Hi all,
I‘ve often wondered why British twins only have two main bearings.
Any motor car engine with any pretensions of performance or quality is equiped with a main bearing between every cylinder.
It therefore has always struck me as odd that British twins that are high performance engines that also battle with crankshaft flex, don’t have a centre bearing.
From a non expert‘s point of view the addition of a centre slipper bearing doesn’t seem all that difficult, Tridents and R3s have simple and effective plain bearings on the inner journals.
As to whether you would have a ‘master crankcase‘ with the middle bearing incorporated into it or have both cases with half a main bearing support, I do not know but it just doesn’t seem that hard.
Surely a middle support on the crank would reduce flex that we know was the nemesis of the Combat, reduce vibration and contribute to a smoother longer lifed bike?
I believe I might have seen on this forum a wildly modified Norton engine with a centre bearing but know nothing more of it.
Obviously the designers of our British bikes must have considered the possibility and deemed it not worth while but thinking it must have a lot of ‘pros’ I wonder what the ‘cons’ were. Surely the fact that Turner didn’t include it in his twin or Hopwood in Norton’s original design didn’t mean it couldn’t have been added at a later stage when the limits of the original layout were being reached?
regards
Alan
I‘ve often wondered why British twins only have two main bearings.
Any motor car engine with any pretensions of performance or quality is equiped with a main bearing between every cylinder.
It therefore has always struck me as odd that British twins that are high performance engines that also battle with crankshaft flex, don’t have a centre bearing.
From a non expert‘s point of view the addition of a centre slipper bearing doesn’t seem all that difficult, Tridents and R3s have simple and effective plain bearings on the inner journals.
As to whether you would have a ‘master crankcase‘ with the middle bearing incorporated into it or have both cases with half a main bearing support, I do not know but it just doesn’t seem that hard.
Surely a middle support on the crank would reduce flex that we know was the nemesis of the Combat, reduce vibration and contribute to a smoother longer lifed bike?
I believe I might have seen on this forum a wildly modified Norton engine with a centre bearing but know nothing more of it.
Obviously the designers of our British bikes must have considered the possibility and deemed it not worth while but thinking it must have a lot of ‘pros’ I wonder what the ‘cons’ were. Surely the fact that Turner didn’t include it in his twin or Hopwood in Norton’s original design didn’t mean it couldn’t have been added at a later stage when the limits of the original layout were being reached?
regards
Alan
