BA Mainshafts Interchangeability?

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paul.wirdnam
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BA Mainshafts Interchangeability?

Postby paul.wirdnam » Fri Jan 10, 2020 2:03 pm

Quick question:

Are the early short splined mainshafts interchangeable with the later long splined ones? I know the clutch centres are different: the later one has the internal boss to cater for the long splines on the mainshaft, but apart from that, can I use either?
Paul

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paul.jameson
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Re: BA Mainshafts Interchangeability?

Postby paul.jameson » Fri Jan 10, 2020 8:58 pm

Quick answer - No.

Long answer. When Burman did the 1948 redesign which gave the long splines for the clutch centre, they also put a top hat bush into some of the gears which had previously had a plain bush. The top bit of the top hat meant that the spine lengths on the mainshaft had to be altered (shortened, as far as I remember). You can change the mainshaft and everything will work just fine, until you get to the point where the shaft and gear have gone to the wrong end of the travel now available to them. At this point, you are able to engage two gears simultaneously which leads to the inevitable loss of teeth from at least one gear. Depending on your luck that day, the newly freed gear teeth may, or may not, see fit to lodge between other gears, thereby removing even more teeth from more gears.

I discovered this the hard way, around 1988, if memory serves me correctly.
Paul Jameson
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.

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paul.wirdnam
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Re: BA Mainshafts Interchangeability?

Postby paul.wirdnam » Sat Jan 11, 2020 7:18 am

Thanks Paul...I'm glad I checked.
Paul


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