Torque and RPM relation

[bhall II]

I was gonna say, if you can't measure torque directly, then how the hell would these work?


"Energy" wrench

[jz11]

yes, try using that on a crankshaft of a running engine

and what how do you think that stick indicator works exactly? you still let the engine do the work through some sort of slip clutch - very direct way of measuring I must say

[wuzak]

Some variants of Pratt & Whitney's R-2800 were fitted with torque meters for the pilot and/or the flight engineer to monitor the engine.

[xpensive]

Gentlemen, a little something from ABB on the subject of measuring torque;

The Torductor® 500 System is primarily a torque measuring device. It measures the torque in a rotating propeller shaft, together with the shaft rpm, and it calculates the shaft power and the energy produced by the shaft

http://library.abb.com/global/scot/scot ... 1_-001.pdf

It seems that Torque-measuring is already in use in racing, most probably on the drive-shafts I would think.

[CBeck113]

I was gonna say, if you can't measure torque directly, then how the hell would these work?


"Energy" wrench

This just made my day...thank you.

[jz11]

http://miravim.org/avimlibrary/Manuals/ ... 0Guide.pdf

this is the description of the torque sensing system used in P&W 2800, essentially it is the same thing as the ABB, which I assume is piezoelectric sensor, oil pressure in one, voltage from the other, but here is a question - you have the fancy ABB torque sensor in a space between engine and clutch, you drive the it on the track and suddenly go over an oil spill and the reading of your sensor, which red for instance 200nm instantly dropped to lets say 50nm and then even negative value maybe (depending on what the driver did), how accurate and correct was this reading in regards to what torque the engine actually made?

And then - is that a direct measurement of the torque the engine or was it torque transmitted from which actual engine torque could have been derived and estimated?

[autogyro]

http://miravim.org/avimlibrary/Manuals/ ... 0Guide.pdf

this is the description of the torque sensing system used in P&W 2800, essentially it is the same thing as the ABB, which I assume is piezoelectric sensor, oil pressure in one, voltage from the other, but here is a question - you have the fancy ABB torque sensor in a space between engine and clutch, you drive the it on the track and suddenly go over an oil spill and the reading of your sensor, which red for instance 200nm instantly dropped to lets say 50nm and then even negative value maybe (depending on what the driver did), how accurate and correct was this reading in regards to what torque the engine actually made?

And then - is that a direct measurement of the torque the engine or was it torque transmitted from which actual engine torque could have been derived and estimated?

Sensors like the ABB sensor measure the 'twisting' force in the shaft or component they are fitted to.
It is then a mathematical calculation either external to the machine or built into the instrumentation that gives you a torque reading for the particular output or input you require.

[xpensive]

..., which I assume is piezoelectric sensor,...

Not at all, there are surface-mounted strain gauges, which should be obvious by the images, insensitive to contamination.

[xpensive]

A comparison between Ferrari's 3.0 12 cylinder engine's, 1979 and 1995;

1979 Tipo 015: 510 Hp at 12 500 Rpm



1995 Tipo 044: 700 Hp at 17 000 Rpm.



A 37% Power increase, while Rpm is up 36%. Power comes from speed, as Mauro Forghieri said.

[jz11]

ok, lets add resistance of the strained conductor to oil pressure and voltage of piezoelectric sensors that can accomplish the same thing, but neither of you addressed the important part of my question which was - how would you estimate absolute engine torque from the measurement of transmitted torque - which is the actual thing you are measuring here when the shaft is being twisted in either direction

and the load on the other end may not and is not constant when you talk about props or cars driving around the track, that measurement is good enough to see what just went on compared to what went on just before the last measurement, but not what is NOW and certainly not absolute torque of the engine, if you do know how, please tell

and before you go on explaining that you can calculate how much energy is required to keep the plane flying at constant speed through atmosphere and knowing the speed of the prop you can then go and calculate the load the prop makes on the engine, that is not what the measurement was there for, I assume it was there to spot a change, and react by trimming the output of the engine and fly more efficiently, but not to tell exact absolute torque the engine is producing, same thing with the ABB shaft in the car, it may give some estimates, but in order to calculate the output torque of the engine they have to know how much load was there on the other side of the shaft

and then you come to the really interesting part - all things aside, you now have a reading of 500nm on your torque indicator, what exactly does it tell you? and what can you do with it without any knowledge of time, acceleration or rotation speed? and the answer is - you come here on the forum and ask why bugatti can achieve 400km/h with its slow 6500rpm 922lb/ft engine, and me, with my fast 7000rpm 106lb/ft 4banger cannot get past 200km/h?

p.s. bhall, if you are fast enough with that energy wrench, can I employ you next time I will need to measure a torque of an engine, a V12 from early 80ties?

[xpensive]

Perhaps you should post those questions to ABB, I'm sure they will be happy to answer, as their Torductor is already in use?

Do get back to the forum with your findings!

[GitanesBlondes]

Here's another question...

Max torque and max power do not occur at the same RPM.

What causes the torque measurement to be at it's highest at a different RPM?

[TurboLag]

Because speed increase is bigger than torque drop off. Power is a result of torque and speed.

Torque characteristics are largely dictated by the volumetric efficiency of the motor. This can be altered by valve timings, lift and duration, but with a fixed cam profile like in F1 you are stuck with a compromise for a given rpm range. Generally speaking, longer duration is better suited for high rpms, the same goes for valve overlap.

Port size and profile can also be changed for a different operating range, but this is also a compromise as a bigger port will reduce gas velocity an will lead to a less efficient engine at low rpms.

[GitanesBlondes]

Because speed increase is bigger than torque drop off. Power is a result of torque and speed.

Torque characteristics are largely dictated by the volumetric efficiency of the motor. This can be altered by valve timings, lift and duration, but with a fixed cam profile like in F1 you are stuck with a compromise for a given rpm range. Generally speaking, longer duration is better suited for high rpms, the same goes for valve overlap.

Port size and profile can also be changed for a different operating range, but this is also a compromise as a bigger port will reduce gas velocity an will lead to a less efficient engine at low rpms.

Thank you!

[strad]

and once again . six pages