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DS 821 throttle?

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Old 01-19-2012, 07:44 AM
  #1
ant1
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Default DS 821 throttle?

Doing my first 30 cc gas. I have all premium metal gear servos for the surfaces,but I also have a bunch of Spektrum ds821's hanging around.
Am I safe using this as a throttle servo,or do should I go with a metal gear??

Thanks
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Old 01-19-2012, 07:55 AM
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Default RE: DS 821 throttle?

I wouldn't use that servo anywhere on a gasser including the choke.

If you fancy flying around without throttle control, make sure you have an optical kill.
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Old 01-19-2012, 08:13 AM
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ant1
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Default RE: DS 821 throttle?

Lol,that's why I asked. Thanks ,I'll pick up a no frills hitec mg for throttle.
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Old 01-19-2012, 08:52 AM
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Default RE: DS 821 throttle?


Quote:
ORIGINAL: BarracudaHockey

I wouldn't use that servo anywhere on a gasser including the choke.

i have a friend/flying buddy that uses them on all his gassers ranging from 20- 116cc
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Old 01-19-2012, 09:18 AM
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Default RE: DS 821 throttle?


Quote:
ORIGINAL: MetallicaJunkie


Quote:
ORIGINAL: BarracudaHockey

I wouldn't use that servo anywhere on a gasser including the choke.

i have a friend/flying buddy that uses them on all his gassers ranging from 20- 116cc
Just because you know someone who's gotten away with it doesn't mean it's a good idea, those servos are NOT recommended for gassers nor models above a certain weight/size.
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Old 01-19-2012, 09:31 AM
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Default RE: DS 821 throttle?


Quote:
ORIGINAL: MetallicaJunkie


Quote:
ORIGINAL: BarracudaHockey

I wouldn't use that servo anywhere on a gasser including the choke.

i have a friend/flying buddy that uses them on all his gassers ranging from 20- 116cc
That doesn't make it smart.

JR/Spektrum specifically warns against their use in larger planes and nitro helicopters.

I've used the jaws of life to extract drunks from their cars that swore they did it all the time and they were fine.
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Old 01-19-2012, 10:50 AM
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Default RE: DS 821 throttle?


Quote:
ORIGINAL: Zeeb


Quote:
ORIGINAL: MetallicaJunkie


Quote:
ORIGINAL: BarracudaHockey

I wouldn't use that servo anywhere on a gasser including the choke.

i have a friend/flying buddy that uses them on all his gassers ranging from 20- 116cc
Just because you know someone who's gotten away with it doesn't mean it's a good idea, those servos are NOT recommended for gassers nor models above a certain weight/size.
i should have clarified my self...he uses them on his throttle and choke
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Old 01-19-2012, 11:19 AM
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Default RE: DS 821 throttle?

Ah, well in that case I hope he's got a kill switch because in high vibration installations they are a really bad idea.
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Old 01-19-2012, 11:50 AM
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Quote:
ORIGINAL: BarracudaHockey

Ah, well in that case I hope he's got a kill switch because in high vibration installations they are a really bad idea.
i emailed him the link as a heads up

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Old 01-19-2012, 12:07 PM
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Default RE: DS 821 throttle?

Quote:
•Manufacturer Warning: "Not recommended for planes over 1.20-size or helicopters over .30-size. Loads and vibration in larger models may cause premature failure of the servo, resulting in damage or injury to property and persons."
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Old 01-25-2012, 06:39 PM
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Default RE: DS 821 throttle?

Dang... just realized how fortunate I've been. I've had them on all controls including quad flaps in an Ultra Stick Lite with a Zenoah G-20 since May of 2007... that is four and a half years and... it is my go to plane that gets flown as much as all others combined. And... I live in Texas and fly all year long. Plus, it suffered a crash into the top of an oak tree without any servo damage.
The time log shows 89 hours on the stick... and I rarely fly over 10 min so that equates to better than 500 flights on the 821s in a gas powered plane.

There is a difference of course in a 20cc and 30cc and I've not used DS-821s in my 30cc size planes.

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Old 01-25-2012, 06:59 PM
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Default RE: DS 821 throttle?

Key word in that warning MAY cause failure. All things MAY fail. Why are you guys so afraid of those servos?I wouldnt put them in a 3d 30cc or bigger but they work great in 25 percent planes.
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Old 01-26-2012, 04:53 AM
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Default RE: DS 821 throttle?

Personal experience with the shafts shearing and the amplifiers dying. That and the manufacturer warning.
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Old 01-26-2012, 05:39 AM
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Default RE: DS 821 throttle?

That sucks maybe the application was harder on them than mine is?
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Old 01-26-2012, 07:40 AM
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Default RE: DS 821 throttle?

Not at all.

One of them sheared on the bench by trying to put a servo horn on it.

Its your stuff, you're free to ignore all warnings and others experience you want, please just don't fly your stuff around other people.
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Old 01-26-2012, 08:12 AM
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Default RE: DS 821 throttle?

I respect your personal judgment to not fly DS-821s in gassers but it seems excessive to generalize that they should not be flown in any gasser and that any one who does should not fly around others. 20cc gas engines are displacement and power equivalent of a 1.20 rating and thus within the manufactures guidelines.
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Old 01-26-2012, 08:27 AM
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Default RE: DS 821 throttle?

Nobody i fly around is worth more than the cost of a cheap servo anyway .I didnt ignore the warning in my 10 pound to 15 pound gassers they work fine.I had a friend break a futaba 9151 on the bench before . Good thing people dont use them i guess?
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Old 01-26-2012, 09:59 AM
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Default RE: DS 821 throttle?

I have used a DS821 on throttle since 2007 on different gassers. It has performed flawlessly all these years but I were to replace a throttle servo, I'd go with metal or titanium gear. There's a luck element with any component and perhaps a cheap 821 can outlast a 7955. Statistically, expensive servos last longer but not necessarily. Such is life.
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Old 01-26-2012, 12:40 PM
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Default RE: DS 821 throttle?

I really like the 821's on the 20cc gassers. Check the AW Proxy, I've got little mini servo's for throttle on that guy per the instructions. A good inexpensive servo is the 5645MG's. I use them on all my throttles and choke for the 50cc and up models. You can get them pretty regularly on RCU for around $35. fyi, I did have two 821's strip on me when I used them as throttle servo's on my 50cc rides. As noted I guess the vibration finally gets to them on the larger models. Jerry.
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Old 05-20-2012, 10:23 PM
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Default RE: DS 821 throttle?

been using ds821's on throttle on 3 different 50cc gassers since 07. they hold up pretty well. these servos have been oiled up, gassed up from being located close to the carb and havent had one that failed. will use one again for throttle, i think i still have one more from the spektrum dx7 package from way back. it will be going into a carf edge 2.6m.
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Old 05-21-2012, 08:34 AM
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Default RE: DS 821 throttle?

I never understood why people insist on using stuff beyond mfg specs when there are so many other options available.
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Old 05-23-2012, 07:34 PM
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Default RE: DS 821 throttle?

I had an 821 fail rather quickly while being used on a G26 cdi. To be fair, the servo was not brand new and was used as an elevator servo in a foam plane that probably could have used a HS55 micro. I also took TBM's recommendation and used a Hitec HS255MG for large gas throttle. It failed within 25 flights. From now on, its full size servos for me
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Old 05-24-2012, 11:26 AM
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Default RE: DS 821 throttle?

HS 85 MG . if your needing something really small


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