Spectrum DS-821 Servos (Full Version)

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freeair -> Spectrum DS-821 Servos (5/12/2008 6:34:50 AM)

Hi Guys, what are your opinions of these DS-821 digital servos ? i have no complaints about these its just that i have some and want to use them in my Katana 40 Freestyle. thanks.



alan0899 -> RE: Spectrum DS-821 Servos (5/12/2008 7:26:20 AM)

G'day Mate,
They are good servos, I use them in my Katana, OS160FX. see pic.
No problems at all, just don't put locktite on the servo arm screws, no need anyway, but it will shatter the plastic.



BarracudaHockey -> RE: Spectrum DS-821 Servos (5/12/2008 9:31:44 PM)

The manufacturer warns you not to use them on anything bigger than 120 size airplanes.



alan0899 -> RE: Spectrum DS-821 Servos (5/12/2008 11:19:17 PM)

G'day Mate,
Maybe that's for extreme 3D, which I don't do with the Katana, they have been in it since May last year, & are still performing beautifully.



dick Hanson -> RE: Spectrum DS-821 Servos (5/12/2008 11:25:05 PM)


quote:

ORIGINAL: BarracudaHockey

The manufacturer warns you not to use them on anything bigger than 120 size airplanes.

The real problem is with the output shafts on these and other filled plastic type setups
I use these servos on ailerons on 80CC powered models
BUT adding long aluminum arms makes for too much load on the output gear and you can bust em
The 3D craze has added to the upset as many ad big long arms with big surfaces and totally overload things
A "fix" for plastic outputs is to disasemble the gears and drill thru the output -then self tap a machine screw at least 1/2"long into the plastic.. This distributes the load further down the shaft - If this sounds tricky - forget it.




CustomPC -> RE: Spectrum DS-821 Servos (5/13/2008 12:54:39 AM)

I've got over a dozen of them on 40 - 90 sized models and have never had one fail yet.

They are fine for sport models but i would not use them on a heli or 3D plane with large control surfaces.



BarracudaHockey -> RE: Spectrum DS-821 Servos (5/13/2008 8:52:55 PM)


quote:

ORIGINAL: alan0899

G'day Mate,
Maybe that's for extreme 3D, which I don't do with the Katana, they have been in it since May last year, & are still performing beautifully.

JR/Spectrum makes no such distinction, they say not to use them on over 30 size helis and 120 size airplanes due to vibration problems. They don't say 3D, sport flying, or long servo arms.

For my larger models, I personlly prefer servos that are not being pushed beyond the manufacturer reccomendations because IMO its cheaper to use decent servos than to replace a big plane or heli but thats just me.



dick Hanson -> RE: Spectrum DS-821 Servos (5/13/2008 11:45:48 PM)


quote:

ORIGINAL: BarracudaHockey


quote:

ORIGINAL: alan0899

G'day Mate,
Maybe that's for extreme 3D, which I don't do with the Katana, they have been in it since May last year, & are still performing beautifully.

JR/Spectrum makes no such distinction, they say not to use them on over 30 size helis and 120 size airplanes due to vibration problems. They don't say 3D, sport flying, or long servo arms.

For my larger models, I personlly prefer servos that are not being pushed beyond the manufacturer reccomendations because IMO its cheaper to use decent servos than to replace a big plane or heli but thats just me.

The servos are more than decent . They are very good .
The load on gear train is what causes most servo failures.
My applications have very low vibration and based on lots of use on gassers -I have no qualms about using em.
The recommendations are conservative - and I understand why they do it .
Many modelers can bust an anvil with a rubber mallet.



freeair -> RE: Spectrum DS-821 Servos (5/14/2008 6:23:45 AM)

alan0899, what size Katana do you have in pic ? also what size engine ? thanks.



Eric.Henderson -> RE: Spectrum DS-821 Servos (5/15/2008 2:56:06 PM)

JR or SPEKTRUM UPDATE.

Since I posted about using a longer servo arm screws (JR actually sells them BTW), I have employed 31 821's in a variety of powered aircraft incluiding sevral 1/4 scale ships.

To date, there have been no failures at all.

I did accidentally, during construction, use a short screwthe one that they supply, and it popped the top off the output shaft when lightly tightend. A new output shaft later and a longer screw and all was well again.

Regards,

Eric.



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