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Model Forum / Radio Controlled / Air Models / July 2006Best option for multiple servos
I am assembling an ARF that has 2 separate elevator halves each with its own servo. The 2 choices I see are a Y cable and drive each servo off the same channel or, if the radio offers the option, of driving each servo off a separate channel. Is there an advantage of one option over the other? Ed | I am assembling an ARF that has 2 separate elevator halves each with its own | servo. The 2 choices I see are a Y cable and drive each servo off the same | channel or, if the radio offers the option, of driving each servo off a | separate channel. | | Is there an advantage of one option over the other? Sure! Pros of a Y-cable -- 1) easier to program your radio 2) you don't need a computer radio at all 3) often easier to use a buddy box with (this is due to #1) 4) you might need to adjust the linkages of one of the servos or reverse it in some other way so things go the right directions. 5) you can use a TX with only four channels. Similarly, you only need a four channel RX as well. To do seperate channels, you may very well need a six channel TX and RX, as the second aileron servo is usually on channel six rather than five, but some TXs let you put it on five, and some 5 channel RXs do channels 1,2,3,4 and 6 for just this reason Pros of seperate channels -- 1) you won't need to change any servos or servo linkages. 2) you can program in flaperons or spoilerons if you wish. 3) you can use aileron differential if your radio supports it. 4) if one channel in your RX fails, you still have the other one, so you might still have enough control to bring the plane down. (Granted, I've never heard of this happening like that, and it's very unlikely.)  SignatureDoug McLaren, dougmc@frenzied.us Eject, Buckaroo! Eject! > In article <12cfcs9o9lptk34@corp.supernews.com>, Ed Smega > <smega@en.com> wrote: [quoted text clipped - 16 lines] > reverse > it in some other way so things go the right directions. That sounds like one of the cons of the Y-cable to me. One more option that I'll throw in, just for completeness- if it's a big plane, you could have 2 separate radios (Rx & battery) on-board, on the same frequency. One configuration would have on radio for each half of the airplane - rx & batt on the left side controls the left aileron, left elevator half, left flap (if any), maybe the rudder; the right side controls all the right side stuff and maybe the retracts (if any). The theory then is that you could have a really serious failure - say, a bad battery or a complete Rx failure - and still have a good chance at getting your airplane down safely. Frankly, I haven't had that many radio failures. I've had radio hits, but if there are 2 identical Rx's on the same frequency, it's likely that both would suffer the same hit. So unless you're doing some really big beautiful expensive scale plane, I wouldn't resort to multiple Rx's. But I thought I'd mention it for completeness, and because sometimes I'm just in a mood to type. Signature"Whatever will have been, will have been." - Douglas Adams, "Life, The Universe, and Everything" You did say Elevator. use a Y. The benefits of using another channel are not so needed on the Elev. Ailerons, now I prefer using 2 channels. mk >I am assembling an ARF that has 2 separate elevator halves each with its >own servo. The 2 choices I see are a Y cable and drive each servo off the [quoted text clipped - 4 lines] > > Ed | You did say Elevator. use a Y. The benefits of using another channel are | not so needed on the Elev. Ailerons, now I prefer using 2 channels. That's a good point. I was thinking ailerons when I answered. Not many ARFs are set up with two seperate elevator servos -- the plane must be quite large! I have seen a few really large planes with seperate servos for each side of the elevator, and in one case they were on different channels and he had it programmed so that when he used the ailerons the elevators changed similarly to the ailerons, to give you a little higher roll rate. That's really the only advantage I see to having them on their own channels. SignatureDoug McLaren, dougmc@frenzied.us You can't cross a large chasm in two small jumps. The fairly common Great Planes U-Can-Do 3D requires 2 elevator servos. I have this set up using a Y lead and servo reverser. The Reverser is necessary unless one uses to different servos which rotate in different direction i.e a JR servo on the left and a Futaba on the right. It is far simpler to set up this way as no mixing on the transmitter is required. Hope this helps Gerry > | You did say Elevator. use a Y. The benefits of using another channel are > | not so needed on the Elev. Ailerons, now I prefer using 2 channels. [quoted text clipped - 10 lines] > higher roll rate. That's really the only advantage I see to having > them on their own channels. Some of the reversers I have seen tend to drift with temperature changes. Constantly having to retrim the servos. Best to use your radio if it has the capability. Another option is to use a Y-harness and reverse one servo by swapping the internal wires. I did this with a Hitec servo in my Showtime and it has worked perfectly. The only potential problem is that you may not get identical elevator allignment as the servos cannot be adjusted separately. In my case, they lined up perfectly. John VB > The fairly common Great Planes U-Can-Do 3D requires 2 elevator servos. I > have this set up using a Y lead and servo reverser. The Reverser is [quoted text clipped - 25 lines] > > Doug McLaren, dougmc@frenzied.us > > You can't cross a large chasm in two small jumps. Which wires would I need to switch? (on an futaba 148)? > Some of the reversers I have seen tend to drift with temperature > changes. Constantly having to retrim the servos. Best to use your [quoted text clipped - 36 lines] > > > Doug McLaren, dougmc@frenzied.us > > > You can't cross a large chasm in two small jumps. You need to reverse the wires on the servo motor and reverse the wires on the servo potentiometer. Phil AMA609 > Which wires would I need to switch? (on an futaba 148)? > [quoted text clipped - 40 lines] > > > > Doug McLaren, dougmc@frenzied.us > > > > You can't cross a large chasm in two small jumps. > You need to reverse the wires on the servo motor and reverse the wires > on the servo potentiometer. > > Phil AMA609 It will probably have to be an older servo, since most of the newer potentiometers have no wires, since they are surface mounted to the circuit board. SignatureJim in NC Open the servo to see if it has wires that can be moved. As pcoopy said, switch the two wires on the pot and motor. The two outside wires. I did one this spring on a new hitec digital servo. You could also purchase (for hitec servos) a Hitec servo programmer. It will allow you to change rotation direction and make all kinds of changes to hitec digital servos. It is pricey at about $150 though. A friend of mine just bought one so guess I don't need to be switching wires any more. John VB > > You need to reverse the wires on the servo motor and reverse the wires > > on the servo potentiometer. [quoted text clipped - 4 lines] > potentiometers have no wires, since they are surface mounted to the circuit > board. | Open the servo to see if it has wires that can be moved. As pcoopy | said, switch the two wires on the pot and motor. The two outside [quoted text clipped - 4 lines] | mine just bought one so guess I don't need to be switching wires any | more. It only works on digital servos. If you only use digitals you're probably set, however. You can also buy a small electronic device for less than $20 that will reverse a servo, and it's put inline with the connector. There's also a version that has a Y-cable with a reverser in one side of the circuit. SignatureDoug McLaren, dougmc@frenzied.us Boycott shampoo! Demand the REAL poo! You need to reverse the wires on the servo motor and reverse the wires on the servo potentiometer. Phil AMA609 > Which wires would I need to switch? (on an futaba 148)? > [quoted text clipped - 40 lines] > > > > Doug McLaren, dougmc@frenzied.us > > > > You can't cross a large chasm in two small jumps. My seagull models Razzle uses two elv. servos. Ed, may I ask what plane your building? mk >I am assembling an ARF that has 2 separate elevator halves each with its >own servo. The 2 choices I see are a Y cable and drive each servo off the [quoted text clipped - 4 lines] > > Ed > My seagull models Razzle uses two elv. servos. Ed, may I ask what plane > your building? > mk SEAGULL LASER 200 >I am assembling an ARF that has 2 separate elevator halves each with its own >servo. The 2 choices I see are a Y cable and drive each servo off the same [quoted text clipped - 4 lines] > >Ed I don't know what you're building but on some models you can merely turn one servo horn upside down. I have a U Can Do that I did that way. The center line of the servos are in line with the center of the elevator on this airplane. Ken Ken, Normally that is what I would do if both servos were mounted in such a way that the linkages would be mirror images. But this ARF (Seagull Laser 200) has the 2 servo openings in assymetrical positions, so the one push rod would be at right angles to the 2 horns, but if I tried your suggestion in this plane, the second push rod would be at an angle, so I don't think there would be equal movement of both elevator halves. Ed >>I am assembling an ARF that has 2 separate elevator halves each with its >>own [quoted text clipped - 13 lines] > > Ken >Ken, > [quoted text clipped - 4 lines] >this plane, the second push rod would be at an angle, >so I don't think there>would be equal movement of both elevator halves. >Ed I agree. Like I said I didn't know what you're building. Both servos would have to be at the same angle to have equal travel. My vote would be for the Y with servo reverser. Don't know if this is the best way , but thats the way I would do it. Ken >>>I am assembling an ARF that has 2 separate elevator halves each with its >>>own [quoted text clipped - 13 lines] >> >> Ken |
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