Burman Mainshaft

[Marvel]

Does anyone have a drawing of the mainshaft for a Series A Comet Burman gearbox? I want to make sure the one I’ve got is for a Series A so only need the relevant dimensions. Thanks.

 

[A_HRD]

Hi Marvel

According to my research over the years, starting from the clutch splines end, 'A' Comet/Meteor lengths are as follows (+/- 1/64"):

A. Thread Length (5/8" x 20tpi): 9/16"
B. Spline Length: 3/4"
C. "Collar" length: 3/16"
D. Thick Diameter (0.9325') - Overall Length: 6-29/32"- of which Spline Length is 4".
E. Smaller Diameter (20mm/0.7874') - Overall Length: 2-13/32" - of which spline length is 3/4".
F. Thread Length: 5/16" (varies - not critical). Thread is usually 1/2 x 20 Pre-War; 5/8 x 20tpi Post-War.
G. Finally, you should have a 9/32" hole right through the shaft!

That should give you an overall length of about 11-1/8".

Guess what:
TTC/TTR are different - if a close ratio box is fitted.
'A' Twins are different again.
Post-War B/C Comets are different again again - as are Ariels and Panthers etc.

I think Mr Burman was out to confuse everyone; he's still succeeding to this day!

Peter B
Series 'A' Joint Section Organiser

 

[Marvel]

Thanks for the detailed reply. This and the drawing will allow me to identify whether the mainshaft I have is Series A.