Need Help!- diy gearhead

[eloid]

need someone to confirm my thoughts

when designing a two stage gear box with timing blets or spurs gears
you just multiply the 2 stages or add them?

ie both stages are 3.5:1 70 teeth and 20 teeth when both stage are combined... is the gear caluation stage1 x stage2=12.25 a 12.25:1

or stage 1 + stage 2=7 a 7:1 ratio

please advise

[BobF]

multiply

[mc-motorsports]

12.25:1 is what I come up with

[eloid]

thank guy for the quick replys, has any one make a 2 stage gear box, look
for some ideas to use with a rack and pinion design.

[LazyMan]

Take a look at Greolts build.
http://www.cnczone.com/forums/showthread.php?t=28979

He made a very nice gearbox with 4:1 reduction useing 60 and 15 tooth pulleys. I designed one based on his design.