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Advice on tender pickups?


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Am in the process of making a Wills etched tender chassis for my truly dreadful (hopefully not when I'm finished...) K's Q1 whitemetal kit I am rebuilding and detailing.

 

It's therefore an inside bearing 'U' etch of typical format.

 

My question is on tender pickups. I will be compensating the loco chassis.

 

I've retrofitted various pickups to RTR tenders: brass or PB wire/strip on front and rear wheels.

 

Given I have a virgin etched U here it has crossed my mind to use Gibson plungers (F&R only) - the appeal being an uninhindered chassis space (aside brake gear which will be well below) and so easy to attach a thin straight brass wire to the two pickup spigots on each side, giving them the best possible chance of springing freely. Then the conducting wire can come off anywhere suitable.

 

It is a (very) heavy tender so I'm thinking drag would not be much of an issue - or at least broadly the same as any other method such as wipers/spring wire etc.

 

My reservation is that I've never failed to get wipers/wires etc. to work, but am a bit less enthusiastic about plungers. The theoretical neatness seems often overcome by practical trouble...

 

Thoughts please? Thank you.

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Not a fan of plungers myself, you have to in stall them before the wheels, and you can't adjust their pressure.  And if they seize up, you've got a problem.  I've had a couple of non-working chassis come my way, where the only problem was seized plungers.  I had to break them out to remove them, and then fitted wipers instead.

I've successfully fitted wiper pickups to tenders on several occasions, see my SR workbench, but I seem to do them slightly differently each time!

Best of luck, Dave.

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I've had mixed results using plungers, I had to abandon them on my NL 4-4-0.  In addition to the objections mentioned above, you have to keep the backs of the wheels clean as well as the treads.  Whenever there is room on the top of the wheels and they are hidden, as in outside frame tenders or tank locos, top wipers are I believe preferable.

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Hmm, this echoes my foray into plungers. Airfix 14xx useless due to plungers and a scratchbuilt chassis I rebuilt and tried them but they prove very unreliable. Also they seem not to like steel tyres. So Gibson plungers and wheels were not a happy marriage!

 

I am minded to go PB strip wipers with a small dimple (or my other experience of fine brass wire with small loop to tyre) - the minimum force, max pressure that Miss Prism speaks of...

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I've only tried plungers once, on the loco of a J36 (0-6-0 tender) - for a small loco there was too much braking effect.  It was rebuilt with tender pickups only, and that's been my preferred MO ever since. See -

I have several other tender locos (which were built for me) which have the "American" system: I found this works fine, although one of my fellow club members has no time for it. I believe it's a problem for DCC, but I can't confirm as I'm determinedly analogue DC !

 

HTH.

 

Alasdair

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I use plungers almost exclusively. My solution is home made , costs very little, virtually invisible, does not catch fingers like wipers, permits wheels to have sideplay without loss of contact and can be easily removed for cleaning without taking the wheels off. 

 

The photo below shows the construction but basically a piece of brass tube soldered into the frames behind the tyre has a plastic tube liner glued inside. The pickup is a piece of brass or copper wire, I use brass, with a scrap brass fret tag soldered near one end and the wire to the motor goes onto the tag.  Opposing plungers are pressed against the wheel by another bit of brass tube with one end closed off containing a spring and a plastic rod plunger.  Think toilet roll holder!  The pressure can be adjusted by shortening or lengthening the plunger.  You need less pressure than you think!

A couple of my smaller locos use a piece of foam rubber as the pressure source.

 

Ian.

 

44D12FF6-F51E-4225-86F7-75FE3CC40559.jpeg.422afa2cfd17fd5bc4d4c63867abab84.jpeg

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I've only used plungers very occasionally and never on unpowered wheels but I couldn't count the number of locos that have passed across my bench to have them removed because they have subsequently failed to work..... I replace them with simple, easily adjustable phosphor bronze wire wipers.

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If the loco is a compensated 0-6-0 I would question the need for tender pickups - most of my loco's have 6 wheels at best and no tender, and they don't stall. If I did make them I would use brass wire. Have you considered split axles for the tender? I only say this as a friend is currently building a tender loco with split axles on a compensated tender, and no other pickups at all. These are doubtless much easier to arrange than with driving wheels though I must confess my experience of all this is zero!

 

Then again as stated above there's the 'American' system where the tender is live to one side and the loco to the other. I have done this and it works just fine. If the tender chassis is isolated from the rest of the tender with plasticard sheet you don't need to worry about insulated connections between the loco and tender.

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The "American" system is no issue at all for DCC. I have converted numerous 70s era brass imports of American locomotives (Samhongsa, Key, and others) to DCC. Provided the motor windings are isolated from the frame (There is no continuity between the motor's connection points and the locomotive, which should be the case with virtually all modern can motors) there are zero DCC issues. Just have a care if using metal couplings to double head; Kadees in plastic boxes, plastic tension locks, and the like ensure this never happens.

If it were me, I'd make the loco live (one side with insulated wheels, so wipers on the insulated side only) and then set half the tender live as well. This way you can 1) hook things up without ugly wires between the loco and tender, and 2) you can test the loco without the tender connected. If you plan on using DCC, a keep alive capacitor will smooth out any hiccups, and you can do away with the wipers if you wish and just run the "american" system straight as-is. For DC... more contacts the better, I think.

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I've used the American system with complete success for many years in O gauge with cast iron wheels (which are very easy to insulate one side only) but not had the same results in 4mm scale. For my own stock I always put tender pickups on (at least on the outer axles) in addition to the driving wheels.

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Thanks for the continuing guidance and suggestions.

 

I take the point about 'is it necessary with a compensated loco?'.

 

Maybe not, but I find myself looking at all those extra wheels and given it's not difficult it seems a shame not to.

 

I think I have a solution: the K's tender has no floor (you had to juggle 3 pinpoint axles between the sides as you glued/soldered it up!).

 

It now will have a 60-thou plasticard dummy floor in order to secure the etched U-chassis which has inside bearings. However, where it is naturally captive it is too 'high' so will need packing to get correct buffer height.

 

So, I will use a layer of PCB, copper side down, which will overhang the 'U', thus allowing me to solder fine brass wire contacts for the wheel treads, with lots of space/flexibility without having to keyhole it all in between brake rodding and so on.

 

Suitable cuts in the PCB will allow me to insulate fully and/or have conductivity to body on LH side as I see fit.

 

I will then employ my amateur go at disguising the connecting wires as pipes. See unpainted version below, which shows how I like to have them 'pluggable' - I have a bit of an aversion to permanently-tethered tenders.

 

IMG_6595D.jpeg

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