Structural failure due to harmonic vibration

Bertie

2P is twice propeller speed. With two blades it means each blade
caused one of the vibrations points each revolution.

The T-28B (Navy) version had a 1425 HP Wright R-1820. They must have
added some strength to wing for big engine? I never saw what mods they
did to 'A' version to make the 'B' ??????

The AF also modified some A's for VN with the R-1820 (think they were
called T-28D's???)

Long time ago in a far away land )

Big John

*****************************************

On Fri, 9 Nov 2007 00:36:27 +0000 (UTC), Bertie the Bunyip
wrote:

Big John wrote in
:

Bertie

I did some service testing at Edwards on the T-28A. Things found
there. Bird had a bad 2P vibration in cockpit. Was caused by each of
the big wide blades of prop blowing big chunk of air back on the
original canopy which was much taller that the one ending up on bird.
Felt like sitting inside a base drum.


OK, you're going to have to tell me what 2P means...

A C-47 or T-29 (forget which one) 3 blade'd prop was cut down to the
correct size and the three thinner blades cured the problem but Aero
Products had completed their order for the big fat props and they were
in storage in a warehouse so it was felt too expensive to can them and
put new props on bird.

Also the engine was a 7 cylinder 800 HP Wright and not the smoothest
running engine ever built. Almost 115 HP per cylinder. Chug,
chug,chug.

Oh, OK, I thought they had 1830s or R2000's In fact, didn;t they
eventually go to R2800's with them? an awful lot bigger than a T-6 for a
"mere" 800hp.

I ferried one of the first group (5) of birds delivered to the USAF
from LA to Enid, OK. Willie refused to accept the birds like they were
scheduled to due to the prop problem. Give to the multi engine school
)

We didn't have much trouble with the T-6 and students. When we finally
got the T-28A at Willie (after they machined the crank) there were
several wings bent which would have broken off and crashed if plastic.
I like metal wings.

I like wood ones!


Bertie

James Robinson wrote in
:

Bertie the Bunyip wrote:

Big John wrote:

Bertie

I did some service testing at Edwards on the T-28A. Things found
there. Bird had a bad 2P vibration in cockpit. Was caused by each of
the big wide blades of prop blowing big chunk of air back on the
original canopy which was much taller that the one ending up on
bird. Felt like sitting inside a base drum.

OK, you're going to have to tell me what 2P means...

These are terms typically used in diagnosing engine vibration
problems.

1P vibrations are those which are at the same frequency of the engine
RPM. 2P vibrations are those which are at twice the frequency of the
engine RPM. 1/2P vibrations are those which are at 1/2 the RPM of the
engine.

If you have 1P vibrations, you look at things like prop balance or
that you have all the right size pistons in the engine.

With 2P vibrations, you look at things like the effect of two bladed
props, or anything that might be attached to the engine with 1:2
gearing.


OK, got it. Thanks

Bertie

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we finally
got the T-28A at Willie (after they machined the crank) there were
several wings bent which would have broken off and crashed if plastic.
I like metal wings.

I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by Bellanca,
jumping up and down on the wing tips of a Viking at one of the show
sites where I was performing. If I remember right, it was Bobby Bishop
or Debbie Gary who was demonstrating the Viking at that time.
VERY impressive....and a very strong airplane!

--
Dudley Henriques

Big John wrote in
:


Bertie

2P is twice propeller speed. With two blades it means each blade
caused one of the vibrations points each revolution.

The T-28B (Navy) version had a 1425 HP Wright R-1820. They must have
added some strength to wing for big engine? I never saw what mods they
did to 'A' version to make the 'B' ??????

The AF also modified some A's for VN with the R-1820 (think they were
called T-28D's???)

Long time ago in a far away land )

OK, I flew a DC 3 with the 1820 (the rest had Pratts) and I'm pretty sure
it was about 1100HP in that incarnation. I'll look it up now, but the T-28
is HUGE! The 1340 in the T-6 was rated at 600HP so I would have thought
pound for pound they would have had to go a lot more than an extra 33% for
it.

Bertie

Dudley Henriques wrote in
:

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we finally
got the T-28A at Willie (after they machined the crank) there were
several wings bent which would have broken off and crashed if plastic.
I like metal wings.

I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by Bellanca,
jumping up and down on the wing tips of a Viking at one of the show
sites where I was performing. If I remember right, it was Bobby Bishop
or Debbie Gary who was demonstrating the Viking at that time.
VERY impressive....and a very strong airplane!



Yes, lovely airplane, though someone did pull one apart doing aerobatics as
I recall. It was someone who had a reputation for knowing what he was
doing, too, not someone who just decided to roll one one day.

I always thought the little LeBlond powered Junior would be a nice little
thing to have, or even the later Crusairs. Such a pretty airplane..


Bertie

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we finally
got the T-28A at Willie (after they machined the crank) there were
several wings bent which would have broken off and crashed if plastic.
I like metal wings.
I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by Bellanca,
jumping up and down on the wing tips of a Viking at one of the show
sites where I was performing. If I remember right, it was Bobby Bishop
or Debbie Gary who was demonstrating the Viking at that time.
VERY impressive....and a very strong airplane!



Yes, lovely airplane, though someone did pull one apart doing aerobatics as
I recall. It was someone who had a reputation for knowing what he was
doing, too, not someone who just decided to roll one one day.

I always thought the little LeBlond powered Junior would be a nice little
thing to have, or even the later Crusairs. Such a pretty airplane..


Bertie



I've flown the old Cruisair. Real nice airplane and I always thought
ahead of it's time.

--
Dudley Henriques

Dudley Henriques wrote in
:

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we
finally got the T-28A at Willie (after they machined the crank)
there were several wings bent which would have broken off and
crashed if plastic. I like metal wings.
I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by Bellanca,
jumping up and down on the wing tips of a Viking at one of the show
sites where I was performing. If I remember right, it was Bobby
Bishop or Debbie Gary who was demonstrating the Viking at that time.
VERY impressive....and a very strong airplane!



Yes, lovely airplane, though someone did pull one apart doing
aerobatics as I recall. It was someone who had a reputation for
knowing what he was doing, too, not someone who just decided to roll
one one day.

I always thought the little LeBlond powered Junior would be a nice
little thing to have, or even the later Crusairs. Such a pretty
airplane..


Bertie



I've flown the old Cruisair. Real nice airplane and I always thought
ahead of it's time.


well, when you look at the competition, no contest. Same engine as a
108-1 and a good thirty knots faster. Also, that wing is so elegant
looking I just now it has to do exactly what you ask with two finger
control.
I've seen a lot of them for sale recently for very small money, but I#ve
already got too many toys!


Bertie

On Thu, 8 Nov 2007 11:01:14 -0600, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote:

Steven P. McNicoll wrote:
I think most people would agree with you. I'd say a "trans-
continental" flight that started in Spokane and proceeded east failed
to transit about 400 miles worth of continent.

Would you count KSEA to KJFK as Trans-continental? If so the difference in
the distance of a great circle route flight would only be 193 miles.

That 192 miles includes a major mountain range (the Cascades)....

Ron Wanttaja

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we
finally got the T-28A at Willie (after they machined the crank)
there were several wings bent which would have broken off and
crashed if plastic. I like metal wings.
I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by Bellanca,
jumping up and down on the wing tips of a Viking at one of the show
sites where I was performing. If I remember right, it was Bobby
Bishop or Debbie Gary who was demonstrating the Viking at that time.
VERY impressive....and a very strong airplane!


Yes, lovely airplane, though someone did pull one apart doing
aerobatics as I recall. It was someone who had a reputation for
knowing what he was doing, too, not someone who just decided to roll
one one day.

I always thought the little LeBlond powered Junior would be a nice
little thing to have, or even the later Crusairs. Such a pretty
airplane..


Bertie


I've flown the old Cruisair. Real nice airplane and I always thought
ahead of it's time.


well, when you look at the competition, no contest. Same engine as a
108-1 and a good thirty knots faster. Also, that wing is so elegant
looking I just now it has to do exactly what you ask with two finger
control.
I've seen a lot of them for sale recently for very small money, but I#ve
already got too many toys!


Bertie

It is indeed a beautiful wing. Getting the gear up could earn you a sore
shoulder once in a while (The Grumman F4F Wildcat took some work to get
the gear up and stowed as well) but aside from that, both were beautiful
to fly.



--
Dudley Henriques

Dudley Henriques wrote in
:

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:
Dudley Henriques wrote in
:

Bertie the Bunyip wrote:

We didn't have much trouble with the T-6 and students. When we
finally got the T-28A at Willie (after they machined the crank)
there were several wings bent which would have broken off and
crashed if plastic. I like metal wings.
I like wood ones!


Bertie

I once saw two Sumo wrestlers that I assume were hired by
Bellanca, jumping up and down on the wing tips of a Viking at one
of the show sites where I was performing. If I remember right, it
was Bobby Bishop or Debbie Gary who was demonstrating the Viking
at that time. VERY impressive....and a very strong airplane!


Yes, lovely airplane, though someone did pull one apart doing
aerobatics as I recall. It was someone who had a reputation for
knowing what he was doing, too, not someone who just decided to
roll one one day.

I always thought the little LeBlond powered Junior would be a nice
little thing to have, or even the later Crusairs. Such a pretty
airplane..


Bertie


I've flown the old Cruisair. Real nice airplane and I always thought
ahead of it's time.


well, when you look at the competition, no contest. Same engine as a
108-1 and a good thirty knots faster. Also, that wing is so elegant
looking I just now it has to do exactly what you ask with two finger
control.
I've seen a lot of them for sale recently for very small money, but
I#ve already got too many toys!


Bertie

It is indeed a beautiful wing. Getting the gear up could earn you a
sore shoulder once in a while (The Grumman F4F Wildcat took some work
to get the gear up and stowed as well) but aside from that, both were
beautiful to fly.



Mmm, I can see the F4F would be nice to fly allright. wouldn't have
thought it would be too good to do a routine in, though. I don't know
what type ailerons it had or how they were rigged but nothing about it
screams out sportscar to me. Maybe it's just it's pugnacious looks. Cae
to set me straight?

Bertie