- Joined
- Dec 27, 2017
- Messages
- 340
I have always wanted to make a couple redrives for automotive / air conversions. I figured I could run some beefy spur gears to make it happen. One of the first questions that entered my mind was how to figure out just what size of gear would be a safe bet for the required torque to the prop? The next question was what kind of steel to use. I thought that perhaps some pack carburized 1018 would be a good starting point? I tried to get some information from people I knew, but none of them make gears. The only advice I got from someone was that he suggested that the mating gears be lapped together and polished so the contact surface would be as perfect as possible.
I made a quick sketch of what came to mind as a pinion gear that the crank would run. The addendum is 3.75" diameter with a 25deg pressure angle and 4 pitch. it is about two pounds worth of steel. Also, I have a gear image of a RR Merlin that would appear like they went with some hefty spur gears as well. One retired AP mentioned to me that those gear boxes that the Merlins ran would outlast the engines they were bolted to.
The only other indication I got was that perhaps people use pressure angle and the gear root cross section to calculate shear strength. Only issue is that would think that whatever answer is given from that would have to have more strength because the gears are not static.
I made a quick sketch of what came to mind as a pinion gear that the crank would run. The addendum is 3.75" diameter with a 25deg pressure angle and 4 pitch. it is about two pounds worth of steel. Also, I have a gear image of a RR Merlin that would appear like they went with some hefty spur gears as well. One retired AP mentioned to me that those gear boxes that the Merlins ran would outlast the engines they were bolted to.
The only other indication I got was that perhaps people use pressure angle and the gear root cross section to calculate shear strength. Only issue is that would think that whatever answer is given from that would have to have more strength because the gears are not static.