RCU Forums - Servo Question

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I'm building a Dynaflite Super Decathlon, with a 89" wingspan. The instrustions say to use 5 High Torque Servos. I would like to know which servos would be the better ones to use. This is my first larger plane and i'm not sure which is best. I was told maybe try servos from Spectrum DS821. But I don't know anything about Spectrum. Are these good Servos, or should I look at different ones?

http://www.spektrumrc.com/Products/D...ProdID=SPM3702

RE: Servo Question

The DS 821's are pretty darn good sport digitals. I've been using two on split elevators. You may not need 5 digitals onboard, but they are a definite asset on elevator. You can use analog's on the other control functions. A good strong economy analog is the HiTec 625 metal gear. You can check out HiTec specs here. > http://www.servocity.com/html/hitec_servos.html

You can also find some pretty good deals on ebay, when dealers split up the Spektrum sets, and sell new DS-821's in sets of 4.

> Jim

RE: Servo Question

The Hitec 645MG servos would do the job also and are relatively inexpensive.

RE: Servo Question

I agree, the 645's are good ones. I had 3010 Futaba's in a 1/4 Pilot Super D and they worked fine for the plane. Not as strong a servo as the 645, but they were sufficient.

RE: Servo Question

Funny thing aboput the Hitec 645s. I was going to order some from Tower, but they've discontinued them.

RE: Servo Question

[link=http://store.obrienhobbies.com/hihshimegese1.html]Here[/link] you go, get 'em here

RE: Servo Question

Quote:

ORIGINAL: GeeBeeJim

The DS 821's are pretty darn good sport digitals. ...

I would be very careful on where I use the DS821 servos.

Quoted from here: [link]http://spektrumrc.com/Articles/HobbyWire.aspx[/link]

Quote:

New Guidelines for DS821 Servo Use
Tuesday, February 20, 2007

The DS821 servo is a powerful, accurate sport digital servo recommended for RC airplane applications up to 1.20-size. For helicopters, the DS821 operates best with 30-size glow models, and up to 50-size electric. Loads and vibration in larger models may cause premature failure of the servo resulting in damage or injury to property and persons.
Important: Do not use liquid thread lock with the DS821 servo!

Do not use any form of liquid thread lock to secure the servo arm screw to the output shaft of the DS821 servo. Chemicals in these liquids react with the polycarbonate gear set causing the plastic to become brittle, fracturing the final output gear.

Read between the lines of the statement in bold and underlined. I am unsing a "set" of 821 in a 30 sized helicopter and will keep a very sharp eye on them.

Rafael

RE: Servo Question

With larger models you're typically looking at a high torque metal geared servo with at least 100 oz/in of torque. Hitec 645 MG's are good as well as JR ST125MG servos. Don't skimp on cheap servos, your airplane will thank you. ;)

While those Spektrum servos are great servos, they are not well suited to giant scale.