Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Identifying an electric ship's log device
    From: Michael Bradley
    Date: 2017 Aug 14, 16:01 -0700

    Hi Carl

    My guess is an early wide range electrical rev counter, which read the voltage from a small wandering generator, mechanically linked to the shaft whose speed required measurement, the generator wired into your panel..

    The electrical machine on the panel itself, I guess,  is a motor, driven by the aformentioned external generator, itself driven by the shaft whose rotation speed needs measuring.

    The disc rotating between fixed magnet is almost certainly an 'eddy current brake' or oscillation damper which provides a light load and a braking force linearly related to the motor's shaft speed. ( See Wikipedia )

    The wide range of operation implies a general purpose instrument rather than one for a single purpose. The possible 40 to 1 switchable ratio is the clue to that. 

    Too many connections and techy bits on the front panel to be left on the bridge of a ship in the hands of a junior navigating watchkeeper .... more likely to be engine room  equipment.

    The nice linear relationship between shaft speed and generated armature voltage from a generator with constant  field  magnetisation came as an ideal early instrumentation system once shaft speeds got too fast to measured by 'counting the thumps'.

    Only guesses ........ nothing in principle prevents it being part of a log, but ......

    Michael Bradley

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site