Stage 1 is about 2, and stage 2 is about 8 (2+8)?
So, if you want to buy off shelf, then what do you do?
If you take 20mm as the face width, you would need 53, 260, 53. 260 which is way to big.
So do you up the module? or add another reduction stage?
19, 93, 19, 93 gives 40ish rpm out, but 19 gives a fw needed to be around 40mm and module 2.
So do you change the module, or just go for customer gears and get large face width?
If you up the module, you tend to get a bigger face width right?
The off shelf cat i am using only goes to 120 teeth, and thats £140, so your right about cost.
So if you use 18, 87, 18, 89 then you get 40rpm, but would need to have a face width of 36 to be within stress with hard gears using a module of 2.
So i tried a module of 3 and using 18, 87, 18, 89 everything was within limits, so i guess i have answered my question that to up the module can reduce the need for more teeth.
But again, these four gears come to £440, so been very expensive.
18 is the least number of teeth you'd want to use right, well if spur gears?
And then to get half of the ratio for doube reduction you take the squareroot of the ratio (24)? Thus 4.899 in each reduction.
18 * 4.899 gives 89 rounded up.