Grumman - Part 11
weeks of cold and rain (not usual in these parts) I managed to get
to the airfield for the first time in a while! - no fun working
in a dank, cold hangar and not a soul on the airfield!
riveting of the nose scoop for the underbelly rad housing and mounted
this up. It is detachable with a dozen screws for any future maintenance.
the motor now revealed a new problem - the thing would not run cleanly
for more than a few minutes. Much pondering and checking left me
no option but to remove the carbs and strip them down - to find
one carb jet clogged with muck! Cleaned this out, then tried another
test run - seemed okay so jumped in and set off for the runway for
a high speed run to run a final check of cooling and brakes. Once
again the motor sputtered to a halt before even reaching the holding
Cube Pump 40105
This time there
was no sign of clogged jets nor was there any dirt in the tank -
but I noticed that my two Facet pumps were only supplying out a
low volume of fuel to the carb inlet. After much messing about without
any success in getting the pumps to actually pump adequately I gave
up for the day and resolved to buy a new pump as I have not been
happy with the cube Facets of late - just a nagging feeling but
I think that feeling was right.
Some days later
I picked up a new-design Facet - this one, model 60106 has a rounded
composite body and is supposed to definitely deliver 120
litres per hour - better yet it needs no head of fuel to the inlet,
as it has the ability to suck! Much better!
Then of course
I found that I needed some fittings etc to link it up, so final
installation, albeit in a temporary position, had to wait - but
eventually, yesterday 2010-05-16 all was hooked up and testing showed
that it was delivering 120 litres per hour to the carburettors -
success. And after a thorough test the engine keeps on running strong!
Posiflow 60106 Pump
One thing though
- apart from the fact that the cube Facet pumps had apparently packed
up, perhaps blocked up by the muck which I found at the carbs, and
evidenced by a definite change in the sound they make when pumping
and the lack of volume pumped, some of the piping connecting those
pumps to the carb was of 6 mm diameter - and the inlet pipes to
the carb float bowl are 6m as well. Changing those delivery pipes,
but not the inlet pipes which are part of the carburettor has been
part of the success I think - testing shows that the pump which
will deliver 120 lph through a 8mm pipe, will only deliver 60 lph
though a 6 mm pipe - so a 2mm (33.333%) increase in pipe diameter
results in a doubling of the flow - hmmm!
So for our next
trick we need to remove the cube Facets from the firewall - a two
man job unfortunately as someone has to be each side of the firewall!
- and mount our new facet (pictured right) in place, along with
the second backup Facet I still need to buy. hopefully we can get
that done sometime this week, work and weather permitting!
I am thinking
that the last pump shown here - almost identical to the Benix pumps
fitted as original equipment on many light aircft will be the way
to go however.
now can say that our engine, cooling and sytems testing phase is
complete! I reckon I have identified and hopefully rectified all
the 'problem' areas - and it has been quite a lengthy task - better
to do all this on the ground though, no matter how long it takes!
Next we will
take the wing, still hanging in the rafters of my garage at home,
to the airport, to join it's mate already at the hangar - that could
happen as early as this week too, and while I have a helper we better
get both those wings mounted on to the carry through spar stubs.
Hey! - a new
note has appeared on my list of things to do - "Take wing to
airfield" - proof that we have made progress!
Over the past
weekend we got the wing to the airfield and fitted both wings -
still some connecting of piping and wiing to do and we will complete
that next weekend with any luck - but I did manage
to get the left wing fuel piping connected up - so could pour some
fuel into that wing as a test of the tank seals, which are now several
years old - I guess at least 6 years has gone by since I installed
new seals and the worry was that these would be no good by now having
been dry for those years! It seems though that all may be well,
as after 1 hour with fuel in the tank nothing appeared to be leaking
the Facet pumps - there was muck inside them! After cleaning they
appear to work okay, at least to judge by the fact that they make
plenty noise once again. Once I have tested them for fuel flow rate
I expect I will reinstall them, along with the new Facet - thus
giving me three pumps - sufficient redundancy I think. This time
however we will be adding at least two upstream fuel filters!
Voila! Wings are installed! Almost.
the wings slide on to the
carry-through spar - a tube within a tube
- plus the aux tank tube arangement
a visit by the SAAF Silver Falcons
with their Pilatus PC7s - nice airshow!
Falcons practicing for their later
display at Rand FAGM