Steam engine speed terms

[Philjoe5]

I'm getting near the end of finishing a reversing marine steam engine. It's Ray HasBrouck's #10. It has four positions for the valve settings in both forward and reverse. What are the official terms for the four settings?

Many thanks,
Phil

 

[steamer]

full astern


2 linked up ahead



full ahead



That's my guess....you generally never have a need to link up in astern....
Ray was a very practical man.

Dave

 

[Maryak]

full astern


2 linked up ahead



full ahead



That's my guess....you generally never have a need to link up in astern....
Ray was a very practical man.

Dave

In Marine engines, using Stephensons link, the links are arranged so that when going astern the linking up mechanism is vertical to the link shaft so no adjustment is possible and the engine is operating line in line.

OK so what does that mean. ???

Linking in - This is is when the cut off of steam to the cylinder is made earlier and the steam expands for a greater portion of the stroke. More economy, less power

Line in Line. The point where the eccentric rod is directly in line with the valve rod. i.e. the design position of the mechanism. Where top and bottom lap and lead equal the design parameters between the valve and the cylinder steam ports.

Linking out - This is when the cut off of steam to the cylinder is made later and the steam expands for a smaller portion of the stroke. More power, less economy.

The general idea is to get each cylinder to do an equal amount of work on each stroke. e.g. in a 3 cyl triple expansion engine of 900 HP each cylinder should indicate 300 HP, (150 up and 150 down). Running ahead.

Finally, as you don't normally bop around flat out, these settings are usually refined for economical cruising speed. Say 90-100 out of a possible 140 rpm. This is for a typical merchant / passenger ship. All this changes with a warship where shaft speeds are generally higher and economy is intrinsically lower. Still it was fun playing around if ever they stayed at one speed for long enough.

Hope this helps

Best Regards
Bob

Hope this helps

 

[Philjoe5]

Thanks Bob, Dave

Now some ship's telegraphs have 4 positions (more or less) in each direction denoting ship speed:
• Full Ahead
• Half Ahead
• Slow Ahead
• Dead Slow Ahead

So I assume there is an appropriate connection with these positions and those indicating engine speed.

So linking out = full ahead?

Phil

 

[terrywerm]

I am thinking that the OP's question is relating to four positions of the crank that are used for setting the valves. Such as TDC, BDC, etc.

If my assumption is correct, then there are no official names that I can think of other than the two for Top Dead Center and Bottom Dead Center. The other two positions would be at 90 degrees in between the dead centers, correct? And I can't think of names for those two positions.

Anybody else??

 

[rhankey]

I agree with Terry in that I think we might be answering the wrong question, and that the question really relates to cycle of the valves to that of the piston stroke.

In somewhat simplistic terms, I can think this is what the OP is asking about for a single acting (or the top half of a double acting) engine:

• Input - feeding steam/compressed air to the cylinder to power the piston. This will start around TDC and end a little bit before BDC
• Transition form input to exhaust - around the bottom of the piston stroke
• Exhaust - let the consumed steam/compressed air out of the cylinder. This will start around BDC and end a little bore TDC
• Transition from exhaust to input - around the top of the piston stroke

In a double acting engine, the top and bottom half of the cylinder will be 180deg out of phase with one another, in that while the top half is accepting incoming steam/air, the bottom half will be exhausting.

Robin

 

[Maryak]

Thanks Bob, Dave

Now some ship's telegraphs have 4 positions (more or less) in each direction denoting ship speed:
• Full Ahead
• Half Ahead
• Slow Ahead
• Dead Slow Ahead

So I assume there is an appropriate connection with these positions and those indicating engine speed.

So linking out = full ahead?

Phil

OK

Dead slow is a set No. of RPM as is Slow.

On a typical recip DS = 25, S = 40.

Half is the speed at which the RPM telegraph is set; anywhere between >40 and around 120.


Full Ahead or Astern is an emergency order and means give it heaps, (as fast as you can swing the links and spin the throttle open). Nobody is the slightest bit interested in fiddling with the linkage. There is a passing curiosity as to why, and will we have a hole appearing right where we don't need one. There is always a considerable pucker factor associated with a Full.

Some merchant ships bop along at Full Ahead and have no RPM telegraph so again it's a pre-ordained number, usually that which I previously called economical cruising speed. Linking out may be required on either the IP or LP cylinders for balance. Other than for post refit full power trials, I personally have not seen an engine with the HP linked out. In this case Half Ahead is the same as Half Astern at 60 RPM. To give the emergency ahead signal, a double ring is employed, i.e. the telegraph is moved from and to the full position 2 times.

Whew, I hope that has covered it.

Best Regards
Bob

 

[Philjoe5]

Thanks for the explanations guys. I have it now!

Phil

 

[Maryak]

I just remembered that the USN has even more on their telegraphs:

Stop
Slow
1/3
Half
2/3
Full.

(At least that's how I remember it)

We changed them to the British system before we had to try and figure it out, perhaps one of our US members could explain.

Best Regards
Bob