Signals

THE SIGNAL BOX


Railway signalling discussion

Bell for Tyers No6 tablet instrument.

Technical talk on signalling matters

Bell for Tyers No6 tablet instrument.

Unread postby John Hinson » Thu Mar 29, 2018 4:47 pm

The following post was made by Pete2320 but was accidentally lost during upgrade work:

Having almost completed the restoration two No6 machines I'm having difficulty finding bells that are comparable. I have tried several normal block bells, sometimes with the coils in series, but non are satisfactory without increasing the operating voltage beyond what is reasonable given that the bell is in series with the lock coils.
Alistair Larter has connected his bells in parallel, presumably with the relay, rather than series which may be a way forward but I'm concerned that back emf from the bell could operate the relay in the wrong direction.
The specification for the intended bells is 12ohms, 150mA which would give an operating voltage of 1.8v.
I'm thinking in terms of using a relay to drive a normal bell. Has anybody done this with a tablet machine and/or can anybody suggest a suitable relay type, preferably "off the shelf"
Image
‹(•¿•)›
User avatar
John Hinson
Site Admin
Site Admin
 
Posts: 6951
Joined: Thu Nov 8, 2007 1:13 pm
Location: at my computer

Re: Bell for Tyers No6 tablet instrument.

Unread postby Pete2320 » Thu Mar 29, 2018 11:56 pm

Thanks John!
Pete
Pete2320
Main line box
Main line box
 
Posts: 2147
Joined: Wed Feb 20, 2008 10:50 pm
Location: Barton on Humber

Re: Bell for Tyers No6 tablet instrument.

Unread postby John Webb » Fri Mar 30, 2018 11:29 am

Pete - our two Tyer No.6s at St Albans South use ordinary block-bells, but I'm uncertain of the way they are connected. The one person who could tell me is away at the moment and not due back for a couple of weeks or more; I'll ask him on his return.

If the voltage to the bell isn't reversed as part of the system during operation, could you use a reverse diode to cut out the back EMF? Or if the voltage is reversed and a diode not possible, use a snubber (capacitor-resistor in series) instead?
John Webb
(Member, St Albans Signalbox Trust)
User avatar
John Webb
Main line box
Main line box
 
Posts: 1873
Joined: Tue Jul 8, 2008 1:22 pm
Location: St Albans, Herts

Re: Bell for Tyers No6 tablet instrument.

Unread postby Alistair Larter » Fri Mar 30, 2018 6:12 pm

The tablet machines have been in use doe sometime now Pete with no issues at all
User avatar
Alistair Larter
Branch line box
Branch line box
 
Posts: 271
Joined: Mon Jun 14, 2010 8:33 pm
Location: East Yorkshire


Return to S&T Department

Who is online

Users browsing this forum: No registered users and 2 guests