Vintage RC Helicopters - MFA Restorations

MFA Sport 500 restorations  Joe William Richardson

MFA Sport 500 Fixed Pitch and Collective pitch restoration

By 2010 the MFA Sport 500 had picked up a reputation of being remembered, for want of a better word as crap.  However, comments in the magazines of the time were positive; so who was actually right?  I had picked up a number of the MFA 500 variants so I thought it was about time to put the record straight and dispel the myth's, or not as the case may be.  After this length of time it would not be fair to comment on a currently running example; I therefore decided to take two good examples i.e. not crashed or completely worn out, re-kit them and then rebuild to 'as new' condition.  I had two donors that would suit; the first was an early fixed pitch version that had belonged to a friends grandfather having built it, tried to fly it and not succeeded, he put it in the attic.  I had attempted to set it up for my friend to learn on but though it would hover the engine quickly overheated; I thus swapped him a Mini Titan kit for it (which he did learn to fly with).  The second was a collective pitch model which had the upgraded tail wire drive and an Autorotation clutch fitted.

OK!! - what do I have?

Both helicopters were fully stripped down in order to determine what was needed for the restoration.  Both were in surprisingly good condition but again, that was why they were chosen in the first place.  The following faults were found:-

MFA 500 Fixed Pitch strip down

When the fan casing was removed it was immediately obvious why the engine was overheating......  The engine fitted was a very powerful Super Tiger 40, unfortunately it was fitted with a very large carb which protruded past the front of the prop driver.  Now this would not have been a problem with a propeller fitted but in the helicopter it fouled the fan blades so they had been cut down to about 50% of the original size.  Cooling of an engine with an aero type head is only adequate at best and this kind of 'modification' had made it totally inadequate.  I would therefore have to replace the engine with a good Irvine 40 out of one of the other MFA's in order to allow an unmodified cooling fan to be fitted.

The body woodwork had also started to split apart and had not been particularly well glued in the first place.  Finally, no threadlock had been applied anywhere?  Good job the helicopter had not been used very much in its life!!!!!!!!!

So, a reasonable base for a rebuild.

MFA 500 Collective Pitch strip down

The strip down of this one immediately highlighted a big difference; threadlock had been used everywhere and by the difficulty experience in undoing the fastenings I suspect that it was actually studlock.  Apart from this nothing untoward or badly worn was found and so the rebuild should be straightforward.

Originally I had though to restore the two of them in tandem however I then changed my focus and decided to restore the fixed pitch version first which would allow some flying time to get used to it before the collective pitch version could be flown and thus provide a more 'realistic' comparison.

Fixed Pitch restoration

The aluminium as originally supplied came as 'clean' but not polished however, every attempt to clean parts also resulted in them getting polished to some degree.  OK, it is never going to be valuable or perhaps even desirable; but that is no need for it to look like a dogs dinner with varying levels of cleanliness etc.  I therefore decided to polish all parts up so as to give it an overall 'even' look.

The rebuild was carried out following the original build manual but also with experience of modern machines and the faults identified over many years of its use.  Because of this I made some alterations though attempted to keep these to a minimum and concentrate on reliability, controllability issues.

Step 0ne - Main chassis & drive.

Built up in order to provide a base to work from.  For the clutch drive I decided to grind a small flat on the output shaft and also to drill and tap the clutch drum so as to use a bolt for security instead of the 'split pin' as originally used.  This was commented on during rebuilds of the time and the reason for this method of drive was that it provided a 'weak' point between the engine and head in case of a heavy landing with engine power still on.

Additionally I fitted a lower bearing housing with bearing in place of the standard 'plain' upper bearing.  Not so much required for the FP version but would provide better longevity and less 'play'.

Step Two - Tail gearbox

As this helicopter had very little running time, when inspected the tail gearbox was in perfect condition.

NOTE

Dec 2010 restorations put on hold as due to circumstance (i.e. packing to move house) no time for carrying on the rebuild.

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