I'v run into an odd RF interfenece problem in my latest project.
I have a plastic model that I've converted to twin screw RC. I used my standard plastic model conversion process:
1/16 inch diameter brass rod for the shaft(s), running in the matching brass tube. A stanard model airplane wheel collar keeps the shaft from falling out of the tube.
The prop is a Raboesch brass 20 mm.
Nylon HO scale locomotive universal joint to connect the brass shaft to the motor.
Motor is a standard servo, removed from the case, and attached to a home made plastic motor mount.
Standard 2 channel AM radio, using a 6 volt rechargable pack instead of the four AAs.
I've used this setup in a number of Lindberg tugs and other models in the past-- it has always been very reliable.
In this model, I'm getting a lot jitter - classic RF interfernece symptoms- when I run the model. It happens when I apply power, so it seems to be coming from the drive train. It is the same kind of interference I see if I hit the trim pot with a metal screwdriver while making adjustments-- that metal on metal contact causes a little servo glitch. That's why I use non-ferrous (brass) for all the moving parts-- I know that metal on metal contact can casue RF interference otherwise.
At first, I thought it might be the antenna lead or the radio itself. I replaced the Hitech 2 channle receiver with a Futaba unit on a different channel, and temporarily laid the antenna wire fully extended out on deck to improve reception. That didn't help-- I still get a lot if interference-type of hits.
The one thing that is different in this model from my others is is that I am using two motors this time. Instead of a single servo, I have two of the same type, one for each shaft. I spliced the servo leads together so both are driven off of the throtle channel on the 2 channel radio. (A home made Y cable, in effect.) I know that you can drive two servos off of one channel-- airplane guys do it all the time for aileron control on bigger models. They use a Ycable adapter to allow them to conenct two servos to the same channel on the receiver.
I have one last thing to try-- I once had an old rudder only Lindberg Fletcher that suffered from interference when the cheap can motor was onl. I made a little metal box out fo sheet aluminum, and placed it over the moter like a cover. That kept the interference from the motor from getting to the receiver. I am going to try that next--it is the last thing to try, short of replacing the entire drive train.
Any ideas/comments?
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