full close instead of full open but, it went past full close and ended up opening the throttle a little. It was the end of the day on the last tank. I was doing my last couple autos and heard the motor cut out then come back. I thought I was out of gas soo I hit throttle hold and the motor was still running fast enough to beable to hover at a VERY slow head speed. I only had wait a couple of mins before it ran out of fuel and am really glad I wasnt inverted on the deck when it happened.

So now I have to tear the 600 down for major cleaning and save up some cash for new servos.

DK

aevans692
11-05-2007, 09:55 AM
I am glad that I have changed mine out, I have heard so many bad things about them, I am sure if I had kept using them sooner or latter I was going to have one go on me..

I think you have been lucky this time, are you going to change all of them??

rototiller
11-05-2007, 05:19 PM
I am glad that I have changed mine out, I have heard so many bad things about them, I am sure if I had kept using them sooner or latter I was going to have one go on me..

I think you have been lucky this time, are you going to change all of them??

Well, I had a hs65 fail on me this summer, put my 450 in the dirt hard enough to bend the alum head block!! Crash wasnt too bad. These are not my first servos to just fail on me. It can happen to $100+ servos too.

Well, winter is pretty much here soo my nitro flying well become a thing of the past. I am gonna strip the heli down to check EVERYTHING over and make sure all is as it should be. Then put it up for the winter. I will put a new throttle servo in there just incase I get some good weather and have to fly but will probly fly the electrics till spring. Ya, after the holiday's I will try and get some real servos in here. Would like some faster servos for sure.

DK

Pinecone
11-05-2007, 10:45 PM
a) Any servo can fail.

b) If you run DS821s on a 50 nitro bird, you are taking a greater risk than most other servos used.

c) Don't cry if one breaks and you go in hard.

d) You are all adults and capable of making your own decision.

e) I personally would not run them in a 50 nitro heli.

Tom Burgess
12-03-2007, 03:02 PM
Well said Pinecone, If JR are saying don't use them on a 50 size nitro, I wouldnt! Its not easy for a company to say my product isnt good enough for a particular application so they dont say it for no reason. If your car manufacturer told you that your car was not for use on a motorway would you drive on a motorway? I wouldnt!!:thumbdown:

alchemist
12-05-2007, 06:15 PM
The output shaft is made of cheap plastic and painted to look like steel, use a DS821 on a 600 class heli and sooner or later it will fail.