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COMSUBBBS
Posts: 2672
Location: New Jersey | Subject: Question for enginmen...
Over the years, after I got out of the navy and began participating on these BBS's, I heard about "airless" starts of our engines, which were Fairbanks. Never having been involved in one of these evolution's, I am interested in finding in how to do one. I understand it has something to do with reversing the generators??
Has anyone been involved an airless start?
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COMSUBBBS
Posts: 3669
Location: Kansas City Missouri | Subject: RE: Question for enginmen...
Um, might you be thinking of an airless surface? Wasn't an EN, but, pretty sure an internal combustion engine needs air to operate.
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COMSUBBBS
Posts: 6180
Location: Summerville, SC | Subject: RE: Question for enginmen...
Having been involved in a number of them it's a simple but dangerous operation. The generator was energized like a electric starter. As soon as the engine turned over you engaged the fuel rack and as soon as the engine fired the generator was deenergized. If not done correctly you'd wind up with a slipped vertical drive or a broken crank shaft or a ruined generator.
Never had any experience with GM's doing this. |
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COMSUBBBS
Posts: 2672
Location: New Jersey | Subject: RE: Question for enginmen...
Thanks Ralph. I thought it had something to do with the generators. Sounds like I’m glad I never was involved with it. |
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Senior Crew
Posts: 183
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What were the conditions when this might be done and why would it be done> |
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Plankowner
Posts: 9165
Location: Upper lefthand corner of the map. | Subject: RE: Question for enginmen...
Let me see if I can dredge up so long unused memories.
Diesels were started using, I think, 600# air. In the event no air was available this would be a means of starting one.
From what some others have just said it seems like it would be a risky business to practice due to the chance of damage to equipment.
I have no memory of this even being talked about for our lone auxiliary. During quals we were taught and used the air start procedure only. |
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Historian
Posts: 190
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If the air banks are depleted enough so engine air starting pressure/volume cannot be provided the engine must be started by an airless start.
An airless start is done by energizing the generator as a motor to spin the engine for starting.
The energizing voltage/current is supplied from one of three places.
1. The main motor spinning and acting as a generator. Boat comes up to some relatively fast speed. The motor lever is shifted to stop and the motor continues to spin driven by the screw moving through the water.
2. Another generator with a running engine.
3. The battery
All three methods require interlocks being defeated/bypassed, for example the interlock that prevents a dead generator (not running) being attached to the motor bus. There are others. Defeating these interlocks is in direct violation of BuShips and/or NavSea instructions. Thus the operation needs Captains approval and he is liable to answer for the violation.
I remember discussing and rehearsing the operation of airless starts and being asked as a Senior Controllerman qualification question to describe the procedure. However that was 50 years ago and that part of my mental notebooks seems to be deficient in details.
I would refer a person who wants to figure it out to go to HNSA website, look in the fleet submarine manual, electrical section and wade through the interlock portion of the cubicle discussion.
The airless start has been done and is possible however, the chance of killing a generator, motor, cubicle section or all three is not insignificant.
Be Well
Oldsubs |
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Master and Commander
Posts: 2490
Location: East Coast of Wisconsin | Subject: RE: Question for enginmen...
As matter of fact. Did several. The thing starts with going ahead on one screw while dragging the other. It spun because of the travel through the water. The electricians did their magic and put a field on the spinning motor making a generator out of it. It then fed the juice to the generator and spun the engine for a start. As the engineman on watch I only had to pull the throttle to the full fuel position same as I would have done on a regular start. When the turns were up the EMs did their thing and we were generating.
A variation was done by just motorizing the generator from the battery without involving a main motor.
The practice was stopped when at least one boat broke the elastic coupling which was part of the crankshaft gear meshing with the rest of the gear train. The sairless start flexed the spring packs in the opposite direction. Didn't have that problem on a Fairbanks, I don't think. Thanks for the opportunity to stand another watch in the FER. Grins. I'll see if I can Google the elastic coupling on the Jimmy.
This from Google. Two models of GM main engines are found in fleet type submarines today, Model 16-248 and Model 16-278A. The former ... In the following chapters all references are based on the current Model 16-278A. Important ..... The connection between the crankshaft and the main generator is by means of an elastic coupling.
Edited by Holland Club 2018-04-08 12:13 PM
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Master and Commander
Posts: 2490
Location: East Coast of Wisconsin | Subject: RE: Question for enginmen...
Like most Navy drills. A what if thing. We never lacked for air to spin the engines but I guess it was possible. In case you are interested. There was an air admit valve operated by the camshaft on 8 cylinders to admit air inside the cylinders.. This drove the piston down spinning the engine for a start. Only needed to add fuel via the throttle and you were off to the races. |
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COMSUBBBS
Posts: 3669
Location: Kansas City Missouri | Subject: RE: Question for enginmen...
Ain't it great to be able to learn stuff you thought you knew only to not know you didn't know what you thought you knew? Only took 45 years....dang! |
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Master and Commander
Posts: 2490
Location: East Coast of Wisconsin | Subject: RE: Question for enginmen...
Yep another operation practiced numerous times. Going ahead maybe full and put full rise on the planes. COW had vents open( we normally ran with Ballast tank flood ports open). When the boat popped up, the water was free to drain out of the ballast tanks. As the boat settled down, the COW shut the vents capturing the air in the ballast tanks. All that was left was to start the LP blower to finish the job.
Also did this as HP air manifold operator a few times.
Now sign off my quallie card for airless start and airless surface.
We used to get into all sorts of stuff when we ran as school boat on occasion and PCO training boat. Most of the time we were out there but once in a while we operated out of NL on weekly ops.
Edited by Holland Club 2018-04-08 8:18 PM
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Question for enginmen...
