These were a bear to draw :) First 3D jpg.
Pratt & Whitney style herring bone with oil pressure release.
Pratt & Whitney claims over 99 percent efficiency for the PSRU they
made.
These gears are 48/36 (1:33) reduction after the
9:1 traction drive giving an over all reduction of
12:1. At a turbine RPM of 85.000 the small pulley will
be turning at 7083 RPM.
The big gear has P.D of 2 inches and the small a P.D of 1.5 inches.
each gear is a half inch wide. The herring bone arrangement cancels
out the helical gear thrust. The gears can be reversed as can
the multi V belt pulleys to give a range of adjustable ratios.
The HP is anybodies guess as Boston Gear does not rate them for
3900 FPM pitch line velocity. The formula says 56 HP but they
talk about 1500 FPM max. They are the best Boston Gear makes
with hardened steel and polished teeth. Hopefully they will live
long enough to get some dyno data.
Of course they reverse the direction of rotation making this box
work with a stock Rx7 Turbo II engine turbo charger putting excess
turbine
power into the nose of the e-shaft.
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Here is what the complete box looks like with out shafts and
traction drive
parts. It is a check on fit and assemble. Also no helical gears as
they take
up considerable megabits. Yes There are a few holes missing hear
and there.
I cannot imagine doing projects like this before 3D programs. For
the guys
designing engines in the old days it must have been a major undertaking.
Second 3D jpg.
Paul Lamar ...No rotor no motor.
Hi Paul,
Could you please remind me why you need the clutch(es)?
Thanks,
Matt-
Well the engine has the potential HP to destroy the gear box.
If the engine drives the gear box it would attempt to accelerate the
turbo charger
and the rotational inertia of the turbo charger is enormous as it is
sped up at least ten times faster than the engine. That turbo charger
will look like a huge flywheel to the engine and the gear box is not
designed
to endure those kinds of torques or loads.
In addition to that if that were not enough the engine could in theory
drive the turbo charger to an RPM it was not designed to sustain.
Lets say the best overall fixed ratio is 12 to one without clutch.
At 72,000
RPM from the turbo charger the engine is running at 6000 RPM cruise.
If you took off at 7500 engine RPM the turbo charger would be running
at 90,000 RPM which may be detrimental to its health.
The centrifugal loads on the hot turbine blades are enormous at 90,000
RPM and above. With a waste gate we can limit the turbo charger RPM
to something reasonable.
Paul Lamar ...No rotor no motor.
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Paul,
This is out of my expertise, but I would think herringbone gears are
rather costly to make. Instead, could you not use two helical gears
with opposite thrust angles pined together with or without a spacer
between and get the same end result of no thrust?
Joel
That is eactly what I intend to do Joel. Great minds think alike.
I am about to find out as the FOUR gears, two left hands and two right hands,
are due to arrive any minute. I'll take a picture and upload it here.
Paul Lamar ...No rotor no motor.
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