Gear Set Choice

[jtaphorn]

If one has two gear sets of similar ratio but different teeth count, what is the advantage/disadvantage of employing one over the other? Do more teeth reduce loading on the tooth, improve gear mesh, affect noise, wear, etc?

[scotty82]

Actually there will be a small strength difference . The ratio with the less teeth will have a little more material in the tooth

[Lotus7]

Actually there will be a small strength difference . The ratio with the less teeth will have a little more material in the tooth

... and the set with the lower tooth count will be slightly noisier (who cares), while in theory the higher tooth count set will be slightly more efficient in power transfer due to the higher contact ratio.

[Robert J. Alder]

If one has two gear sets of similar ratio but different teeth count, . . .

As an example???

[TimH]

As an example???

I've seen 24:24 25:25 and 26:26. Also a couple different 1.50 ratios.

[jtaphorn]

I appreciate the insights and Tim for providing a few examples.

Actually, I stumble upon very similar ratios with different teeth counts on this forum frequently. I always check gear sets offered for sale against my personal inventory and noticed the discrepancy.

In my F2000 application where the cars are less powerful and not really stressing the Hewland, better power transfer would be the priority over tooth strength and noise. Thus, the more teeth to accomplish the ratio the better, everything else being the same.

Good to know

[gerhard_k]

As an example???

Back in the late 60's when I was racing Formula B, as the twincams started getting more hp (175 "claimed" for the hotshot 1968 BRM Phase IV), we started breaking gears in the Hewland MK4, so even though we hated abandoning our nice full set of MK4 ratios, we changed to a MK5, which uses a larger shaft and gears with coarser teeth all around - even though the gears are no larger than the MK4 since the shaft-to-shaft spacing is the same.

As an example, WRD lists MK5 gear-sets of 25:26 (what I would call a "MK4-type") and 18:19 (a "true" MK5 set), with nearly identical overall ratio. The 18:19 would be expected to be a good bit stronger.