Aeromodelling

After a break of many years I have started to become more than interested in my old hobby of aeromodelling.  My passion back in the 70s was for radio controlled powered flight. I have dug out, from the loft, an old aircraft, the last one I was flying, and checked the engine out, an OS 90 four-stroke glow plug unit.  It worked a treat given a new plug and new fuel.  Also I had to strip and clean was the carburettor. 

I have made enquiries of our local flying club, the Felbridge Flyers, and in due course will be joining them.  I have found that some restrictions are now in place mainly about noise levels, which we did not have back in the 60s and 70s.  To this end I have purchased a Super-Quiet silencer that should reduce the noise levels to 81dBA, measured at 7m, as required by the club.  I will also have to limit the maximum RPM to 10,000.

Insurance is now obligatory and the national body can offer this so this is something else I will need to join.

I have two part complete models in the loft and will get these out in due course and see about finishing them.  Quite what will be needed I won't know until I have inspected them.  One of the craft is a Twin Comanche and is well on the way to completion so not too much work should be required.  This could be a good model to convert to electric flight.

The radio I have is pretty old but hopefully still serviceable, it was made by a company called Skyleader, sadly no longer in existence.  Fortunately some enterprising electronics wizard has back engineered the circuit and I have a copy of this, so as an experienced electronics engineer I should be able to repair it, should it need it.  The one item that was not shown was the circuit diagram of the charger unit.  I have back engineered this and now have full details of the circuit.  New batteries are necessary as the old NiCad's had developed leaks and were quite unusable!  I suspect the servos will need stripping and cleaning and re-oiling, hopefully they won't need replacing as they can be quite pricy!

I have now checked and serviced the transmitter; the NiCad batteries, two blocks of four cells, were badly sulphated where they had leaked.  Fortunately the leakage had not spread too far and I was able to neutralize this and clean it off satisfactorily.  The replacement batteries are also two blocks of four but this time they are NiMH and size-for-size they are very much more powerful having a rating of 2AH. 

I then checked out the negative cable to see if it had suffered, and sure enough it was suffering the well known 'negative lead corrosion'.  This entailed replacing the negative cable throughout the transmitter.  I did check the cable to see how far the corrosion had gone and I found that it had leached down the entire 150mm length and had started to attack the solder tag, this was easy to clean up.

The transmitter now works but how about the receiver and servos?  This was the next job to check but first I needed to remove the lot from the airframe.  Having done so I connected it all up and found to my delight that all but one servo worked OK.  I soon found the fault in the non-working unit this proved to be a dirty contact on the connecting plug, cleaning this up gave me complete operation.  Just to be safe I will need to clean the plugs and sockets on all connectors.

The hobby has moved on a lot over the past decades, electric flight is a real option today, but again pricy to get into; it would mean new airframes, motors and light-weight servos etc..  Slope soaring is another possibility but this would mean travelling some distance as we do not have too many suitable slopes within easy reach of my home.

I have now started to repair the airframe, it had a heavy landing the last time it was flown!  The rudder has broken but will be easily repaired with some cyano adhesive.