Hey its my first year as a mechanical engineering student so I don't know if this is the right forum as I'm not a professional... if not redirect me to a student forum lol.

We were instructed to design a speed reducer and do simple calculations for it.

I chose to go for a bevel configuration, I guess something that looks like this but with helical teeth.

The requirements are: module of 6 mm, average tooth width must be 12 mm, shaft diameter of 12 mm and pressure angle of 20 degrees. The axes of the input and output shafts must intersect at 90 degrees (perpendicular). Also the speed ratio must be around 120.

I guess my questions is I don't get how to get a speed ratio of 120...I mean I get that I have to pick number of teeth of input/output that would give that ratio but HOW LOL. I mean from this link speed ratios for bevel gear configurations are very low so how do I achieve this? http://khkgears.net/product-category/bevel-gears/

Would I also make one of this bevel gears a planetary gear?

Also could someone explain what a pressure angle is for two perpendicular gears?

Thank you

## Comments rated to be "almost" Good Answers:

Re: Speed reducer question" by Tornado on 03/20/2017 5:24 AM (score 1)Re: Speed Reducer Question" by Rixter on 03/20/2017 8:09 AM (score 1)Re: Speed Reducer Question" by PWSlack on 03/21/2017 4:28 AM (score 1)