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NoBozo · 10-31-2011, 10:30 AM

This is what I was afraid of. However, that cap doesn't look like something that someone added to keep the prop in place on a foundation on the lawn. That cap looks like it's "Original" to the prop. I have NO Idea what that cap is about....ie..how that cap assembly would hold the prop on to a shaft...but I'll take a guess in a moment.

There are only two (normal) scenarios as to how a prop is retained on a "Straight Inboard" shaft.*** The shaft has a "Taper"..and the prop bore has a "Taper" that mates with the shaft. There would also be a "Key" to prevent the prop from rotating relative to the shaft. Then..there would be a BIG Nut and cotter pin on the externally threaded end of the shaft to keep the nut from unscrewing, and the prop from sliding off the shaft.

The other scenario would be the same..Except..the shaft, AND prop bore would be straight. I'm going to make an educated guess that this prop bore is straight..because cutting a tapered bore would have been more difficult in those days than today. If a rough taper or straight bore would have been cast into the hub when the prop was made....then it would still have to be finish machined/reamed.

A Third scenario: The Cap, and relatively small hex head "bolt" in the picture may have been threaded directly into the center/end of the prop shaft. The two square "Nubs" may be some sort of tapered keys that were driven in to prevent prop..or the hex bolt from backing off, and/or prevent rotation on the shaft. This would likely be a straight bore.

SO: In any case, I think this would imply that there is a broken shaft STUB in the bore. I'm not familiar with this method of retaining the prop on a shaft, but I think it would work and perhaps that is how it was done..Back Then.

BTW: Screw propellers came into use elsewhere, in about 1843.

I may have to take ride down to Mystic Seaport and have another look at the propeller and fastening method on Nellie. Nellie was donated to the museum in 1956..and May ....have a modern prop.

NB

NOTE*** Modern outboards and outdrives have straight "splined" shafts and prop hubs.

EDIT: Looking back at RGs pictures of Nellie, the prop looks like a fairly modern prop with a double nut ..(no cotter pin needed) holding it on..just like it would be today.

10-31-2011, 10:30 AM	#26
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	This is what I was afraid of. However, that cap doesn't look like something that someone added to keep the prop in place on a foundation on the lawn. That cap looks like it's "Original" to the prop. I have NO Idea what that cap is about....ie..how that cap assembly would hold the prop on to a shaft...but I'll take a guess in a moment. There are only two (normal) scenarios as to how a prop is retained on a "Straight Inboard" shaft.*** The shaft has a "Taper"..and the prop bore has a "Taper" that mates with the shaft. There would also be a "Key" to prevent the prop from rotating relative to the shaft. Then..there would be a BIG Nut and cotter pin on the externally threaded end of the shaft to keep the nut from unscrewing, and the prop from sliding off the shaft. The other scenario would be the same..Except..the shaft, AND prop bore would be straight. I'm going to make an educated guess that this prop bore is straight..because cutting a tapered bore would have been more difficult in those days than today. If a rough taper or straight bore would have been cast into the hub when the prop was made....then it would still have to be finish machined/reamed. A Third scenario: The Cap, and relatively small hex head "bolt" in the picture may have been threaded directly into the center/end of the prop shaft. The two square "Nubs" may be some sort of tapered keys that were driven in to prevent prop..or the hex bolt from backing off, and/or prevent rotation on the shaft. This would likely be a straight bore. SO: In any case, I think this would imply that there is a broken shaft STUB in the bore. I'm not familiar with this method of retaining the prop on a shaft, but I think it would work and perhaps that is how it was done..Back Then. BTW: Screw propellers came into use elsewhere, in about 1843. I may have to take ride down to Mystic Seaport and have another look at the propeller and fastening method on Nellie. Nellie was donated to the museum in 1956..and May ....have a modern prop. NB NOTE* Modern outboards and outdrives have straight "splined" shafts and prop hubs. EDIT:** Looking back at RGs pictures of Nellie, the prop looks like a fairly modern prop with a double nut ..(no cotter pin needed) holding it on..just like it would be today. Last edited by NoBozo; 10-31-2011 at 01:59 PM.