THRUST MEASUREMENT
THRUST MEASUREMENT
(OP)
LS,
We have recently had a discussion about applying thrust measurement on the propellor shaft of a ship, but so far the most important things are not clear to me:
1. Why is thrust measured instead of the more common torque measurement?
2. What is the best way to measure it, and where is this kind of equipment available?
Thanks in advance,
DYV
We have recently had a discussion about applying thrust measurement on the propellor shaft of a ship, but so far the most important things are not clear to me:
1. Why is thrust measured instead of the more common torque measurement?
2. What is the best way to measure it, and where is this kind of equipment available?
Thanks in advance,
DYV





RE: THRUST MEASUREMENT
TTFN
RE: THRUST MEASUREMENT
Jeff
RE: THRUST MEASUREMENT
TTFN
RE: THRUST MEASUREMENT
That's an interesting link, but it seems to describe tank testing. I think DYV1973 was asking about taking thrust measurements from a ship at sea. I don't know if this is normally done, but it wouldn't be all that hard to do.
Jeff
RE: THRUST MEASUREMENT
It's absurdly difficult to control the conditions for such a field test, which means that the results will always be questionable. Additionally, how are you even going to control or measure the characteristics of the ship itself?
TTFN
RE: THRUST MEASUREMENT
A very cheap and possibly effective way is to use a hydraulic thrust bearing and measure the pressure in the bearing.
Cheers
Greg Locock
RE: THRUST MEASUREMENT
I suggested to him that it might be handy to monitor thrust to check for prop condition. He replied that fuel consumption and power settings soon tell you if the prop is fouled.
I like measuring bearing oil pressure, Greg, but won't that depend on where you read it. Bernoulli makes the pressure lower at larger diameters on the Michel bearing if I remember correctly.
Jeff
RE: THRUST MEASUREMENT
RE: THRUST MEASUREMENT
David
RE: THRUST MEASUREMENT
But that seems to me to be a very small error, as there is no significant axial motion in the shaft.
Cheers
Greg Locock
RE: THRUST MEASUREMENT
I have recently heard of thrust measurement with load cells for POD propulsion systems. Why is thrust measured in a POD, but not on a "normal" (pitch) propeller shaft?
DYV
RE: THRUST MEASUREMENT
Don't overlook the fact that the foundations cannot be assumed infinitely stiff, so you're going to have some frequency dependence in your load measurement. We went to the expense of modelling the entire reduction gear and local structure and decided that the foundations were not much stiffer than the shaft itself.
I'm a proponent of shaft torque measurements to be used to optimize engine operations - at least in smaller high speed diesel plants. I haven't considered the benefits - if any - for large slow speed diesel installations.