Maintaining RC Planes For Beginners
This is a follow on from my last post – Preventative Maintenance For RC Planes Beginners Fly – and here we will look at more ways to ensure that any of the RC planes for beginners are completely safe to fly. I propose to deal with such things as ensuring nose and tail wheels are working correctly and, where necessary, modifying main wheels and their fixings.
Trike or Tail Dragger?
Although the majority of trainer type planes feature tricycle or ‘trike’ undercarriages, you will occasionally come across the ‘tail dragger’ configuration. Whichever type you acquire, there are major considerations regarding whether you use a steering mechanism or not.
Many experienced flyers prefer a trainer to have a ‘fixed’ nose wheel or tail wheel as it simplifies the control of the plane during take-offs and landings. It also means there is no potential damage to servo gears through the abuse caused by difficult take offs and hard landings. This problem is particularly relevant where a grass patch is concerned.
The other school of thought is that eventually you will need to learn to control this function on future planes so you might as well master its control at the outset. Whichever option you decide on, there are ramifications so let’s look at them.
A fixed non-steering arrangement needs to be securely fixed at either end. A non-steerable nose leg will require fixing at the main bulkhead using ‘saddle clamps’ as shown in the picture right.
One of the saddle clamps fits over the upright section of the wire whilst the other fits over the horizontal section. I strongly suggest that you use set screws with nuts and washers behind the bulkhead to fasten the leg. This will give added protection in the event of a hard landing. Ordinary screws will easily rip out of the bulkhead. It is also important to ensure the coil spring is at the rear of the leg.
If your kit comes with a steerable nose leg then you will need to purchase the above fixed version to replace it.
A fixed or free castoring tail wheel similar to the picture right is screwed to the rear underside of the fuselage. The shaft of the wire passes up through the hole and is retained by the collet and grub screw above the bracket. This arrangement allows for a measure of steering control via the rudder.
If you decide to go for the steerable options for either then please refer to the kit manufacturers instructions and be sure to follow them to the letter. The most important items to pay attention to are the security of the servo fixings, the control horns and the free running of the pushrods. The loads imposed on the servo gears is considerable without them having to contend with excessive friction.
Wayward collets have been the weak link in many flying mishaps so it is essential to ensure that they are completely secure. They are particularly important when it comes to retaining wheels and other undercarriage components. We discussed the use of a collet on the free castering tail wheel assembly a couple of paragraphs previously. They are also used on some steerable nose legs and most frequently of all, they retain the wheels on the axles.
When tightening the grub screws in collets it is essential that the correct size hexagon key is used. To big and it won’t go in, to small and you will remove the corners in the sockets.
I always take the precaution of filing a small flat on the wire to which the collet is to be tightened. This ensures that the grub screw locates in the correct place and prevents it falling off in the event of a slight loosening.
Once the correct position is determined, apply a small spot of Cyano glue or ‘Threadloc'(TM) to the grub screw thread before finally tightening it up. Vibration, although not so much of a problem with electric planes, can result in the grub screws coming loose and wheels or other components falling off in mid flight. For a learner this is the last thing you want to be worrying about.
Free Running Wheels
It is not unusual for the wheels supplied in an ARTF kit to have different size centre holes to the diameter of the axle wire (usually smaller). If the axle holes in the wheels are too large they can often be brought down to a good fit by bushing with short lengths of brass tube chosen to provide a smooth running fit on the axle.
The best way to do this is to select the tube that provides a smooth running fit over the axle then check whether this tube will fit inside the hole through the centre of the wheel. If it does, cut the required length using a modellers pipe cutter and glue it inside the hole using Cyano adhesive.
If the tube that gives a smooth fit on the axle is too large to pass through the wheel then refer to the explanation below for enlarging the hole in a wheel.
Tools You Will Need
The holes in wheels supplied are often smaller than the axle so they need to be bored out to provide a smooth vibration free fit. This is best achieved using a Pillar Drill or Drill Press (see picture right). If you intend to develop your modelling skills beyond your first ARTF trainer I would highly recommend purchasing this tool. It has so many uses and virtually guarantees accurately drilled holes in anything. It can also be adapted for other uses, for example, as a rotary sanding device.
For security it is recommended that a Drill Press Vice is used with this tool (see picture below right). This vice can be secured to the height adjustable drill table so that vulnerable hands and fingers can be kept clear of the rotating drill whilst holding the item to be drilled in the correct position.
Both of these items can be purchased on-line here. American readers just click on the images. UK readers can obtain them through these links:-
Enlarging Axle Holes
You will need to place the wheel inside the jaws of the vice and tighten up the jaws until the tyre (US spelling ‘tire’ I believe!) is depressed somewhat on both sides. This will prevent the wheel from spinning around in the vice whilst drilling out the hole. Make sure the wheel is absolutely horizontally flat by placing a piece of scrap wood under it on the vice base.
Now place the vice on the drill press adjustable table and raise the table until the top of the wheel is about 1″ (25mm) from the tip of the drill bit that you have selected (to create the correct size hole) and fitted into the drill chuck .
Here is a tip for ensuring the centre of the wheel is vertically below the tip of the drill. Initially, fit a ‘countersink’ bit into the drill chuck and lower this into the centre of the wheel. This will automatically centre the wheel beneath the drill chuck. Whilst holding the bit in the un-drilled hole, tighten the clamping nuts and bolts so that the vice cannot move.
Raise the chuck to its retracted position and swap the countersink bit for the selected drill bit. Now you can start to bore out the axle hole confident that it will remain completely central in the wheel hub.
Note:- Most countersink bits are much shorter than drill bits so you will need to position the adjustable table at the correct height for the drill bit, not the countersink bit. There will be plenty of drop on the chuck to wind the countersink bit down to the wheel hub for centring.
When drilling out the hole be sure to select a medium speed setting for the drill press. Turn on the drill press and bring the tip of the drill down to engage the existing hole. Using gentle pressure slowly allow the drill bit to cut through the material of the hub. Most trainers are supplied with plastic hub wheels but occasionally they may be aluminium. Whichever you have, take care not to apply too much pressure. Keep retracting the drill bit and if necessary clean away any waste to prevent binding in the hole. Always turn off the drill press when removing this material.
The end result should be a perfectly centred hole that is a smooth fit on the axle providing you have chosen the correct size drill bit!
I hope this and the previous post have helped you understand how you can check and improve the standard of finish of any of the ARTF RC planes for beginners you may encounter.
Catch you next time with more useful information.