Big Ship Repair Job For Our Shop

[6bra1k]

Stupidity is expensive !

right now i think most pople in the USA understand that

 

[mike mccormick]

The most common failure point is always between the ears. That's what keeps repairmen in business. Good looking work ,Jackie

 

[jackieschmidt]

Jackie, what is your occupation classification? Ship builder, Millwright etc. ?

All of the above, LoL
My actual skill is a machinist, but there is very little in the Marine Industry that I don’t have a pretty good knowledge of.

Most important is my 33 1/3 % ownership of our business with my two brothers, who each own a third.

 

[jackieschmidt]

How do you maintain tolerances over the length of that shaft?

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”.

 

[Old Navy]

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”.

I am a retired Millwright and for a shaft that long I would call that exceptional.

 

[jackieschmidt]

I am a retired Millwright and for a shaft that long I would call that exceptional.

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.

 

[knguyen]

View attachment 1340971how hard is for you guys to fit the cutless bearing into the strut?

 

[Old Navy]

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

That is a tight tolerance for something that big. I bet that was a lot of work dialing that in.

 

[jackieschmidt]

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.

 

[knguyen]

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.

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 guys

 

[F Class John]

Thank you for posting this Jackie. While not firearm related I'm always drawn to your posts because I am always in awe of what you guys do there. I'm no machinist and know nothing about the industry by any measure but for better or worse at least it seems there's an ever constant flow of people keeping you in business.

 

[ronsatspokane]

Wow! the force required to create that kind of wear over that short a period of time is beyond significant. I'm surprised the vibration didn't break welds in the hull superstructure.

 

[Will Henry]

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

 

[jackieschmidt]

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

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.

 

[boltfluter]

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.

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

 

[KMart]

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.

On a job of this magnitude, what is the turn around time from when you get that frantic phone call, until you give it back to them to launch? Assuming everything goes as planned.

 

[jackieschmidt]

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

That is a typo. But it is even more.

On a bearing this size, the actual interference fit is more like .055 inch.

I know that sounds like a lot, but we machine the bearing OD to a set formula furnished by Thordon. The ID, which comes finished, takes into consideration the amount of closure when the bearing is installed, plus a factor for moisture absorption.

in the end, if you follow the guidelines, it all comes out right.

 

[Liven The Dream]

Thanks for this post, trip down memory lane for me.
As my memory tells me Cutlass Marine Bearings ?
I worked on the Chicago Subway Deep Tunnel Pumps 30 years a go.
Had those bearing made by BF Goodrich . The Pumps were made in 1927 and 1929.
Finding those bearing was some fun.

The Guy that located them made us Buy six.
Thanks for the Trip.
Don

 

[GetReal]

So....if my car starts making a funny noise, I shouldn't just push the gas pedal harder?

 

[Preacher]

Fun mornings reading this stuff !!