Maintenance

 

 
After the last flight:

You should drain the fuel tank and clean the model - methylated spirits will remove the exhaust residue. If you find that the oily residue is black, look for a loose screw or bolt which retain something like an aluminium tail brace(the black colouris cauesd by the aluminium being chafed).

Draining the fuel tank servers two purposes. It prevents the methanol from evaporating in the tank and leaving just the oil and it also provides a useful check on the plumbing to ensure that all the fuel is available when flying the model. this means that you must drain the tank by using your fuel pump in reverse to suck the fuel out through the line which goes to the carburettor.

You should also check the whole model for loose(or missing) nuts, bolts and screws every time you put it away, not forgetting the muffler bolts and the bolts which hold the engine mount in the frames.

 
Vibration:

Vibration is a killer. It destorys models and radios faster than anything else and should never be ignored.

If the vibration has developed suddenly and you have changed nothing, the chances are that something is loose or bent. If the main blade tracking is also out, that will produce vibration but you should investigate to find out why the tracking has gone out. If you have removed the main blades since the last flight, check that the blades have been refitted in the original holders and not swapped over. Make sure that the blade bolts are equally tight and that the blades can swing equallt freely.

 

Persistent problems:

Assuming that nothing is bent or damaged, it can be worth re-checking the balance of the main blades if they are wooden. Woods does dry out ir absorb moisture and it is possible that the blades have become unbalanced for this reason.

If the tail vibrates and a boom stay is an option, try fitting one, in order to reduce the flexibility of the tail end. Check the balance of the tail blades.

Turn the main gear slowly to check that the mesh is constant throughtout the rotation. If there is a high spot on the gear or it is warped or the teeth are damanged, change it.

If there is a high frequency vibration or the fuel foams in the tank, use a dial gauge to check the clutch and flywheel alignment.

Finally, if all else fails, try swapping components to discover which is causing the problem.

Radio problems:

If you have noticed any twitching of the controls, particularly when the engine is running, shut down immediately and look for any loose nuts, bolts or screws. If two metal components touch and vibrate together, they will produce static electricity which will cause the servos to twitch(called 'glitching'). Switching on the radio and touching the boom or the engine mount with a screwdriver will often produce this effect if you are using a PPM receiver and you may also notice it when you connect the power supply to the glow plug.