I have some bad news. The 5:1 planetary gears I had was only rated for 3700 max rpm input, which means 740 rpm output.
The real downside was maximum output load, only 18nm (13.276 ft-lbs).
740 rpm at 13.276ft-lbs translates to 1400W shaft output from these gears. Way to small for my needs.
Yes, I know it's fairly easy to make belt reduction gears but I wan't to build a slender submerged outboard for easy use.
There is two big advantages. One is the water cooling at higher powers and the other is cushioning of noise for an enjoyable ride.
Another advantage, maybe not so important, is the weight distribution. Having the heavy duty part placed at bottom ensures
the outboard being stable in various operating conditions.
I have attached a couple of 4-blade prop designs. They are both the same except velocity, being 4m/s and 8m/s.
Can I ask you why the efficiency increases and loading drops when the pitch increases? It sounds a bit odd.
Increased pitch has more water to work against and should increase loading on the blades but it doesn't according to Javaprop?
See the attached prop files for Javaprop. The 4m/s file shows really high loading, even though it has lesser pitch and speed.
Regarding reduction gears, I have been looking around to find a supplier of parts to a DIY planetary gear (strong enough) but I haven't been lucky.
Best of all would be a gearbox made from helical gears that is virtually silent compared to regular gears. But those are even harder to find.
I might be possible to harvest a planetary gear from a scraped car but I wouldn't know what type of car to look for (with helical gears of the right size).
The outer dia of the planetary ring should be no bigger than 90mm to fit my motor design without to much hassle.
Thanks for listening to me, Jeremy