G: Gearbox (Twin) Gear Teeth

[ogrilp400]

Dear All,
I have just spent two hours attempting to get a gearbox together and turning. Fitting the cover plate causing it to bind up and be notchy. Refering to probably the least used page in the spares list, MO12.
I have always found that pairs of gears in a gearbox add up to the same number. Not so with a Vincent box it seems. The gear A, G6/1 I have fixed to the main shaft has 19 teeth. This is paired with gear B, G7 29 teeth on the lay shaft adding up to 48 teeth. How come all the other options for A G6 are 18 teeth paired with the same B G7 adding up to 47 teeth? Note that gear pair E and H are 27 and 20 teeth adding up to 47. Going by the table again the center two pairs of gears are mismatched as well.

Phelps.

 

[Vincent Brake]

dont add them up, its to no use at all, just take it apart, hold both axles in hand with gears, and you quickly see if one set is un machted.
btw, the book info is OK

 

[chankly bore]

See "Know thy Beast" chapter12, "Ratios and Gear Pinions". As you know, I'm no mechanic, but this section of the book suggests that a smaller number of teeth were cut at the same diameter {P.C.D.?) on gear G8. If someone tried a reverse trick without adequate forethought there could be "trooble at Mill". You would need to check you gear G6/1 for tooth form and working diameter, then go looking for more tricky dramas, such as deviant shaft and misaligned bearing registers. Also worth checking that the gears appear genuine. Just my two cents worth.

 

[BigEd]

You might also check MO16 to see if you have washers/spacers in the right places.

 

[ogrilp400]

Yes Ed all the spacers are in their correct positions. Yes Charlie, I'm begining to think that the G6/1 gear is the problem in that it is incorrectly made. Putting just G6/1 and its mate G7 in the box on their shafts and the binding nothiness is there. Leaving one out and fitting up all the other gears and all is good.

 

[tatty500]

Further to what Mr C Bore said about reading KTB Ch12, it does say there: " The spares list also gives details of a Close Ratio box giving higher ratios all round, but as far as is known, the pinions have never been available."
Your G6/1 is one of these so perhaps there was always a problem that needed hand fettling.
Tatty

 

[van drenth]

Put the cam plate in the correct position.

 

[ogrilp400]

Put the cam plate in the correct position.

? The cam plate doesn't control gears G6 and G7

 

[john998]

Hello, make sure the layshaft is the correct way round , if it is reversed the box will stiffen up when the cover is bolted up. John.

 

[vibrac]

Yes that almost mirror image layshaft is a real show stopper