EM wheels on P4 track

[martin goodall]

given the clearances people mention on P4 steam locos with outside valve gear I would imagine an EM wheel at P4 back to back would make life even more difficult.

That would certainly be so if you were to use standard EM driving wheels set to the P4 back-to-back. The distance over the outsides of the tyres would then be (approximately) 22.2mm.

However, Ultrascale can supply any of their wheels (not just loco wheels, but also their coach and wagon wheels) to their 'EMF' or 'Pendon' profile. These wheels have the EM flange profile, but the tyres are only 2mm wide, i.e. the same as P4 wheels. So, if these 'EMF' wheels are set to the P4 back-to-back, the clearance behind outside valve gear, etc. is exactly the same as with orthodox P4 wheels. The distance over the outsides of the tyres in both cases is approximately 21.7mm.

I have not attempted to use 'ordinary' EM loco wheels set to the P4 back-to-back gauge (although they should work in cases where there is no clearance problem behind o/s cylinders, valve gear, etc.). I have stocked up instead with Ultrascale 'EMF' loco wheels, and am in the process of fitting these to various GWR locos.

[jim s-w]

Hi Martin

Are you using 'proper' EM wheels at all then or just EMF?

Cheers

Jim

[gruntphuttock2000]

Purely as a result of reading this thread, I decided to try "suck it and see" tactics, which may be of some interest to other readers. I converted a rake of three Hornby 57' Stanier corridors using Gibson's 18.83 wheels in one and regauged EM wheels in the other two. This involved a reduction of the thickness of the bogie sides a tad and repositioning of the brake blocks but otherwise it was a simple wheel replacement.

My initial individual test for each coach was to push start the EM conversions on the main line through a junction and down the branch, the initial 10 feet or so of which is on a 4' radius curved 1 in 40 gradient with a slight reverse curve at the bottom, followed immediately by a tad less than 3' radius curve on the level. This also involved the negotiation of 3 trailing and two facing points. Both the EM conversions travelled over 30 feet before coming to rest and neither derailed. The 18.83 conversion also completed the test successfully although the distance covered was about 3 feet less (the push start might not have been quite as robust).

The trackwork over which they travelled is largely SMP except for the points all of which are ply and rivet. The latter are by no means expertly built ; probably no more than average or possibly less as stock is prone to frequent lurches traversing many points (although this and derailments to wagons being shunted particularly has been much reduced since I embarked on a thorough fleet wide gauge, buffer and coupling check). The wheel back to backs were all set using a combination of the old P4 gauge and the recently released "flatpack" gauge and the EM wheels were treated identically to the others.

I've done a limited about of testing using them as part of a 6 coach rake with a little shunting to boot but so far none of the test coaches have derailed, although I've had a couple of derailments of the other (not on test) coaches in the test rake.

As yet I've reached no firm conclusions other than that regauged EM wheels would seem to work and the jury remains out on the question as to whether they derail more or less or neither. I only hope that in saying all this I've not invited Sod's Law to take a hand. I still seem to encounter the odd session or two where everything seems to want to derail without any obvious cause!

Rog

[martin goodall]

Are you using 'proper' EM wheels at all then or just EMF?

All my carriage and wagon wheels are 'proper' EM wheels (mainly from Kean-Maygib, with some from Alan Gibson).

It is only the loco wheels which are now being fitted that are 'EMF'. However, even these wheels are 'proper' EM wheels, as they have exactly the same flange profile as other modern EM gauge wheels (such as those by KM and AG mentioned above). The only difference between the EM wheels made by US, KM and AG and the Ultrascale 'EMF' wheel is a slight difference in the overall tyre width (2.25mm for EM compared with 2mm for the 'EMF' wheels).

Some manufacturers make EM wheels which are even wider (e.g. Markits, which are nominally 2.54mm wide, but in practice seem to be about 2.6mm wide). These simply won't fit between bogie frames and wagon W-irons if set to the P4 back-to-back. And obviously some older EM wheels (such as Nucro, etc.) would definitely not be suitable for use on P4 track.

The object of my experiments was not to prove that all or any EM wheels could be used in P4, but simply to find a wheel or wheels with a slightly deeper flange which could be run on P4 track in place of the standard P4 wheel profile, with its miniscule flange, and thereby achieve a higher level of reliability than is possible using P4 wheels.

I tried out various wheels, and proved that some (such as those turned to the RP25.88 profile) definitely won't run on P4 track, but the wheels which are most commonly used in EM gauge nowadays (by Ultrascale, Kean-Maygib and Alan Gibson) will run perfectly happliy on P4 track when they are re-set to the P4 back-to-back gauge. EM loco wheels will also work, but as Jim has pointed out, there might be clearance problems behind outside cylinders, valve gear, etc. and this is where the use of Ultrascale 'EMF' wheels comes to the rescue, so that the overall width of the wheelsets is exactly the same as the corresponding P4 wheelsets.

I was interested to read Rog's findings. I think, with respect, that he may need to take a closer look at his track (whether using P4 wheels or EM-profile wheels), if it is as rough as he says it is. Even deep-flanged '00' wheels can derail on badly laid track. One point that also needs to be watched (as I have mentioned before) is that the track gauge is nowhere less than 18.83mm, and this can best be checked with a P4 roller gauge. On my layout, even where the track proved to be slightly under-gauge, I only got the odd bump or jump, but no derailments. These were entirely eliminated when the under-gauge track was tweaked to correct the gauge.

None of the converted stock on my layout is sprung or compensated in any way, although I have 'equalised' the bogie mountings simply in order to eliminate any wobble in the motion of the coach bodies.

[John Fitton]

Dear Everyone,

I know this is a frightfully exciting subject for some but I think this whole thread is off topic for the scalefour society. In my view the MRSG did a super job in 1967 and produced a set of workable standards that the trade and the average person could implement. My trains use the standard jigs and tools and run through B7 turnouts, mainly flat bottom, at about 80 scale miles per hour, and round 3 foot curves at about the same, and stay on the track except when I act silly and race them. I only have working diesels and electrics right now, and all are lead weighted to about 450 grams, and all passenger cars are weighted to NMRA standards as a minimum.

So, if an alternate standard is sought, why does it belong in the scalefour forum? I don't think I am being elitist, but it just seems like a frightful waste of viewing time to be re-inventing this subject over and over. Much prefer to hear the experiences of modellers pushing the envelope, so to speak: why is there so much retro soul searching......

[craig_whilding]

I think it shows the maturity of the modern S4 Society that is can be discussed on here civilly. Many members of the S4 Soc don't model P4 anyway so a method of combining P4 track with slightly coarser flange wheels isn't really an issue in my eyes.

I can see why Martin has done it and that it works though personally I like to spent the time on springing. Its a broad church.

[James Moorhouse]

Although I welcome the new subsection on the forum I felt my Youtube link
was pertinent on the EM wheels on P4 track thread and perhaps I should explain this.

I wanted to dismiss the idea that the flange is the only device on our models that stops our trains running off the track. I also felt it important to spell out that Martin's use of EM wheels was in the context of a system with a distinct lack of rolling stock suspension
Throughout the course of the discussion Martin said that the use of EM wheels obviated the need for springing, but, had springing been applied instead, wheels would have maintained contact with the railhead and the P4 profile could do what it's supposed to. I'm sure running on the Burford branch would have been much improved this way.
However, what Martin has come up with is a system that works for him and is a wholly pragmatic approach which, as he pointed out, obviates all the bother of springing. What has also transpired is that Martin, in using wheels of a particular EM profile, is working to a tolerance less than that used by most P4 modellers, since the increased EF (effective flange thickness) of his chosen wheel gives a smaller running clearance which in turn means that there is less tolerance for wheel wobble.

[martin goodall]

James is right; it was a desire to convert RTR rolling stock without any form of springing or compensated suspension that first prompted me to experiment with EM wheels re-gauged to run on my P4 track. However, having successfully converted a number of RTR vehicles, it then occurred to me that the very time-consuming process which is involved in adapting various kits in order to fit compensated suspension could equally well be avoided by using EM wheels rigidly suspended in the cast or moulded axleboxes of kits assembled as their manufacturers intended.

As to whether my rolling stock would run more smoothly if sprung or compensated, I am not convinced they would. My uncompensated stock does not bump or jump about to any noticeable extent, but it does stay on the track, whereas even compensated stock with P4 wheels did occasionally derail (admittedly fairly rarely, but in a random and unrepeatable manner which made it impossible to pin down any identifiable cause, and I found this irritating). That just doesn't happen when using EM wheels.

I noticed a theme running through one or two comments in this thread recently, to the effect that the writers had adopted P4 standards more or less as an act of faith, and they had no wish to depart from those standards. I certainly don't criticise that approach - everyone to his own taste. But my own approach is (and always has been) somewhat different. [See the opening paragraph of my article in the May 1978 issue of Model Railway Constructor.] I simply see the adoption of particular dimensional standards as a means to an end rather than an end in itself. So I am very happy to compromise on those standards and to adapt them if I feel that the objective of achieving smooth reliable running can be achieved by quicker and easier methods – hence my use of EM wheels reset to the P4 back-to-back gauge, combined with the elimination of springing and compensation.

I already had a P4 layout, so it made no sense to relay the track to EM gauge (although the possibility did cross my mind at one point). Use of EM wheels proved to be a very practical compromise.

[Incidentally, if anyone objects to this item, as well as James’ comment above being posted in this thread, they should perhaps bear in mind that the original title of this thread was “EM wheels on P4 track”.]