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Old 05-28-2020, 04:50 PM
Ezflyr is offline
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Electronics for a giant scale DC-3

Hi All,


I'm in the process of completing a multi-year build of a giant scale Douglas DC-3. This airplane has a 150" wingspan, and will weigh approximately 50 lbs. It is powered by two DLE-55 gasoline engines.

I'm at the point where I need to finalize my plans for the electronics in the airplane. There are 8 high torque servos (HiTec HS-645MG) and 2 standard torque servos (not yet selected) in the aircraft, 1 landing gear controller, and 1 electronic switch for lighting.

The high torque servos are as follows:

Left Elev.
Right elev.
Rudder
Tailwheel
Left Aileron
Right Aileron
Flap 1
Flap 2

The standard torque servos are:

Throttle 1
Throttle 2

It's been a while since I've completed a giant scale airplane, and never a multi-engine one, so I'm not necessarily up on the latest offerings for electronics.



I fly Futaba radio equipment using the 18SZ transmitter.



For this project, I'd like to build in dual receiver and dual battery redundancy, as well as gyro operation. My current thinking is to use a PowerBox Mercury system with two Futaba R7008SB FASTTest receivers, and two LiPo flight batteries. Thoughts?


This plan seems to 'check all the boxes', but I don't have a sense as to whether this is overkill for a project like this or not?


Open to suggestions!


John
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Old 05-29-2020, 02:34 AM
The Hodge is online now
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Wow great Model, We need to see pics of theis

A power expander of some type will be great for this, will give a neater setup, Regulation and Battery backer function.

I feel this unit will be more than enough, You could look at the Booma rc / Advanced radio unit.

Awesome unit with some neat gear, Like a screen Has Gyro etc.

http://www.boomarc.com/en/smart-bus-smoothflite

But there is no regulation So you would have to use Li-Fe packs for the Servos. 6.6V
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Old 06-02-2020, 09:04 AM
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My only comment would be that you are selecting a Mercedes radio setup while using Yogo grade servos that are not HV compatible.
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Old 06-02-2020, 10:06 AM
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I would think on a gasser that size if you want to stay with hitec servos go with the new d955. If you are going to use an electronic matching system like the extreme power X24 check to see if hitec has any issues but there is programming steps.
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Old 06-02-2020, 10:09 AM
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No need for a battery backer or power distribution - the futaba recs are fine. You can set it up so each receiver is powered by both batteries. You want to ensure that the servos are okay with long leads. Some aren’t.

My brother is a DC 3 pilot. Sounds like a great project!
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Old 06-02-2020, 12:06 PM
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I have personally seen any and all of the Hitec 6** line of servos that absolutely do not center well. They might be hi torque, and thats fine, but if a servo doesnt center well, then whats the point of having a servo with high torque?

If you have the servos, go with it. But if your looking for servos, lots of positive reviews on ProModelers. On the DC 3, I would look at their 270oz servo. $44/servo.

25 years ago, we flew 1/3 scale Godfrey Lazer 200s on Futaba 9202s. So, you dont need $130 digital brushless servos for this airplane. Whoever mentioned really expensive servos, has deeper pockets than you do.

I do agree, you are using good Tx/Rx combo, but your scrimping on your servos. 2 Rx's and 2 batteries with 1 lead going to each Rx, will provide the best solution. No power distribution, you dont need it.
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