Hi Brian,
Something didn't sound right about sandwiching ANYTHING between the
prop flange and the drive flange, so I went out to my workshop and
looked at my Hartzel props. Sure enough the spinner bulkhead is
attached
to the OD (outside diameter) of the prop flange. Its an elaborate setup
but, the bottom line is there is DIRECT CONTACT of the prop flange and
the drive flange, no bulkhead, no RTV, no aluminum disks, no carbon
fiber or fiberglass. I have 2 props --a 2 blade & a 3 blade-- both are
done the same. Hope this helps. Dave M
>Dave,
>Would it be possible to send a photo?
>Thanks,
>Brian Trubee
Hi Brian,
Photo would not show much. Take a look at the attached sketch. It's not
to scale but all the parts are there. If you need sizes or more info
just shout. Dave M
My Spitfire came with the Spinner and a front and rear flange. Showing
the rear flange between the prop and prop hub, the front on front of the
prop. Prop bolts holding all this together. Is this an improper
installation?
Bob Mears
The smaller three rotor torque pulse is a positive while the additional
average torque is a negative. What is the back plate made out of? If
aluminum
you will probably be OK.
Paul Lamar ...No rotor no motor.
Hi Bob,
The two flange faces in contact are constantly fretting against one
another. This action tries to pulverize everything in between. It will
beat the epoxy in a composite to dust leaving only the carbon fiber
(because it's harder than either aluminum surface) then the prop bolts
are loose then the prop is allowed movement and so on to self
destruction. Paul's correct on the aluminum. Hopefully it's an alloy
similar to either or both flanges. As a reference, prop extensions,
commonly used on piston engines up to O-360's, are machined from solid
bar stock of 2024 T-351, but also notice that the extender bolts to the
drive flange, then the prop bolts to the extender -- the extender is not
sandwiched in place as a loose piece. Also be very careful to follow
your designers torque requirements exactly- both in pattern sequence and
re-torque frequency. BTW: Wood props don't suffer any of this because
wood has no memory (as long as you don't crush fibers, it doesn't
remember it was cycled, as opposed to aluminum or composite which will
cycle fatigue at some point in time. The design &/or material simply
determine the time of failure, ie. TBO). Ahh, but beware of the crack in
your varnish on that beautiful wooden masterpiece. Dave M
both plates are aluminum
Bob Mears
Hi Guys;
My Lyc 0-360 has a Hartzell constant speed with a steel hub and has two
items between the prop hub and the crank flange. It has a phenolic disc and
a cast aluminum disc that has a pulley for the alternator belt cast in and
has the starter ring gear at the rear and the outer edge has the spinner
attach screws. Why the phenolic disc I don't know. Heat insulator or a high
frequency vibration damper? The Crank flange has six steel threaded bushings
that the prop bolts screw into,. four of which are longer and extend through
the two discs and into the prop hub to drive the prop. The blades with hub
weigh just north of 70 pounds so it acts as a pretty good flywheel for
those 90 cubic inch cylinders banging away. The hub is heavily cad plated
and I put a thin coat of chromate on the crank flange. Never had any problem
in many many years.
Bob
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