Originally Posted by
Onceapilot
Can I ask, does anyone have the details of how the BMEP indicator system on the Convair operated? I understand the function of the BMEP indication but, I have drawn a blank on what parameters the indicator or the system used to calculate the BMEP that was displayed. Thanks for any detail or reference.
OAP
As I said in a previous post, its really a torquemeter. The way it measures torque is the outer ringgear of the planetary gear reduction unit has helical splines around it's rim. These fit into helical splines in the nose case of the engine. the reaction to engine torque tend to shift this ring gear backward (Or is it forward?, it's been a while) opposing that axial thrust are a series of hydraulic pistons which operate off engine oil pressure from the nose case scavenge pump. there's some sort of metering mechanism so that the pistons exactly offset the axial thrust of the ring gear, and the actual measurement is of the oil pressure required in the pistons to balance that axial force, the signal from the oil pressure transducer is displayed on the BMEP gauge. As a side note, on other radial engine installations, the torque meter was calibrated in units of "Torque oil pressure" which is a more accurate description of what is actually being measured that BMEP, But again, the units are arbitrary, learn what numbers you should see for what power setting on your engine and it doesn't matter the actual units are.