Phosphor-bronze wiper pickups.

[Re6/6]

On Monday evening's DRAG meeting David B brought in his 36xx 2-4-2T tank..

 

I took a couple of cameraphone snaps of his wiper pickup method which I thought was rather good with the p/b wire 'fixed' as it tracks on the wheel tread.

 

 

 

[RedgateModels]

are they pcb frames too?

 

this is what I did on my neverwazza BR Standard 2-8-2

 

 

totally hidden, and uses the frame outer faces as the "bus bar". All I had to do was cut an insulation track around the wheel bearings and the weighshaft/cylinders to avoid shorts

[RhBBob]

Another gap in my knowledge !!

 

I never realised that p-b wire was available having always used the p/b strip sold in various widths - does the wire 'spring' like the strip, I wonder ?

[RedgateModels]

Yes, far more springy than brass wire. I also added pickups to the Comet tender chassis

 

 

Got mine from Eileen's

 

 

[John_Hughes]

Looks neat, but I must admit that I'm not a fan of pickups running on the tyre - they pick up too much general crud, apart from the danger with some prototypes of shorting out on the splashers. Still I can see how they could be slightly adapted to pick up on the edge of the flange, which I might give a try to.

[sej]

Hi John, very interesting and useful shots of pick-ups there. I've recently be soldering small pieces of gold wire to the ends of my pb wipers as I'd read that you can get unwanted reactions/dirt build up between steel and phosphor bronze. And, I rather like using tiny bits of gold in my models (I got a small piece of wire for a fiver from my local jewellers.

I'd love to see some photos of the complete 36xx model, do you have any? It's one of my favourite types of loco.

 

Cheers

Simon

[PGC]

Another gap in my knowledge !!

 

I never realised that p-b wire was available having always used the p/b strip sold in various widths - does the wire 'spring' like the strip, I wonder ?

 

Eileens Emporium sells 0.35mm PB wire, and that's what I use for my pickups. You can see how my locos run if you look at yesterday's entry on my blog - I don't like bad running and the PB pickups are just one part of making sure the locos run well.

 

Phil

[davidbr]

As the maker of the loco in the original post, I ought to answer some questions, but first, a correction.  This is actually 4600 and a 4-4-2.  This was an A F Hammond kit but is now one of the Gibson range.

 

The p/b wire is 0.35 from Eileen's and yes, it is springy.  I have also wound it round the pins on the bracket to increase the springiness.

 

I have connected the p/b wire to the p/b sheet between the frames via some 0.7 brass wire which has been bent to shape, one end soldered through a hole (and underneath) to the p/b between the frames.  You can see the two stubs in the first photograph.  The other end is soldered to a bracket made from scrap brass with a couple of pins projecting at right angles.  Round these pins, the p/b wire is wound with the 'loose' end soldered to the bracket with low melt to prevent the whole lot falling apart!  The bracket is insulated from the frames with a thin piece of plasticard, the whole lot glued to the frames.

 

I prefer to have the rigid connection between the pick-up and p/b strip as I think it tidier and it does not mean having floppy wire around.  This way, I determine exactly where it goes.

 

The motor has some insulating tape round it to stop it shorting on the bracket and to hold the grey flex which goes to the p/b strip.  The flex is decoder wire, very thin and flexible with a 2amp rating.

 

The decoder wire is connected to the p/b strip via a 2 pin micro connector, the socket end soldered to the p/b strip.  This makes it easy to change the polarity but also to uncouple the motor  from the chassis.  I am thinking ahead to when I might put a DCC chip in.

 

I hope this explains things and helps.

 

David

[davidbr]

Something else:  There are no splashers.  4600 is a tank and as such, ideal for top wipers.  There is plenty of space though I have packed the inside of the tanks with sheet lead.

 

I made the hook over the flange to stop the pick-up wandering off the tyre.  If you get it bent right, it rubs the back of the tyre, increasing the area in contact and improving the reliability.  So far, it has run very well.

[Pugsley]

I'm not sure where I heard this, so it might not be right, but someone did once tell me that phosphor bronze can cause pitting on steel wheels when used as pickups. I use stiff brass wire instead, for that reason.

[Horsetan]

Here's another variation

[Re6/6]

Apologies for my incorrect wheel arrangement!

 

It's good that there's been more input from others. That's how we progress in the hobby!

[sej]

Hi John and David, this is turning out to be a fascinating thread! Can we see pictures of the 4-4-2? It's my second favourite wheel arrangement.

 

Cheers

Simon

[davidbr]

Your wish, Simon . . . .

 

[sej]

That's beautiful David, thank you very much. I think I'll be buying a kit in the near future then!

 

Cheers

Simon

[John_Hughes]

Now that is a lovely bit of building!

[Scale7JB]

Very nice!!

 

JB.

[mantheakis]

I've recently be soldering small pieces of gold wire to the ends of my pb wipers...

Simon, could you please tell me what type of solder you use to join gold wire with phosphor bronze?

[sej]

Simon, could you please tell me what type of solder you use to join gold wire with phosphor bronze?

Hi Harry, sorry for not replying sooner; I soldered the gold wire onto the end of the phosphor bronze wipers using Carr's 179' solder and safety flux "O Gauge Online". Then I trimmed the wire to length. It seems to have worked well so far.

 

Cheers

Simon

[bertiedog]

Phosphor Bronze on steel tyres does have a reputation to spark erosion occurring, and hence pitting of the tyre, but if the wire is well sprung against the tyre there should not be any sparking. With nickel silver tyres there is never a problem. Brass wire has usually not enough spring, and can tarnish. Nickel silver is overall the best, it is nearly as springy as phosphor bronze. An alternative if you can source it is Beryllium Copper strip or wire, used in relays for the springy leaf arms, it is corrosion free and very springy.

 

A old Post Office Telephone relay will yield a good supply of strip to cut into fine springs. It can be heat treated like steel, heat to red and quench in water, to restore spring.

 

Old PO relays contact tips can be used as they are palladium or platinum, very tough and corrosion free. They are welded to the spring, which can be filed down to a smaller section to fit to the model.

 

The contact springs will yield a good supply from a 3000 type GPO relay, sold regularly on Ebay.

Stephen

[mike morley]

I've recently be soldering small pieces of gold wire to the ends of my pb wipers (I got a small piece of wire for a fiver from my local jewellers.

Is it gold wire you've used or some other wire that has been gold plated? I'd have thought straight gold would be too soft to be springy enough to be effective

[mantheakis]

Hi Harry, sorry for not replying sooner; I soldered the gold wire onto the end of the phosphor bronze wipers using Carr's 179' solder and safety flux "O Gauge Online". Then I trimmed the wire to length. It seems to have worked well so far.

 

Cheers

Simon

Thank you Simon - that solves a mystery for me!

[DCB]

Interesting stuff, My experience of pickups running on the tyre tread is that it works really well for 00 gauge shunting locos which run both backwards and forwards and slip frequently but that crud builds up between pick up and tread on locos running mainly in one direction at line speed.  Some of mine have had this on Romford wheels for 30 years or so.

[RedgateModels]

On 26/04/2016 at 15:39, Mersey507003 said:

Hi Redgate Models

 

I remember seeing your loco in model rail magazine ( although I can't remember which issue it was shown in ) and the feature inspired me to build a never wazza standard loco almost like the loco you built but I decided to try and make mine using the chassis that had wheels more akin to a freight loco and built it as a 4-8-2 powered by a smooth running XO4 motor. She needs a lot of weight added to enable a good haulage capability. I numbered it as 71100 although I think a renumber might be required. Do you have any pictures of your loco and I will try and post a picture of mine.

 

 

How's this?

 

[Will L]

Ah that phosphor bronze pick-ups will corrode steel wheels chestnut again. 

 

It is true that unlike metals in electrical contact can cause "Galvanic Corrosion", see Wikipedia here where it is all explained.  It would truly be a problem if you could ran your locos under salty water.  There is a potential for corrosion (of the steel) if stored in a damp atmosphere but a warm dry storage should cause no problems.

 

Interestingly, if you read the Wiki article you will notice that on steel, Brass and Bronzes are similar in this respect, and are actually less likely to cause Galvanic Corrosion than nickel silver.  And silver and gold would be even worse.  The corrosion resistance of the material itself is a total red hearing, it's what happens to the steel it is contact with that is the issue.

From experience over the years, (at least 25) I've never noticed any problems, nor with nickel silver which I used before phosphor bronze.  Clearly I do tend to store my stuff in a dry atmosphere and I'm not given to running my model railway in the rain.

 

 

Will