Pazmany PL4

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:

I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------

Well... mebbe it wasn't quite that bad... :-) But with multiple vee
belts it's impossible to keep ALL of them at the same tension. The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Several of us who had experience flying behind VW's (Paz wasn't a
pilot back then) tried to explain the realities of VW engines to Paz
but he made it pretty clear that our experience-based opinions were
not welcome. (Come to think of it, a kid named Burt Something did
exactly the same :-)

In the final analysis the PL-4 -- at nearly 700 pounds -- is a heavy,
complex, expensive airframe that needs more power than a stock 1600 VW
engine can provide. With the same engine, a Teenie Two can fly rings
around it and is a lot easier to land, while a VP-1 is more fun than
either. But of course, those aren't 'real' airplanes... :-)

-R.S.Hoover

wrote:
On Feb 25, 10:58 pm, flybynightkarmarepair wrote:


I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------


Well... mebbe it wasn't quite that bad... :-) But with multiple vee
belts it's impossible to keep ALL of them at the same tension. The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Eh? I can't visualize it. Either all, or none, slip.

Beryl wrote:
wrote:

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:


I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------



Well... mebbe it wasn't quite that bad... :-) But with multiple vee
belts it's impossible to keep ALL of them at the same tension. The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.


Eh? I can't visualize it. Either all, or none, slip.

Nope. That's not how it works, Beryl.

Oh, maybe if all the belts really were teh exact same size.
Or if the pulleys were really exactly parallel.

In the real world neither of thoese little details ever work out - quite
that exactly.

The biggest one slips.

How can you tell which is the biggest one?
Easy.
It's the one that slips!

As tehy say, YMMV...



Richard

cavelamb himself wrote:

Beryl wrote:

wrote:

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:


I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------




Well... mebbe it wasn't quite that bad... :-) But with multiple vee
belts it's impossible to keep ALL of them at the same tension. The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.



Eh? I can't visualize it. Either all, or none, slip.


Nope. That's not how it works, Beryl.

Oh, maybe if all the belts really were teh exact same size.
Or if the pulleys were really exactly parallel.

In the real world neither of thoese little details ever work out - quite
that exactly.

The biggest one slips.

How can you tell which is the biggest one?
Easy.
It's the one that slips!

As tehy say, YMMV...



Richard

My mileage varies. I tink teh biggest belt is just along for teh ride.
And in teh real world, even teh tightiest belt slips if you're talking
about microscopically wobbling pulleys.

On Feb 26, 8:23*am, cavelamb himself wrote:
Beryl wrote:
wrote:

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:

I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------

Well... mebbe it wasn't quite that bad... :-) *But with multiple vee
belts it's impossible to keep ALL of them at the same tension. *The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Eh? I can't visualize it. Either all, or none, slip.

Nope. *That's not how it works, Beryl.

Oh, maybe if all the belts really were teh exact same size.
Or if the pulleys were really exactly parallel.

In the real world neither of thoese little details ever work out - quite
that exactly.

The biggest one slips.

How can you tell which is the biggest one?
Easy.
It's the one that slips!

As tehy say, YMMV...

Richard- Hide quoted text -

- Show quoted text -

Caveman, you cannot have one belt slipping and not the others. Think
about it - the pulleys on each shaft are all the same size and
rotating at the same speed. You can only have slip if one pulley is
rotating at a different speed to the other. If one slips they *must*
all slip.

On Tue, 26 Feb 2008 03:00:47 -0800 (PST), JohnO
wrote:

On Feb 26, 8:23=A0am, cavelamb himself wrote:
Beryl wrote:
wrote:

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:

I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------

Well... mebbe it wasn't quite that bad... :-) =A0But with multiple vee
belts it's impossible to keep ALL of them at the same tension. =A0The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Eh? I can't visualize it. Either all, or none, slip.

Nope. =A0That's not how it works, Beryl.

Oh, maybe if all the belts really were teh exact same size.
Or if the pulleys were really exactly parallel.

In the real world neither of thoese little details ever work out - quite
that exactly.

The biggest one slips.

How can you tell which is the biggest one?
Easy.
It's the one that slips!

As tehy say, YMMV...

Richard- Hide quoted text -

- Show quoted text -

Caveman, you cannot have one belt slipping and not the others. Think
about it - the pulleys on each shaft are all the same size and
rotating at the same speed. You can only have slip if one pulley is
rotating at a different speed to the other. If one slips they *must*
all slip.

The longest one slips on both pulleys.

On Feb 26, 2:46*pm, (Drew Dalgleish)
wrote:
On Tue, 26 Feb 2008 03:00:47 -0800 (PST), JohnO
wrote:





On Feb 26, 8:23=A0am, cavelamb himself wrote:
Beryl wrote:
wrote:

On Feb 25, 10:58 pm, flybynightkarmarepair wrote:

I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------

Well... mebbe it wasn't quite that bad... :-) =A0But with multiple vee
belts it's impossible to keep ALL of them at the same tension. =A0The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Eh? I can't visualize it. Either all, or none, slip.

Nope. =A0That's not how it works, Beryl.

Oh, maybe if all the belts really were teh exact same size.
Or if the pulleys were really exactly parallel.

In the real world neither of thoese little details ever work out - quite
that exactly.

The biggest one slips.

How can you tell which is the biggest one?
Easy.
It's the one that slips!

As tehy say, YMMV...

Richard- Hide quoted text -

- Show quoted text -

Caveman, you cannot have one belt slipping and not the others. Think
about it - the pulleys on each shaft are all the same size and
rotating at the same speed. You can only have slip if one pulley is
rotating at a different speed to the other. If one slips they *must*
all slip.

The longest one slips on both pulleys.- Hide quoted text -

- Show quoted text -

Are these belts zero stretch? If they are then I'd agree with you. The
only zero stretch belts I am familiar with are kevlar reinforced
toothed belts running on cogs.

As long as the belts in the original question are stretched so that
the longest one is now the same length as the shortest one there can
be no slip.

"Drew Dalgleish" wrote

The longest one slips on both pulleys.

Think about it for a moment...

If one belt is a little longer, it would not be able to carry as much power,
because it is not as tight as the others.

The others tight belts will carry nearly all of the power, up until the
point where they can not carry all of the power. Then the tight ones will
start to slip.

If the long belt is not able to carry power, but the short tight ones can
carry all of the power being produced, then there will be no slippage.

It is counter intuitive, but that is the situation. If there are 4 belts,
and three can carry all of the HP, and the 4th one is loose, it will not
slip. It will not be carrying any power, though.

If all 4 belts have to be pulling equal load to be able to carry all the HP
being produced, and one belt is loose, then the tight 3 will slip, because
the 4th loose belt can not carry its share, and is slipping.

In my experience of multi V-belt farm type equipment, if you start with 4
new identical belts, and they are a well matched set of identical lengths,
they all will pull evenly. If one is loose, they will slip like I said
above, and will often times stretch to be more closely matched and start
pulling more evenly, if there is enough tension to pull them back tight, and
you do not completely glaze the belts from the initial slipping.

I bet the multiple V-belt reduction unit is running at a very high
percentage of maximum HP recommended by the belt manufacturer. It would be
more likely to smell like burned belts than most farm type applications,
where the loads are kept more conservative by just adding more belts.
--
Jim in NC

"Morgans" wrote in message
...

"Drew Dalgleish" wrote

The longest one slips on both pulleys.

Think about it for a moment...

If one belt is a little longer, it would not be able to carry as much
power, because it is not as tight as the others.

The others tight belts will carry nearly all of the power, up until the
point where they can not carry all of the power. Then the tight ones will
start to slip.

If the long belt is not able to carry power, but the short tight ones can
carry all of the power being produced, then there will be no slippage.

It is counter intuitive, but that is the situation. If there are 4 belts,
and three can carry all of the HP, and the 4th one is loose, it will not
slip. It will not be carrying any power, though.

If all 4 belts have to be pulling equal load to be able to carry all the
HP being produced, and one belt is loose, then the tight 3 will slip,
because the 4th loose belt can not carry its share, and is slipping.

In my experience of multi V-belt farm type equipment, if you start with 4
new identical belts, and they are a well matched set of identical lengths,
they all will pull evenly. If one is loose, they will slip like I said
above, and will often times stretch to be more closely matched and start
pulling more evenly, if there is enough tension to pull them back tight,
and you do not completely glaze the belts from the initial slipping.

I bet the multiple V-belt reduction unit is running at a very high
percentage of maximum HP recommended by the belt manufacturer. It would
be more likely to smell like burned belts than most farm type
applications, where the loads are kept more conservative by just adding
more belts.
--
Jim in NC

Thanks Jim,

That is all in keeping with what I had always understood, and also makes a
great point about conservative versus optomistic designs.

Peter

"Beryl" wrote in message
...
wrote:
On Feb 25, 10:58 pm, flybynightkarmarepair wrote:


I've since heard from Veeduber (who knew Pazmany, and flew out of the
same airport as the prototype) that you could smell the first ship
before you could see it, as it burned, errr flew off the first 40
hours with the belts constantly slipping.
------------------------------------------------------------------


Well... mebbe it wasn't quite that bad... :-) But with multiple vee
belts it's impossible to keep ALL of them at the same tension. The
loosest of them would slip and there was a definite pong of hot rubber
after every flight.

Eh? I can't visualize it. Either all, or none, slip.

I must admit that I am having a little trouble visualizing this one as
well--unless that loosest belt was either the farthest from the engine or
the farthest from the prop. In those cases, I have no trouble at all.

Peter