Plunger or wiper pickups.

[ian@stenochs]

On 07/02/2022 at 16:42, Bbhants said:

Hi Ian,

 

I have only just seen this post. Any chance you could give exact dimensions of the various items, please? I am building a small tank loco, 0-4-0, in 7mm and if you don’t mind me nicking your idea, that would be great!

 

Have you thought of going commercial with them? Best I have seen!

 

Best,

 

Bob

 Bob,

 

Here is a couple of pictures which might help make things clearer.  It is an 0-6-0 industrial with flangeless centre drivers.

 

 

I use stock brass tube and plastic rod and the spring is a Slaters buffer spring which gives a nice soft action without too much braking effect.  The actual contact is 0.75 brass wire with etch fret as the solder tag. I have tried nickel silver, and phosphor bronze wire but brass works best for me.
 

 

A little bit of experimenting is needed to get the pressure just right, sometimes a stroke of the file on the plunger is all that is required, sometimes it needs a slightly longer one.

[Bbhants]

Many thanks Ian, much appreciated!

 

Bob

[Jeff Smith]

I have used Gibson plungers with varying success.  I find it hard to solder a wire to the plunger without danger of melting the nylon holder.  Also on some chassis there is a g/b in the way of the driven wheel so forcing you to not fit them or fit wipers.

 

On a NL 4-4-0T (thread below, picture end of page 2) I abandoned the idea and fitted top wipers bearing onto the wheel treads.  This is a solution available to many tank locos and tenders, out of sight, you only have to keep the treads clean (not the backs of the wheels as well), and the downforce tends to firm up the compensation.

 

With wipers I try to bend the tip to produce an edge contact, this allows greater contact pressure without too much braking force.  It also reduces the chance of debris getting caught - flat wipers can accumulate dust enough to break the contact.  However edge contacts probably wear quicker!

Edited February 9, 2022 by Jeff Smith
Added info