Chris's Build of Battleship Ohio Engine

[sid pileski]

Thank you!

Sid

[crueby]

Todays CAD tidbits added, the pistons...  The two LP piston heads are the same diameter. All four on conical shapes, hollow underneath, with rings on the rims.

[Vixen]

Hello Chris,

For someone who considers himself a 'dyed in the wool' I/C engine guy, I find this Battleship Ohio Engine blog to be fascinating reading; and your 3D CAD drawings to be both a technology revelation and also beautiful to look at.

I see from your latest CAD drawing that Ohio's crankshaft throws were arranged to be in multiples of 90 degrees to each other. You explained the modular construction of the crankshaft and base (bed) plates earlier; so the 90 degree interval is quite logical.

In exploring other four cylinder triple expansion engines' I came across this Titanic website http://www.titanicology.com/Titanica/TitanicsPrimeMover.htm  which also made for some fascinating reading. It is interesting to note not only the different location of the two LP cylinders, but a completely different timing intervals for the four cylinders. This diagram explains the Titanic's arrangement far better than I can.



I guess reduced vibration for passenger comfort was considered more important than ease of construction, or component interchangeability to simplify through life repair and maintenance in the Navy Yards.

Mike

[crueby]

Hi Mike!  I had known that some engines put the two LP cylinders at opposite ends, but had not known of the alternate crank angles, quite interesting. That web site is great reading, thanks for the link!

 

[steamer]

Hello Chris,

For someone who considers himself a 'dyed in the wool' I/C engine guy, I find this Battleship Ohio Engine blog to be fascinating reading; and your 3D CAD drawings to be both a technology revelation and also beautiful to look at.

I see from your latest CAD drawing that Ohio's crankshaft throws were arranged to be in multiples of 90 degrees to each other. You explained the modular construction of the crankshaft and base (bed) plates earlier; so the 90 degree interval is quite logical.

In exploring other four cylinder triple expansion engines' I came across this Titanic website http://www.titanicology.com/Titanica/TitanicsPrimeMover.htm  which also made for some fascinating reading. It is interesting to note not only the different location of the two LP cylinders, but a completely different timing intervals for the four cylinders. This diagram explains the Titanic's arrangement far better than I can.



I guess reduced vibration for passenger comfort was considered more important than ease of construction, or component interchangeability to simplify through life repair and maintenance in the Navy Yards.

Mike

That probably reduced the amount of pressure pulses hitting the center turbine from the LP exhaust.     I suspect it was to reduce surging of the center turbine which was fed from the 2 LP's

[crueby]

Got a start on the HP cylinder drawing, still a LOT to do on it (like adding the valve chamber, passages, top cap... ) These shapes are quite complex and there are lots of cross section views at different angles to wade through, so I can do a few sections at a time before the brain overheats.

One good thing is that the four cylinders are independent parts, not all joined up in one massive unit. That will make fabrication a bit easier later on. They will have a series of horizontal rods connecting them in the front and back, that is what those brackets with horizontal holes are for. The HP valve is a piston valve, and will be on the right in the picture. The rest of the cylinders have massive D valves with Lovekin assist valves at the top to support their weight, more on those later.

[cnr6400]

 

[Kim]

Great progress Chris!   

I'm looking forward to learning what a Lovekin assist valve is.  I tried googling it and didn't come up with anything meaningful.  I'm hear to learn!

Kim

[crueby]

Great progress Chris!   

I'm looking forward to learning what a Lovekin assist valve is.  I tried googling it and didn't come up with anything meaningful.  I'm hear to learn!

Kim

Dave pointed it out to me when I got the plans from him, I had never heard of it before either. At the top of the valve rod (valve being vertical) it goes through the top of the valve chest, like a tail rod normally does. But, rather than being enclosed to seal with the valve chest, it connects to another little piston that is open to the valve chest underneath, and open to the atmosphere above. That way, the steam pressure is pushing on the bottom of the little piston. It is sized so that pressure, at normal operating pressure of the engine, is about equal to the weight of the slide valve. That way the eccentric doesn't have to work hard to lift it. For a small engine, this is not needed. But, the slide valves on these giant engines are very large and very heavy, so they can operate over large ports for best flow to huge cylinders.

Hope that helps for now, I'll show it later on when its modelled in on the CAD engine...

[steamer]

the other interesting thing that is definitely a part of BIG engines,   the HP valve ports have stay bolts....which if you think about it for a moment, and remember that its running at 250 psi  ( locomotive pressures)  makes absolutely perfect sense....but it had me baffled as I looked at the prints at first....When I asked my Friend John Mathiews who had a British Unlimited license,   he rubbed his chin and said.  Probably stay bolts!....and the light dawned.....you have to remember the size of these things...they're enormous!

Dave

[steam guy willy]

Hi "C" interesting parts to make that you only get to model when you copy a prototype !!  and all these extra parts can be included in the brass label plate ... so good to see the progress 

Willy

[crueby]

Hi "C" interesting parts to make that you only get to model when you copy a prototype !!  and all these extra parts can be included in the brass label plate ... so good to see the progress 

Willy

Thanks Willy,
There ARE a number of the cylinder/valve housing parts that I expect will be modelled correctly on the outside, but will have to be simplified a bit on the inside, like the passages which were done for real with casting cores but which would be impossible from bar stock. Well, without a silly amount of piecing up parts, I guess. Shhhh, I won't tell if you don't!   

[crueby]

the other interesting thing that is definitely a part of BIG engines,   the HP valve ports have stay bolts....which if you think about it for a moment, and remember that its running at 250 psi  ( locomotive pressures)  makes absolutely perfect sense....but it had me baffled as I looked at the prints at first....When I asked my Friend John Mathiews who had a British Unlimited license,   he rubbed his chin and said.  Probably stay bolts!....and the light dawned.....you have to remember the size of these things...they're enormous!

Dave

Yeah, the SMALL piston is almost 3 feet across...!      My lathe would fit into the steam inlet with plenty of room to rattle around.

[crueby]

For those interested, here is the patent for the Lovekin valve discussed yesterday...

[cnr6400]