If those hose clamps are not constant torque clamps,
please consider upgrading them before first flight. They're available
from McMaster.
Mark;
I have no objection to the use constant
torque clamps, of course. But I will express my conclusion/opinion that this
clamp thing has been over sold. Certainly not picking on you, and I know our
friend on the other list makes a big issue of the constant torque clamp. IIRC,
the main point raised was the effect of thermal expansion, more exactly the
differential thermal expansion between the inner metal tube (aluminum in this
case) and the clamp (usually SS). Doing the math will show that this is less
than infinitesimal. The temp change of the coolant may be about 80 C cold to
hot. The clamp heats up maybe 15C less than the aluminum. Assume a 1 ½”
diameter. So the aluminum expands about 0.000037” on the diameter while
the SS expands only 0.000012”; a huge difference of 0.000025”. I
am certain that this effect on the thickness of the elastomer hose is entirely
negligible. And besides, having that clamp just a wee smidgeon tighter when it
is hot and pressurized can’t be a bad thing.
Now, it is true that over time the elastomer
loses some of its elasticity, mostly over the first few months, and then very
slowly over the next few years – depending on the type of elastomer, of
course.
So whether they are regular good quality
clamps, properly tightened (not over-tightened), or constant torque clamps
properly tightened; I’d suggest that the important factors are: re-torque
the clamps after a few weeks or a month of use; use the widest clamp for the
diameter, and consider high quality silicone hose – although contemporary
automotive coolant hose can be expected to last 6 – 9 years. The other
thing, of course, is that on our planes we will probably change out the hoses
every second annual or so anyway.
One more thing. Consider putting a Schroeder
valve on the system somewhere so you can easily pressure test the system before
you fly (or before you start your engine), and maybe at annual time. It is so
much easier to deal with any leak while things are cool and on the ground.
Sorry; did I go on too longJ?
Al G