Fall maintenance tips & tricks

Oct 11, 2013 No Comments by

In many areas of the country, the fall flying season is here and soon it will be time to put up your helicopters for next year. These next few weeks, however, when you have nothing better to do on a bad weather day, is a good time to inspect your helicopters and get them ready for the long winter ahead so they’ll be ready for the first signs of spring and another season of flying.

START WITH THE HELICOPTER
To make sure something isn’t missed, I recommend a close inspection of the entire helicopter, starting from the nose. Certainly the following list isn’t complete, depending on your particular helicopter and the degree to which you perform the inspection, so modify as needed. Starting from the nose:

Canopy. Remove and check for any cracks or splitsóespecially at the seams if it’s the type that is glued together. Check the rubber mounting grommets, latches, etc., to see if they are in good condition and not worn from vibration. Sometimes mounting holes get enlarged from vibration, but they can easily be repaired with large flat washers from your local hardware store. Epoxy them to the inside of the canopy, and then mount the rubber grommet to the washer so the canopy will look as good as new.

Servo tray. Check for stress cracks. Twist, push and pull gently to check for a solid tray and ensure it is well-mounted to the frame.

Pushrods. Check ball links for wear and an overall snug fit. Both the balls and links can wear very easily if they get dirty or have fuel on them from the engine exhaust. Disconnect pushrods from the servos and push and pull with your hand to check for slop or binding. Ensure that all pushrods are straight.

Bearings. Rotate the shafts going through the bearings by hand, feeling for any slop, grit or binding. Clean and lubricate (or replace) the bearings as needed.

Landing gear/skids. Check that they’re secure and straight and that the helicopter sits level. If needed, use a shim between the frame and gear to level the helicopter.

Frame. Check that all nuts and bolts are secure, but don’t over-tighten them. Check for vibration or stress cracks, especially around the engine and skid mounts. A dark oil residue is a good indicator of a loose part that should be checked frequently.

Rotor head. If you have not already done so, mark one blade grip and its corresponding rotor blade with a marker to designate them as the master. All future adjustments should be made to the master blade, bringing the other in balance and on track as needed. Remove the rotor blades and head, then inspect and grease the thrust bearings. This will also enable you to check the head more closely and inspect for any cracked links or bent pushrods. Check the balance of the overall head and flybar using a Robart High Point or Du-Bro balancer.

The rotor blades should receive special attention. Even if you believe they are in suitable condition for another season of flying, give them a close inspection. Are the tips in good condition, or have they been scraped on a slight tip-over? Check the blade roots where they mount to the head for any signs of fatigue or an enlarged mounting hole. If there is any doubt about their condition, send them back to the manufacturer for a professional inspection.

Tail boom If belt-driven, check the belt for signs of wear and release the tension until the next flying season. If shaft-driven, check the coupling at each end of the shaft for signs of wear that could allow slop and vibration into the tail rotor.

Tail-rotor gearbox. All gearboxes should be disassembled, inspected and re-lubricated. Be especially careful to check the security of the tail rotor and associated linkages; they are under a lot of stress from high rpm and this may cause bolts to become loose. Check your owner’s manual to see if your tail rotor has thrust bearings. If so, clean and lubricate them.

Set screws. Now that you are sure everything is lubricated and free from binding, add Loctite to all set screws. I remove the set screw and clean both the hole and screw with lacquer thinner or denatured alcohol. Using a removable type of Loctite (usually designated by a blue color) place a drop in the hole and another drop on the set screw, and then tighten the set screw. This extra Loctite will fill any small air gaps and secure everything. I have used this technique for years and have virtually eliminated set screws coming loose. Try it!

Fuel tank. Do not store the helicopter with fuel remaining in the tank. Disassemble the fuel tank and check all fuel lines in and around the tank for holes or splits that will cause the engine to run erratically. The clunk weight should be secure to its tubing and free to move throughout the tank, especially if you plan to fly inverted.

 

Measure the distance between the tips of the tail rotor (with the servo centered) to re-adjust the tail rotor at a later date after maintenance, etc.
Spiral wrap in various colors is available from your local hobby shop and RadioShack to add a little bling to your helicopter and protect the electrical wiring.

CHECKING THE RADIO SYSTEM
I talked with Larry Sribnick at SR Batteries about storing NiCd and NiMH batteries for the winter, and he said they can be stored in any state of charge at normal room temperature. However, Mark Byrne of Duralite Batteries says lithium-based batteries should not be stored with a full charge or they could build up an internal resistance that will decrease their performance. Instead, he suggests charging them every month, then discharging to 50 percent for storage.

Servo arms also take quite a stress load from a summer’s flying, so make sure they aren’t cracked, or have enlarged holes, and replace as needed. I also like to disconnect the servo arms from the servo and inspect the shaft output splines. To check for broken or deformed servo gears, slowly rotate each servo by hand throughout its full range of motion. They should all rotate smoothly, requiring the same amount of pressure.

Check the antenna for cracks, rubs, etc. Any minor problems with the wire covering can be corrected by placing a small piece of heat-shrink tubing over the bad spot. Accidentally tugging on the antenna could have weakened the wire or solder connection to the receiver circuit board. You may want to take the receiver case apart and check the circuit board.

Servo wires that come in contact with the frame, or other parts of the helicopter, can easily be damaged due to vibration. Protect these wires with a spiral wrap or protective covering available at your local hobby shop or RadioShack. Excess servo wires near the receiver can be grouped together with tie wraps and then protected with larger spiral wraps. Also, closely check the connectors and wires for any breaks, frays, etc. Look particularly closely where the wires go into the connectors because it’s possible for the wire to become dislodged from the connector.

When everything looks as good as it can get, refer to your owner’s manual and give the entire system a range check as if you are going to fly the helicopter. Do not route the receiver antenna in a different manner or remove the canopy or some other piece of the helicopter because you may not get an accurate range check. Compare this range check to the distance you were getting during the flying season, and make sure it’s more than the minimum recommended by the radio manufacturer. If your radio does not pass this check, it isn’t going to get better by itself so have a qualified technician check it out.

Moving on to the gyro, check the wiring and connectors. As a precaution, replace the double-sided mounting tape. Also check for proper servo movement as the helicopter nose is moved gently right and left. The gyro should give smooth commands to the tail rotor servo, commanding full movement in both directions in the heading hold mode. Check that the tail rotor pushrod is in a straight line by looking down the pushrod from the tail rotor, and adjust the pushrod guides as needed. Then check that the pushrod is free from binding by disconnecting the pushrod from the servo and moving the pushrod with your hand throughout its full range of movement.

QUICK TIPS

  • Remove and inspect the rubber mounting grommets from your servos. Apply a small amount of petroleum jelly (available at any drug store) to lubricate the rubber and prevent it from drying out.
  •  To check the tightness of nuts and bolts, hold the bolt with an Allen wrench and use a nut driver to tighten the nut. This will prevent over-stressing, and possibly deforming, the bolt.
  • With the radio on and rudder at neutral, rotate the tail rotor blades so you can measure the gap between the blade tips. This represents the pitch angle of the blades and can be used to adjust the tail rotor after maintenance, etc.
  • To keep the skids securely in place, drill a small hole through the gear and into the skid and secure with a small sheet metal screw.

 

Use a nut driver to check the tightness of all screws. This will pull the bolt into proper position (don’t over-tighten it, though!).

ENGINE AND MUFFLER
Take off the carburetor and glow plug. Disassemble the carburetor as much as possible and check for dirt, and then clean with solvent and lubricate. If the engine has caked-on black oil residue it can be brought back to a near-new condition with Demon Clean, an engine cleaner available at your local hobby shop. However, be careful because this cleaner is quite corrosive to paint, tabletops, etc.

I’m sure there are more points you can come up with to suit your particular helicopter, but this checklist should get you on the right track. This may seem like a pretty time-consuming check, but once you get started it shouldn’t take long to check the entire helicopter, unless you find some other problems.

The West Mountain cycler connects to your computer providing easy-to-read (and save) discharge graphs of your battery. Compare these graphs to find potential battery problems.

Helicopters

About the author

A regular contributor to Model Airplane News, he is also the columnist for our “Rotor Speed” helicopter column. Paul has been flying RC helicopters since the early ‘80s and now enjoys all types of rotary machines, including scale and aerobatics, and he continues to experiment with modifications to improve performance.
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