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Jul 22, 2019, 10:28 AM
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How to pick servos and related items for Large scale plane?

I am working on my first 2 large scale planes

1. 80" clipped wing cub
2. 82" Top Flight Cessna 182

I have only done small planes, so i don't know how to handle the servo side of things. they seem to take "standard" size servos ( as in the size that is used in my 1/10 RC cars)

What is this servo size called? I am used to gram ratings like 5, 9 or 17. How do i refer to these?

Power for servos - Now this is a new one for me. I know i need a BEC, but I imagine my receiver can not handle the amps needed to run 5-7 of these, so i am guessing i need a power distribution center? something like this?

Also, what am i looking for in a servo? how do i determine the strength i need? Metal gears or no? digital or analog? cored or coreless?

can someone point me in the right direction or make some recommendations on so products?
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Jul 22, 2019, 12:34 PM
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I use this when needed. But you don't need that in those planes.

Info would help, what receiver. For those two planes, I'd use Hitec HS645mg servos. You're not gonna do 3D so no need for digital. Just my opinion.

Don't use a park flyer receiver.
Jul 22, 2019, 12:39 PM
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What receiver would you recommend? I have a dx8 and a 8010T receiver. I was hoping to add in a gyro of some type but the large one i have seen work inline of the receiver and servos.

Looks like each of those servos only pulls about .5 amp when moving? If so, a 5A BEC should work, correct?
Jul 22, 2019, 01:36 PM
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That's a good receiver and will do fine. Sounds like you're going electric, true? I'm a wet power guy so someone else might give better electric advice. But for receiver and servo use, I generally go with around 3000ma. Overkill, but better than a voltage brown out. On my bigger more expensive planes, I run that split power bus which gives you a dedicated battery for the receiver, prevents brown outs. Then the servos get their own battery. I usually rate them receiver- about 2000ma, servos- about 3000ma.
Jul 22, 2019, 02:51 PM
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koppterX's Avatar
8010T is fine for your application. You can run two switches and two batteries if you want redundancy. You do not need a distribution device. As far as servos, neither airplane requires a lot of torque or speed. If you are in the $30 to $40 range they will be cored digital. I have used Spektrum 6150s in a number of planes, but there are a variety of suitable servos.
Jul 22, 2019, 05:11 PM
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I think I will actually go gas. 20cc dle 2 strokes more then likely.
Jul 22, 2019, 06:32 PM
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DGrant's Avatar
Believe it or not, those planes aren't monsters. You can use good quality components with servos in the 150oz torque range, and that would be very sufficient. You can use Dubro heavy duty servo arms, those are fine for these planes... unless you like to spend money on bling... but that's up to you.

Depending on what your favorite equipment might be, I'd suggest the Hitec D645's for all the surfaces, and maybe something with a bit less torque for throttle and such. The D645's will have about 160oz if you use a 6.6v LiFe battery... That's plenty for anything your planes would need. They're a nice digital servo from a well known company.

As for a BEC....If you go gas that is... You want to at least look at the TechAero Ultra IBEC. You can run your ignition right through your Rx... using the same battery. I'm betting a good quality 3000mah LiFe would run it all day. There's other devices too, but at least look at this one. There's thousands of them in use these days. I wouldn't have a plane without one.

They're not monsters by any stretch. Good luck.
Jul 22, 2019, 06:32 PM
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Now you're talking. I prefer the 20cc catagory from Valley View, great out of the box performance. I would suggest getting with someone in your club that's a gasser to help. There are several things you need to know about. Throttle linkage can be agrivating the first time. Also, I've tested ignition module current draw at full throttle to be around 350ma on most ignitions. It's not a lot, but your battery needs to be sized accordingly.
Last edited by edwin1; Jul 22, 2019 at 06:48 PM.

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