ds821 dx7 servo defect
09-10-2007, 10:11 PM
#101
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RE: ds821 dx7 servo defect
Good picture!
Made my mind up for me ....its the screw causing it.
Another brand had the same problem and went to a longer screw which fixed the problem, I think it was 2mm longer
Made my mind up for me ....its the screw causing it.
Another brand had the same problem and went to a longer screw which fixed the problem, I think it was 2mm longer
09-10-2007, 10:50 PM
#102
RE: ds821 dx7 servo defect
If the gears are made of a polycarbonite type of plastic, threadlocker, gas and allmost any strong chemical will have disasterous results if exposed to it. Take a piece of polycarbonite (LEXAN) and put a drop of loctite on it. It will spider crack in a fiew hours just sitting on your bench. I know they are strong, but are not nearly as durable as simple nylon when it comes to a impact or exposure to many common chemicals. If the screw was just a little longer I think you would see the breakages stop. H***c made a longer screw and it stopped it instantly. I remember when people used to fly 1/4 scale planes powered by Quadra 35's back in the late 80's with stanard type servo's and I never seen this happen to them. To say that you have to use them carefully is a big excuse not to own up to the problem. Remember the sport 125MG, they went around and around with that one too, untill it was quickly discontinued.[:@] What a shame, I have been useing there equipment since Circus hobbies radio's were sold, but I am beginning to wonder about there quality myself. I am running them in my 11 lb GP RV-4 on the flaps and ailerons, and am wondering if I am on borrowed time. There was no way in hell that I was useing them on the elevators.[X(]
09-10-2007, 10:57 PM
#103
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RE: ds821 dx7 servo defect
Photos of my solution showing two longer screws and how they hold the shaft togther.
For what it's worth.
Regards,
Eric.
For what it's worth.
Regards,
Eric.
ORIGINAL: Eric.Henderson
I have installed and flown a dozen or so of these servos and one of them broke in situ tonight. Never even ran eth engine let alone flew it so thee was no excessive load put on the arm. The break occurred in a static position on an aileron after the servo arm an hour or so after it had been screwed into place. No thread locker or excessive force was used.
I have owned over 30 JR radios as far back as the MacGreggor Unlimited-8 in the UK and the Circus Circus Galaxies in the USA. I have probably used every servo they have ever made. Once in a while I would wear out the nylon hole in the output shaft and resort to using a longer screw to cure the problem.
I have NEVER had an output shaft snap, EVER! even in some distasterous full bore crashes.
While we wait for a fix, I would suggest using a longer screw would give some some added insurance. Make sure the screw is not too big a diameter. Mine looked like it expanded and cracked with the supplied screw. I will take care and test fit the screw without an arm in place first to see if the shaft distorts or if the screw is too long. That is to say whenever I can find a hobby store that carries the DS821 gears .
Regards,
Eric.
ORIGINAL: dsnyder
Yes, thread lock can make the shaft fail, and that is the only thing we have found that causes a failure outside of use in an incorrect application. You wouldn't necessarily see any deterioration.
As long as the servo is used in 1.20 size aircraft and under, and 30 size glow/electric helis and 50 size electric helis they work great.
Yes, thread lock can make the shaft fail, and that is the only thing we have found that causes a failure outside of use in an incorrect application. You wouldn't necessarily see any deterioration.
As long as the servo is used in 1.20 size aircraft and under, and 30 size glow/electric helis and 50 size electric helis they work great.
I have owned over 30 JR radios as far back as the MacGreggor Unlimited-8 in the UK and the Circus Circus Galaxies in the USA. I have probably used every servo they have ever made. Once in a while I would wear out the nylon hole in the output shaft and resort to using a longer screw to cure the problem.
I have NEVER had an output shaft snap, EVER! even in some distasterous full bore crashes.
While we wait for a fix, I would suggest using a longer screw would give some some added insurance. Make sure the screw is not too big a diameter. Mine looked like it expanded and cracked with the supplied screw. I will take care and test fit the screw without an arm in place first to see if the shaft distorts or if the screw is too long. That is to say whenever I can find a hobby store that carries the DS821 gears .
Regards,
Eric.
09-11-2007, 08:39 AM
#105
RE: ds821 dx7 servo defect
Longer screws are not necessary, the only problems we have seen have been due to improper application, installation, or the use of thread lock. This thread has run its course and all questions have been answered. I'm closing it down.
