panhndl

My Feedback: (10)

I'm in the process of building a couple of my first more expensive planes. One is a T-28 and the other is P-51, and I have some questions about how some of you might be setting up the reciever to handle the servos and other stuff.

I'd like to keep the aelerons, flaps, and elevators on seperate channels, if possible. I have a Spektrum DX8 tx. How are people going about this?

My thought was to put in two RX's, each running one side of the plane and other functions.

A good example would be the T-28. Number of channels: 1. throttle 2. aeleron 3. aeleron 4. flap 5. flap 6. elevator 7. elevator 8. rudder 9. kill switch 10. landing gear. If I put 2 8 channel RX's in there, connected to two batteries via a Bat Share from Smart Fly, I'd have some redundancy. I could have the aelerons, flaps, and elevators all on the same 3 channels, just buying reverse servos for the opposite side of the aircraft. Additionally, it would split the load that the RX has to push out to the servos. I don't know at what point I would have more electric needing to go out than my system would produce, but I'd think that I could get twice as much out with twin RX's I don't know anything about problems with running this set up, so please let me know if you know of any.

Also, and this might not be the right board to ask this question on, with the DX8...when I add extra aelerons, flaps, or elevators to the list of channels, it bumps my retracts on down to another channel/switch. There has to be a way to switch the retract channel or the switch back to the original place on my radio, but I haven't found it. Don't bother telling me how. Just tell me that it does, in fact, actually exist and I'm not crazy. I haven't figured out how, yet.

Lastly, My P-51 is the Comp Arf, and I'm still a ways away from starting it, but I thought I'd ask this question now. I really like the scale exhaust that Keleo produces, but don't want to take up all the space with the tank up front his system needs. I've got a couple ideas on how to mount the system to a pits muffler, but don't have any knowledge of a custom exhaust manufacturer. Is there someone out there that will build a set of scale stacks I could contract with in the US?

Thanks and Merry Christmas!

jimamosn8cah

First off, Spectrum has a programming guide for this radio that you should maybe look at. Also, Ithink Iwould attempt to keep this to a single receiver, and also keep as many functions to the standard channels as possible. Nothing Isaw in the DX8 Manual suggests that you can add channels with a second radio.

1. Throttle
2. Aileron (Right)
3. Elevator
4. Rudder
5. Gear
6. Aux1 / Left Aileron
7. Aux2 Flap
8. Aux3 Flap

Wing type, you need to select the wing type for the DX8 and there are a few of wing types that can be made to work. For full control (and setup zeroing functions and positioning) a servo per channel is the most flexable which is the 2 Aileron and 2 flap mode. A good compromise might be the 2 Aileron and 1 Flap system. You can still use 4 servos but would require a Ycable for the flap connection if you need control of another function (actually, I dont' think you do). So, the fist setting can be and allow for a seperate servo trim for each servo. This makes it easer as you can somewhat avoid fiddleing with the mechanical links for that list little bit of correction.

There are other things you can do as well. The Aux 3 knob can be used to drive the flap setting for variable flap deployment, etc. The switch select fuction is used to map the aux channels to the transmiiter trim functions and control switches.

The throttle cut function is typically on the trainer switch, and does not require a seperate channel. It is mapped to the throttle function already.

This setup should work for a lot of models with flaps and gear including you T-28 and P-51.

With regard to loading the receiver, I can undestand your concern, but you are really talking about 2 different things. Power to the servos is seperate from control. Ther are some products out that would allow the power to the servos to not be routed through the receiver and still use the standard servo control functions. You didn't mention how big of a plane these were, but anyting up to a 60 sized plane should work through the receiver. But, Check http://electrodynam.com/rc/EDR-111/index.shtml (this is not an endorsement as I have not used these products) for a board that allows the servo power to be routed around the receiver. This boards does also allow for separate batteries for servos and receiver.

Jim

Zeeb

My Feedback: (41)

Well I don't intend to be callous but you've got a lot learn before you tackle something like the Comp-Arf P-51 and it has primarily to do with power distribution and servo control.

1. The DX8 isn't going to have enough channels to control everything on a Warbird by itself, my slightly smaller AW P-51 uses 11 channels and there aren't any bomb drops, servo operated sliding canopy or such.

2. All of the Spektrum/JR rx's can handle enough power for the whole model quite easily, the issue is getting that power into the rx and for that the PowerSafe rx's make it a piece of cake.

3. Since you won't have enough individual channels to cover everything needed, suggest you look at either a PE or Matchboxes to get you started.

As I said, not trying to put a pin in your balloon but the above is just a tiny bit of what you need to figure out before you start assembling things....

91zulu

My Feedback: (2)

I`m just trying to figure out why folks have to make things so complicated. Is it because we now have the equipment to make it so or is it we feel we have to make it so. Cant remember things being so complex before computer radios. Things were simple and straight forward and it worked with out a hitch. No match or power boxes or fancy stuff just an extra battery, MAYBE, with an extra switch and no DIGITAL nothing.
So my question to you all is, does the setting up of large scale planes have to be complex. If yes please tell me why. What is wrong with Y harnesses, analog servos extra battery and switch.

CorsairJock

My Feedback: (90)

I'm with 91zulu, whatever happened to K.I.S.S.? The more complicated you make it, the more likely something will go wrong/ fail. Not to mention: the added weight (don't care what anybody else says, I say lighter is better).

panhndl

My Feedback: (10)

Well, my thoughts were that if I had dual recievers, I could utilize the redundancy of the two RX units and each servo on a seperate channel while not having to have a 12 channel RX/TX combo.  That way if one aeleron servo failed, I could still have a servo left so I might be able to get the plane back to the ground.  If I had a failure of an aeleron servo on a y harness, it could lock up the other servo, causing the plane to go in.  Same thing for the elevator servo.  I could certainly leave the flaps on the y harness.  That doesn't worry me as much. 

The Smart Fly Bat Share unit would put both RX's able to use either battery in case either battery failed.  Again, just some added redundancy.  The entire Bat share unit weighs an ounce or so.  The additional 8 channel RX wouldn't weigh much more than three y harnesses.  I'll have 2 batteries no matter what set up I have.  Additionally, I'll be able to shorten the servo leads by at least 6" for both flaps and aelerons, further making the single reciever less advantageous. 

jimamosn8cah-  I'm actually talking about a seperate kill switch besides the throttle kill.  This would actually kill the motor in the event of loss of signal with the TX unit.  I'll have the throttle kill set up as well.

91zulu

My Feedback: (2)

So if you regain signal, which happens most of the time what do you do about the now dead engine? I think you are over compensating for an issue that MAY accrue by putting in a bunch of things hoping that it will keep your plane safe from crashing. If you have that fear then you are in the wrong hobby, because guess what, none of what you are doing can compensate for piloting skill. Plain and simple. I had an aileron out once and I brought the plane in with rudder with no dings on the runway. So did many people. You have to get your skills up to the point where you don`t have to think about what it is you need to do in case of an emergency, instinct takes over. That only comes with many hours of flying not complex installations. I`m doing my Meister Me 109 and it will have one RX two batters two switches, no digital servos. Thats it.
However they are many that feel the need for complexity like you and I`m sure they will help you along.

panhndl

My Feedback: (10)

The optical kill switch is for safety.  It isn't for redundancy, which everything else I listed was for.  If you lose signal, you engine dies.  That way, the plane doesn't continue flying away with a full tank of fuel.  At least it will be more likely to wreck in a sparsely populated area, like your flying field. 

I don't see how you're saying that what I'm talking about is overly complicated.  It is exactly like you're planning to do except I added an additional RX to keep away from a two servos running on the same channel on the same RX.  If you're going to have two batteries, you're either going to use a more complicated RX, or you're going to use a device that ties two batteries into one.  Unless you're calling your ignition battery your extra battery.  With my IBEC, I'll be using two batteries to power both RX's and the ignition. 

But I get your point.  I'm sort of glad you mentioned that it doesn't have to be this way.  The only thing I would like to have is more satellite recievers than the 1 that comes with the 8 channel Spektrum RX.  I guess with all the extra $$$ thrown at these projects, I sort of felt that I needed to buy some better, more redundant systems.

The problem I have with most analog servos is that they're old technology.  All the R&D $$$ is going into the digital equipment.  All the higher end electronics are going towards the new stuff.  I'd like to have all brushless servos.  They eat less energy, last longer, resist vibration better, and are generally better than brushed motors.  I know that Hitec has brushless analog servos, but I don't know any other brand that has them.  To me, that's telling.  Yes, some old technology is still the best, most reliable.  I don't really think that would be the case in servos. 

None-the-less, all points well taken.  Are you Y harness'ing your aelerons/flaps/elevators?  And what servo are you planning on using?  I'm kind of interested in the Hitec 985MG's.

91zulu

My Feedback: (2)

Well my set up is..
Aileron - 2 Hietc HS77
Elevator - Futaba FP-S134 on each half.
Rudder- - Hitec Hs645
Flaps - MPI-MX460 or Hs 545
Throttle - Standard plastic gear servo
Retract - Standard plastic gear servo
Regular momentary kill switch operated by a micro servo, ignition on or off. I`m using a Sachs 5.8 mag engine.
Aileron on Y, Flaps on Y, Elevators on Y.
The RX is a Hitec Opti 9, I`m using the Hitec A9 radio. It has a separate port for a battery pack that only power the RX then you plug in a separate battery to power the servos. This is done because the 2.4 Rx are energy hogs by itself. Plus if using digital servos it gets worse causing brown outs. So Hitec solution to this issue was to have a separate port to power just the RX up to I think 36 volts. That`s why it is not tied in to the servo circuit. So that`s it nice and simple. It also has a feature that tells you the RX voltage on your TX and the bells go off if battery gets too low. Nice feature. Also if you get to the field and try to fly with a low or dead RX battery the TX will not arm, so there is no taking off with a dead battery.

panhndl

My Feedback: (10)

The set up is not much less complicated than I'm considering.  You're able to take advantage of some features of your radio I'm not able to use.  My retracts are electric for both the T-28c and the P-51.  You're more optimistic about the torque needs of your servos, too.  Although, I'll be the first to admit that I'm much more likely to go over what is needed than to buy just enough. 

Which 109 are you building?  80" or the 100" 

91zulu

My Feedback: (2)

The 102. Yes the torque I have is more than I need. Believe me in the 80s and 90s the Byron and other giant scale stuff flew with Futaba 148s and not much more. More so than not folks go way over board with servo selection. Yea you want to be sure you are not going to strip gears doing a loop or roll. But there is no need to buy a Porsche just to go to the corner store when a Corolla will do just fine.