Drilling Reduction Gear Foundation for Body Fit Bolts,,,,Push Boat Engine Room
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  1. #1
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    Default Drilling Reduction Gear Foundation for Body Fit Bolts,,,,Push Boat Engine Room

    We do quite a bit of this, on new installations and repair.

    Since the Reduction Gear in a vessel takes the thrust of the propeller, it is customary to install Body Fit Bolts to hold it solidly in place.

    Here is a simple setup We have employed for years. It allows me to drill and ream precision holes in which we custom fit bolts with about .001 interference fit.

    These particular bolts are for a new Reintjes 1200 HP reduction gear.

    These bolts have a .937 body with a 7/8 NF thread. I machine the bolts from 1 inch grade 8 bolts.

    The angle drill is a Ingersol Rand #3. We use a #4 and #5 for larger holes.

    To install, I just dip each bolt in Liquid Nitrogen for about 5 minutes and slip them in.

    This is just another way to accomplish a fairly difficult job in a out of the shop environment

    YouTube

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  3. #2
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    Thank you for taking the time to document this.

    I really like the liquid nitrogen trick as well.

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    I assume that the reduction gear box has the thrust bearing incorporated into the box? Is it a Kingsbury type bearing or can tapered rollers handle the thrust?

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    Thanks Jackie, as you know I've followed your post and shot BR with you for 25yrs.Some would like a thread on your 540CID engined 66 Chevelle street car or your brothers high horse powered Cadillac CTSV grocery getter.

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    Now you make me curious, how or where do you get your liquid nitrogen?

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    Quote Originally Posted by ChipSplitter View Post
    Now you make me curious, how or where do you get your liquid nitrogen?
    There's a truck.....Seriously, your LWS can get it for you (Local Welding Supply)

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    Interesting post, that generates two questions. Both of which may inadvertently reveal my lack of smarts.

    First, most of the Grade 8 stuff I see is probably case-hardened, as the center is not as tough as the outer shell. (Hardware/auto bolts, probably offshore.) When you machine away the outer part, are they still Grade 8? Or are you using bolts with a paper trail and testing behind them?

    Next: Umm, how hard are they to get back out, if needed? Or do you not know, because that's someone else's challenge?

    Nice little drill rig, too.

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    Body bound bolts....

    In the olden days (up to about 1985) they would use body bound bolts when connecting motor to compressors. This required the holes to be left undersized by about .030" then reamed in the field after being mated to the compressor flange. The number/size of bolts and the bolt circle diameter were all a function of the torque being transmitted. The bolts had clamping force and shear force at work.

    But...that was a pain, and costly, and made it hard to later fit a different motor or crankshaft. It drove the industry to dropping the body bound bolts and use loose fitted bolts....they did this by increasing the number of bolts and going to larger diameter flanges. Now, it is all clamping force. It works well and saves lots of time and money.

    img_1037.jpg

    rotor-end-view.jpg

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    Quote Originally Posted by tdmidget View Post
    I assume that the reduction gear box has the thrust bearing incorporated into the box? Is it a Kingsbury type bearing or can tapered rollers handle the thrust?
    Kingsbury thrust are primarily used in larger vessels where you have a direct direct drive, such as large Diesel engines in container ships. Also, most of your large vessels with steam turbine drives, such as nuclear aircraft carriers, use a Kingsbury Thrust.

    Smaller vessels such as inland push boats, tugs, offshore supply boats, etc use a reduction gear box with a built in roller bearing thrust. This particular gear has a 7 to 1 reduction. The engines are tier four QSK 38 Cummins rated at 1300 HP.

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    Quote Originally Posted by Chip Chester View Post
    Interesting post, that generates two questions. Both of which may inadvertently reveal my lack of smarts.

    First, most of the Grade 8 stuff I see is probably case-hardened, as the center is not as tough as the outer shell. (Hardware/auto bolts, probably offshore.) When you machine away the outer part, are they still Grade 8? Or are you using bolts with a paper trail and testing behind them?

    Next: Umm, how hard are they to get back out, if needed? Or do you not know, because that's someone else's challenge?

    Nice little drill rig, too.
    Grade 8 bolts are not case hardened. They are hardened and tempered to a specific RC to achieve the desired tension and yield strength.

    Keep in mind,the term Grade 8 is not a specific material. It is a specification. Individual manufacturers have their own proprietary alloy that they use to meet these specifications.
    Also, bolts are hardened and tempered after they are finished. Unless you are talking about very large bolts, the RC harness is pretty consistent throughout. I machined these bolts, which are about 7 inches long, from 14 inch long grade 8 bolts. You just cut the bolt to length and and use what remains.

    I first cut the bolt body to length. I then chuck each one up and machine that round end on the head. I then turn it around with the head past the chuck and center each one.

    Now, I can chuck on the round part of the head with the other end on center for turning and threading.

    I rough out the bodies to within about .015 of finish and turn the thread diameter. I then single point thread the bolts.

    After I drill and ream the holes and get the size, I set each bolt up and size the body and establish that radius relief under the head.

    Freeze and install.

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    Quote Originally Posted by JACKIE SCHMIDT View Post
    Kingsbury thrust are primarily used in larger vessels where you have a direct direct drive, such as large Diesel engines in container ships. Also, most of your large vessels with steam turbine drives, such as nuclear aircraft carriers, use a Kingsbury Thrust.

    Smaller vessels such as inland push boats, tugs, offshore supply boats, etc use a reduction gear box with a built in roller bearing thrust. This particular gear has a 7 to 1 reduction. The engines are tier four QSK 38 Cummins rated at 1300 HP.
    Learn something new here everyday.
    I thought I heard that anything with much HP was an electric drive.

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    Quote Originally Posted by GregSY View Post
    Body bound bolts....

    In the olden days (up to about 1985) they would use body bound bolts when connecting motor to compressors. This required the holes to be left undersized by about .030" then reamed in the field after being mated to the compressor flange. The number/size of bolts and the bolt circle diameter were all a function of the torque being transmitted. The bolts had clamping force and shear force at work.

    But...that was a pain, and costly, and made it hard to later fit a different motor or crankshaft. It drove the industry to dropping the body bound bolts and use loose fitted bolts....they did this by increasing the number of bolts and going to larger diameter flanges. Now, it is all clamping force. It works well and saves lots of time and money.

    img_1037.jpg

    rotor-end-view.jpg
    We went through the exact same thing in the Marine Industry. For years the reduction gear output flange and the shaft couplings all had body fit bolts. They were a royal pain to remove. The vessel owners finally had enough and asked the major manufacturers to use clearance bolts with twice the holes. Since the flanges have a male and female fit, it works just as well.

    Where it used to take shipyard a entire shift to just get the bolts out, now it can be done in 1/10 the time with a lot less hassle.

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    Kingsbury bearings, due to their thrust-ability, have a lot of losses.

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    Quote Originally Posted by GregSY View Post
    Kingsbury bearings, due to their thrust-ability, have a lot of losses.
    Huh? No more so than any fluid film bearing. They would not be used on big gas and steam turbine generators, hydro-turbines, and so on, if losses were significantly greater than other kinds of bearings.

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    Sure they do. How can they not? They are used on those pieces of equipment because they provide a function...not because anyone 'wants' to use them. They'd much rather use a 'normal' cylindrical hydrodynamic bearing, which has much lower losses. But....they need the thrust handling ability of a Kingsbury type bearing.

    KTB's are also used for their damping characteristics, at times. But regardless of why they are used, they have a lot of losses.

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    The power loss trough a properly lubricated and cooled canted pad thrust bearing is approximately .3 percent.

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    Most such applications have a separate thrust and journal bearings. There is more loss pumping oil to them than lost in the bearing itself.

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    In the Hoover Dam’s original 115,000 HP hydro Turbines, the Kingsbury Thrust Bearings have never been replaced. These bearings carry the weight of the 30 inch diameter shafts, the Francis Turbine Wheel, and the thrust generated by the transmission of power by the water acting on the turbine blades.

    It is estimated that the power loss of the Thrust Bearing is less than 350 HP.

    Before the invention of the “tilt pad” thrust bearing in the late 1800’s, the size of installations was limited by what the then available trust bearings could efficiently support.

    In today’s installations, it seems the size is almost unlimited. In the larger installations, where shaft HP exceeds 750,000, the Kingsbury Trust can me as large as 15+ ft in diameter.

    That seems large until you consider the massive weight and downward force that the bearings support.

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    With all the re-machining your doing to make the new bolts, I'm wondering why not just use 4140-ph or similar bar stock ?

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    Quote Originally Posted by JACKIE SCHMIDT View Post
    It is estimated that the power loss of the Thrust Bearing is less than 350 HP.


    I wish I had 1/10th of that lost power for my lathe!


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