Shane B

My Feedback: (3)

I am using a Futaba 9C radio, I have electric retracts in my plane, When i cycle the gear, my servos go "CRAZY", the antena is out the way, and the receiver is also, I read where (not on RCU) copper stops or helps stop RFI , so i wrapped the electric motors with very thi cooper but, this did not help out all,,, Please give me all the info you can,, These gear were made special for this plane many years ago, and i hate to have to trash them,,

CP140

Just a guess here, but any chance you can but a voltmeter on your battery as your gear is cycling? Are the gear motors pulling more than the battery can give? I don't know if a temporary low voltage would cause your servos to react like you've described or not.....

Maybe an RF choke on your servo leads?

Geistware

My Feedback: (16)

How are the motors wired to the receiver?
I am wondering if it is grounded properly.
Is it a seperate power supply or does the retracks use the receiver pack for power.
If they are seperate packs, maybe connect a ground between the two systems and check again.

Shane B

My Feedback: (3)

It has its own power supply, a 800MA battery, there are three switchs the are are mounted on a bracket inline, and a servo that throws the switch, one way gear up and the other gear down,,, each gear has 2 limit switchs to stop them at the right angle,,, the nose gear dont seem to be affecting it, its coming from the mains,, There is a compositor on each motor wired to positve and negative,,,

dirtybird

My Feedback: (5)

Try grounding the metal case of the gear driver motor to the negative receiver power supply lead

Shane B

My Feedback: (3)

Ground it to the receiver battery or the battery running the retracts

apteryx

I don't know anything about the type motors you are using but typically they are pretty heavy duty. If they are brush type motors, add a small capacitor (.01mfd) across the motor terminals to help reduce the arcing. Again I've been out of this hobby for many years and maybe they have slick brushless retract motors, or use solenoids, or ?

It's generally a good idea to tie all the grounds together at ONE point near the batteries.

Shane B

My Feedback: (3)

They are brush type motors and already have a capacitor on them,,, I hooked one up today by passing the receiver, and just had it sitting on top of the wing, and i still got interference, I wrapped the retract and some of the wire with aluminum foil and pretty much got rid of it, but i just cant trust that,,, If i cant come up with a sure fire way to make this work, i will have to convert them to air,,,,,

Geistware

My Feedback: (16)

I think you need to run a ground from the retract to the receiver.

Shane B

My Feedback: (3)

Do i run the ground from the receiver battery and just hook it to the retract frame,,, The retracts do run off of its own battery,,, should i ground to it also,,,,

Rodney

Tie the negative terminal (ground) of the reciever battery to the negative terminal of the retract battery. Also tie the frame of the retract motors to this same ground. Use as short and as heavy a gauge wire as you can. Also put a 0.1 microfarad capacitor from each motor terminal on the retract motors to this same ground.

Shane B

My Feedback: (3)

I already have a capacitor on each motor, as for as i know they are still good, but i will check them anyway, I have not tried to ground them yet,, I will go and try that right now,,,, Thank You for your help,,,and i will let you know how it goes

kingair41

My Feedback: (13)

Warbirdbuilder, You need to put a capacitor from the can of each motor to EACH terminal on that respective motor and then ground the can to your retract battery. Try a .1 or as suggested a .01 mfd. NOT one cap across the terminals. So there should be [4 ][/color] caps if there is two motors. One motor for each main gear I presume. A ceramic disc with number 103 or 104 on the side. Give 'er a try.

Shane B

My Feedback: (3)

Each motor has a capasitor on it, going to the positive and negative terminal,, The numbers on them are (103k100v) , there is a total of 3 motors, each main and the nose wheel,,, I am going to change all the capacitors to be on the safe side, and run a good heavy ground to the gear frame,,,, and the motor can,,,,,

apteryx

Once you put the correct capacitors on the motor (and just because there is a capacitor on there does not mean the capacitor is good),
and if your foil shielding works somewhat you might try REAL shielding.

The fact that you have brushes means that you have a broadband spark transmitter with long antenna wires. On the capacitor value I said .01mfd before but since we're talking 72Mhz a smaller value is more appropriate (say .oo1mfd or less). The capacitors perform 2 functions; one is to quench the arc which requires the larger value capacitor, and one is to bypass RF noise to ground which requires the smaller capacitor value. If neither motor terminal is tied to ground, I would put the larger capacitor across the terminals and the smaller capacitors (bypass) from the terminals to ground.

Now for shielding: 1) you want no current flow on the shield so all current carrying conductors must be inside the shield 2) shielding can
be accomplished by using some cable TV coax, etc. Remove the coax shield, route the wiring through the shield, and stretch the shield to close it down on the wires. Solder the shield at ONE end to the best ground you have in the plane.

If the brushes are worn, you will have more arcing. If the motor is under load (binding) you draw more current and you will have more arcing.

apteryx

I just read Warbird builder's response, guess we're both online (but I gotta go get a pizza). 103K 100V is a .01mfd capacitor rated at 100V and add .001mfd caps trom each terminal to ground (noise bypass caps).

Let me add that, on these capacitors, it is very important to have SHORT lead lengths. By "SHORT", I mean as short as you can make them. At 72Mhz, these leads are "inductors" which will impede the desired RF current flow to the capacitor.

Shane B

My Feedback: (3)

I think your right on the ball now, I'm not sure how short i can get the leads but i will do what i can,,, I want to thank you for the great detail you went through,, Monday I will get all the capacitors and set up everything like your saying,, ,,,, One other thing should i do anything with the switch's, I dont think it is causing a problem, but maybe it needs to be sheilded also,,,

kingair41

My Feedback: (13)

apteryx, a cap designated a 103 is a .01 mfd and a 104 is a .1 mfd. A 103 has three more 0's to the right hence .010-000 and a 104 .10-0,000. Guys racing electric cars do so with no problems and they pull more current and emit alot of emi's and do so with no interference. I'm sure these motors are more refined and more efficient now days than when those retracts were made. I'm sure those guys may offer more input as to their success's with noise. I have an old set of Kraft electric gear that worked fine in the older days. I'll take a look and see what preventive measures where used if any and let you know.

apteryx

OOPS [:@] can't blame it on a typo so I'll say it was a thinko. Yep, of course, 103K is 1st digit, 2nd digit, multiplier, and 10% tolerance.
I corrected my previous note. That also says they had the correct value of .01mfd (in my opinion) across the terminals.

Back to Warbird builder on the switches. I guess these are some sort of limit switches ? I would put a .01mfd across them also and I would make sure they make/break "cleanly". What I mean is that it does not stop with the switch "partially closed" and arcing. I don't know what they look like but snap action limit switches would be the best.

apteryx

OK, I just dug through the boxes and came up with a brand new Kraft 3 wheel landing gear system with LG-52 amplifier. This may be completely different from what you have. I took one of the gear assys apart and it has a .05mfd capacitor from one motor lead to ground (motor case). The other lead is connected directly to the motor case. Since one lead is grounded to the motor case, you don't need the RF bypass capacitors, just the one .01mfd to .05mfd capacitor. The gear uses a slider to set limits with two diodes to reduce arcing when it "breaks". The power to the gear is reversed and it goes in the other direction until the slider again "breaks". This one is new but if the slider was dirty/loose it would arc while moving generating noise. This one is new and thus clean/tight with good grease. Might check to see how your's is.

Shane B

My Feedback: (3)

OK,, I done everything, all new capacitors, grounded everything, check all solder joints and made evrything as short as i can get it,,,, It reduced my problem alot but it is still there,,,, """One other thing i did is changed my receiver to a PCM and it got rid of all the interference, but i am not sure this is a good idea, If i start to get interference would it cause my plane to go into FAIL/SAFE and i looe control,, I have never used PCM, so i dont know much about ti,,, I have read where people running gas engine (electronic ignition) that it could cause a problem,,, What do you think i should do,,, Go with PCM , stay with PPM and try and solve my problem,,,,, This is realy giving me a "HEADACHE" ,,,,

While i am at it I THANK YALL very much for all your help,,,,,

apteryx

Are all the battery connections and cable connections tight (so they don't arc under load) ? Put a .001 cap across the gear battery at that end of the cable. Can you run one gear at a time to see if one is really bad ? or if it's all three ? Is there any way you can put a scope on the DC to the retracts ? Do you use some sort of a buffer amp between the receiver output and the actual motors ? Try driving 1 gear motor then two, then three. See if adding the "third" regardless of which one causes the problem. You did say the gear battery is separate from your receiver battery and the other servo batteries ?

dirtybird

My Feedback: (5)

If you have done all of this there is not much more you can do but go get new units. If it were mine I would probably use the PCM and hope for the best. I don't think the PCM will go into fail safe. If it does it will come back as soon as the gear stops moving. Just cycle the gear when you are up high.

kingair41

My Feedback: (13)

War bird, you can check the gears operation like you do a range check. Collapse the ant. and walk out 50-75 feet. If all is o.k. then at that point cycle the gear and see if you get interference. Alot safer and nothing gets damaged. If I know there is a potential problem I certainly would not try to find it in the air, or see if it's o.k. that way. I see that aperyx had a set of electrics. I'll look as soon as I can and if different than his I'll post.