Help with servo chatter
05-16-2005, 10:49 AM
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Help with servo chatter
Sorry this may get a bit long but I want to give everyone the history which may help resove our problem. Last summer my 12 year old son wanted to start flying. I used to fly but had been out of RC for about 5 or six years but I thought this would be great fun to build and fly with my son. We purchased the Tower trainer 40 ultimate combo package. After building the plane we charged charged the batteries according to instructions then we flew the plane. On the third flight the plane went nuts! Fortunatly I was able to get control just before hitting the ground which saved the plane. Not much damage. I called Tower and told them I thought we had a problem with either the transmitter, receiver or batteries. We sent it in for them to check and they found no problems. I wasn't convinced but I thought OK we'll try again. This time I decided to fly at my dads farm which is in the middle of nowhere thus eliminating interference from other radios or whatever. Same results this time on the first flight shortly after take off the plane went nuts and this time went in a nose dive to the ground and destroyed the plane. This time I did find a stripped servo on the elevator after the crash. I thought maybe this was our problem but I just didn't trust that radio system .I told my son that I would get another plane. This time I purchased the Nextar 40 package with new radio, servos etc. We flew this plane with zero problems. My son has done very well and flys this plane now with no help from me.
Now here is the problem. We decided to build the Pheonix Funstar for his second plane. We used the engine from the Nextar but I used the radio and transmitter from the Tower plane with three of the servos from that plane and two Futaba servos that I had left from my earlier flying days. Last night we were ready to give the Pheonix her maiden flight. When we did our preflight radie check we had sever servo chatter from only 60 feet away. I thought here we go again this radio is just screwed up. So we went home and switched the transmitter and the reciever from the Nextar into this plane. Went back to the field and started again. This time on the preflight radio check we had just a little bit of chatter at about 100 feet. OK here is where I screwed up....shouldn't have flown the plane but I thought OK the chatter isn't bad we'll just take a quick flight and not get to far away. Yes I should have known better! The plane tracked down the runway perfect requiring almost no rudder to stay straight. Took off perfectly only needed about 3 clicks of down elevator! Did a slow circle to the left about halfway around the plane decided to roll right and head straight down. I got control again and decided to land right away. Just before hitting the runway it did it again but still landed pretty good all it did was hit one wing tip which resulted in a slight tear in the covering. No big deal. Very lucky that this was the only damage.
I am going to change out the servos from the Tower plane and put the Futaba servos from the Nextar in this plane as well as the battery pack from the Nextar plane. If anyone has any ideas on what they think could be going on or any suggestions we would really appreciate it. I could tell on this very short flight that this is going to be a great plane!!!!
Thanks for your help.
Now here is the problem. We decided to build the Pheonix Funstar for his second plane. We used the engine from the Nextar but I used the radio and transmitter from the Tower plane with three of the servos from that plane and two Futaba servos that I had left from my earlier flying days. Last night we were ready to give the Pheonix her maiden flight. When we did our preflight radie check we had sever servo chatter from only 60 feet away. I thought here we go again this radio is just screwed up. So we went home and switched the transmitter and the reciever from the Nextar into this plane. Went back to the field and started again. This time on the preflight radio check we had just a little bit of chatter at about 100 feet. OK here is where I screwed up....shouldn't have flown the plane but I thought OK the chatter isn't bad we'll just take a quick flight and not get to far away. Yes I should have known better! The plane tracked down the runway perfect requiring almost no rudder to stay straight. Took off perfectly only needed about 3 clicks of down elevator! Did a slow circle to the left about halfway around the plane decided to roll right and head straight down. I got control again and decided to land right away. Just before hitting the runway it did it again but still landed pretty good all it did was hit one wing tip which resulted in a slight tear in the covering. No big deal. Very lucky that this was the only damage.
I am going to change out the servos from the Tower plane and put the Futaba servos from the Nextar in this plane as well as the battery pack from the Nextar plane. If anyone has any ideas on what they think could be going on or any suggestions we would really appreciate it. I could tell on this very short flight that this is going to be a great plane!!!!
Thanks for your help.
05-16-2005, 01:14 PM
#2
RE: Help with servo chatter
Provided your transmitter AND receiver batteries are fully charged, I can see a few possible causes.
1. Since this happened on your other radio and plane and presumeably you are using the parts salvaged from the other plane (the crashed one), I would replace the on/off switch. The servos usually either work or don't work, especially when new. The switches are usually reliable, but the switch may be faulty and not providing full contact when the engine is running and putting vibrations through the airframe.
2. The antenna is picking up rf from the servos. Make sure the receiver (antenna end ) is at least an inch from the servos/servo leads and the antenna is not next to/rubbing against the push rods. Also make sure you do not have a metal to metal connection with the engine/pushrod/throttle servo. The easiest way to prevent this is to use either a nylon clevis on the engine or a ball link.
3. The next cause is interference on the channel you are on. I presume the Tower radio and the radio from the Nexstar are on different channels. Change the crystals on the transmitter and receiver to a channel AT LEAST 3 channels away from the one that is giving you problems. For instance, if you are on channel 56, you would want to go to channel 53 or 59. I have had Tower radios/receivers in the past and they were reliable units (The receivers are "rebadged" Futaba 127 and I believe the transmitters are rebadged Futaba also)
4. If you have a cell phone on, turn it off. There have been several unsubstaniated reports of cell phones causing interference.
In any case, if you have servo glitching OR the plane will not pass a range check of at least 100' (preferably more ) with the antenna down AND the engine running do not fly. So far it has just been the plane that has been damaged and no one has been injured or property damaged.
1. Since this happened on your other radio and plane and presumeably you are using the parts salvaged from the other plane (the crashed one), I would replace the on/off switch. The servos usually either work or don't work, especially when new. The switches are usually reliable, but the switch may be faulty and not providing full contact when the engine is running and putting vibrations through the airframe.
2. The antenna is picking up rf from the servos. Make sure the receiver (antenna end ) is at least an inch from the servos/servo leads and the antenna is not next to/rubbing against the push rods. Also make sure you do not have a metal to metal connection with the engine/pushrod/throttle servo. The easiest way to prevent this is to use either a nylon clevis on the engine or a ball link.
3. The next cause is interference on the channel you are on. I presume the Tower radio and the radio from the Nexstar are on different channels. Change the crystals on the transmitter and receiver to a channel AT LEAST 3 channels away from the one that is giving you problems. For instance, if you are on channel 56, you would want to go to channel 53 or 59. I have had Tower radios/receivers in the past and they were reliable units (The receivers are "rebadged" Futaba 127 and I believe the transmitters are rebadged Futaba also)
4. If you have a cell phone on, turn it off. There have been several unsubstaniated reports of cell phones causing interference.
In any case, if you have servo glitching OR the plane will not pass a range check of at least 100' (preferably more ) with the antenna down AND the engine running do not fly. So far it has just been the plane that has been damaged and no one has been injured or property damaged.
05-16-2005, 01:54 PM
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RE: Help with servo chatter
Campy,
Thank you very much for your response. You bring up several good points. You are right the switch is from the old (crashed) plane. I will replace it right away. Two other points you bring up really concern me though. That is the antenna end being at least one inch away from the servo leads. As you probably know the rudder and elevator servos are mounted on the rear of this aircraft. I will have to look tonight but I think the antenna wire is very close to the elevator servo. We will change this! Second is the metal to metal to the motor. This kit came with a z bend for the throttle hookup which I used! Never thought about it this does give me metal to metal to the throttle servo! And lastly I did have my cell phone in my pocket last night. I usually don't. I darn sure won't have it with me next time.
Lastly you are right I should never have flown the plane in the first place! Trust me we won't fly again unless the plane will pass the chatter test with the antenna down at well over 100 feet.
Thank you very much for your response. You bring up several good points. You are right the switch is from the old (crashed) plane. I will replace it right away. Two other points you bring up really concern me though. That is the antenna end being at least one inch away from the servo leads. As you probably know the rudder and elevator servos are mounted on the rear of this aircraft. I will have to look tonight but I think the antenna wire is very close to the elevator servo. We will change this! Second is the metal to metal to the motor. This kit came with a z bend for the throttle hookup which I used! Never thought about it this does give me metal to metal to the throttle servo! And lastly I did have my cell phone in my pocket last night. I usually don't. I darn sure won't have it with me next time.
Lastly you are right I should never have flown the plane in the first place! Trust me we won't fly again unless the plane will pass the chatter test with the antenna down at well over 100 feet.
