Difference in genset speeds i.e. 3600/1800 rpms

[mellotango]

Can anyone explain why gasoline gensets generally run at 3600 rpms and diesel gensets at 1800 rpms? Because apparently gasoline models run at high speeds of 3600 rpm, hence they are cheaper to manufacture and lasts only half as long. I'm interested to know why diesel technology is different that it is able to achieve a lower speed of 1800 rpm and hence, last much longer? Is it simply built-in gears that lowers it from 3600 rpm to 1800 rpm? But if diesels are geared down from initial speeds of 3600 rpms, don't they still suffer the same wear and tear of a 3600 rpm gasoline genset?

Confused...

 

[anorlunda]

No. Merely using a 4 pole generator instead of 2 pole, the required speed is divided by two. No gears required.

The optimum speed for engines depend on many factors. I would not say that it is universal that gasoline engines are best at higher speeds than diesel engines.