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Hi all , I am building a 4mm kit in E m gauge, My first in this scale, So what is best plunger or wiper pickups, I have used plunger on O gauge builds, But i am not sure what is best in the smaller scales.

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It depends to some extent on the type of locomotive.

However wipers work for me and I see no reason to try any other type.

They were the option going way back on any kit that I have built and looking at the work of Tony Wright and others on here I see little evidence of plungers.

Bernard

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I have run into trouble recently with a (00) bash of an Airfix 61xx into a Collett 1938 31xx (Skills & Knowledge/Modifying & Detailing RTR/'The Bodgerigar Attempts to Built a Collett 1938 31xx for the sorry saga so far), because the Markits wheels I was using for the project are insulated between the wheel centre and the tyres, whereas the orignal Airfix wheels are insulated at the interface between the axle and the wheel centre.  The Airfix pickups, being wider than the rear of the insulated part of the Markits tyres, bear on to the rear of the metal wheel centres and cause short circuits, and are difficult to adjust to avoid this problem.  With that in mind, were I to have continued with the project in that form, I would have preferred to use sprung plunger pickups which could be accurately postioned behind the insulated part of the tyre rear, or wiper (or bent wire) pickups bearing on the tops of the wheel flanges.

 

As has been said, much depends on the individual loco and perhaps on how easy or otherwise it is to hide or disguise the pickups.

 

In the event I am going in a different direction with the 31xx, and have sourced a suitable running donor chassis with the correct axle spacing and correctly sized wheels, from a Baccy Ivatt 4MT mogul on eBay.

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1 hour ago, mswjr said:

DT it is a tender loco, 2-6-0 class N. Alan gibson wheels.

 

I hate pick-ups.  They tend to be the last bit of any kit-build I come to and fitting them can be a nightmare.  I especially hate kit instructions which, while going into every possible detail about the rest of the build, then merely say something like "Finally, fit pick-ups of your choice".

 

But things are easier with a tender loco because you can fit your pick-ups to the tender wheels.  Of course, that too poses problems.  Pick-ups, whether plunger or wiper (I've never ever got on with the former) act as brakes on the wheel.  On driven wheels that doesn't matter too much, but it does on undriven wheels, eg bogies and tender.  So if fitting wiper pickups to the tender (mine tend to be very thin phosphor-bronze wire on top, bearing down on the wheels) you'll find that if the tender is lightweight, as in an etched kit, the wheels might then not go round easily.  So weight then has to be added to the tender, although that does not usually apply if the tender is white metal!  And of course you can also fit your stay-alive in the tender if you're on DCC and using one.

 

Anyway, I've got a couple of tender locos where I haven't bothered fitting pick-ups to the loco at all, just to the tender.  They work fine.  Ideally I'd fit split axles to the tender, but making 2mm split axles is a faff, although if you manage it they should work well.  And if you feel that pick-ups to the tender wheels is insufficient, then you can fit a couple to the lcoc as well - the more pick-ups the better!

 

DT

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Only ones I’ve tried/know of are Alan Gibson. IMHO dreadful things to be avoided at all costs. They simply don’t work well below 7mm scale. Wiper pickups on loco and tender wheels, if possible. However, this is easier if using Markits wheels with only one side insulated.

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On the other hand, I have used Gibson plunger pickups to great effect on many locos big and small and found no problems with them. They work well if very fine wire is used so the plunger isn't restricted from moving and following the wheel plus if there is very little space between the wheel and the frames then shortening the plunger to suit is the way to go, that will ensure the lightest of touch between the plunger and wheel.

Just my humble opinion.

 

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5 hours ago, Torper said:

I hate pick-ups.

 

Me too.  They cannot possibly be the best way to get current from the rails to the motor, and are IMHO lazy engineering design, something that has been made to work rather than something that works as a natural part of it's innate behaviour.  They work very well in modern RTR locos despite this, but when it comes to fitting your own, them and me do not get on at all well!  I certainly sympathise with the 'finally, fit the pickups of your choice' thing; it indicates the general afterthought and lack of prominence paid by far too many people who should know better to a process that is fundamental to the performance of the model. 

 

What we are looking for is good slow speed performance under control, and smooth starts and stops.  With a bogie diesel or electric (or articulated steam) and to some degree with a tender loco this can be done by having one bogie/the loco chassis live to one side and the other bogie/the tender chassis live to the other, buy my locos are all steam outline tank engines that have to be uncoupled from their trains to run around or shunt, so there is no chance of this arrangement.  It is my opinion FWIW (which is what you pay for it) that the best possible performance results from the use of split chassis pickup, in which there is no mechanical resistance to the ability of the wheels to revolve at very low voltages (I 'don't do' DCC). 

 

It is a big ask, reliable contact from rails to motor terminals at the lowest voltage that will turn the motor.  There are several places at which the current can be easily interrupted; firstly, the rail/wheel interface, which requires all the wheels to be sitting correctly on the rails all the time.  This in turn requires precise dead levelling of trackwork, especially over turnouts and baseboard joins, or full compensation aboard the loco, both actually quite diffiucult to achieve at an acceptable price in RTR, and good railhead and wheel tyre hygiene.

 

The next interface is be considered is that between the wheel (tyre rear or top) and the pickup, wiper or sprung plunger, and, if it doesn't work properly, it's a 'mare; guess who is to blame for this if we are talking about a rebuild,kit, or scratchbuild, 'now fit the pickups of your choice'.  This needs to be very precisely adjusted to achieve the best possible compromise (the one which provides the least mechanical resistance and thus braking effect) and, in the case of Markits and similar, they have to be very precisely positioned in the first place.  The wheels have to have sideplay, especially if you have setrack curves, so the the pickup must self adjust in use as well.  And, again, good hygiene at the interface is vital to success, and in this case it is an interface that is not the most accessible.

 

In the case of a split chassis pickup arrangement, this very awkward interface is replaced entirely by that between the live axle and the frame or chassis half-block.  Matters are still not ideal, as the this equates to the axle bearing and must be lubricated.  If you use a non-conductive lubricant, the pickup transmission of current between the axle and the frame/bearing/chassis half-block/whatever is compromised, and if you use a conductive lubricant, there is a good chance it will spread itself around and cause short circuiting.  But, once in place, this type of current collection needs no adjusting or maintenance beyond regular cleaning, and will easily tolerate lateral play in the wheelsets, and even vertical play if you use sprung hornblocks. 

 

It was popularised in the 70s and 80s in kit and scratchbuilds which featured in magazine articles, in conjuntion with the legendary Portescap coreless motor and gearbox, and provided near perfect running on fully compensated locomotives that could manage seriously bad tracklaying, a feature used deliberately on industrial micro-layouts to evoke the character of such rough'n'ready prototypes.  There were examples of locos runnig over obstacles such as matchsticks laid across the rails at very low speeds without faltering.

 

When Palitoy entred the market with the Mainline range, they were clearly aware of all this and, rather bravely IMHO, opted for a range of locomotives with split half-block chassis pickup.  Unfortunately, they combined this with weak pancake motors that had to run at high speeds to develop enough power (and some of us would have said they failed quite significantly in that respect) and drive through a series of plastic spur gears that were prone to splitting and did not revolve freely on their pivots, which introduced more mechanical resistance in the drive than wiper pickups would have, making the effort counterproductive.  Furter problems were caused by the plastic axle centres and the way the live stub axles each side were fitted into them, which led to quartering issues. 

 

A potentially very effective design was poorly executed with an unsuitable motor and drive train and inferior materials, and the poisonous reputation that RTR split chassis gained as a result is, I'm sure, a major reason that current RTR producers use wiper pickups.  In a similar way and an equally brave but doomed attempt to my mind, concurrent Airfix produced a 48xx/14xx with sprung plunger rollerball pickups, which worked very well when the loco was new but once a bit of dirt had got into them were hopeless, resulting in a similarly poisonous reputation, but as Davefrk has said, they can be made to work very effectively.

 

I would prefer to see frames and chassis blocks made out of non-conductive material to reduce the possibility of shorts, and more use of split pickup by RTR manufacturers, along with roller or ball pickups in open frames, lever sprung to bear against the rear of the wheels.  Good hygiene will still be needed but I believe performance can be improved, and cleaining made easier.

 

Ultimately, I would prefer my locos to have their own rechargeable battery power supply carried aboard them and not require pickups at all.  The track can (within limits) be less than perfectly laid and made of plastic, as can the loco's driving wheels, or perhaps out of soft rubber for better grip, and control would be from chips aboard the loco and NFC/WiFi.  Not gonna happen in my lifetime...

 

 

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All my locos except one have plunger pick-ups on the loco wheels.  The exception is my latest build, a J6 where i have experimented and used DCC off the shelf pick-ups.  Works very well, easy to install and makes the wheels self centering.  All my tender pick-ups are DCC Concepts wiper pick-ups. 

DCC Pickup-3.jpg

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43 minutes ago, Theakerr said:

All my locos except one have plunger pick-ups on the loco wheels.  The exception is my latest build, a J6 where i have experimented and used DCC off the shelf pick-ups.  Works very well, easy to install and makes the wheels self centering.  All my tender pick-ups are DCC Concepts wiper pick-ups. 

DCC Pickup-3.jpg

 

I've used these a number of times, both on loco chassis and also coach bogies. Only minor issue is the drag they cause but you can bend them in a bit to reduce that.

 

 

IMG_20171208_142819.jpg

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Its wipers every time wherever possible for me.  They are pretty simple to produce and install, and there's many examples on my SR Loco Workbench topic (link below).  I like to build the pickup system as a separate assembly that is then screwed in place.  

Plungers have to be fitted before you install the wheels, and then can't be accessed without removing them again.  Several times I've had a non-working loco brought to me, and the problem is seized plungers.  Often the only solution has been to break them out, and I've then replaced them with wipers.

If your pickups are acting as brakes, then its possible that the tension on them is too tight.  With a wiper you can lengthen it or use a finer wire.  I find 15thou Nickel-Silver wire to be the optimum; springy enough to achieve sufficient pressure for reliable pickup, but without any of the dreaded braking force.

Hope this helps,

Cheers, Dave.

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16 hours ago, DLT said:

Plungers have to be fitted before you install the wheels, and then can't be accessed without removing them again.  Several times I've had a non-working loco brought to me, and the problem is seized plungers.  Often the only solution has been to break them out, and I've then replaced them with wipers.

If your pickups are acting as brakes, then its possible that the tension on them is too tight.  With a wiper you can lengthen it or use a finer wire.  I find 15thou Nickel-Silver wire to be the optimum; springy enough to achieve sufficient pressure for reliable pickup, but without any of the dreaded braking force.

Hope this helps,

Cheers, Dave.


Sorry but I disagree Dave.
 

I use plungers on all my locos.  However instead of using the commercial offerings, which tend to be bulky and difficult to hide, I make my own.  Sitting behind the wheel the only visible part is the wire plunger and if sited behind the brake block even that cannot be seen. The construction is from stock brass tube, wire and plastic rod with springs from Slaters intended for their sprung buffers. Think ‘toilet roll holder’ for the basic principal!

 

The actual pickup can be taken out with the wheels still in place for cleaning or adjustment of the spring pressure.  There is only one spring which pushes both plungers against the wheel so equalising the pressure and with the added benefit of no loss of contact if there is sideplay on the axle. The assembly simply slides with the wheels.  I always adjust the spring pressure to the minimum required so ensuring the least braking force.  

The attached photos should be self explanatory.

 

Ian.

 

64647D43-E70E-4F90-A514-6F931B9D8219.jpeg.6f47a34d16cc867ff131f6a707e4b30c.jpeg3632B4B3-D866-453B-9D6D-25FB6E267525.jpeg.aa083da32b14c06e52e8ff50d3a34669.jpeg5C9032DA-02D0-4D91-A18A-99C41B7C0D1F.jpeg.d2cd481398b4b8329c179531ae871e6d.jpeg

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Wow, that's a highly ingenious solution Ian! 

 

And I like the toilet roll holder analogy.  Please could you explain the principle to the rest of my family???

Your loco looks to be 7mm scale where the issues are less of a problem.  Some of my 0-Gauge friends use plungers intended for 4mm scale on their locos.

My experience has been with the commercial plungers which have to be fitted from the outside of the frames before the wheels are installed, and are foreverafter inaccessible.

 

All the best, Dave.

 

PS  Do you have a topic running on your modelling?

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Dave,

 

The example shown is 7mm but some of my P4 locos used the same system. However instead of toilet roll holders the pressure was supplied by a piece of foam rubber.  I do still sometimes use foam on 7mm locos when testing during a build as it is quicker and I don't loose as many springs.

 

I don't spend much time on RM web now as the adverts are so annoying and off putting.  I do post on Western Thunder though.

 

Ian.

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Plungers are good if you don't have springing, model in 5mm scale or larger and either don't use coil springs or don't have live frogs.    The ready to use ones, Airfix 14XX etc fry their tiny springs instantly when they straddle an insulated rail joint with positive and negative one side and both rails the same polarity the other.   A same side short.  If you use a decent size coil spring  or a Hairpin or torsion bar they are fine but in 4mm and below no one does.   Tender pick up works sort of, but tyre cleaning is tedious as is loco wheel cleaning with tender drives. Some of my wheels haven't been cleaned for years  relying on good old Triang style wiper pickups on H/D or Romford wheels.   All my Airfix 14XX chassis, 10 I think, died of plunger failure.

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14 hours ago, DCB said:

Plungers are good if you don't have springing, model in 5mm scale or larger and either don't use coil springs or don't have live frogs.    The ready to use ones, Airfix 14XX etc fry their tiny springs instantly when they straddle an insulated rail joint with positive and negative one side and both rails the same polarity the other.   A same side short.  If you use a decent size coil spring  or a Hairpin or torsion bar they are fine but in 4mm and below no one does.   Tender pick up works sort of, but tyre cleaning is tedious as is loco wheel cleaning with tender drives. Some of my wheels haven't been cleaned for years  relying on good old Triang style wiper pickups on H/D or Romford wheels.   All my Airfix 14XX chassis, 10 I think, died of plunger failure.

 

All my locos are sprung or compensated and plungers work fine!  I do not rely on the coil springs to carry the current which may be where your problem lies.  Always use a hardwired current path, mine is fine flexible wire soldered to the plunger and led a terminal block, piece of pcb, then leads to motor.

 

Ian.

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8 hours ago, ian@stenochs said:

 

All my locos are sprung or compensated and plungers work fine!  I do not rely on the coil springs to carry the current which may be where your problem lies.  Always use a hardwired current path, mine is fine flexible wire soldered to the plunger and led a terminal block, piece of pcb, then leads to motor.

 

Ian.

How do you keep the plunger on the back of the flange when the wheel moves up and down?    Do you have live frogs?  Its running into the toe of a wrongly set live frog point causing a same side short which destroyed all my Airfix plungers 

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4mm modeller here. An interesting debate. I too am firmly in the wipers camp, and the overwhelming majority of my stock is thus fitted; however I have one exception. I built one of Peter Stanger's 52F Models Class H1 4-4-4T chassis, and this (fully compensated) kit is designed to use Gibson plungers. As others have commented, thin wires are a must, but I was pleasantly surprised at how well it worked out, even in 4mm scale. However, setting up is a lot more intricate than wipers, particularly when using Gibson wheels, as realistically you only get the one chance to fit the drivers to the axles without running the risk of them slipping in the future, if you have to take 'em off & replace 'em...

Edited by MarkC
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2 hours ago, MarkC said:

4mm modeller here. An interesting debate. I too am firmly in the wipers camp, and the overwhelming majority of my stock is thus fitted; however I have one exception. I built one of Peter Stanger's 52F Models Class H1 4-4-4T chassis, and this (fully compensated) kit is designed to use Gibson plungers. As others have commented, thin wires are a must, but I was pleasantly surprised at how well it worked out, even in 4mm scale. However, setting up is a lot more intricate than wipers, particularly when using Gibson wheels, as realistically you only get the one chance to fit the drivers to the axles without running the risk of them slipping in the future, if you have to take 'em off & replace 'em...

my locos follow the same path with the exception of a 52F T1 which has plungers. It was the easiaet loco to get running without tweaking I have built.

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6 hours ago, DCB said:

How do you keep the plunger on the back of the flange when the wheel moves up and down?    Do you have live frogs?  Its running into the toe of a wrongly set live frog point causing a same side short which destroyed all my Airfix plungers 

If they are on the centre line of the wheel then the up and down movement should't be a problem unless your track is awful

Edited by Paul Cram
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9 hours ago, DCB said:

How do you keep the plunger on the back of the flange when the wheel moves up and down?    Do you have live frogs?  Its running into the toe of a wrongly set live frog point causing a same side short which destroyed all my Airfix plungers 

 

Even in 7mm scale you only need about 1.5 mm maximum travel about 1mm in 4mm scale. If you need more than that you need to sort out your track work!

 

If you position the plunger as near wheel centre line and just over 1/2 the tyre thickness, measured on the back of the wheel, in from the rim you will still have more than enough wheel travel without the plunger falling off the contact area.

 

One last point  pickups should be considered right from the start of the build. Too many kit instructions omit or don't mention current collection.  I know I got caught out in my early kit building days.  Trying to bend up wire pickups to miss detail like brakes, sanders and springs without shorting and still reliably contacting the wheel. That nearly drove me mad. My home made plungers go on right at the start of any new model and then get forgotten about because they work.

 

Ian.

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  • 2 months later...

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

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