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Thread: snagboat accumulator

  1. #21
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    Quote Originally Posted by Bguns
    I was onboard it in Everett. They had the Spuds down, and main engine set at ahead dead slow...

    Watching the connecting rods and cross slides run several feet back and forth was interesting.

    At both ends of the stroke, was a small pool of oil that a leather strap dipped in, and spread along the ways...
    Don't forget that these boats were used for a very specific purpose, and are adapted to that purpose. The helm could be tied down in this case, as the boat is going nowhere.

    The telegraph appears pretty much standard, the dual handles are for acknowledgement from the engine room. Multiple telegraphs are not uncommon as the operation from multiple locations is needed for different situations. The Titanic had three stations, and many ships had more;

    http://titanic.marconigraph.com/mgy_eotelegraphs1.html

    I believe the pointer in front of the wheel is rudder position, to prevent confusion from counting turns of the wheel. I have seen a few different variations of this on modern ships as well as sailing vessels.
    Jim H.

  2. #22
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    There are two pointers by the helm because one is commanded position and the other is actual position. The commanded position pointer moves immediately as the wheel is turned, and the actual position pointer tracks the resulting rudder movement.

    And a minor nitpick to an earlier response: a Pilot doesn't steer. He gives rudder commands to the helmsman who is actually steering. Technically (in a legal sense), he gives suggestions to the helmsman who is under orders from the Captain or the Mate on Watch to do what the Pilot says.
    I added "in a legal sense" because the ship is still technically the Watch Officer's responsibility even though he's following the Pilot's instructions.

    Quote Originally Posted by topct
    I would really like to see what is going on with those telegraphs. I am confused at this point. Nothing new.

    Valid points have been made.

    Another thing I wonder about is the indicator on the helm itself. I can see two pointers. I have seen the use of one to indicate wheel position. What might the other indicate? Actual position? Or a bow rudder?

    And why the rope to tie the wheel in place?
    Last edited by lwalker; 08-12-2009 at 11:39 AM.

  3. #23
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    My mistake, usually the pilot is aboard as a legal requirement to enter harbour waters and frequently does nothing at all, let alone actually steer. There are times they earn their keep though. In the straight of Juan de Fuca there are the Race Rocks outcrop in the shipping channel that has claimed many ships over the years. The channel is also very narrow in some places, only a hundred metres wide even though it appears to be wide open.

    And of course, the watch officer is always responsible for the vessel, and the captain is responsible for the watch officer.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  4. #24
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    Back in the early 70's I spent 2 1/2 years stationed aboard the Coast Guard Bouy tender Whitebush. She was 133' long. Engines were Direct drive direct reversable. Underway the Captain had a helmsmen at the wheel and an Engineer at the engine controls. Vessel was twin screw. Captain never touched the wheel or the engine control he just gave voice commands that were carried out by the people on watch. Our captain could come along side a bouy in the middle of the Columbia River and hold the vessel on station as long as it took for the deck dept. to do the work needed for that bouy.
    We also had duel engine order telegraphs that the engineers in the engine room could answer engine commands on. We only used those in emergency if the bridge engine contols stopped working.

    Direct drive direct reversable engines have a querk that if you shift to reverse and restart the engine before it has stopped turning in the the ahead direction it would restart but going still ahead but intaking throught the exhaust and exhausting throught the intake and fill the engine room with black smoke.

    Dave

  5. #25
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    Default Steam Steering Gear

    In the link posted by willy

    http://www.maritime.org/conf/conf-stroh.htm

    there is mentioned a 'followup gear' and a hydraulic system to stop the rudder in the desired spot. It sounds like a stop is moved to limit the motion of the rudder and the followup gear keeps the rudder from being pushed back to center.

    No diagrams though. I should look in my naval architecture books to see if more info can be had.

    The steering gear info is at the bottom of the linked page.

  6. #26
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    With follow up steering because the helm can be turned faster than the rudders can move if the captain calls for 10 degrees right rudder the helmsman repeats the command back and moves the helm to 10 degrees right rudder then went the follow up indicator reaches 10 degrees the rudders stop moving and holds at 10 degrees the helmsman then again reports 10 degreees right rudder. Each steering command from the captain is handled the same way.

    Engine commands are handled the same.

    Dave

  7. #27
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    Default Followup gear at least on this boat...

    The description in the link mentions 'screw type followup gear' and indicates that it assists in holding the rudder in position. Apparently this is different from the rudder position indicating mechanism, though that might be called followup gear as well, or might be part of the same mechanism

    If you have more info or links please post.

  8. #28
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    Quote Originally Posted by lunkenheimer
    In the link posted by willy

    http://www.maritime.org/conf/conf-stroh.htm

    there is mentioned a 'followup gear' and a hydraulic system to stop the rudder in the desired spot. It sounds like a stop is moved to limit the motion of the rudder and the followup gear keeps the rudder from being pushed back to center.

    No diagrams though. I should look in my naval architecture books to see if more info can be had.

    The steering gear info is at the bottom of the linked page.
    If you look at the photo of the steering gear posted above, the follow up gear would be the screw arrangement that controls the position of the steam cylinder. The hydraulic cylinder is at the far end of the assembly and probably acts much the same as a shock absorber, shuttling the hydraulic fluid from one side to the other with a damping valve in between to control the flow. When the rudder is stopped, the valve could be closed to lock the rudder in position.
    Jim H.

  9. #29
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    If we look back at post #5 with the picture of the steering gear. We see to the left of the picture cable running down from the overhead to a chain running around a sprocket. That sprocket is attached to the screw shaft that runs through the nut block that is over the shieves at the end of the steam cylinder. from there it goes to the control valve for the steam cylinder. The helm in the pilot house is attached to the cable on the pilot house end with a corrisponding sprocket. when the helm is turned it in turn moves the shaft left or right because the nut block is stopped. This then moves the steering valve admitting steam to the proper side of the steering cylinder. this then causes sheeves and nut block to move in the correct direction closing the steering valve and the cylinder stops moving. When the helm is returned to amidships the steering cylinder will move back again until the valve is closed again. This is follow up steering because the rudders are following the helm verse the helm having direct control of the rudders as in a small boat where the cable from the helm goes direct to the rudder quadrant.

    Dave

  10. #30
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    Quote Originally Posted by Dave S.
    This is follow up steering because the rudders are following the helm verse the helm having direct control of the rudders as in a small boat where the cable from the helm goes direct to the rudder quadrant.
    Dave
    The steering is unusual in having rudders fore and aft of the stern wheel, as shown here. This arrangement allowed the snagboat to turn in its own length when working in tight quarters on the rivers.

    Although the vessel belonged to the Army Corps of Engineers the crew were in the Coast Guard. I wonder what bureaucratic headaches that caused?

    Allan

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