Metric thread

jackie schmidt said:
There are designs that do feature a hydraulic installation, and removal. They are keyless. The only draw back is if, for some reason, the fit will not hold the pressure, and you can't pump it up.
The vast majority of large props are on a tapered fit, either 1-12 or 1-16, with a key. It is held secure on the taper by means of a large nut.
For instance, a typical 8 inch diameter shaft will have a taper fit that is 18 inches long, 1-12 taper, or "one inch taper to the foot", with a 2 inch wide keyseat. The thread that is used to secure the prop will be in the vacinity of 5 inch diameter, 4 tpi, 6 inches long. Shafts under 6 inch diameter will have a taper that is 1-16, or "3/4 inch taper to the foot".
Installation for most is hammering the nut up as tight as possible, (20 pound sledge hammer on a big slugging wrench), and then heating the prop hub up to about 300 degrees, and re-hammering the nut. After it cools, the slug the nut again, and lock it with a welded strap.
To get them off, they heat them, and use a big 100 ton jack with a "strong back", and pull bolts in the hub to apply the tonnage. Or, at least that is the correct way. If the pull bolt holes are all messed up, or the jack is in the shop, or the crew just doesn't feel like dragging it all out, (this IS a shipyard), they just heat the prop up, and "beat it till it bleeds". Crude, but affective.........jackie
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The Rolls Royce thruster props I've removed have a hydraulic removal system that's quite effective. They have double o-rings with a test port between them you test as part of the installation procedure, before torquing the keeper hub. Apparently, on large ships, when the hydraulics fail they use explosives (det cord) to remove them. :eek: I've never seen this, but it is supposed to work well.
 
Ben

It just so happens that Baumann Prop Shop brought two Rolls Royce Thruster props by our shop about a month ago, along with a main shaft out of the thruster. They were about 8 ft in diameter. It seems they had to do a lot of pitch work on the blades, and the subsequent moving of all that metal warped the bores to where they did not fit the tapers with a sufficient blue fit. They wanted us to re-fit them.
We re-fit the wheels, and the Rolls Rep tested the hydraulic installation and removal in our shop. They lost almost 3/16 of draw, but still were within the limits of position on the shaft.
This is pretty expensive stuff. The only vessels that use them in our area are the Harbor Tugs. Their infinite manuverability allows them to handle ships with greater efficiency. Of course, the big draw back is they do not tolerate much abuse, like getting big two inch steel cables wound up in the Kort nozzle and wheel, or backing into the bank. Lots of expensive parts can become scrap in a second..........jackie
 
jackie schmidt said:
It just so happens that Baumann Prop Shop brought two Rolls Royce Thruster props by our shop about a month ago, along with a main shaft out of the thruster. They were about 8 ft in diameter. It seems they had to do a lot of pitch work on the blades, and the subsequent moving of all that metal warped the bores to where they did not fit the tapers with a sufficient blue fit. They wanted us to re-fit them.
We re-fit the wheels, and the Rolls Rep tested the hydraulic installation and removal in our shop. They lost almost 3/16 of draw, but still were within the limits of position on the shaft.
This is pretty expensive stuff. The only vessels that use them in our area are the Harbor Tugs. Their infinite manuverability allows them to handle ships with greater efficiency. Of course, the big draw back is they do not tolerate much abuse, like getting big two inch steel cables wound up in the Kort nozzle and wheel, or backing into the bank. Lots of expensive parts can become scrap in a second..........jackie
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And the good news is, the way the oilfield is going right now, the guy behind the wheel probably couldn't get a job at McDonalds. :(
 
Wow ! This metric thread thing really blew up.
Here in Australia we converted to metric over thirty years ago and we still have those stupid tape measures and verniers with metric on one side and imperial on the other. We also have an older generation to whom metric is incomprehensible, and a younger who only ever learned and understand metric. I, thankfully was at school in the change over time and learned in both. Fact is everything old stayed imperial, and most new things went metric. So you must learn to work in both,as neither ever goes away,and being versatile is always usefull to everyone no matter how old or young.
Common here for people to ask for such things as a piece of 1 inch pipe 2 meter's long. Or a kilogram of 3 inch nails. We have cup head bolts with a whitworth thread, sold as 4 - 4 1/2 - 5 inch ect long and the spanner to fit the nuts is 1/2 inch diam bolt- 18 mm 3/8 - 15 mm 5/16 - 13 mm .
Work that out.
 
I was of that generation that learned both as well here in the US in the 70's/80's. it has helped me alot. I really don't care either way except for the simple fact I don't want to be like the rest of the world. next thing you know we'll be paying with euros.:eek:
 
that is true. sad but true:(
we just got a shipment of shackles in and had to cut every one of em up because they said china on em and there was a safety bulletin on some breaking
 
blunt shooter said:
Wow ! This metric thread thing really blew up.
Here in Australia we converted to metric over thirty years ago and we still have those stupid tape measures and verniers with metric on one side and imperial on the other. .
Work that out.
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You folks in Australia gave up your guns too, apparently without a fight. That worries me about America. I'm afraid most people here would just give their guns up too as long as they got to watch American Idol, Despriate Housewives or some stupid reality TV show.
 
damn

JerrySharrett said:
You folks in Australia gave up your guns too, apparently without a fight. That worries me about America. I'm afraid most people here would just give their guns up too as long as they got to watch American Idol, Despriate Housewives or some stupid reality TV show.
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Right, we didn't fight too well
Living in the lucky country we are generally known as an apathetic mob.
Not seeing a threat we were under organised, not unified and small. We got sucker punched, started to fight late and wounded. The wedge was in and getting hammered. Take a lesson.

I see a lot of political comment on these forums, Obama this, Hillary that,distractions. Fellow shooters keep your eyes on the thin edge of the wedge. If it goes in hammering works,if not, all the hammering does you the honest shooter no harm.:eek:
 
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