Here’s the factory type Bill
http://www.minispares.com/product/Class ... o%20search

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I wouldn't call MK 2 S gears close ratio. One more tooth on the 1st motion shaft does not a close ratio gearset make.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

All helical gears produce a side thrust in proportion to the helix angle.
Manufacturers minimise the thrust angle as far as possible so that there is always two teeth in contact with the mating gear at all times, consequently a wider gear can have a lower helix angle.
The side thrust from all of the gears in the driving gear train has to be taken by either thrust washers (laygear and drop gears) or roller bearings (main shaft and differential).
Straight cut gears have clearance just like helical gears, but there is not the same smooth transition from one tooth to the next as there is with helical, hence they make more noise.
Straight cuts are stronger because the entire tooth width is taking the load compared to a relatively short section of a helical tooth.

There is no side thrust imparted on the diff output shafts as these are driven by the parallel splines on the diff sun gears.

Hope this helps
Phil

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