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Some pictures of possible interest

cme CPP machining dartmouth (6).JPG


Blade getting set up for some clean up on the bottom of the palm - need to take off about 0.004"

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Machining the hub section of the propeller. Manufacturer says it was out of spec. It measured only about 0.0008" out of round - yes 8/10ths on a seriously huge chunk of CUNIAL (Copper Nickle Aluminum) alloy.

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A very nice surface finish!

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These are the blade "carriers" and essentially will rotate with the blades to increase or decrease the pitch. By doing so the ship can go ahead or astern. Same principal as that used on air craft : CPP or controllable pitch propeller.

Pretty nice large mills and lathes.

CNC:

DSCN3395.JPG
 
Nice thread @Brent H . The scale of that place is amazing!

We visited the East coast a few years ago. Loved it. Been drinking Alexander Keith's ever since, after touring the brewery, lol

Cheers,

Shawn
 
Brent H said:
Machining the hub section of the propeller. Manufacturer says it was out of spec. It measured only about 0.0008" out of round - yes 8/10ths on a seriously huge chunk of CUNIAL (Copper Nickle Aluminum) alloy.
Click to expand...

Holy cow @Brent H !!! Although the precision is truly impressive, I can't help but think there is something wrong with anything that big having tolerances that tight. I don't know squatt about it, but it just doesn't square in my tiny little brain. Water temp variations are not zero - especially for an ice breaker - so I'm thinking the temp expansion alone for such a big part would blow that number out of the water. In fact, is the number a spec for a certain temperature? Then add strain...... It's not a static component! That thing sees several thousand HP. If I were you it would drive me crazy wondering and worrying about stuff like that. Maybe it's a good thing that I don't know squatt.....

And why the exotic alloy? Are all big ships built like that?
 
I was having trouble with the photo of that big collar as well but for a different reason....scarf/cuttings appear to be much courser than a .0008 cut would produce.
 
Hey @Susquatch, you are correct with your concerns regarding the tight tolerances. It is pretty crazy. I had a big fight with the manufacturer many years ago about the tolerances and what were the actual "wear limits" as 8/10ths over 38 years on a blade/hub assembly that beats the shite out of itself in ice is trivial. The reply was along the lines that I knew jack about machining and tolerances and that I should be "happy" the assembly lasted 35 years. I asked for the original measurements of our assembly - evidently they lost this data or they are hiding behind proprietary copy write laws etc. I call the work on the hubs (although pretty cool) a big money grab.

The CUNIAL material is specifically designed for ice breaking purposes. Strength and ductility I would say. Prop hubs differ in materials from ship to ship depending on application - Stainless, cast steel, different alloys for different applications.
 
Brent H said:
Hey @Susquatch, you are correct with your concerns regarding the tight tolerances. It is pretty crazy. I had a big fight with the manufacturer many years ago about the tolerances and what were the actual "wear limits" as 8/10ths over 38 years on a blade/hub assembly that beats the shite out of itself in ice is trivial. The reply was along the lines that I knew jack about machining and tolerances and that I should be "happy" the assembly lasted 35 years. I asked for the original measurements of our assembly - evidently they lost this data or they are hiding behind proprietary copy write laws etc. I call the work on the hubs (although pretty cool) a big money grab.

The CUNIAL material is specifically designed for ice breaking purposes. Strength and ductility I would say. Prop hubs differ in materials from ship to ship depending on application - Stainless, cast steel, different alloys for different applications.
Click to expand...

That's funny! I was actually gunna suggest a money grab but didn't want to risk offending you.

With big huge bills like that - especially partially funded by tax dollars, the markups always look reasonable to pass audit. But a 10% markup on $100 is 10x the markup on $10. So they bake up the base to pad their markup pockets! Accountants and bureaucrats don't challenge technical details. Yup, it smells like a money grab.....

Two decades ago, I served as an external member of a building committee for a new building at the local university. The base cost plus quotes were mind boggling. You should have seen the various contractors faces when they saw me sitting at the bid table. It's impossible to explain away millions of tax dollar gouging. Chewing on boot rubber really sucks....

But I doubt it's even possible to have an industry rep on a new ship purchase contract review......
 
How did they measure the out of round? On a CMM?

I know propeller hubs on aircraft have very tight tolerances. They are nowhere near the size of yours though.
 
RobinHood said:
How did they measure the out of round? On a CMM?

I know propeller hubs on aircraft have very tight tolerances. They are nowhere near the size of yours though.
Click to expand...

The CEO of Pratt & Whitney tried to embarrass me at a conference we both spoke at by comparing the extreme quality of a jumbo jet airplane to a crummy automobile. Bad move. I didn't choose to embarrass him back about sloppy seats, cheap table trays that sit at 45 degrees, or carpets that look like a 5$ motel room. Instead, I just pointed out that nobody would ever buy a car if they all started at 5 million.

But ya, to your point, an airplane engine is a different beast for sure. You can't pull over and call CAA when it stalls. Even so, there are many car parts that have extremely tight tolerances too. But it's almost never in big parts - only tiny ones.
 
@RobinHood : the original measurements were done in a pigeon infested warehouse that was open to the weather by an alcoholic that was soon to be fired by the company using an inside mic calibrated to a large outside micrometer. Just the changing weather over the course of the day would be enough to change everything, not to mention the active shite bombs from the nesting birds taking offence to the techniques being used. I suggested the measuring be completed at a certified, controlled shop....but ya see...I know jack.....

The way things are going we are being caught up in the inspections being based on OEM recommendations. Those can either be decent or they can be terrible and expensive.

On this one I just have to accept it before it destroys me as the fight is now a moot point (they have been machined) Frustrating but I may get a chunk of CUNIAL to make something neat out of :)
 
Brent H said:
Machining the hub section of the propeller. Manufacturer says it was out of spec. It measured only about 0.0008" out of round - yes 8/10ths on a seriously huge chunk of CUNIAL (Copper Nickle Aluminum) alloy.
Click to expand...

What are we looking at here @Brent H ? Looks to me like we are looking through the mounting hole for one blade through to the mounting hole for another blade. So I assume the hub we are looking at rotates with the drive shaft and the blades all rotate on those openings to change pitch.

If so, what actuates the pitch change? Do the Blades rotate pitch individually to provide differential (collective) thrust like a helicopter hub or do they all change together with thrust changing from prop assembly to assembly (port and starboard props)?

And while I'm asking dumb questions, does that lady of yours have through hull thrusters and/or underwater stabilizer wings?

If it has wings, do the pigeons identify at all?
 
Another dumb question.

Did those brain dead inspectors also dictate truing of the matching prop plates? And doesn't that all collectively increase clearance between the parts? Or is the precision all in the face?
 
Btw, there is no such thing as a professional career that doesn't have to deal with idiots from time-to-time. Your career choice still looks like a very rewarding one to me.
 
Brent - thanks for the pics, all the machines are interesting. What rpm do the props turn and what is the diameter?
 
This is AWESOME stuff! I thought touring a commercial fishing boat in Lake Erie was fun! We should all charter a plane from Vancouver to the east coast stopping at every machine shop in between so we could all go visit Brent, tour the facility, render dumb opinions, learn a lot, be entertained, embarrass Brent silly, and fill our belly with fresh seafood for a week.
 
@Susquatch

What are we looking at here @Brent H ? Looks to me like we are looking through the mounting hole for one blade through to the mounting hole for another blade. So I assume the hub we are looking at rotates with the drive shaft and the blades all rotate on those openings to change pitch.
Click to expand...

Yes, there is a large piston that is moved hydraulically back and forth. Off set pins are fitted with slipper blocks. These blocks slide back and forth in the blade carriers (the round parts with the 2 pins in the pics) and those rotate through 31.5 degrees ahead and 28 degrees astern.

The Ship has a bow thruster and stern thruster - both are a tunnel type thruster (picture a fan in a tube that can blow either side of the ship). The bow is 600 hp and the stern is 400 hp.

The clearances are in the fit between the blade carriers and the big hub holes - 2 o-rings seal the assembly. The blades are bolted to the carrier and sealed to the face of the hub with a super large viton o ring about 12 mm in diameter. there are 10 x M72 bolts to holt each blade on and those are sealed to the blade palm with dubo rings (X profile o rings).

The clearances in question were the fit of the hub hole to the round blade carrier. The new carriers all came oversized and were then machined to the fit in reference to the re-machined faces of the hub. I am hoping to get those measurements as machining to 0.005mm is pretty darn tricky.

Each prop is driven through a reduction gear box that is powered by either one or two engines. In 2 engine mode the shaft can rotate at a max RPM of 210 and see's roughly 4400 Hp. The props assembled are 4 blades and roughly 10 feet in diameter. Each blade is 1250 Kg with the assembled hub being about 8 tons.
 
Brent H said:
@Susquatch



Yes, there is a large piston that is moved hydraulically back and forth. Off set pins are fitted with slipper blocks. These blocks slide back and forth in the blade carriers (the round parts with the 2 pins in the pics) and those rotate through 31.5 degrees ahead and 28 degrees astern.

The Ship has a bow thruster and stern thruster - both are a tunnel type thruster (picture a fan in a tube that can blow either side of the ship). The bow is 600 hp and the stern is 400 hp.

The clearances are in the fit between the blade carriers and the big hub holes - 2 o-rings seal the assembly. The blades are bolted to the carrier and sealed to the face of the hub with a super large viton o ring about 12 mm in diameter. there are 10 x M72 bolts to holt each blade on and those are sealed to the blade palm with dubo rings (X profile o rings).

The clearances in question were the fit of the hub hole to the round blade carrier. The new carriers all came oversized and were then machined to the fit in reference to the re-machined faces of the hub. I am hoping to get those measurements as machining to 0.005mm is pretty darn tricky.

Each prop is driven through a reduction gear box that is powered by either one or two engines. In 2 engine mode the shaft can rotate at a max RPM of 210 and see's roughly 4400 Hp. The props assembled are 4 blades and roughly 10 feet in diameter. Each blade is 1250 Kg with the assembled hub being about 8 tons.
Click to expand...

Gotcha! Yup, I really need to go and lay an eyeball on all that! Very cool @Brent H !!! Very very cool!
 
Here is the hub Assembled on the shaft. Hopefully you can sorta see how it goes. The open space in the middle is the centre of the yoke that turns the blades and you can see the oil feed pipe in the middle. On the back side is a feed pipe that allows fluid to push the yoke out. The centre pipe you can see will allow oil out and back to the system. The pipe also acts as a feed back to the controls and will close the hydraulic supply when the desired pitch is met.
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the above picture is the end cap and has an integral piston that fits into the yoke - you can see the piston ring at the top end.
 
I still don't see any reason why such close tolerances are required.....

Also, I noticed earlier that the Blades seem to be oppositely loaded on both sides of their radial axis. I presume that's to reduce the power requirements of the variable pitch system. If so, does that Hydraulic piston really need to be that big? Regardless, I bet it moves those Blades like yesterday!

I was a guest on a naval frigate 20 years ago doing battle exercises in Lake Huron. I was amazed at how fast that ship went from full ahead to full astern! Those props of yours explain a lot! No need to stop and reverse engines...... Just keep the power full up and reverse the pitch! Gotta wonder what cavitation does to those huge Blades under those conditions!
 
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