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Propeller rotation - important? - Yes, it is.
"JAXAshby" wrote in message ... There is also a thrust bearing needed for going in reverse as well. However, as the horsepower used in reverse is much less and the time it is used is hugely less the reverse thrust bearing need not be anywhere near as big. Now, change the prop so the former reverse thrust bearing becomes the new forward thrust bearing and operates at 100% power over extended time the potential to trash that bearing becomes very real. Either I am not following what you are saying or I am envisioning something totally different. As you said, the thrust on the shaft must be countered someplace, and that someplace is the thrust bearing(s). The thrust will either "push" or "pull", it shouldn't matter which direction the shaft is rotating. If you attempted to drive the boat by having the propeller in front, like an airplane, then the shaft will be pulling and the thrust bearing surface associated with "pull" will bear the brunt of the load. But I didn't think this is what we were talking about. I know that several models of Velvet Drive transmissions don't care which direction the input and output shafts turn, as long as they turn the same direction in "forward". You can have a Left Hand and Right Hand rotating engine turning Left Hand and Right Hand props and the transmissions don't care. If you attempted to have the Left Hand engine turn the Right Hand prop, however, then the transmission would be using the "reverse" clutch for forward which is not nearly as robust as the "forward" clutch and you would likely have reliability issues. The web page for the Hurth transmissions indicated that many of their models were capable of full engine horsepower in either "forward" or "reverse" operation. I don't know if that really means you can use them for reversing the rotation for counter rotation or not. There are many outdrive designs that has the drive shaft come down and drive two gears, one towards the front and one towards the rear. A "dog" or cone clutch will engage one gear or the other, which will make the prop shaft turn one way or the other. The clutches are identical and the thrust is carried on the shaft bearing (not the gears) so it doesn't matter if the gear more towards the front is considered "forward" or not. Rod |
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