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Old Sep 09, 2012, 05:54 PM
Goingboeing is offline
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...only the depth varies...
Discussion

Servos?


Hi All,

New to the forum, and relatively new to rc gliders...have a question regarding recommended servos for an Olympic 650? I have received a little differing info, and also note that technology has moved on a little since Sailplanes and Soaring was published.

Any helpful tips/info gratefully appreciated.
cheers,

GB
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Old Sep 11, 2012, 01:25 AM
lincoln is offline
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No need for anything high tech there. Anything small enough to fit that is not tiny will work. You might try HS-81. Or even standard servos, if they fit. Advantage of standard servos is that they're cheap and the gears are harder to break. If your Oly is coming in especially heavy, then maybe you can use the HS-81's or something like them. I suspect HS-55's are too small, except possibly for the spoilers, but the HS-81's are probably more than you need, especially for the elevator. My 650 had ancient Kraft servos that were wearing out.

I learned to fly with an Oly 650. Not bad for the size.
Old Sep 11, 2012, 01:57 AM
Goingboeing is offline
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Many thanks Lincoln - noted. And, to be fair the HS-81's have also been recommended by a couple of folks here so you are reinforcing the view. Looking forwqard to getting on with the build and flying the beastie before too long...

cheers,

GB
Old Sep 11, 2012, 02:04 AM
lincoln is offline
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Remember that this type of glider is designed for a 2 ounce receiver, 4 ounce battery pack, and 2 ounce servos. So you don't have to get the very smallest servo that will do the job.
Old Sep 11, 2012, 04:42 AM
Goingboeing is offline
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Got it - and appreciate the follow-up and initial response - thanks.
Old Sep 11, 2012, 06:55 PM
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Mark LSF # 3792
Weight is an important factor in a 2 meter. I would recommend the smallest servo you are comfortable buying. HS-81's and HS-85's are a good small analog choice. My 100" OD from the day of the Oly 650 was designed around standard servos, all I could afford, and has ATX 94102's in it with an after market BB top case. I now have to use a 4S 1000 ma AAA pen cell pack to get the CG back where the airfoil is more happy. Even still I can fly for more than an hour on that tiny pack.

I would strongly recommend ball bearing top cases. They last much longer and the centering can be seen and felt even in a low tech RES. Small servos give you more room under the canopy and you can put the balance weight much further up front in electron storage or lead. Lead being more dense than servos. IMO the HS-85MGBB would be an almost bullet proof application for your Oly.

Mark
Old Sep 11, 2012, 11:28 PM
Goingboeing is offline
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Hi Mark,

Thanks for the post...I do note that the HS81's also have a ball bearing top case, however, could not find any info on the HS85MGBB's (not on the HK site). If you can send me a link I'd be grateful.

thanks again,

GB
Old Sep 12, 2012, 02:57 PM
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Buy quality if you can afford it.


Quote:
Originally Posted by Goingboeing View Post
Hi Mark,

Thanks for the post...I do note that the HS81's also have a ball bearing top case, however, could not find any info on the HS85MGBB's (not on the HK site). If you can send me a link I'd be grateful.

thanks again,

GB
I would recommend buying a higher quality servo that you can afford. I prefer digital servos because they deliver higher holding torque per unit weight than an analog servo. Brands I would suggest are Hyperion, RJ, and Airtronics, Futaba.

I have had two rudder servo failures in RES planes. One plane I was able to return to my mini field by flying upside down at the correct intervals.
But the second failure resulted in a devastating crash.

It seems to me that the servo (electro-mechanical) is the most likely item to fail in a control system. Consider moving up to a hyperion digital servo.

In a 3 meter RES I use a Hyperion HS-DS13-TMB. It is a digital servo, top ball bearing, metal gears,19.2 grams, 36.4 in-oz torque at 4.8 volts for $35 from Isthmusmodels.com.
Or the cheaper carbon-poly gear model HS-DS13-TCB, 17.9 grams, same torque, $30.
So, you spend a little more but have more reliability.

Craig
Old Sep 12, 2012, 05:47 PM
Goingboeing is offline
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Wow....would have liked to see the inverted fly-by to landing!

Thanks for the post Craig - I have noted digital servos and one of the recommendations was a Spektrum A3030, however, it is a micro and I believe I'll follow Lincoln's advice regarding needing the weight up-front.

Spektrum have another standard digital servo which would compare with the Hitec 81's (A6060) so I'll investigate a little further...

cheers and thanks again,

GB
Old Sep 13, 2012, 03:10 AM
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I suspect that, if you're worried about reliability and durability, a standard servo from a reputable manufacturer is hard to beat. Bigger gears are harder to break. And this is just an Olympic 650 we're talking about here.

If you have two different servos, put the tougher/stronger one on the rudder, or the more precise one on the elevator.
Old Sep 14, 2012, 07:59 PM
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Appreciate all the feedback - thanks (well...except for the 'just' comment....)

Have ordered ther HS81's and after much reading/research (and now much less confusion) I'm sure they'll do the job.

thanks again,

GB


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