Spinner, aluminium or fibreglass? Safety?

Ebby wrote:
Is there any particular reason for using six bellevilles?

I wanted to ensure that I had more than enough deflection capability.
Probably 4, or even 2, would be adequate protection.

... Are they stacked parallel?

No, series. I wanted more deflection with the same force.

... I read the whole story about the Cozy that threw a prop and
checked out the graphical data piece and think I understand why the
bellevilles are better than conventional. Due to the fact that a
belleville is a spring, if the prop hub shrinks or expands, the
belleville acts as a buffer. Yes?

Exactly.

I have a wooden prop, not yet installed and a sudden departure due
to improper torque is not a pleasant thought. If possible I'd like
more specific installation recommendations.

I'm in the process of writing an article for as yet unnamed
magazine(s) about this, and I'll be presenting a summary of the
article as part of the COZY forum at Oshkosh. I don't have enough
time on the installation yet (due to ignition problems, right now) to
make recommendations to other folks - I want to get at least 25 - 50
hours on the system before telling other folks exactly what I did and
what to use.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

Ebby wrote:
Is there any particular reason for using six bellevilles? Are they stacked
parallel? I read the whole story about the Cozy that threw a prop and
checked out the graphical data piece and think I understand why the
bellevilles are better than conventional. Due to the fact that a belleville
is a spring, if the prop hub shrinks or expands, the belleville acts as a
buffer. Yes?


With any spring, you have a 'spring rate' and a 'maximum deflection'.
Those who really know what they're talking about probably use different
terms, but you get the idea. The rate is how much the pressure
increases with each increment of deflection. Maximum deflection is the
range from no pressure to completely squashed.

The goal is to have some reasonable range of deflection, then obtain the
pressure you want somewhere in the middle of the range. Like you said,
the spring is a buffer, filling in when the wood shrinks, and giving
back a little when it expands. Spoon the belville washers together, ie
(()), and you increase the rate, takes more pressure to crush them. Put
them to back-to back, ie ()(), and you increase the maximum deflection.
You have twice as far to travel, but you don't really have to apply
any more force.

From that point, it's a mix'n'match game to get the characteristics you
want. Pick a washer, and get its nominal spring rate that'll be
specified by the manufacturer. Calculate how much pressure it'll apply
at half its max deflection. Calculate how many you'll need to get that
magical 600 PSI at the prop flange. Now how much will the prop hub
shrink and expand. The flange pressure drops with shrinkage, and
increases with expansion. You don't want to much pressure or to little,
so calculate what the pressure the belville will apply at the bottom and
top of the prop expansion range. Add a ()-belville pair, and you cut
down on for each pair. They share the prop hub expansion. Now the
pressure range they provide doesn't vary as much. Keep adding pairs
till the pressure will remain within comfortable limits.

On Mar 31, 9:59 am, "Marc J. Zeitlin"
wrote:
stol wrote:
I see you have the .edu in your email address so you must be a teacher
or professor.

Nope. I'm an aeronautical engineer, and I work for Scaled Composites.
Does that somehow change the facts of the matter?

... Now tell me how you came up with 30 square inches of
surface area on a a SAE-2 crank hub...Thanks in advance.

Math. My prop extension is about 7" in diameter. If I subtract the
area of the large hole in the center and the small holes for the
bolts, I get about 30 square inches.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

Sorry. My SAE #2 hub must be different then yours.

My math shows: and my plane has on it...................

6.0000" od
2.2500" id
6 holes@ 33/64

total square inches of surface is 23.048467

Now. since the bushing are not in shear and carrying any load I will
remove them to save some weight, so that opens up the six holes to .
625.

So my new surface area is now 22.457533 square inches.

When I grow up I wanna be a aeronautical engineer too.

stol wrote:

Sorry. My SAE #2 hub must be different then yours.

Probably not. As I said, MY PROP EXTENSION has a 7" diameter. Very
likely, the SAE-2 hub is identical.

But my prop is on my extension, so the area of the extension is what I
use.

total square inches of surface is 23.048467

Good. For your plane, with your setup, with a wood prop mounted
directly to the SAE-2 hub, 600 psi will get you about 13,800 lb total,
or about 2300 lb/bolt.

Now you know what you're shooting for.

Now. since the bushing are not in shear and carrying any load I will
remove them to save some weight, so that opens up the six holes to .
625.

Removing the bushings, which are used for ensuring alignment of the
prop during installation, will make aligning and balancing the prop
difficult, not to mention leaving you with nothing to screw the bolts
into (assuming that your bushings are threaded). Plus, you'd be out
of luck if you ever want to use a metal prop.

So my new surface area is now 22.457533 square inches.

BFD.

When I grow up I wanna be a aeronautical engineer too.

Not very likely, with your attitude.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

Marc,

Thanks for the additional info. Please keep me in the loop on your progress
regarding test results. I am a long way off from installing the propeller.
So patience is mandated at this point. I read the installation manual from
Sensenich and it seems straight forward yet the climate I live in the
humidity can get very low in the winter and extreme in the summer so I am
thinking the wooden prop will be shrinking and expanding with the seasons.
I think the bellevilles would be a suitable method of "auto adjustment" as
the seasons change. I could go with a metal prop but think the biplane will
look more authentic with wood.

Ebby


"Marc J. Zeitlin" wrote in message
...
Ebby wrote:
Is there any particular reason for using six bellevilles?

I wanted to ensure that I had more than enough deflection capability.
Probably 4, or even 2, would be adequate protection.

... Are they stacked parallel?

No, series. I wanted more deflection with the same force.

... I read the whole story about the Cozy that threw a prop and checked
out the graphical data piece and think I understand why the
bellevilles are better than conventional. Due to the fact that a
belleville is a spring, if the prop hub shrinks or expands, the
belleville acts as a buffer. Yes?

Exactly.

I have a wooden prop, not yet installed and a sudden departure due
to improper torque is not a pleasant thought. If possible I'd like
more specific installation recommendations.

I'm in the process of writing an article for as yet unnamed
magazine(s) about this, and I'll be presenting a summary of the
article as part of the COZY forum at Oshkosh. I don't have enough
time on the installation yet (due to ignition problems, right now) to
make recommendations to other folks - I want to get at least 25 - 50
hours on the system before telling other folks exactly what I did and
what to use.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

Ebby wrote:

Thanks for the additional info. Please keep me in the loop on your
progress regarding test results.

Check the web pages on occasion, and feel free to ping me via email
for updates.

.... the climate I live in the humidity can get very low in the
winter and extreme in the summer so I am thinking the wooden prop
will be shrinking and expanding with the seasons.

Absolutely. All the wood prop MFG's say to check the prop bolt torque
every 25 hours or so, AND when moving either way between a dry climate
and wet climate. Moving from MA to CA is what got me - I didn't check
the prop often enough (or correctly).

I think the bellevilles would be a suitable method of "auto
adjustment" as the seasons change.

Yes, I'm hoping to be able to come up with a generic formula that will
allow folks to plug in their hub size, bolt size and hub thickness,
and will spit out what washers to use and how many.

We'll see how it goes. Hopefully by OSH I'll have everything
determined, tested, and written.

... I could go with a metal prop but think the biplane will look
more authentic with wood.

Plus weigh less :-).

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

On Mar 31, 2:16 pm, "Marc J. Zeitlin"
wrote:
stol wrote:
Sorry. My SAE #2 hub must be different then yours.

Probably not. As I said, MY PROP EXTENSION has a 7" diameter. Very
likely, the SAE-2 hub is identical.

But my prop is on my extension, so the area of the extension is what I
use.

total square inches of surface is 23.048467

Good. For your plane, with your setup, with a wood prop mounted
directly to the SAE-2 hub, 600 psi will get you about 13,800 lb total,
or about 2300 lb/bolt.

Now you know what you're shooting for.

Now. since the bushing are not in shear and carrying any load I will
remove them to save some weight, so that opens up the six holes to .
625.

Removing the bushings, which are used for ensuring alignment of the
prop during installation, will make aligning and balancing the prop
difficult, not to mention leaving you with nothing to screw the bolts
into (assuming that your bushings are threaded). Plus, you'd be out
of luck if you ever want to use a metal prop.

So my new surface area is now 22.457533 square inches.

BFD.

When I grow up I wanna be a aeronautical engineer too.

Not very likely, with your attitude.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007

Just few few comments for you.

1- Bushings are also called Drive Lugs, if those are not in shear
then you are not a very good aeronautical engineer.

2- The reason stated I was going to replace my 1/2" prop bolts with
smaller diameter ones was to drive home the point that the bolts can
also be in shear too. If you don't comprehend that then you are not a
very good aeronautical engineer.

3- For centuries all aviatiors knew that wooden props swell and shrink
and a smart pilot/engineer would check the torque to maintain the
CORRECT setting.

4- After reading this post several things are obvious.

You are the idiot that forgot/ neglected to perform the proper torque
and you crashed your plane because of it.

For weeks you can't seem to get your ignition to fire properly. Come
on buddy, I have 8 cylinders and I get them to fire perfectly every
time and on BOTH ignition systems. I ain't even a aeronautical
engineer and as reported earlier I didn't stay at a Holiday Inn last
night either. As you should know your idea for the" spring nuts" to
keep the prop properly torqued is a good concept but flawed. All steel
will lose its spring value over time and your torque WILL default to
the loose side over time. Can you calculate that value safely??? I
bet not. I have spent several thousand hours building my experimental
plane and I engineered my firewall forward installation myself. To
have some schmuck that has crashed his plane because he was too f
_ckin lazy to check the torque on his prop talk down to me is the
ironic thing. Now that you have stated you moved from Ma to California
it is crystal clear that is the land of "fruit and nuts" and you are
the poster child.

I am going flying in a few hours in my plane, you, on the other hand
are going to be standing there,playing with yourself and trying to
get four cylinders to fire properly. In closing, your previous
question" Did ya learn something today" . You bet, if someone claims
to be an aeronautical engineer, run, don't walk away from him/her
because sooner or later they will kill themselves because of their
idiotic attitude.

Seeya Marc....................................

Ben
www.haaspowerair.com

"stol" wrote a bunch of oter crap like this:

1- Bushings are also called Drive Lugs, if those are not in shear
then you are not a very good aeronautical engineer.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

What's your problem, Ben? I've always been on your side, but right now, you
are acting like a jerk.

You don't need to tear someone down, to be the big man. Let it go.

It is possible that this guy has his expertise in other areas than small
single engine piston airplanes. He also has other things to do, (like a
job) and that might actually get in the way of getting his ignition fixed.

In fact, I would think it is probable. He is, after all, one of the people
responsible for building Spaceship One and putting it into space, and the
record books.

When you do something that can top that, come back and crow about it. Right
now, you need to grow up, because you are definitely not coming off as the
bigger man.
--
Jim in NC

On Apr 1, 6:14 am, "Morgans" wrote:
"stol" wrote a bunch of oter crap like this:

1- Bushings are also called Drive Lugs, if those are not in shear
then you are not a very good aeronautical engineer.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

What's your problem, Ben? I've always been on your side, but right now, you
are acting like a jerk.

You don't need to tear someone down, to be the big man. Let it go.

It is possible that this guy has his expertise in other areas than small
single engine piston airplanes. He also has other things to do, (like a
job) and that might actually get in the way of getting his ignition fixed.

In fact, I would think it is probable. He is, after all, one of the people
responsible for building Spaceship One and putting it into space, and the
record books.

When you do something that can top that, come back and crow about it. Right
now, you need to grow up, because you are definitely not coming off as the
bigger man.
--
Jim in NC

After sleeping on this and listening to Jim ,who's comments I have
read for years and respected I agree I went way too far. It is my Type
A personality that probably drives me. Also the years of competition
as a driver has formed my actions of taking no prisoners. On the track
it's either them or me to the finish line first and I will work to be
a better human. After all one day I will come face to face to Marc and
I respect the fact he is a fellow experimantal aircraft builder and
would like to debate him in a calm way.. As for Spaceship one,,,, my
take is those guys will make NASA obsolete and stand aviation on its
ear. You guys rock.....And thanks Jim for pointing out my bad
attitude...

Peace to all... aand mostly to you Marc..

Ben.

Ps. As for the Steven. P Mc Nicoll thing I will have a harder time
resolving that issue. G

stol wrote:

1- Bushings are also called Drive Lugs, if those are not in shear
then you are not a very good aeronautical engineer.

With metal props, the drive lugs are in shear. With wooden props,
with the friction force providing 100% of the drive force, they are
not in shear. Ask any of the wood prop manufacturers if you don't want
to believe me - Sensenich, Hertzler, Catto, etc. Sensenich's
documentation says as much.

2- The reason stated I was going to replace my 1/2" prop bolts with
smaller diameter ones was to drive home the point that the bolts
can also be in shear too. If you don't comprehend that then you are
not a very good aeronautical engineer.

If the bolts are in shear, you're in big trouble, as I found out. With
wooden props, the bolts are their to ensure the compression force, NOT
to act as shear members. Again, the prop manufacturers will bear this
out. Even in metal props, the bolts are NOT in shear - the drive lugs
are.

3- For centuries all aviatiors knew that wooden props swell and
shrink and a smart pilot/engineer would check the torque to
maintain the CORRECT setting.

Centuries?

Having admitted that it was MY fault that I didn't check the prop bolt
torque often enough (or correctly), you're hardly telling me something
I don't know. I guess, however, that since Dick Rutan lost his
propeller twice, he's not smart either, eh? I'm not the first person
to lose a prop, but I hope to lessen the frequency by doing this
testing and publicizing it.

People screw up on occasion. At least I'm big enough to admit my
screw-up in public, so that others can learn from it rather than
trying to hide it and be defensive.

You are the idiot that forgot/ neglected to perform the proper
torque..

See above.

and you crashed your plane because of it.

I hardly call a safe landing at a paved airport a crash. It wasn't
even an incident, much less an accident or crash.

For weeks you can't seem to get your ignition to fire properly.

What are you talking about?

... As you should know your idea for the" spring nuts" to keep the
prop properly torqued is a good concept but flawed. All steel will
lose its spring value over time and your torque WILL default to the
loose side over time.

While steel does "creep", the "spring value" you refer to is called
Young's Modulus, and it does NOT change over time. Creeping is a form
of plastic deformation, and is, in fact, well understood in steel.

.... Can you calculate that value safely???

Yes, actually, if you know the type of steel, the stress it's under,
and the temperature, you can easily calculate the amount of creep
(strain) that will occur over time. At the temperatures and stress
levels that these bellvilles will see, the strain is microscopic over
the lifetime of the washers/aircraft. It's also fairly simple, with a
go-no go gauge to determine whether or not the bellevilles have
retained their compressive force.

... I bet not.

How much?

I suppose you're going to tell me that the other folks (such as
Jabiru) that are using this technique (and there are many others that
have done so over the past 60 years) are also all idiots, and that it
hasn't ever worked for any of them, no matter what the evidence shows.

I am going flying in a few hours in my plane, you, on the other
hand are going to be standing there,playing with yourself and
trying to get four cylinders to fire properly.

Funny you should mention that. I have over 466 hours on my aircraft
over the past 4.5 years. I've flown it all over the USA, and average
over 100 hours/year on an aircraft that cruises at over 200 mph. The
plane is flying well and safely, and I rarely play with myself while
working on the engine.

... In closing, your previous question" Did ya learn something
today" . You bet, if someone claims to be an aeronautical
engineer, run, don't walk away from him/her because sooner or later
they will kill themselves because of their idiotic attitude.

Yes, all AE's are morons - god knows how any airplane ever got
designed. Only through the sarcasm and ignorance of garage mechanics
does advancement in the aeronautical field ever occur.

Feel free to ignore everything I say, Ben - no one's forcing you to
listen. I can back up everything I say with facts, data, theory, and
empirical evidence. Co-workers, some of whose names you might
recognize, agree that bellevilles are a methodology for increasing the
robustness of prop bolt tension retention, and thereby increasing safety.

If you have data to the contrary, please, present it.

Or you can choose to pay no attention - it's a free country. Others
may be interested, however.

Peace to all... aand mostly to you Marc..

Same.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2007