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Radio - Servo - Gyro - Gov - Batt > JR 821 Servo Failure
 
 
hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		I have been using the new JR 821 digitial servos in my Raptor 50 for about 30 flights now. I just do basic flying as I am still learning.

Yesterday I took off and while sitting in a 3 foot hover the Raptor starting going to the right. I went to correct it with left aliron an nothing. It hit the ground but not too bad. Upon inspection I found the aleron servo to be dead.

This is the first failure like this I have had. Is this common? Anybody else had trouble with the 821's?

I ordered Futaba 9252's today which I will replace the 821's with. I know this could happen to any servo but I just don't trust them now. The pitch servo is also starting to get a lot of play in the gears.

Thanks for any info,

Harold
10-23-2006 Over year old.
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hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		821 Servo Update

I opened up the servo and when you give the motor a little help it will turn. It appears the motor in this servo died.

I don't think I will use them in my Heli's anymore. I just don't trust them.
10-24-2006 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Sounds like the motor overheated for some reason....
10-24-2006 Over year old.
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coolice
Key Veteran
Location: Northamptonshire, England

My Posts This: Topic  Forum		Hey,

I am guessing this is JR's entry level Digital servo, in the UK it is designated the 811.

I had good success with some on my Falcon50, they lasted over 15 months before the aileron went on mine to. However they were being used for 3D and so they lasted well.
On the other hand some of my fellow club fliers, at this time were still hovering about, had two of these 811's fail within two months of fitting them. Again this was with Raptors and the Aileron again, whether there is any connection to them failing here I do not know.

Needless to say none of us now use them either, although one guy is using them on a Swift for the eCCPM and they are working well.

The 9252's will be great and are a reliable servo.
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Ian Contessa
Team Robbe SchluterUK
10-24-2006 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Problem with Rappies and JR servos is 99% incorrect installation !
usually the anti-vibration mounts are bypassed by accident....

http://www.macgregor.co.uk/faq/Serv...vo%20Killer.htm

10-24-2006 Over year old.
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hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		We had 811's here also but they were discontinued and replaced with the 821's. About the same servo but the 821 has 72 oz of torque and is a little faster. They are both single ball bearing. I use them in planes up to a 125 size and havn't had any problems.

They should handle a 50 size heli but I guess not. My 9252's will be here tomorrow.

Thanks for your reply.

Harold
10-24-2006 Over year old.
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hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		The correct link is http://www.macgregor.co.uk/radio/mount.htm

And yes it is possible that I had the screws to tight. I will have to pay attention to this on the new install. I am still surprised the servos fail after less than 20 flights.
10-24-2006 Over year old.
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coolice
Key Veteran
Location: Northamptonshire, England

My Posts This: Topic  Forum		Anti vibration mounts were used on both occasions and so that theorys out the window

The only area of concern on the Raptor is the Aileron servo wire having to be looped back under the case to clear the collective cradle. However in these cases the servo has power just no control.
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Ian Contessa
Team Robbe SchluterUK
10-24-2006 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		The link I was trying to show is correct but for some odd reason RR doesnt like spaces....

http://www.macgregor.co.uk/faq/Servos/Servo Killer.htm

Grrrrrr !!! I'll have to modify the page itself....
10-24-2006 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		http://www.macgregor.co.uk/faq/Servos/Servo_Killer.htm

Hopefully thats it corrected...
10-24-2006 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Ian, the vast majority of servos I get back that have knackered motors, show web marks....

10-24-2006 Over year old.
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dkshema
rrMaster
Location: Cedar Rapids, IA

My Posts This: Topic  Forum		The 821 is the replacement for the 811.

Dave
10-24-2006 Over year old.
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hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		The main thing I learned from all this is to check you controls with the engine running before you take off. I do this on my planes by haven't gotten into the habit on the Raptor.

This servo was dead when I lifted off. I just got a little high before I realized.

The key is to learn from your mistakes. And I will not tighten the screws so tight on the new servos.

How about the little servo plates that come with the Raptor 50's that mount on top of the rubber. Should I be using them? I would think they would keep the servo a little tighter and cause a problem.

Harold
10-25-2006 Over year old.
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coolice
Key Veteran
Location: Northamptonshire, England

My Posts This: Topic  Forum		Hey Mac Man,

Ah yeah, I know what you mean now about the strengthening web on the case. That can be the case for the tail rotors and other control's if you are using the metal servo clamp plates you can buy.
I noticed Century ones actually have a cutout in the middle to miss the servo casing web which is handy, assuming you fit it the right way round.

I think the trick here is as Harold mentioned, remember not to over tighten your servo mounting screws. Inturn this will allow the rubber grommets to do their job properly.

It's still puzzling about these servos failing though and well before they should show signs of wear and use.
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Ian Contessa
Team Robbe SchluterUK
10-25-2006 Over year old.
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solo
Senior Heliman
Location: San Antonio Tx, USA

My Posts This: Topic  Forum		YES!!

I had the same problem with my 821s. Had about 12 flights on them in my Hawk Pro. My aieleron servo went out and I almost crashed ... had no control and the hawk was heading toward me and others at the field. As I ran away I kept moving the control sticks and about three feet off the ground the servo starting working again. I thought maybe a bad glitch. The next week at the field as I ran the heli up on the pad ... I move all control surfaces and my aieleron did not move. I stoped the engine and check the servo and the servo was frozen. One of the piolts at the field force the servo to move and it freed up. I change out that servo. Im not to sure about the 821s. I have the DS 811s in my Rappy 50 and no problems.
10-28-2006 Over year old.
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hrosee
Senior Heliman
Location: Richardson, Texas

My Posts This: Topic  Forum		I called JR/Horizon to tell them about it and they said I was the first problem with an 821 they had heard about. Maybe other need to call also. It's not worth sending it in to be repaired or replaced because the postage would be half of what a new servo cost. I have a lot of these servos in planes and they seem to work fine. They just can't hold up to heli use.
10-28-2006 Over year old.
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gipper6
Senior Heliman
Location: Mckinney, Texas

My Posts This: Topic  Forum		Yikes! I just bought about 10 of the servos. Man I hope they're not all bad. From what I hear, JR servos are all MILSPEC, but it seems like I hear alot of bad press lately. The big problem is trust. If you don't trust them you can't enjoy the hobby and then there's no point in being a part of it.

The best way to make a small fortune in RC Helis is to start out with a large one. Debt from above!
11-01-2006 Over year old.
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harmdive
Senior Heliman
Location: Colchester. UK

My Posts This: Topic  Forum		Hello all

I know this thread is over a year old but I wanted to find out about this particular servo that has also failed on my Rappy 50. It is the 811 and it is on the aileron control. Flew it last Sunday and nearly crashed because of it. I thought it was the battery failing because of the cold weather. Changed the battery today and did pre flight checks - everything OK. Spooled up the blades and again no aileron control. Checked receiver and switched another servo to aileron - absolutely no problem so I know it's not the rx. It seems this is more than just a coincidence that this servo has failed on the same heli and on the same control with all of you out there. One thing I do have to note is that it has had three years of hard work but I feel it is no excuse as the heli is maintained well. I now have a lot less confidence in the model as the elevator also has the 811 installed. Will now change that to something more reliable.
04-12-2008 Over year old.
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9387ASH
Elite Veteran
Location: UK

My Posts This: Topic  Forum		Just to confirm..... the US 821 servo IS NOT the same as the DS811. Totally different servo altogether.

I'm a bit puzzled why you were using an 811 as the AIL servo.... would have thought it was underpowered for that.
04-13-2008 Over year old.
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harmdive
Senior Heliman
Location: Colchester. UK

My Posts This: Topic  Forum		Servos came with the radio I bought when I was still doing basic stuff three years ago. Up until the day it failed I haven't had a problem and giving the heli a severe bashing nearly every flight. Now I know it's underpowered!. Now going through the minefield of what to replace them with. On my Titan I'm running 8711 on pitch and 8715's on cyclic via lipos/arizona 5.3volts. So far no problems but I think I killed the engine because of severe tic tocs etc.
04-13-2008 Over year old.
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Radio - Servo - Gyro - Gov - Batt > JR 821 Servo Failure
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