Contact Pin

Just got that little contact pin out of the frame. It has no spring action?

Is there a spring in it?

If you have an industrial hardware store near by, you may be able to find a spring that will fit.

let me look in my junk box..

let me look in my junk box..

Without dimensions...

it's a little hard to guess....  would a spring from a cheap ballpoint pen fit? (keeping in mind it can always be cut down...)

That looks a lot like a door latch pin that you'd use in a cabinet, too... might check someplace that sells furniture parts.

"Battery Contact" pins

Dear MRHers,

There is a small but active market in the electronics world for self-contained spring-loaded "contact push pins", often refered to as "battery contact" pins. Diameters from 1mm upward. DigiKey, Mouser, etc should get the references...

Example via Google

https://au.element14.com/harwin/p70-1000045r/spring-loaded-contact-pin-3-5mm/dp/2664910

Happy Modelling,
Aim to Improve,
Prof Klyzlr

all good ideas

Thanks guys, lots of decent ideas. I haven't tried taking it apart yet,..maybe tomorrow. And I'll measure it

Hope to hear something from Hornby,..asked them about traction tire drivers also

Took it apart

I first thought about those small springs on our Kadee couplers, but even those were TOO large.

I'm still waiting for answer to inquiry with Hornby. Meanwhile perhaps I need to look more thoroughly thru that link provided by the Prof.

(the dia of that spring is likely half that of the overall dia of the pin??....photo above)

I'm looking at this PDF,   

I'm looking at this PDF,    https://www.farnell.com/datasheets/1722948.pdf      , and surprised at the lack of a diameter measurement? Or am I missing it??

Data Sheet

I took a look at a larger magnification of that chart. It looks like the pins aren't design to be taken apart. The best judgement I have for a spring diameter is less than .042". The OD of the moveable pin is .042" and the spring fits in a hole inside the moveable pin.

I think the Prof. has a great idea using the "battery contact" pins. They are probably easier to source.

Bernd

I took a look at a larger

The 'moveable pin' (smaller dia) had some sort of crushed portion on its end. I had to file that down such that it would slide thru its outer housing to get it apart.

https://model-railroad-hobbyist.com/sites/model-railroad-hobbyist.com/files/users/railandsail/image%28309%29.png

Hot Springs:

Sounds like the name of a heavyweight Pullman (it was).

I'll bet that at one point in your Allegheny's life the motor may have been stalled or at least a big current draw was placed on that little spring which, in turn, made the spring wire glow like an incandescent lamp filament.

Thus the temper of the spring was lost and the plunger would no longer contact the inside of the wheel face. Not a good design at all.

Regards, Ed

@ Ed

Interesting possibility?  I wonder were else I might look in that engine for any tell-tale signs that such a thing could have occurred?

You mentioned Kadee springs were too big

Did you try HO, or N? I think the N Coupler Springs are a bit smaller.

What about a flint spring (and maybe a flint) from a lighter - or motor brush springs from slot cars?

In the unlikely event you can't find the part or come with a different kind of wiper for the back of the drivers, if you have a lathe or a friend with one, you can wind your own springs to whatever dimeter and pitch is needed. 

Here is a great video for you on making springs.  Springs are really just screws in disguise!

For some weird reason, I can no longer link to a specific post in the Toolroom thread.

Making Springs

Thanks Mike, never really thought about making springs. I found a number of videos on the subject, like this one

Bottom line is I'm not sure I can do this small of a spring,...and will likely look for other options, unless I run out of those.

Making tiny springs,  

But thanks again for bringing this to my attention.

A sewing needle …

… also Makes a great mandrel for tiny spring winding, and already has a hole drilled!
 

But I’m pretty sure old refillable lighters have tiny springs under the flints.  A tobacco shop ought to have them. 

Springs from trucks?

What about springs from sprung trucks.  I think that they are smaller than the coupler springs.  Kadee still makes the sprung trucks.  They sell the springs separately -- in 2 sizes - #637 & #638..

Contact pins on another rivarossi loco

The pins on my Alleghenys is almost half the dia of those,...mine are .0826"?,   and mine have a collar on them.

Link to site of spring loaded contact pins

or here,..  https://www.newark.com/w/c/test-measurement/test-connectors-ic-test-clips/prl/results/2?range=not-exc-nic&st=spring%20loaded%20contact%20pins

wonder if some of t these would work,...even while the pin configurations do not match my Allegheny one
https://www.farnell.com/datasheets/1722948.pdf

or maybe these
https://www.farnell.com/datasheets/2625442.pdf

 

Hornby contacts

I have written an email to both their UK and USA addresses. Yesterday I got a response that the USA operation was no longer stocking parts ( nor participating in the model railroad hobby). The UK operation has not replied yet.