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Seervo Arm Advice

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Old 12-04-2012, 04:43 AM
  #1
crankpin
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Default Seervo Arm Advice

I guess you IMAC guys should know. I am equipping Pilot two 26% Yaks, 30cc. I have used metal servo arms on 115 powered pattern planes, gas is new for me, and have never used these phonelic type. I do not do any 3D flying, just sport, regular stuff. Any reason not to use these ? Appreciate any comments.

Crank
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Old 12-04-2012, 05:09 AM
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Default RE: Seervo Arm Advice

You are fine with those arms. Being new to gas, a few things to keep in mind. The biggest is vibration. I highly recommend that you balance the prop. Keep and eye on those arms, the vibration can put a lot of wear and tear on them depending on what links you re using. If you re using ball links then it will not be bad at all, if you are using a pin type link then the wear can get ugly pretty quick.

Also, it is doubly important that you use locktite on anything that is metal to metal, I would highly suggest metal geared servos so the screw that you re going to use for the arm to servo connection will need some blue locktite. DO NOT USE the red locktite and use only one very small drop of the blue. I would also suggest replacing the standard phillips type of screw head with a allen wrench version. Most hardware stores sell these for a few cents each and it is well worth the change over, especially is you use a bit too much locktite and need to remove the servo arm. Even too much blue locktite can cause you to strip the standard phillips head.

Just remember one thing, think vibration and what would happen if something comes loose because of vibration.
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Old 12-04-2012, 05:22 AM
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Default RE: Seervo Arm Advice

Bubbagates - Thanks for advice. The blue loc-tite was my next issue, you answered it. The servo arm screws are metric threaded, I am using the JR8411's all around on both planes, all ball links.
Horizons description below. I will source the allen head version screws.
Vince
================================================== ================================================== =================

For giant scale and precision competition airplanes, JR’s DS8411 servos are the ultimate choice thanks to their high output torque and incredible accuracy and holding torque. To transfer all that available power to the servo arm, JR’s DS8411 features a composite metal gear train that includes a combination of hard anodized hardened steeland brass gears that are virtually unstrippable. This improving accuracy, combination of metals gives a long, backlash-free gear life. In addition, ball bearing spacing on the output gear has been significantly widened, offering greater radial output play and further improving accuracy. 155 oz./in. torque.

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Old 12-04-2012, 05:32 AM
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Default RE: Seervo Arm Advice

Oh, I'm very familiar with the 8411's. I used to use them on everything and I just rebuilt them and use them for throttle servos on my DA170 and Da200 engines. The will be just about perfect at 6v on the size of your plane, but it's actually more about weight that size when it comes to servos

As far as the servo arm screws. I have 3 different Ace hardware stores where I live and all of them have the screws in allen head form in the isle where they sell individual screws/nuts/bolts (I can it the Yellow Box isle) it's the isle that has all the little plastic yellow boxes in it. Home depot and Lowes cary them as well but metric is a hit or miss thing and Lowes and Home Depot are more expensive than Ace Hardware. I think I paid about 10 cents each the last time I bought them and I bought 25 of them so I could have spares.

I forget the exact size but just take one of the original screws with you and match the threads. You can go about 1mm longer and you will probably have to do that as the original screws are quite short but the 8411's can handle the extra length
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Old 12-04-2012, 05:51 AM
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Default RE: Seervo Arm Advice

I use M3 x .5 x 8mm. for JR and Futaba. Hitec is M2.6 x .45 x 4mm.

Available here:www.microfasteners.com/catalog/products/METSCMS.cfm



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Old 12-04-2012, 05:56 AM
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Default RE: Seervo Arm Advice

JR uses M3x6

http://www.mcmaster.com/#=kg21k3

Package of 100 for 6 bucks
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Old 12-04-2012, 06:36 AM
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Default RE: Seervo Arm Advice


Thanks, will order today.

Vince
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Old 12-04-2012, 07:15 AM
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Default RE: Seervo Arm Advice

To answer your other question, the only place we have had a problem with the phenolic servo arms is on the rudder but since you wont be bouncing the rudder off the grass or dunking it in a kiddie pool you should be fine with them.

Tony produces very high quality kits, he wouldn't supply them if they didnt work.
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Old 12-04-2012, 09:00 PM
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Default RE: Seervo Arm Advice

For what it is worth I personally would never use a ball link on a single phenolic arm. A ball link is offset from the arm and so it introduces a twisting effect to the arm that eventually can cause failure under load. The double phenolic arms found on some models are great in that you can place the ball link between them keeping the load inline. I agree that the pin type can wear but as long as you check them for play once in a while a good quality clevis with a fairly large size pin should last for quite a while and I would much rather deal with a little wear than a broken arm in flight. JMHO

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Old 12-05-2012, 08:23 AM
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Default RE: Seervo Arm Advice

I have the Pilot 30% Yak, and it also came with those arms (G-10). They are sturdy, but I eventually removed them from the elevator servos because they frankly made the control surface throws much too large! I went back to the stock servo arms that came with the servo on the elevator servos.

Brad
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Old 12-05-2012, 08:31 AM
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Default RE: Seervo Arm Advice

I am using the stock arms on another plane, 115 powered, works fine. Being new to gas and more vibration, I will go slow.

Thanks for all info.
Crank
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Old 12-05-2012, 08:42 AM
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Default RE: Seervo Arm Advice

Thats a great looking scheme on that Yak, one of my flying buddies is waiting for the engine for his 40 percent one in that scheme. It may make me want another 50cc Yak
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Old 12-05-2012, 11:14 AM
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Default RE: Seervo Arm Advice

Hey Andy - Get this one in the air, do the other one, thinking of different power, I think Mintor. I had to flip to see which one to put together first. I beleve this is their 30%, same color scheme as the 26, looks good out of the box.

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Old 12-07-2012, 12:26 AM
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Default RE: Seervo Arm Advice

The Fiberglass arm is not the problem, it's bolting it up to a plastic servo wheel. Use a metal wheel....the splines in the plastic will likely strip at some point (when you don't want it to)
I just use a metal arm instead.
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Old 12-07-2012, 03:49 AM
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Default RE: Seervo Arm Advice

I owned and nearly wore out 3 Comp Arf 3.3 Yaks, the servo installation instructions had you install phenolic arms on the stock plastic servo wheels and on all 14 servos. In 5 years of hammering these airplanes not even one stripped out; now they were ganged together mind you, 3 on each aileron, 2 on each elevator and 4 on the rudder. Just saying.

Bob
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Old 12-11-2012, 07:11 AM
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Default RE: Seervo Arm Advice

Do you really need such enormous servo horns for a 26% plane for as you said "just sport, regular stuff" type of flying?
I would have thought much smaller arms would have been better. Make sure you use the servo's full travel (ATV set at 100-125%) for maximum servo power and precision.
For precision flying you don't need more than maybe 15-20° of surface deflection, so your servo arm needs to be less than half as long as the arm on the control surface.

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Old 12-11-2012, 07:34 AM
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Default RE: Seervo Arm Advice

Pilot RC Yaks are designed with 3D in mind.
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Old 12-11-2012, 08:17 AM
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Default RE: Seervo Arm Advice

Mangne - I am using what came with the kits. Gas is new for me, heavier everything, vs YS 110 glow powered pattern planes. I am sure, soon as I get my "gas wings", things will get changed in the future.

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Old 12-11-2012, 08:58 AM
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Default RE: Seervo Arm Advice


Quote:
ORIGINAL: Magne

Do you really need such enormous servo horns for a 26% plane for as you said ''just sport, regular stuff'' type of flying?
I would have thought much smaller arms would have been better. Make sure you use the servo's full travel (ATV set at 100-125%) for maximum servo power and precision.
For precision flying you don't need more than maybe 15-20° of surface deflection, so your servo arm needs to be less than half as long as the arm on the control surface.

Regards,
Magne
For 3D your going to need 45-50° of deflection so the larger horns are needed.

Bob
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