Slaters Plunger Pick-ups (and alternatives)
Prepared by Jim Snowdon Originator Keith Jackson
1. Keith Jackson Jan 23, 2018
Help Required please, what size hole do I need to drill for Slaters Plunger pick-ups.
Thanks & Regards
Keith Jackson (knotty)
2. Gordon Hills Jan 23, 2018
Hello Keith, Slaters give the following information on their website. Item 7157 needs a drill size number 25, ( 0.1495“ or 3.797mm )
Hope this helps Regards Gordon
3. Keith Jackson Jan 23, 2018
Morning Gordon
Many Thanks
Regards
Keith
4. David Littlewood Jan 23, 2018
Ref post #2 -
I rather think a 3.8 mm drill would do!
David
5. Pat Buckley Jan 23, 2018
Or open the existing hole with a taper reamer till the pickup fits - simples !
Pat.
6. Keith Jackson Jan 23, 2018
Evening David & Pat
Thanks for your replies, much appreciated.
Regards
Keith
7. Bob Thompson Jan 24, 2018
Ref post #1 -
Personally, I wouldn't touch them with a barge pole, simply because I have had so many bad experiences with them.
But if you must use them, do be careful to get the mounting holes just the right size to give a nice snug fit. It is better to drill the holes undersize and open them up with a broach until you get just the right fit. You will probably find, as I have so often, that the plastic housings vary in diameter and if you have a oversize hole they wont sit square to the frame and get dragged about by the wheels and are very inefficient as a consequence. Make sure before you fit them that the housing has enough clearance at the end for the tail of the plunger. More often than not the hole in the back of the housing needs cleaning up to remove the moulding flash. If you don’t do this the plunger will likely jam up in the housing.
Also a must is to not solder wires directly to the plunger pins. If you do, you will find that the heat will invariably distort the housing and then everything jams up.
You probably spent hours constructing your model so it is worth taking some time and deciding which is the best current collection method to adopt.
I would advocate either using something like the heavy duty plunger pick-ups that Premier Components supply or possibly the Ex-Gladiator PFS type pick-ups or going for wipers or using the American system of current pick-up from the Locomotive and tender wheels.
I think Jim Snowdon did an article on the PFS pick-ups.
The real problem with the Slaters plungers is that even when they are correctly installed, they seem to wear out very quickly, to the point where they don’t give continuous contact with the wheels or they jamb up in their housings. As a result your Loco runs in fits and starts !!
Sorry, I hate them with a passion, no doubt others will have differing views.
Bob
8. Jim Snowdon Jan 24, 2018
I used them once, on a Slaters kit, and abandoned them before I had even completed the loco. They look good, and they do appear to be competently designed, but I found that I hadn't got the clearance between the backs of the flanges and the frames to get them to fit without them bottoming very solidly. I could possibly have shortened the plungers, by quite a bit, but I just junked them instead. I went over to the PFS type after that and have stuck with them ever since, although as Bob has observed, I do modify them slightly.
Jim
9. Keith Jackson Jan 24, 2018
Morning Bob & Jim
Thanks for the information and I have printed off Jim's article. Have only used Slaters plunger type once before and they are fiddly to say the least.
The kit I have just started doesn't have holes for the pick-ups yet so I can decide which to opt for later.
Regards
Keith
10. John Taylor Jan 24, 2018
Ref post #7 -
Nah !!
I have used them exclusively on my recent set of loco kits and find them excellent.
They need to be carefully and properly assembled. Do not use stiff wiring .
However, I will be controversial, and say they are not for the ham fisted.
They cannot possibly wear out as ,if anything, the springs are too weak and can be changed with slightly stronger springs from Slaters. I have not needed to.
An excellent product and if used as intended provide impeccable performance.
Cheers
John
11. Bob Alderman Jan 24, 2018
I agree with John
Nowt wrong with them properly adjusted and installed.
Some of my locos have done many real miles with them and still going strong.
Bob
12. Keith Jackson Jan 24, 2018
Afternoon John & Bob
Appreciate your replies, all very interesting as I have little experience of loco building using plunger pick-ups, have built one with Slaters, on 3 other locos I have used wiper type.
Regards
Keith
13. Simon Dobson Jan 24, 2018
My experience;
Wipers? fragile, seem to attract dirt!
Split axle? hard work but very reliable especially on sprung tender axles
Slater's style plungers? ok, mostly
Floating plungers? seem to work well, no problems so far (but only one loco built with them)
Hth
Simon
14. Bob Thompson Jan 24, 2018
Ref post #10 -
Each to their own I guess. I still wouldn't use them unless I had to. Quite right about wiring, I use a 0.15 mm2 stranded cable that is Silicon Rubber insulated. Expensive, but extremely flexible and very good heat resistance to boot.
I would question your statement about them wearing out though…Why have I come across so many models where the Slaters plungers were severely worn down?
The problem with all plunger types is that once they need changing, there is no other option but to strip the chassis down and remove the wheels, unless of course one uses the PFS type.
Bob
15. John Taylor Jan 24, 2018
Ref post #14 -
Aha Bob ! they forgot the old Red Indian trick of using Peco`s Electrolube !! or PL-64 Power Lube as it is called nowadays….
John
16. Bob Thompson Jan 24, 2018
Ref post #15 -
Yes John,
A squirt of Lube can work wonders I know - I usually resort to trying to see if I can free them up using some Electrolube but usually end up just cursing the things and fitting something more reliable.
I really have nothing against Slaters Plastikard whom I think have some really good products, but I don’t count their plunger pick-ups as being one of them. Maybe it's just me?
Bob
17. David Littlewood Jan 24, 2018
Ref post #14 -
Personally, I think the reason why Slater's plungers may display wear is that they are formed with a fairly sharp point. I have not studied this question thoroughly, but my feeling is that the frictional resistance in a situation such as that does not depend on the shape of the tip; a larger contact area may increase drag, but the reduced pressure (=force/area) will cancel it out. When I make plungers, I make the ends rounded, and do not notice any obvious increase in drag.
David
18. John Taylor Jan 24, 2018
Ha Ha Bob
I think that`s like the Marmite gene…. you either luv’em or hate’em
I think you mentioned `wipers` well they are my equal favourite pickup types where I can`t use the plungers,
except I solder a round brass nail head to the ends of the phosphor bronze strip to improve contact and friction…..
john
19. Bob Thompson Jan 24, 2018
Ref post #18 -
That sounds like a nice idea John.
I might try that the next time I make some up.
Bob
20. Bob Thompson Jan 24, 2018
Ref post #17 -
Agreed, but the other thing that makes them wear very quickly is if the wheel isn’t perfectly concentric and has a little wobble.
Bob
21. Bob Alderman, Jan 24, 2018
I have usually removed the point of the plunger giving a notionally flat face on the wheel. This has been done to get full movement; better than cutting the spring.
I have not noticed an increase in drag or wear. Indeed the back of the wheel polishes.
Bob
22. David L O Smith Jan 24, 2018
Ref post #14 -
Not so. I have described single-spring plunger pickups (see my posts of the 25th and 26th of May, in particular) that may be inserted and removed without disturbing anything else in the frames. David
23. Bob Alderman Jan 24, 2018
As mentioned earlier this is a Marmite argument.
I think enough pros and cons for various types for an educated decision to be made.
… and, notwithstanding, I favour split axles on my tender locos, but that is another kettle of fish!
Bob
24. David Littlewood Jan 24, 2018
Ref post #20 -
If the wheel wobbles, it is not lack of concentricity, it is lack of squareness to the axle. I'd be surprised if either lack of concentricity or deviation from the perpendicular would have a significant effect on plunger wear, though the latter could conceivably have a slight damaging effect on the fatigue life of the spring.
David
25. Bob Thompson Jan 24, 2018
Ref post #22 -
Any plunger that has a bush with an outer flange like the Slaters set-up requires the wheels to be removed in order to change the bush does it not?
Have I have missed something?
Bob
26. Bob Thompson Jan 24, 2018
Ref post #24 -
Usually yes but, not always the case though.
I can only go by what I see on models that cross my path with wobbly wheels and worn out Slaters pick-ups. Might just be a coincidence of course.
Bob
27. David L O Smith Jan 24, 2018
Ref post #25 -
Well, maybe; I cannot see ever needing to change the bush but, if you look at my sketch in my post to which I referred earlier, particularly at the scrap view, bottom left
you will see that the plunger (part 1), which is what is most likely to wear out, may be removed from the bush assembly (bush part 1 and collar part 2) along with the solder tag (part 3), insulating bush (part 4), the spring and the equivalent parts on the other side. That said, I have never had to replace any of the brass plungers on my locos and some of them have done a fair few scale miles over the years on an extensive garden railway.
David
28. David L O Smith Jan 24, 2018
Ref post #26 -
The point that David made was that a wobbly wheel and one that lacks concentricity are not the same thing. A wobbly wheel swashes (as does a swash plate) because its major plane is not perpendicular to (at right angles to) its axis of rotation; a wheel that lacks concentricity (ie it is eccentric) is not rotating about its geometric centre.
So, yes, a wobbly wheel causes the plunger to move in and out rather excessively with every rotation of the wheel, but I see no reason why that should wear out the plunger any more than a wheel that is running true. I can think of other reasons, such as a rough back to the flange and springs that have too great a pre-set load.
David
29. Bob Thompson Jan 25, 2018
Ref post #27 -
You obviously don’t use Slaters then?
Bob
30. David L O Smith Jan 25, 2018
Ref post #30 -
Yes, I have done in the past but I adjusted the preload very carefully. This requires a bit of care, which is why I 'invented' my own pickups with a single (larger diameter and longer) spring that is very easy to adjust.
My GWR Saint, built from a Slater's kit in 1990 but with many additions and mods, still has its original Slater's pickups on the loco (and my own on the tender) and it has probably travelled more miles than my other locos.
Details at: www.davidlosmith.co.uk/GWR_Saint_David.htm
David
31. Bob Thompson Jan 25, 2018
Ref post #28 -
David,
Perhaps I was misunderstood? I wasn’t trying to imply they were the same things, but the Nett affect is the same…my simple analogy of “wobbly wheel” was only to make things clearer.
Having the swash plate motion (akin to the air conditioning compressor in your car, assuming you have Air Con of course) is just another evil that adds to the weakness of Slaters plungers in particular, whether it be caused due to bad alignment to the axle or because the Brass bush has distorted in the moulding. (Not uncommon in my experience).
Eventually the plunger tends to seize up in the bushing and if you are unlucky that occurs when the “wobbly wheel” is at its outer orbit and the plunger then takes an excess hit every time the wheel reaches it’s inner orbit, shaving a bit off the plunger every time it does.
The real point I think is that yes, Slaters plungers can be made to work properly but IMHO they are fiddly, require very careful fitting and dare I say it…..poor value for money and would never be my preferred choice and I say all this based not only on what I have built but on the many other O gauge models that pass through my hands.
Bob
32. Bob Thompson Jan 25, 2018
So yes of course Slaters plungers can be made to work satisfactorily, there is no questioning that.
My argument is that 9 out of every 10 Locos that pass through my hands with Slaters pick-ups fitted have pick-issues of one sort or another.
If you’re an expert you will know the pitfalls but if your a novice (no disrespect) like the person that made this posting, would you really advocate the use of Slaters plunger pick-ups to them?
I certainly wouldn’t.
Bob
33. David L O Smith Jan 25, 2018
Ref post #32 -
Yes, I know Keith (OP); he will be fine with them, asking for advice and/or assistance if he needs it. David
34. Bob Thompson Jan 25, 2018
Ref post #33 -
Ok enough said
Bob
35. Raymond Walley Jan 25, 2018
I have used Slater's plunger pic-ups on many of my builds and never found them a problem. The sharp point should be rounded off otherwise just follow the instructions and ensure that there is sufficient clearance for the plungers to do their job. I solder wire to the tags before bolting them tightly in place with a couple of nuts as close to the end of the threading as possible.
Raymond
36. John Taylor Jan 25, 2018
I also put a tiny blob of PVA on the outer nut just in case………..
John
37. Bob Thompson Jan 25, 2018
Ref post #35 -
So many modellers don’t do that though Raymond, use the tags and nuts I mean.
A lot of modeller's (a majority from what I see so often) solder a solid strand telephone type of wire directly onto the end of the plunger and then of course the housing ends up getting distorted by the heat and the solid strand wire inhibits the movement of the plunger also.
I probably shouldn't say this, but if I have to use them, I also prefer to solder the wire directly to the end of the plunger rather than try to use those fiddly 12 BA nuts, BUT, I do it before the plunger is installed in it's housing using a very thin flexible Silicon Rubber insulated cable about 6 inches long soldered onto the end of the pin using a good flux. I then clean up the pin and cut off any excess overhang of the wire in the soldered joint before threading the other end of the cable through the plunger housing from the outside of the frame and pull /press the plunger into place. Gives a far better job and removes any uncertainty about the tightness of the 12 BA nuts or the risk of them coming loose.
Still detest them though, sorry!!
Bob
38. Raymond Walley Jan 25, 2018
Well I am trying out a set of PFS for the Rover so might just be a convert, who knows?
Raymond
39. Bob Thompson Jan 25, 2018
Ref post #38 -
You will find the PFS are very good but have some design weakness's, in case you weren’t aware?
1. Where the plunger pin comes through the piece of Copper clad it is advisable to use a plastic bush to keep in square to the frames - Jim Snowdon did a posting showing what he does to avoid the problem. Also make sure you have plenty of clearance to the hole in the frames to avoid any chance of the plunger shorting to the frame due to misalignment.
2. Secondly one has to be very careful to avoid the end of the plunger spring going right through the piece of double sided Copper cladding and shorting on the frame. Best to drill a clearance hole in the frame to line up with the spring fixing hole to avoid this possibility if you have space. I made up a simple drilling jig to ensure I got the holes in the right place.
3. The other thing which will be very obvious to you I am sure, is that they do take up a fair amount of space on the inside of the frames and are therefore not suitable for all applications.
The nice thing about them is that one does not have to fit the plungers until the very end, after painting etc.
Have fun
Bob
40. Bob Thompson Jan 25, 2018
Ref post #38 -
Incidentally, I sold a Lee Marsh Dean Single 4-2-2 (Rover?) to Fred Lewis (driver Lewis) last year. I think apart from driving real trains he does demos at the guild shows?
Bob
41. Peter Marler Jan 25, 2018
I have just removed some old slater pickups from a redundant chassis.
The plastic sleeve appears to 2mm shorter than on some I have just purchased new. All other components remain as the standard offering except that the spring is also shorter and feels more powerful (probably as a result of the shortening). This modification allows a greater range of movement for the plunger. Is this a mod made by the chassis builder or is this an older version of the pickup. If it is a builder modification how much can the sleeve be shortened before reaching the large bore for the plunger which remove the stop for the spring, rendering the pickup useless.
Peter M
42. Harper12013 Jan 25, 2018
What nobody has mentioned so far is the preparation needed to Slaters wheels before installation. Because the wheel comes out of a mould on a production line there are bound to be some bits of excess 'plastic', (I know its not actually plastic but I will use the term to describe the black centre part of the wheel) will need to be removed before use. There is usually a 'pip on the rear face of the wheel tread that is removed by Slaters before packaging but it will not necessarily be flush with the back of the tread. I have also seen some 'flash', for want of a better description, stuck to the rear face of the wheel. These need to be removed before use by placing the wheel on a piece of wet & dry stuck to a hard flat surface and rubbing the back of the wheel, with a circular motion. It also helps to turn the wheel a 1/4 of a turn after 3 or 4 circles to even out any tendency to dwell on one side of the wheel more than another. In most instances this will also sort out any 'wobbly wheel' syndrome by ensuring there is no swarf edge to the brass centre.
I quite like Slaters plunger pickups!
Regards
Sandy
43. Ian Middleditch Jan 25, 2018
Slaters pickups work just fine. There are however a number of things which must be attended to before they work consistently.
1. The plastic moulding needs to be cleaned up and flash removed from the small hole where the threaded part comes through. zz
2. The brass plunger needs the end smoothed off and sometimes it needs a rub with emery on the sides to ensure it slides without binding in the plastic bush.zz
3. The plastic bush needs to be fitted into the loco frame square to the frames and in line with the rear of the tyre. It is not always easy to get it sitting square as the bush is tapered so opening the frame hole with a taper reamer from the outside can be helpful.
4. The collector wire must be soldered to the tag in such a way that it can be allowed to flex and be secured somewhere between the frames. A very flexible wire is really needed, single core phone wire is useless.
5. Attention has to be paid to any sideplay on the axles. As the wheel moves away from the frame the spring pressure lessens but increases as the wheel moves towards the frame. Too much movement can lead to loss of contact.
6. The contact surface on the wheel needs to be smooth and preferably polished. A little lubricant, lead pencil works without migrating to the rail head. It helps too if the wheel runs without wobble.
Having said all that there are some aspects of the design which I don’t particularly like.
A. The size of the bush and its rim is quite difficult to hide, not very prototypical anyway.
B. The thickness of the rim requires the wheels to be set out from the frames by much more than the prototype.
C. Adjusting the spring pressure is difficult. Stretching the spring is hit or miss and shortening just makes it stiffer. The only adjustment that I have found to work is either shortening the plunger point or adding a shim washer between the spring and the plunger head.
D. To change the plunger or spring the wheels need to be taken off. Not something that needs done often but if the springs loose their temper or the plunger sticks through dust or grit then dismantling is the only way to repair.
Because of these 4 points I have been using homespun plungers which address all 4 aspects. The design is very simple, only needs hand tools to make and is virtually invisible when complete.
The pictures below illustrate the principle but basically they consist of a piece of brass tube soldered into the frame with a piece of plastic tube glued inside it and finished flush with the outside of the frame. The plunger is brass wire, 0.7 dia, with a home made solder tag, etch strip, soldered near one end. The spring pressure is made from another piece of brass tube with the end sealed up containing a spring, Slaters buffer is what I use, and a pusher from more plastic tube. Think toilet roll holder!
The components and one fitted. There is no side pressure put onto a wheel set, if the axle has sideplay the plunger assembly moves with it and pickup pressure remains the same on both wheels. Below the view from the side, inside and out can be seen, once painted only the fine wire plunger can be seen and then only from an acute angle. The plungers can be removed from between the frames without removing the wheels.
Ian.
44. Simon Dobson Jan 25, 2018
Similar to DLOS’s design, and the modification thereof that I have used. Floating plungers of this nature should maintain an even pressure, allowing for sideplay, presuming the wheels are reasonably perpendicular to the axles.
I rather like this design, it certainly appears smaller than the ones I made. I shall experiment further in due course.
Best
Simon
45. Ian Middleditch Jan 25, 2018
Ref post #44 -
This design is not new, I built a couple of locos in the 70s, in P4, which had a similar arrangement but using the bushes from the plunger pickups sold by Studiolith and their axlebox springs. I think the wire I used then was 1mm dia copper!
Ian.
46. Raymond Walley Jan 25, 2018
Thanks Bob, this is a Finney 7 kit and is designed to use plungers so, on the showing so far of the kit, it should not be difficult to do. I must find Jim's original posting.
Raymond
47. Bob Thompson Jan 25, 2018
Ref post #43 -
Ian,
I am a little confused here, sorry, but perhaps I am being a little thick?
You start off by saying that “Slaters pick-ups work just fine” and then you go on to list many of the undesirable aspects and the actions that need to be addressed before using them, most of which has already been highlighted in this thread.
You then go on to post photographs of your own home made pick-ups (which incidentally look very good to me) but clearly you are not in “Love” with the Slaters offering, and you don’t really think they work just fine, otherwise why go to all the bother of making your own?
From a personal point of view I have neither the inclination or the time to consider making my own. That view might change if Slaters were the only supplier though.
It’s fine if one has 3 or so Locos a year to contend with, but when the number becomes around 10 times that figure, then one does tend to think differently.
I would contend that buying a set of plungers from a Slaters at £13 plus postage, should mean that all that needs to be done is to assemble them, fit them and forget them. Unfortunately the reality is very different.
I rather suspect Slaters are rubbing their hands together with glee because so many modellers immediately think of a Slaters when the subject of plunger pick-ups come up (rather like wheels). Almost a captive market.
If you want something that is smaller and less obtrusive why not look at the pick-ups offered by Alan Gibson? They are the ones he originally supplied for 4mm scale but will work equally well with 7mm scale (might need a washer under the housing flange). The plungers are made with Brass wire tails and the wires can be soldered onto the back of the plungers because the housings are a high quality Nylon - and all cheaper than Slaters to boot.
Bob
48. Bob Thompson Jan 25, 2018
Ref post #44 -
Yes maybe DLO’S isn’t in love with Slaters either
Bob
49. Chris Simpson Jan 25, 2018
I had problems on my N2 with the chassis sides being wider spaced than other locos I have built, so there was not enough room for the flanges of the Slaters pickups behind the wheels. I made up a combined pickup using plastic tube fixed through the frames, with concentric brass tubes glued inside. The brass tubes are a smooth sliding fit for Slaters plungers, and the whole assembly is fixed between the frames and flush with the outer edge. Works well using standard Slaters springs and plungers, but I had to solder the wires direct to nuts which are then threaded on to the plungers. The plungers just screw from outside the frames through the brass tube into the nuts and can easily be replaced if necessary.
50. David L O Smith Jan 25, 2018
Ref post #42 -
I rub with a 'figure of eight' motion, but I'm sure that it all comes to the same thing in the end.
Ref post #44 -
Indeed, but rather more elegant, I would suggest!
Ref post #48 -
It's not that, it's just that I do believe that I can do better, as is often the case (which is principally why building a model takes me so long!). The main attribute that I wished to achieve was the “Floating plungers of this nature should maintain an even pressure, allowing for sideplay …” as SimonD points out.
On the old Forum, David also described how he makes floating, single-spring plunger pickups (images now sadly hijacked), the original Sevenscale L&YR pug included a design of single-spring pickups and the products of the San Chen Crafts factory (Bachmann, Tower Brass, Fine Scale Brass) also used a design of single-spring pickups that are enclosed within a nylon barrel that floats in the frames.
Makes me think that there's not much new under the sun.
David
51. Bob Thompson Jan 25, 2018
Ref post #50 -
Sorry David,
No intention of diminishing your solution.
Yes I have experience of the Sevenscale Pug pick-ups which used to be available as separate items and of course San Cheng used the same type of single spring pick-ups.
I have a few San Cheng models in my collection and without exception the pick-ups are impeccable.
Bob
52. Ian Middleditch Jan 25, 2018
Ref post #47 -
Hi Bob,
Sorry if I confuse. As I said Slaters work fine but you have to do a bit of work on them as detailed on my 6 points, sorry if I repeated what others have already posted. I have used them quite a lot in the past, mostly on locos where there is no sideplay needed. The most recent was on an LMS compound.
However personally I prefer my home spun version, the 4 reasons given in my post.
There is one other reason for preferring my own, time, they are very quick to make and fit. Oh and they are cheap too! I suppose that makes 6 reasons!
Ian
53. Bob Thompson Jan 25, 2018
Re post #52 -
Hi Ian,
No worries, I think we are saying the same thing anyway, Slaters can be made to work of course, just a bit of a pain.
I might try your solution if I can get hold of some suitable tubing and plastic rod. It’s a bit like Sevenscale used to supply with their Pug kit.
Can you recall what size of Brass tube you use?
I assume you must have a small hole at the end of the piece of floating brass tube where it is sealed up to locate the plunger wire - is that right?
Bob
54. David Littlewood Jan 26, 2018
Ref post #50 -
….And as David L admitted there, they were in turn cribbed from someone else's description in the Gazette! Truly NMNUTS.
David
55. David Littlewood Jan 26, 2018
Ref post #42 -
I don't know the exact composition of the Slater's wheel centres, but I'm fairly sure it is some kind of thermoplastic polymer (a.k.a. plastic) possibly with some filler material. I know this because when I first experimented with reducing wheel flanges by turning on the lathe, I managed to overheat them and some of the plastic softened and even in some cases oozed out next to the steel tyres. (I later managed to devise a set of clamps to cure that problem, but that, as they say, is another story.)
David
56. Ian Middleditch Jan 26, 2018
Re post #53 -
Rob,
Exactly!
I use what I can get but mostly it is K&L from the metal centre in the model shop. I use their 1/8” brass with 3/32” plastic which is a sliding fit.
I solder a piece of the brass tube between the holes, spanning the frames, and then cut out the centre piece with a slitting disc, gets them perfectly aligned, and the bit cut makes the spring sleeve. A smear of Epoxy locks the plastic tube in place and while it hardens I make the toilet roll holder. End cap is just brass etch waste soldered on and a hole drilled to locate the wire, roughly centre is fine. I drill through the plastic to open the bore, 0.8, so the plunger slides easily and the solder tags are from etch waste. Once you make one it takes about the time I took writing this to make another!
Ian.
PS I am not claiming this as my idea, I copied it years ago when I worked in 4mm scale.