Coarse P4?

[6029 King Stephen]

I just want to say at the outset that I am not trying to start a gauge war between OO, EM and P4. 

 

Given the reason why we have OO gauge - when modellers were trying to work to HO gauge and 3.5mm to the foot and could not find motors that would fit in locos built to the UK loading gauge, they increased the scale of the bodies to 4mm to the foot but retained the HO track gauge.  Over time, modellers have developed the track gauge to a prototypical 4mm and so we have seen the development of EM and P4 gauges.  If you are not satisfied with a "narrow" gauge in OO, I can't see why you would be satisfied with another incorrect gauge and this is the reason why I have not bothered with EM gauge. 

 

However, I could be interested in moving to P4 gauge but I do not want the hassle of having to buy specialised and expensive wheels from a few suppliers when Romford/Markits wheels work fine for me and I am happy to build Comet loco and coach kits.  However the problem arises when trying to source P4 axles to fit Romford/Markit wheels.  I realise that it should be possible to use Alan Gibson OO/EM wheels and P4 axles but these wheels introduce problems with quartering and fixing that is much easier to achieve with Romfords/Markits.  I have also been able to build track in OO but the principles should be the same for building trackwork in P4 but I would want the clearances that would allow the use of an RP25 type wheel.  I suspect that had Hornby Dublo and Triang opted for a 4mm scale track gauge to go with their 4mm scale rolling stock at the outset, something like what I am suggesting would have been the result. 

 

My questions are; would it be possible to create a course P4 that would allow items intended for OO or EM to run with the correct track gauge, making use of available mass supplies of wheels for locos and rolling stock?  Would it be possible to make a simple oval of track, as included in a Hornby train set, that is P4 gauge but has a loco fitted with an EM or OO gauge chassis and P4 axles?

 

Regards,

 

Steve

[Ian J.]

The biggest issue with using 'coarse' wheels on 18.83 is one of clearances within the locomotive/carriage/wagon. All the underframe gear would have to be widened out to have space for the extra thickness of the OO wheels, and to allow movement space for the tight radii of trainset curves. It's something the HO manufacturers have to deal with as compromises in their designs.

[pete_mcfarlane]

The Americans got there first, back in the 1930s: https://en.wikipedia.org/wiki/American_OO_scale

[Horsetan]

The biggest issue with using 'coarse' wheels on 18.83 is one of clearances within the locomotive/carriage/wagon. All the underframe gear would have to be widened out to have space for the extra thickness of the OO wheels, and to allow movement space for the tight radii of trainset curves. It's something the HO manufacturers have to deal with as compromises in their designs.

 

Arguably Martin Goodall is already doing this by using EM profile wheels on P4 gauge track. 

[6029 King Stephen]

OK.  I began thinking about this was when recently building a K's kit for a Terrier.  I have ditched the K's chassis, wheels and motor and have substituted a comet chassis, romford wheels and mashima motor.  the body of the loco is 4mm scale and if it were possible, I would have used the comet chassis and romford wheels but utitlised P4 axles in place of the OO ones.  In OO the wheels are touching the sides of the loco body's splashers and so I am going to have to reduce the thickness of these to allow the wheels to turn without causing a short.  However, the same would have to be done if it was being used for P4.  If Ii retained the comet OO chassis and had P4 axles with OO wheels, I would still need to reduce the thickness of the loco body and the extra space between the OO wheel and OO chassis frame, should in theory, allow something gauged to P4 to go round a 2nd radius OO curve.   I believe that most people just exchange wheels from OO gauge to P4 on RTR wagons and coaches so wouldn't a OO wheel with a P4 axle work fine in this situation?

 

Regards,

 

Steve

[Ian J.]

Arguably Martin Goodall is already doing this by using EM profile wheels on P4 gauge track. 

 

With an EM axle as well, I presume?

 

Edit: I wonder if OO wheels attached to an EM axle, would work for train set radii 18.83 gauge...?

[garethashenden]

With an EM axle as well, I presume?

 

Edit: I wonder if OO wheels attached to an EM axle, would work for train set radii 18.83 gauge...?

As far as Gibson wheels are concerned, the EM and P4 axles are the same length. OO wheels on a P4 axles gives you EM gauge wheels, unless they're not pressed on all the way. I think Martin thins his wheels to avoid that issue.

[34theletterbetweenB&D]

...Given the reason why we have OO gauge - when modellers were trying to work to HO gauge and 3.5mm to the foot and could not find motors that would fit in locos built to the UK loading gauge, they increased the scale of the bodies to 4mm to the foot but retained the HO track gauge. ..

 Incorrect premise, it was never the motors that were utimately limiting for those not expecting available RTR mechanisms to suit UK prototype, (Stewart Reidpath found his way around that very early on for UK HO) but the wheels and outside valve gear and the need for well below prototype curve radii are the killers. Good summary:

http://www.doubleogauge.com/history/history.htm

 

Inspect your 'current standard' OO pacific. It will be just under scale width over the driving wheel faces, thanks to the generally finer standards used for commercial OO parts nowadays. That buys just enough wiggle room for those wheelsets inside near correctly scaled splashers to be displaced laterally to get around the R2 minimum radius. Likewise the crankpins, rods and gear have just enough space to clear each other when on the R2 curve. Doesn't matter whether you attempt go true scale with equivalent standard RTR parts in 3.5mm or 4mm: the loco will only go in a straight line!

 

It is a little discussed aspect of RTR HO that a great many steam models are scale distorted: there's no other way but to use getting on for 4mm scale in width for outside valve gear types with wheels in splashers. Pays your money takes your choice: distorted model in HO, distorted track gauge in OO.

[hayfield]

Steve

 

Why not just go for EM gauge ? or P/S4 where you have trade support. If you use a track gauge of 18,83 and presumably widen the back to backs from 16.5 in EM gauge to 17.13 less the extra thickness of the wheels, then have to worry about check and wing rail gaps. Life would be so much easier using existing wheel and track standards for the sake of half a mm or less. Not thinking of gauge wars just practicalities. I can see perhaps the benefits of widening Gibson wheels but Romfords ? Maybe buying a GW models wheel quartering press and try doing it first with a set of Gibsons 

 

Good idea though 

[CloggyDog]

I recall the late Keith Wright had a go at least 10 years ago (he dubbed it 'K4') using EM wheelsets/clearances on 18.83mm track. He tightened the flangeways as close as would work reliably, but they were still noticeably wider than scale. This was using D&E stock, so the lack of clearances around valvegear and splashers wasn't an issue.

 

I think he gave up on it because the thing that jars/catches the eye most was those over-width flangeway gaps, not the odd 0.63mm difference in gauge between EM and P4.

 

On a continuous curve, EM gauge wheelsets will happily run on P4 track, it's only on straight track where narrower profile wheels to EM gauge may drop in the 4ft* - the test track the EMGS usually use at expoEM is all P4 track, but a continuous curve of c4ft radius, IIRC.

 

*I once bought an EM layout off a friend (who is also a member on here) and, when I eventually stripped the layout back to bare boards, discovered the reason for those occasional unexplained derailments of stock on plain track - there were some lengths of P4 track mixed in with the EM...

[MJI]

I just want to say at the outset that I am not trying to start a gauge war between OO, EM and P4. 

 

Given the reason why we have OO gauge - when modellers were trying to work to HO gauge and 3.5mm to the foot and could not find motors that would fit in locos built to the UK loading gauge, they increased the scale of the bodies to 4mm to the foot but retained the HO track gauge.  Over time, modellers have developed the track gauge to a prototypical 4mm and so we have seen the development of EM and P4 gauges.  If you are not satisfied with a "narrow" gauge in OO, I can't see why you would be satisfied with another incorrect gauge and this is the reason why I have not bothered with EM gauge. 

 

However, I could be interested in moving to P4 gauge but I do not want the hassle of having to buy specialised and expensive wheels from a few suppliers when Romford/Markits wheels work fine for me and I am happy to build Comet loco and coach kits.  However the problem arises when trying to source P4 axles to fit Romford/Markit wheels.  I realise that it should be possible to use Alan Gibson OO/EM wheels and P4 axles but these wheels introduce problems with quartering and fixing that is much easier to achieve with Romfords/Markits.  I have also been able to build track in OO but the principles should be the same for building trackwork in P4 but I would want the clearances that would allow the use of an RP25 type wheel.  I suspect that had Hornby Dublo and Triang opted for a 4mm scale track gauge to go with their 4mm scale rolling stock at the outset, something like what I am suggesting would have been the result. 

 

My questions are; would it be possible to create a course P4 that would allow items intended for OO or EM to run with the correct track gauge, making use of available mass supplies of wheels for locos and rolling stock?  Would it be possible to make a simple oval of track, as included in a Hornby train set, that is P4 gauge but has a loco fitted with an EM or OO gauge chassis and P4 axles?

 

Regards,

 

Steve

 

 

You want EM

 

Forget the distance between the rails, but the distance over wheel faces.

 

This is why OO stock usually looks fine, the width over wheels is not that much less than scale.

 

If you want slightly wider wheels than P4, EM is for you.

[brossard]

The problem as I see it is 00 wheel width, touched on by Martin.  Typical 00 wheel is 2.75mm (or more) wide and flange is ~ 0.75mm and quite deep too.  Markits wheels are better with 0.5mm flange and 2.5mm width.  I ran into the problem of the Markits wheels touching the Mazak footplate on my 3F when I tried to use these wheels   instead of Ultrascale (no confidence in their ability to hold quarter) on my Easi Chas.  US wheels are 2.2mm wide with a flange of 0.5mm.  If you're converting an inside cylindered loco that doesn't have splashers you may get away with 00 wheels.  00 wheels really do look gross compared to those made to P4 or even EM standard.

 

I gave up on converting steam locos to EM and I'm back on 00 now.   I haven't completely given up on the idea of EM, but if I do go back I think it's easier to build a new chassis or kit.  Of course there's always diesels.

 

As for splashers, Brassmasters do have fine brass ones for the 3F and 4F.  These may work elsewhere.

 

John

[6029 King Stephen]

So the answer to my question is that it is not possible to have P4 gauge with an RP25 wheel.  I didn't realise that an EM gauge wheel was narrower that a OO one.  From a financial aspect, I will continue with finescale (?) OO so that I don't have to re-wheel all my stock to EM.  The wider sleeper spacing gives the illusion that it is not OO.  Overall it works for me. 

 

I will build some basic P4 trackwork as the basis for the tram tracks for the Corgi and EFE non-working trams that I have.  I have noticed that as they are to 4mm, that includes the gauge of the wheels.

 

Thanks for all the replies and viewpoints.

 

Regards,

 

Steve

[A4CML]

I seem to remember some years back being offered by Malcolm Mitchell a set of EEM wheels for one of his kits. Presumably this stood for 18.8mm gauge using EM profile wheels? I declined at the time as I model in 'standard' EM. I've also heard of EMF which I believe used a 'finer' flange profile although I stand to be corrected.

On a practical point, I've used thin (0.1mm) washers to fit over a Romford axle square to correct an incorrect (tight) back to back measurement before now so this method could be used for coarse P4. Having converted steam outline locos to EM before now using their original wheels works in a crude sense as locos will run but the manufacturers wheel profile means there is very little side play in the track gauge for reliable running not withstanding problems that might occur getting leading crankpins to fit behind slidebars. I've had locos that will sit on the flange on track and not the tread! All rtr wheels I've used needed their flanges refining.

[Guy Rixon]

If you use 00 wheels moved apart by 1.33mm then they will not work properly on P4 track. The check gauge will probably be wrong, which means that your wheels will either jam on the check rails or hit the nose of the crossing and come off. Using EM wheels moved apart by 0.63mm, IIRC, mitigates this but not completely. (I think Martin Goodall has eased his check rails slightly to suite EM wheels.)

 

Of course, you can build track to 00 standards except for a wider track gauge, but it will not look as good as P4 track because the geometry will be visibly different to the prototype. One of the big advantages of P4 is that the track looks better.

 

Anybody is free to make up a new standard based around 18.83mm gauge, but it would be a great kindness not to call it P4 or even to include P4 in the name. P4 is P4 and is a matched set of standards for track and wheels. New standards would be something different and should have a distinct name.

[Horsetan]

.....I've also heard of EMF which I believe used a 'finer' flange profile .....

 

Yes, EMF (it's unbelievable) exists, and is the profile used by Pendon. Ultrascale do offer it, but they don't really publicise it.

 

[iak]

EMF is, I think, a profile conceived for Pendon.

I think essentially it is a P4 wheel with a wee deeper wheel flange.

Some of these are in my possession via Ultrascale and are in use, experimentally, on some of the recent Hornby 21T hoppers. They appear to behave but I must investigate further.

I await my court martial and subsequent flogging... WIBBLE!

[Horsetan]

EMF is, I think, a profile conceived for Pendon.

I think essentially it is a P4 wheel with a wee deeper wheel flange.

 

It's almost like the difference between P87 and HO-pur....

[brossard]

EMF is, I think, a profile conceived for Pendon.

I think essentially it is a P4 wheel with a wee deeper wheel flange.

Some of these are in my possession via Ultrascale and are in use, experimentally, on some of the recent Hornby 21T hoppers. They appear to behave but I must investigate further.

I await my court martial and subsequent flogging... WIBBLE!

 

I seem to remember that an issue of MRJ fairly recently where this was suggested caused a firestorm.

 

John

[t-b-g]

The main visual difference between EM and P4 track is the relationship between the running rail and check rails. In EM, the checkrail gap is wider than the head of the rail. In P4 (and in the real thing)  the check rail gap is narrower than the top of the rail. With plain track, it is almost impossible to tell the difference between EM and P4.

 

If you are going to lose the main benefit of P4, by using wider flangeways capable of taking the larger flanges used by OO and EM, plus you are going to lose the next major benefit, which is narrower wheels with smaller flanges, then I personally cannot see any advantage that "coarse" P4 has over EM.

 

Many wheels used in EM do now have quite small flanges and will run through conventional P4 track to society standards as long as you get the B2B (and also the dimension from the back of one wheel to the outside of the flange of the other wheel) spot on. I cannot imagine that wheels like Romfords/Markits will allow you to get both these dimensions right. even if suitable axles were available,

 

Putting wider than scale wheels set to run on P4 track in a loco, particularly one with outside cylinders or splasher clearance problems, is quite simply going to mean that you run out of space.

 

I am all in favour of people trying new things as that is the only way that the hobby progresses but my instincts tell me that this approach is not going to lead to a happy conclusion.

 

edited for spelling/typo

[iak]

A lot of willy waving more like...

Arf...

[brossard]

So the answer to my question is that it is not possible to have P4 gauge with an RP25 wheel.  I didn't realise that an EM gauge wheel was narrower that a OO one.  From a financial aspect, I will continue with finescale (?) OO so that I don't have to re-wheel all my stock to EM.  The wider sleeper spacing gives the illusion that it is not OO.  Overall it works for me. 

 

I will build some basic P4 trackwork as the basis for the tram tracks for the Corgi and EFE non-working trams that I have.  I have noticed that as they are to 4mm, that includes the gauge of the wheels.

 

Thanks for all the replies and viewpoints.

 

Regards,

 

Steve

 

I used to think that 00 wheels could be used for EM, until I started tinkering.  I tried to convert a Bachmann Jinty by modifying the wheels heavily to refine the flanges and thinning both front and back ( I had planned to use EMGS axles but these were a terrible fit anyway).  I found that the backs tarnished and figure that Bachmann use some kind of plating to keep them shiny.  I finally did a Comet EM chassis which I found to be easier because I was in my comfort zone.

 

Another point, when you reach a certain age, the time it takes to produce the model you want takes on a different value than when you are in your 30s.  I'm upgrading my RTR as far is as practical.

 

Happy modelling.

 

John

[BG John]

As has been said, OO wheels on 18.83mm gauge wouldn't be P4 or S4. It would be something closer to what must have been used for 19mm gauge in the 1920s and 30s. I imagine that had all the problems that HO has, with a need for wider than scale footplates and splashers on steam locos, and presumably wider bogies on diesels and electrics, that would also need wider than scale bodies to match the bogies. So all the HO problems, but in a larger scale. You'd be into retro modelling, with scratchbuilt locos, to make it work!

 

That's why EM works, as the gauge is narrowed to compensate for the wider wheels, so is a practical compromise. I'm happy with EM in 4mm, and OF in 7mm as that's pretty much comparable to EM. That doesn't mean I don't also dabble in P4 though, as trying to get EM wheels in broad gauge locos and rolling stock is unnecessarily complicated, when it's easier to do it to near scale standards.

 

Standards have been developed because they work, and messing with them is generally asking for trouble, says someone who has OF wheels running through Peco OO code 100 pointwork .

[Captain Kernow]

I have occasionally looked into the possibility of using Romford type wheels, suitably turned down in a lathe to the P4 profile, and fitted on Romford EM axles, with washers to give the correct P4 b2b.

 

The reason for this was frustration at poor quartering, despite using a posh wheel press. In the end it always boiled down to too much faff, so I usually ended up waiting for the Ultrascales.

[bertiedog]

 

 

Altering standards...don't do it! P4/S4 is a complete system not just track, but all aspects of copying the real thing,

By all means modify it at your peril, but the points are going to be the problem with non P4 wheels, and do not forget your confined to scale radius track as well.

 

EM is perhaps the best solution, Markits do the right wheels with quartering, if this is the major worry. EM standards allow tighter radius's than P4, and general appearance of the track is pretty close to P4, except for flange ways.

 

Perhaps the missing link is the wheel quartering issue, which is basically down to experience and careful working knowledge.

 

Wheel presses do not always solve quartering, they only work well when a prepared set of wheels with bearings in place are assembled off the loco, and then tested, and dropped into the prepared frames.

 

Pressing on with bearings in the frame is just so darn risky, the chassis gets in the way, the press may foul other wheels, and it is difficult to adjust by twisting the wheel on the axle.

 

But if the wheels are readied outside the frames, they can be adjusted in seconds to a perfect quartering position. Nothing in the way, and you can gently twist the wheel to get it perfect.

 

With Gibson, rough one end of the axle by rolling a file edge on the steel, and press in the axle, with a tiny drop of loctite. The makes a good permanent joint. Then add the horn blocks, and press home the second wheel on to a cleaned  and de-burred axle.

The press may offer quartering or you can make a gauge from brass sheet to check the accuracy. The end with no rough surface allows twisting to get the quartering dead on. ( After it is dead on and tested on the track, the boss of the wheel cab be drilled right through the plastic into the steel with a number drill (70 or so), and a wire superglued in to the hole to lock the quarter).

 

One word of warning, the Hamblings wheel press is not a universal item, they were designed to only assemble Hamblings wheels, they are next to useless with Gibson etc. The Hamblings idea used the stub end of the axle to guide the press, and also the crankpins may not match Hamblings dimensions.

 

However the press can be modified with slots for the crankpins, and with extreme care press home axles like Gibson.

However the best way is a large vice and small socket spanners used as tubes to press the wheels home accurately, with a plate gauge to guide the quartering, the same gauge is used to check all are the same, and that is it.

 

All this assumes the chassis spacing is correct and parallel and the rods match the axle holes. A Gibson set would take well under a half hour to prep and press home and check. once done then it never needs further attention, if done right.

 

Stephen