GScholz more ont turbo props:

[hitech]

Start with the assumption like you stated that no torque is produced by jet engines: If they do, it would just go into more torque for the turbo prop, so lets assume they do not.


Lets say that the shaft is spinning at 10000rpm and 100 ft/lbs torque at the front compressor turbin.


Now when that is sent to the gear box with about a 10 to 1 speed reduction the shaft at the prop would have 1000 ft/lbs torque. This change in torque i.e. 900 ft/lbs would be transmited to the airframe thew the gear box mounts.

Do you agree?

HiTech

[g00b]

No torque would be transmitted to the airframe. Gyroscopic progression would still have an effect though.

g00b

[Roscoroo]

yes a turboprop Produceses  torque  on the mounts and airframe  but only when the Prop pitch is increased . they have a Torque staft w/ a mag pickup between the eng and gearbox that measures the torque .

i would say that most of the torque is transmitted to the shaft and turbine wheel  that drives the gearbox  and not as much on the mounts or airframe.

Remember a turbo shaft /prop engine only uses the last 1-2 stages of Turbine to drive the shaft and gearbox . the rest of the jet engine is basically a seperate enity


for a normal Jet engine very little torque is applied on the airframe . (thats why alot of the engines are hung w/ only 3 bolts )

[Casca]

A propeller powered by a turbine produces the same torque on an airframe as a propeller powered by a reciprocating engine of the same power.  The propeller does not know if it's being powered by a turbine or a recip.

In the aircraft I normally fly the actual torque produced by the propeller is used to indicate the amount of power the engine is producing (PT6-27 and PT6- 6X).  The -27 redlines at 1500 pounds feet and the -60 I think @ 3200 pounds feet.

[g00b]

Ok with the gearbox in mind I think I see how torque could be transmitted to the airframe. If there was no gearbox there would be no torque, correct?

g00b

[GScholz]

Originally posted by hitech
Start with the assumption like you stated that no torque is produced by jet engines: If they do, it would just go into more torque for the turbo prop, so lets assume they do not.


Lets say that the shaft is spinning at 10000rpm and 100 ft/lbs torque at the front compressor turbin.


Now when that is sent to the gear box with about a 10 to 1 speed reduction the shaft at the prop would have 1000 ft/lbs torque. This change in torque i.e. 900 ft/lbs would be transmited to the airframe thew the gear box mounts.

Do you agree?

HiTech

Umm ... no. Only the power lost in the gearbox would be applied to the airframe. All the torque transferred to the prop from the gearbox is not ... I think. So if the gearbox power loss is 20%, up to 20% of the torque will be transferred to the airframe.

I found this document:

http://www.swedflight.com/addons/guide_to_turboprop_aircraft.pdf


"The Gas Generator
is a jet engine that produces a high speed gas stream aimed to the Power Turbine which will then rotate and transfer this power to the Power Generator.
The two parts are not physically connected which makes it possible to start the engine with still standing propellers – actually you can hold the propeller still with bare hands for a while at start-up if you like too.

The Power Generator
is connected to the Propellers via a Propeller Gearbox – necessary as the Gas Turbine spins with a whopping 44.000 RPM and it would be a bit unhealthy to put out the generated power directly to the propeller to say the least."

Since the jet engine is simply blowing air on a windmilling turbine (like my garden hose was) I do not see how any torque is generated.

[GScholz]

Come to think of it; a conventional Sikorsky helicopter layout does not spend 50% of its power countering torque with the tail rotor. Obviously most of the engine's power is transferred directly to the main rotor, and the only torque transferred to the airframe is from the power loss in the gearbox.

Does this make sense?

[GRUNHERZ]

So Hitech are we getting the Westland Wyvern?

[Holden McGroin]

Power = RPM x 2 x pi x Torque

A spinning prop has RPM, there is power, so there is torque.

In a turbo jet, the spinning spool has a torque associated with it, the compressor section aerodynamic forces all wrapping around the rotor in a like direction.  The compressor stators all need to wrap the torsional force around the casing the opposite direction.

In the turbine section, as the combustion products force the rotors to spin, the torque wraps the rotor opposite to the wrap of the compressor.  The turbine stators wrap opposite of the compressor stators.  When the rotor achieves a constant speed, the torsional forces largely balance, leaving pure thrust.

In a fanjet where a few compressor stages act as a ducted fan, I would believe that torque would remain to be absorbed by the engine mounting.

[Angus]

Pistin engines with prop: propeller torque.
Jet engines = very very little torque.
Turboprop = propeller torque.
Helicopters: Stop of tail rotor: You're dead, whooping around the main rotor. Stop the main rotor, you're also dead.
Autogyro with a pusher propeller = some torque. Hell, I tried hopping in a thingie like this.

Right?

[GScholz]

Originally posted by Holden McGroin
Power = RPM x 2 x pi x Torque

A spinning prop has RPM, there is power, so there is torque.

In a turbo jet, the spinning spool has a torque associated with it, the compressor section aerodynamic forces all wrapping around the rotor in a like direction.  The compressor stators all need to wrap the torsional force around the casing the opposite direction.

In the turbine section, as the combustion products force the rotors to spin, the torque wraps the rotor opposite to the wrap of the compressor.  The turbine stators wrap opposite of the compressor stators.  When the rotor achieves a constant speed, the torsional forces largely balance, leaving pure thrust.

In a fanjet where a few compressor stages act as a ducted fan, I would believe that torque would remain to be absorbed by the engine mounting.

How does the torque get transfered to the engine mounting if there is no physical connection?

[Straiga]

Helicopters: Stop of tail rotor: You're dead, whooping around the main rotor

Well thats wrong. I have lost two tail rotors on two different helicopters and brought them back no problem.

The first was a S-76B, I was about 3 miles just off the number 21 oil rigg and sheared a tail rotor shaft I flew it back to the base and did a run on landing with no tail rotor. The other was a Huey 212 it also ended in a run on landing.

I can tell you that Jets and turbo props have torque assosiated with them. Jets- acceleration of mass and gyro scopic processionial torque. Turbo props-Prop torque, acceleration of mass, and gyro procession.

If there was no gearbox there would be no torque, correct?

Gear box or not there is torque.

High bypass fan jet have a rotational airflow from the bypass section and this rotational airflow creates a rotational torque.

for a normal Jet engine very little torque is applied on the airframe . (thats why alot of the engines are hung w/ only 3 bolts )

How about jet trust on the airframe is this not torque. when a engine hangs from a pylon with jet thrust present that pylon has a large torque force applied to it. Have you seen how big these bolts are? On a Be-200 there are 4 bolts an F-14 there are 12 bolts per engine. This thing about bolts doesnt wash.

Straiga

[Angus]

Holy cow, rotorless lander!
Did you autorotate? Wasn't there some turning?

[Straiga]

http://www.mcasco.com/p1rdy.html

[Holden McGroin]

Originally posted by GScholz
How does the torque get transfered to the engine mounting if there is no physical connection?

There is a physical connection.  It is thru the gas going thru the engine.  The stators in the engine are connected to the engine mount, rotors are connected to the engine shaft.  Both the stators and rotors have aerodynamic forces associated with them.

The gas being forced thru the engine aerodynamically reacts with the stators.  The stators transfer the force to the engine mount.