I guess you call this homework?

BUT It isn't my home work.

A friend Emailed me this and asked if I knew how to work it out.

Th answer was no - do any one help - No teaching involved here my friend is in his 70's.

A car engine has four camshafts each supported by three journal bearings. The engine runs at a maximum of 8000rpm, and the camshafts rotate at half engine speed. Assuming the engine oil to be 40 degrees - Determine the maximum power absorbed by the camshaft bearings. Other data given below

journal bearing = 35 mm

bearing axial length = 20 mm

radial clearance = 0.018 mm

oil grade = vg32

oil density = 890kg m   ̅³̇

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Here's the maths


rickharris (author)  steveastrouk3 years ago

Thanks - you must go to work early

petrov equation is what my office copy is based on anyway, and you can follow the maths. Like I said though, it's only a very crude approximation, because the minimum film ithickness is really <<2um, only that's almost a line

rickharris (author)  steveastrouk3 years ago

Ta, Students !

Tricky, because the actual oil film in a fired engine bearing is not uniform, but highly thinned in the area of maximum pressure.

I've got all the maths at work for the power calculation: we use it all the time. Power is propotional to the viscosity x (gap/peripheral speed) ^2

rickharris (author)  steveastrouk3 years ago

Any help is appreciated

mh76dk3 years ago

Seems a common text-book example (I have no idea if the given answer is actually correct):


rickharris (author)  mh76dk3 years ago

Thanks, looks like a lazy tutor.