brakehorsepower.net

In current HTPs it is now necessary to specify the No. of teeth on any Final Drive ratio's adopted.

From Hom. Form 37 (Plus 4 1961) it references the following options:

3.73 (No. of teeth 11/41)
4.1 (No. of teeth not specified but known to be 9/37)
2.8 (No. of teeth not specified)

From Hom. Form 64 (Plus 4 Super Sports) it references the following options:

3.73 (No. of teeth 11/41)
4.1 (No. of teeth not specified but known to be 9/37)
3.56 (No. of teeth not specified)
2.8 (No. of teeth not specified)

Does anyone know the No. of teeth for the 2.8 and 3.56 ratios?

Thanks,

Simon

Hi simon

Good question, and yes, fia 37 and 64 don't help. Cjl..I believe, just copied the factory's efforts from 37 into 64!

The 11 in 11/41 is the number of teeth on the pinion (drive) gear, 41 is the number of teeth on the ring (driven/crown wheel) gear. The axle ratio is then 41 divided by 11. This gives 3.727 or 3.73.

D'you think I knew that? No!...the wonders of Google.

You can therefore hazard a guess to what 2.8 is. I would go for pinion gear of at least 11, perhaps 12, giving ring gear of 31 or 34. You can play about with ratios to see which two numbers become closest........28 and 10 work!!!!!!

Not sure this helps too much. But good question.

Billy bellinger would know!

Cheers

John

Thanks John.

Just so this topic isn't left just hanging I do now have some teeth numbers. Unfortunately, for a new HTP it's not just a case of specifying numbers that would correlate with the specified ratio. There must also be period supporting evidence that the combinations are valid. I will update again once I have looked into this aspect further. So for now, my understanding is that the ratios of 3.73 (11/41) and 4.1 (9/37) are accepted by the FIA.

Simon