Why doesn't F1 use Top Fuel style clutches for launch?

[riff_raff]

PZ- The F-35B does use a composite driveshaft to power the lift fan.

Indeed it does. The composite drive shaft used to drive the F-35B lift fan is very high performance. The diameter of the drive shaft is partially determined by the critical speed limit required from the shaft. A light, stiff composite material works well for this application. And due to the shaft length and speed, the composite shaft is probably several pounds lighter than a steel shaft.

The composite driveshaft is connected to the lift fan clutch input flange with a set of titanium flex couplings.

[autogyro]

I posted a comprehensive answer to Riff raff's promotional descriptions of the F35B combat aircraft which I believe show it up as a failure.
My post was removed as being off topic.

[autogyro]

Lockheed are still tendering for someone to design and build them a clutch for their F35B lift system.
The clutch they are using in the aircraft at present is limited to 9 vertical take offs.
IMO it is impossible to design a clutch to achieve a better combat life in service than this.
Lockheed have been forced to change the designation of the aircraft to STOVL because of this.

Perhaps readers of this thread can suggest a way forward with this clutch design?

[riff_raff]

autogyro-

Sorry to hear some of your posts on this thread were removed. But there is some relevance with F-35B clutch to the topic of discussion. F1, Top Fuel and the F-35B lift fan clutch designs all use similar materials, are air-cooled, require minimum weight, and perform a similar function. They all serve as a variable speed coupling device capable of connecting a spinning engine output shaft to a stopped driven member and then progressively reducing slip until the engine and driven member speeds are synchronized. The only difference is the duty cycle imposed on each clutch design. The F1 clutch is very compact, does not transmit high torque, and only gets used a few times each race when starting or leaving the pit stall. The TF clutch is fairly large, transmits a large amount of torque, and typically only is used twice between servicing. The F-35B clutch is massive, absorbs huge amounts of power during engagement, is engineered to provide extremely high operational reliability, and the current clutch design has passed a 1500 cycle qualification test.

I don't know where you got that 9 vertical T/O lifecycle number from. Technically, the F-35B is a STOVL design (Short Take Off Vertical Landing) which means it rarely performs a vertical take-off. Normally it does a short rolling take off since it has a much higher GW than when it lands. Regardless, the wear on the lift fan clutch from an engagement while the aircraft is on the ground versus an engagement while the aircraft is transitioning to hover is not much different.

Going back to the question asked in the OP, both F1 and the F-35B clutches are modulated with electronic aids, while TF clutches are modulated without electronic aids. But all of these clutches perform the same basic speed synchronizing function.

[autogyro]

Sorry to hear some of your posts on this thread were removed. But there is some relevance with F-35B clutch to the topic of discussion. F1, Top Fuel and the F-35B lift fan clutch designs all use similar materials, are air-cooled, require minimum weight, and perform a similar function. They all serve as a variable speed coupling device capable of connecting a spinning engine output shaft to a stopped driven member and then progressively reducing slip until the engine and driven member speeds are synchronized. The only difference is the duty cycle imposed on each clutch design. The F1 clutch is very compact, does not transmit high torque, and only gets used a few times each race when starting or leaving the pit stall. The TF clutch is fairly large, transmits a large amount of torque, and typically only is used twice between servicing. The F-35B clutch is massive, absorbs huge amounts of power during engagement, is engineered to provide extremely high operational reliability, and the current clutch design has passed a 1500 cycle qualification test.

I don't know where you got that 9 vertical T/O lifecycle number from. Technically, the F-35B is a STOVL design (Short Take Off Vertical Landing) which means it rarely performs a vertical take-off. Normally it does a short rolling take off since it has a much higher GW than when it lands. Regardless, the wear on the lift fan clutch from an engagement while the aircraft is on the ground versus an engagement while the aircraft is transitioning to hover is not much different.

I think you do know where I got my information on the lift component lifecycles and also why I cannot quote chapter and verse.
Wear on the lift fan clutch is not only dependant on electronically modulating and balancing input to output rpm using a set input torque for testing.
It is also dependant on the capability of the clutch drive components in this case the weakest link which is the engine turbine that drives the lift fan mechanically.
To reduce load on this turbine the clutch apply has to be electronically modulated.
Either you reduce clutch plate life or you reduce engine turbine life.
Lockheed have been unable to build a lift system to achieve an operationally acceptable full load vertical take off which was the original design target for the aircraft.
This is why the F35B is now a STOVL aircraft and not as originally planned a VTOL aircraft.
Rolls Royce build the lift fan but will not allow their engine to be used in the aircraft.
Why not riff raff?

[riff_raff]

Pratt & Whitney won the production contract for the F-35 engine. RR/Allison won the contract for the lift fan and drive system. The 30,000hp lift fan is driven off the engine fan shaft, which is driven by the LP turbine stage. Most of the vertical lift in hover comes from the counter-rotating lift fan, and almost all the rest comes from the swivel nozzle on the engine exhaust. A tiny amount of lift comes from the wing tip roll control nozzle flows.

The clutch wear from a vertical TO is not that great because the relative speeds of the engine fan and lift fan at idle are not that large, the amount of torque transferred is lower, and so the amount of slip produced to synchronize the fan and engine speeds is low. The clutch wear from engaging the lift fan prior to hovering and a vertical landing, is reduced by the windmill effect of airflow passing over the lift fan helping to spin it up.

[autogyro]

Pratt & Whitney won the production contract for the F-35 engine. RR/Allison won the contract for the lift fan and drive system. The 30,000hp lift fan is driven off the engine fan shaft, which is driven by the LP turbine stage. Most of the vertical lift in hover comes from the counter-rotating lift fan, and almost all the rest comes from the swivel nozzle on the engine exhaust. A tiny amount of lift comes from the wing tip roll control nozzle flows.

The clutch wear from a vertical TO is not that great because the relative speeds of the engine fan and lift fan at idle are not that large, the amount of torque transferred is lower, and so the amount of slip produced to synchronize the fan and engine speeds is low. The clutch wear from engaging the lift fan prior to hovering and a vertical landing, is reduced by the windmill effect of airflow passing over the lift fan helping to spin it up.

A well considered response riff raff.
P and W did indeed get the contract.
The RR engine is a better engine however, although that will be difficult to prove I suspect.

Your description of the fan drive is fine, are you trying to convince us that increasing the combat payload to maximum during vertical take off places no increased load on the clutch or the turbine?
Are you saying that there is no need to slip the clutch during this flight condition?
Of course the relative speeds of the turbine and fan are going to be similar at idle!
Can you explain how the fan output thrust is modulated during a maximum payload vertical take off.
I understand the electronic control system has to vary the various component rpm to maintain flight stability.
It is of course essential to balance the lift fan thrust with the thrust from the swivel tail nozzle.
How is this done at full vertical take off payload?
Might be a bit difficult to throttle the turbine when it is at max thrust burning holes in the ground.
Yes I have seen the huge concrete pads being built for landing the thing on.

[riff_raff]

Let's compare the F-35B lift fan clutch to an F1 clutch.

When engaging the F-35B lift fan clutch prior to a vertical TO, the clutch must slip while accelerating the lift fan from 0rpm to around 13,000rpm. The lift fan is not highly loaded during this time since the airflow over the fan is regulated by the variable stator vanes in the duct. So most of the power transferred thru the clutch is used to overcome the inertia of the fan.

An F1 clutch must slip enough to synchronize an engine turning over 12,000rpm to a drivetrain starting at 0rpm. The speed increase from launch to lock-up is much smaller in the F1 clutch than the F-35B clutch. But it's the thermal energy the clutch must absorb from slipping that matters. The F1 clutch must only absorb the thermal energy from say 300-400hp over less than 1 second of slip. The F-35B clutch must absorb the thermal energy from several thousand hp over 10-15 seconds of slip.

Regardless, the operating principles of F1, Top Fuel and the F-35B clutch are all similar.

[J.A.W.]

Perhaps you would know r-r, if much R & D effort has been put into an electromagnetic clutch?

[autogyro]

I do not believe an electro magnetic clutch applied to the lift fan problem on the F35B would achieve much.
There is a way to use electro magnetic torque transfer in the design of a VTOL turbine powered combat aircraft to achieve an increased operational performance over conventional types however.
If I had even a fraction of the Lockheed budget for the failed F35, I could show you what I mean.
As things stand, that is ALL I am prepared to say.

[riff_raff]

Perhaps you would know r-r, if much R & D effort has been put into an electromagnetic clutch?

I believe the initial design for the F-35B lift fan used a wet clutch, but the final design was an air-cooled C-C clutch. If you consider the full requirements for the clutch, you'll appreciate why an air-cooled C-C clutch was selected. 13,000 rpm, 30,000 hp, extremely low weight and very high reliability rates.

[autogyro]

I believe the initial design for the F-35B lift fan used a wet clutch, but the final design was an air-cooled C-C clutch. If you consider the full requirements for the clutch, you'll appreciate why an air-cooled C-C clutch was selected. 13,000 rpm, 30,000 hp, extremely low weight and very high reliability rates.

Basically the clutch and the lift fan system is extra dead weight the aircraft has to lug around and would not even be there in a properly designed VTOL multi task combat aircraft.
Find me a budget and I will show you how.