right now i think most pople in the USA understand thatStupidity is expensive !
right now i think most pople in the USA understand thatStupidity is expensive !
All of the above, LoLJackie, what is your occupation classification? Ship builder, Millwright etc. ?
As in any machine work, knowing exactly how to do it is paramount.How do you maintain tolerances over the length of that shaft?
I am a retired Millwright and for a shaft that long I would call that exceptional.As in any machine work, knowing exactly how to do it is paramount.
That shaft in the pictures for all purposes runs dead true. That being, you can place it between centers with a steady rest in the middle an no part on it will run out more than .003 inch.
in machinist terms, we call that……”round and truly straight”.
The coupling end of the shaft has a coupling that fits on a 1 inch in 12 inch taper per foot. We have to “blue fit” the coupling o he shaft just like the prop end.I am a retired Millwright and for a shaft that long I would call that exceptional.
View attachment 1340971how hard is for you guys to fit the cutless bearing into the strut?
That is a tight tolerance for something that big. I bet that was a lot of work dialing that in.The coupling end of the shaft has a coupling that fits on a 1 inch in 12 inch taper per foot. We have to “blue fit” the coupling o he shaft just like the prop end.
The coupling has about a 18 inch diameter flange that mates to the reduction gear. The gear manufacturer requires no more than .0015 inch run out on the face of the flange when installed.
her is a picture of the shaft coupling mated to the reduction gear.
View attachment 1341095
how funny, on my we soaked the cutless bearing in very cold media and warmed up the stru with some beat when I had to replace the cutless. mine itty bitty small cutless bearing compared to your job. way cool project for guysWe install the Thordon Rivertough Bearing by shrinking it in liquid nitrogen and slipping it into the strut barrel. The interference is around .025 inch.
the brass shell cut less bearing is pressed in with around .002 to..003 inch interference.
Jackie,
Just out of curiosity, what is the clearance/tolerance between the sleeve and composite bearing? What is the interference on the shrink fit? WH
Jackie,We install the Thordon Rivertough Bearing by shrinking it in liquid nitrogen and slipping it into the strut barrel. The interference is around .025 inch.
the brass shell cut less bearing is pressed in with around .002 to..003 inch interference.
Will, in a fresh bored hole, or a hole that is not compromised by corrosion or some other malady, we machine the OD of the composite bearing to a formula. We plug the size into the formula and it tells us what to machine the OD too. The ID comes finished to compensate for the amount of ID closer. There is also a water swell factor figured in, as the composite bearings do have a certain amount of moisture absorption.
On holes that are in “less than pristine“ condition, we get bearings that we actually glue in with a LocTite compound that is designed for this purpose. Since there is no ID closure, the bearing comes with the appropriate ID dimensions. When ordering bearings, you have to know what installation procedure you will employ.
After installation and any moisture absorption, these bearings have approx .040 to .050 running clearance over the shaft journal. The accepted life of a Thordon Rivertough Bearing used in conjunction with a NCB coated sleeve is around five years, barring any abnormal occupancies.
One of the biggest causes of premature wear or failure is the lack of free flowing water traveling through the bearing. The biggest culprit in this is getting something like a rope caught between the prop hub and the aft end of the strut barrel, blocking off the water channels. Even though it is under water, the bearing can literally burn up without the required amount of water flowing through at shaft speed.
This I not uncommon. There is often no way the crew can know if the prop had picked up something like a nylon rope that can be wrapped up between the prop hub and strut barrel.
Jackie,
Is the .025 dimension a typo error for .0025? If not I don't think anything is going to work it's way free. That would seem to be an extreme interference fit. To say the least!!
Paul