7mm Wheel Standards

[81A Oldoak]

I have friends in both camps and while I was editor of the Gazette would tone down comments likely to offend one or the other. When moving up to 7mm I was faced with a choice but as I had no layout but could take my stuff to run on local 0 gauge layouts that was the choice I made. I am certain progress would have been slower if I had adopted S7. When ever someone gets a bit high minded about there finescale stuff I usually ask if they have scale diameter wire in the armature windings.

We all need to compromise. Clarey Edwards probably less than most he built his steam locos to 1:45 which is right for 32mm track. If the real loco had three cylinders so did his model. His West Country had working chain drive valve gear. He did have to abandon the Gresley conjugated gear as the link was not rigid enough (due to scaling factors) although it was reportedly a bit iffy full size. 

 

Do what suits you admire what is good in others layouts and accept that we all make different compromises. S7 wheels would look good on a static model without requiring a lot of work. 

Don

In the end, it's all about about doing what you enjoy as the hobby is supposed to be fun. At Ixion we are frequently asked if our locos can be easily converted to S7 standards. I suppose the answer depends on what equipment you have, the main job being turning wheel flanges if desired. The Hudswell Clarke is a simple inside cylinder 0-6-0ST with the wheels entirely below the footplate so there are no outside cylinders or splashers to worry about. The Fowler 0-4-0 diesel is also simple. On both locos, the brakes can be gently eased out for the wider gauge. At Railex last year someone showed me a Fowler that had been converted to S7 in less than a couple of hours.

[hartleymartin]

I'm sure that it wouldn't be a too-difficult job to convert the HC, Fowler, MW and the up-coming Peckett and Terrier models to S7. Admittedly, it is always easier to do this to an unbuilt kit, but these things are not impossible.

[Osgood]

I understand that angling is the most popular pastime in the UK and that with the right sort of bait one can get a bite every time.

And here is more evidence to back up Simond's claim (you need to turn volume right up):

 

 

I wonder if you can get bi-scale glasses.........

[Donw]

I agree with a lot of what you say Simon. I wouldn't accept that Z gauge is proof of finer flanges. For one thing the wider the gauge the more it is affected by any crosswind in the track not much difference between 32 and 33 but  z is only 6.5mm. The other thing is you need to have well laid track and compensation although it can be left out if the track is really well laid. Agreed it may well avoid a lot of problems if building S7 from scratch but some kits may be compromised to suit 32mm which can be a pain for the S7 modeller.

These days some progress is possible in 0 gauge using rtr stock and peco track which is much easier for some. If you are building kits or from scratch and making your own track then it becomes more practical to go for S7 the more you are doing yourself.

Don

[Jeff Smith]

Surely the ability for keeping a wheel flange in its place while rolling is more dependent on the flange size/wheel diameter ratio. From P4 experience if a large diameter wheel with a fine flange lifts just a little, especially on the outside of a curve, the flange will roll up on top of the rail. Z scale wheels are tiny but with relatively large flanges. The smaller wheels will not so easily roll up onto the rail top

[jim.snowdon]

Simon,

 

In contrast to the attitudes of some of the S7 fraternity, I found your comments well considered. As you said, if we wanted to end up with close to scale appearance, we wouldn't have started from where we did. But history is history, and cannot be altered. To me, there is nothing wrong with S7 as a concept; the down side is that if you are starting from scratch in 7mm scale, you will be much more on your own than in Finescale 0, And therein lies the attraction of 31.5 and finer - in a club environment we can build layouts that everyone can run on. Rather like the saga of Betamax vs VHS - it wasn't technical quality that counted, but weight of numbers. I started in Finescale, and I doubt that I will ever deviate from that. Plus, like EM and P4, the former generally wins by being that bit more tolerant of the ups and downs in model railway track.

 

Jim

[Simond]

I blame Henry Greenly. In one of his books, he expounds the delights of narrower track than scale as "looking better". I have the book, and one day I'll find the quote, but his influence on the new hobby was both too great and entirely a personal view. We live with the results of it today in every popular scale.

 

As of course do the Ratty and the RHDR, being built to one third scale, but running on one quarter scale track.

 

But as Jim says, we can't change history, and whilst it might be the case that building from new in S7 is easier than 0F, it certainly wouldn't be easier to change what I've already collected, so I'm staying with 32mm on the plain track & 31.5 on the fiddly bits.

 

And keeping it on the track? Compensation or springing on everything that isn't a normal 4w wagon, and track built to reasonable standards. If it comes off everywhere, it's your pride & joy that needs fixing. If everything comes off at that point, then it's the track... As the meerkat reputedly said, "simples".

 

Best

Simon

 

Edit - typo

[Simond]

Simon,

 

I don't buy the scale/gauge issue - it's clear that there were constraints on what could be done at any given point of history for any given cost, but the refinement evident in the better continental models (which are typically HO thus a smaller scale, despite sharing a track gauge, and having a larger loading gauge) suggests that this is not a justification.

 

I think there might be some roots in the post war austerity that the UK suffered - trying to sell "toys" would require a firmer hand on the costs than might have been the case, ironically, in Germany or Japan.

 

I'm interested by your views on compromise. I'm a professional engineer, and my view, as noted earlier in the thread, is that everything is a compromise. Your explanation of beer and champagne is, in my view exactly that, but I don't see compromise as emotive at all - nor do I view compromise as in any way a "less than ideal outcome", (although, of course, a bad compromise will satisfy nobody) - what you describe as "constraints & consequences" is my "compromise". For me, it is simply the dispassionate consideration of many variables, some of which will be in conflict with others and some of which may not be at the discretion of the person required to generate the most satisfactory outcome. And I think this is exactly your point.

 

But I still blame Henry Greenly!!!

 

Best

Simon

[raymw]

I guess you don't blame Greenly as much as LBSC https://en.wikipedia.org/wiki/Curly_Lawrence The one thing, in all this, I think it was one of Curly's mantras, -'you can't scale nature'. Even in the finest of fine scale models, the best you can do is make it look right. The current high resolution photos can show up all the compromises that have to be made, in order to get a working model. It just depends how much you want to be bothered.

 

Best wishes,

 

Ray

 

('bothered' relates to time, money, skill, eyesight, vision, materials, permissions, etc.)

[Simond]

Hi Ray

 

funnily enough, I don't blame Curly at all - he's 110% right about not scaling nature - the viscosities, and densities, and heat capacities of air, water, coal, meths and oil are the same in 1:1 or 1: whatever you choose - witness the dreadful "storm scenes" in most wartime movies, which were clearly done in a swimming pool with scale ships.  So dimensions of boilers, grates, firetubes, water pumps, injectors, blowers, petticoats, and so on cannot be true to scale unless you are prepared to put up with woefully poor performance  - but that largely doesn't concern those of us who use electrickery to drive our models.

 

Curly was dealing with the consequences of his decision to build live steam in small scales (I'd say he had to compromise, but t'other Simon D would prefer "consequences" )

 

We do not have those constraints, and AFAIK, neither did Mr Greenly - he took an absurd decision for what I understand to be entirely personal aesthetic preferences, and we are living with the results of that, nearly a century on.  The Continentals and Colonials did not suffer from such a luminary to blight their futures!

 

(and yes, I agree with "bothered" )

 

best

Simon

[raymw]

What i wrote was a bit ambiguous

 

I guess you don't blame Greenly as much as LBSC

 perhaps I should have written it as  'I guess you don't blame Greenly as much as LBSC blamed Greenly' - instead of allowing the interpretation of 'I guess you don't blame Greenly as much as you blame LBSC'.

[jim.snowdon]

How do you follow that? Taken right back to the basics, it comes down to there being two ways of working out the track and wheelset dimensions, given that the starting point, ie 0-F is flawed. I believe it is no secret that S7 eveloved, in a large part, from dissatisfaction amongst a group of modellers with the less than ideal behaviour of fine scale wheels on 32mm track and a wish to do better. Either you can start from first principles and calculate the critical dimensions, or you can, as it were, cheat and crib from the full size on the basis that it demonstrably works. If you are going to borrow from full size, there is little point in sticking to 32mm either - it is, essentially, an arbitrary figure. From a loco building point of view, at least for steam outline models, the extra 2mm between the wheels has unarguable benefits for engines with large boilers sat down on to of and/or between the wheels, but that is hardly a universal problem for 0-F modellers. I wouldn't argue either that putting the fronts of the frames rather closer to the prototype dimensions has its benefits in terms of getting firebox and smokebox profiles right, particular where they are exposed. But then, and here is where I start to view the S7 argument as somewhat overdone, departures have to be made from scale simply to get engines to go round unprototypically tight curves and cope with proportinately oversize tolerances. Whereas a modeller might have to use a pair of 1:8 or 1:9 turnouts to form a crossover, the full size would be using 1:13 or 1:15. So S7 rolling stock and locomotves are often running on rather non-S7 track geometry.

 

The development of the sub-32mm gauges was an approach to solving the same problem of poor running by starting from first principles and taking the existing wheels as the starting point. Wheel and track dimensions are inter-related, but there is no fixed starting point; either the wheelset or track dimensions have to be fixed at some value first. For the majority of modellers, it is the wheel that has to be the pre-determined component, either because we individually or collectively, in the case of the club environment, have rolling stock collections that we do not want to re-wheel, or want to make use of the greater range of wheels that are available off the shelf. Whatever its imperfections, the availability of wheels to 0-F standards is a dominating factor by a very great margin. Thus, with the wheel dimensions fixed, it is inevitable that the track dimensions come out as they are. In this, gauge is a secondary figure; the important dimension is the check gauge, which is the same whether the track is to 31.25, 31.5 or 32mm (except for Peco points, where it has been altered to an inconsistent value, presumably to cope with the vagaries of the US market).

 

That, coincidentally with better runing, we get a track which looks nearer to the prototype is a useful by-product. The gauge may be around 1.5mm different from S7, but that is not visible on its own; the flangeways are noticeably smaller (and for 31.25 gauge, are the same as S7). The lead lengths of turnouts will differ, but that is not visible to the viewer, never mind that they are much shorter than they should be, and any arguments about the spacing of the timbers in theguts of a turnout are specious. The only areas in which the spacing of the timbers is critical is through the switch and the crossing, as they are determined by the dimensions of the those chairs/baseplates which support the rails of diverging routes. In between, the spacing of the timbers is nominal, being a best fit between the maximum spacing and the space available.

 

Jim (who spent a good part of his later career in railway engineering dealing with the wheel:rail relationship and track dimensions full size)

[ixionmodels]

Can anyone on this thread post a photo showing the difference in flange depth and tread width between Slater's 7mm finescale and Slater's S7 wagon wheels? A Google search proved fruitless, and Slater's themselves have no images of S7 wheels on their website that I can find.

Thanks in anticipation,

Lindsay, from Newcastle, NSW.

 

[Simond]

Simon, Jim,

 

Thanks for an interesting diversion. I stand by the word "compromise", and I think this quote from the OXfordDictionaries website justifies my choice of word :

 

"An intermediate state between conflicting alternatives reached by mutual concession:"

 

Of course, I'll readily accept that there are alternate definitions, and there are clearly other ways of expressing the concept, about which I think we are in agreement.

 

Regarding the "bothered", it perhaps hinges on choice and responsibility. I have a responsibility, a duty, to do a good job, at work. I have a choice to do a lousy, adequate or superlative job of my model making, and given that there are few objective standards by which model making can be judged, apart from measurable accuracy to scale (which we have agreed is perhaps not appropriate in some circumstances), it's down to personal & subjective views. Which is ironic, considering my comments about Greenly.

 

Anyway, back to the workbench!

 

Lindsay, sorry, can't help, but I'm sure there must be someone who can

 

Best

Simon

[raymw]

Hi Lindsay,

 

Hurriedly snapped, below. The s& ones have a better profile, which doesn't show here. I can't be 'bothered' to get my decent camera a macro lens set-up.

 

 

 

 

I guess you can tell which is which.

 

Best wishes,

 

Ray

[bbishop]

Take a black marker pen to the tyres.

 

Bill

[ixionmodels]

Thanks Ray. I can see enough to judge the difference.

 

I can see that the moulded centres are the same, and the tyre thickness (viewed side on) looks to be the same, which is interesting. I somehow thought they'd be more 'spidery' for want of a better word. You know how old photos show wagons with wheels which look like they're all spoke and no tyre - very open and see-through and delicate. It's something that model wheels rarely seem to capture.

 

Is that due to manufacturing methods, etc do you think? Just another one of the compromises we encounter when scaling everything down. I know when we made our Ixion 7mm locos, we got the wheels as right as we could allowing for the Guild's guidelines, so the locos would run on everyone's track. But when we made our first model, the N gauge Manor, our (genius) Technical Director Phil Badger went with a finer wheel profile than any RTR loco in that scale had ever had before. "It'll work", he said. And it did. And now most of the other manufacturers have caught up; but we were very proud of the innovation. I wonder if a brave manufacturer in the future will give a similar idea a crack in 7mm. Maybe not us, we're doing a series of HO locos for NSW at the moment! :-)

 

Cheers,

Lindsay.

 

Hi Lindsay,

 

Hurriedly snapped, below. The s& ones have a better profile, which doesn't show here. I can't be 'bothered' to get my decent camera a macro lens set-up.

 

WP_20150804_19_37_24_Pro.jpg

 

WP_20150804_19_36_03_Pro.jpg

 

WP_20150804_19_37_24_Pro.jpg

 

I guess you can tell which is which.

 

Best wishes,

 

Ray

[raymw]

I didn't have the same size/style of wheel to hand. if you want some dimensions than this may help http://scaleseven.org.uk/index.php?id=70 there is more information linked from that page. I'm not sure if Slaters (or any one) get it consistently accurate. Unless you are looking for it, you possibly wouldn't see the difference between the wheel profiles once on a wagon from a normal viewing distance and with moving wagons.

[hartleymartin]

 I suspect some of his statements were post hoc rationalisation - post hoc ergo proctor hoc.

 

 

Sorry to be the pedant, but that should be "post hoc, ergo propter hoc."

[Simond]

Martin

 

You're merely A pedant...

 

Simon

[Donw]

Surely the ability for keeping a wheel flange in its place while rolling is more dependent on the flange size/wheel diameter ratio. From P4 experience if a large diameter wheel with a fine flange lifts just a little, especially on the outside of a curve, the flange will roll up on top of the rail. Z scale wheels are tiny but with relatively large flanges. The smaller wheels will not so easily roll up onto the rail top

 

That would rather suggest that big wheels would need deeper flanges not something you see full size.

Don

[raymw]

If the full size ran at the same speed, around the same radius, and weighed the same then they would need big flanges, too, if to the same wheel/rail profile as the model. I won't go into the details, but it is the same reason as you don't get ten foot high insects, scaling nature isn't just linear ratios.

[Jeff Smith]

That would rather suggest that big wheels would need deeper flanges not something you see full size.

Don

Full sized railways use check rails to prevent this. Also the suspension and frame flexibility tends to keep the wheels in contact with the rails, together of course with the weight that does not scale well.

[jim.snowdon]

I would suggest it has more to do with the toy origins of our hobby and keeping stock with rigid chassis on indifferently laid track. In simple terms, the deeper the flange, the greater the track twist it can tolerate, particularly when it is negative twist in curved track. As long as the wheel:rail contact point strays no further than the flank of the flange, derailment is unlikely. The problem is when the wheel lifts far enough that the contact point starts to roll beyond the flank and into the rounding at the tip of the flange, when the angle starts to decrease. Deeper and/or sharper tipped flanges delay that point, as some P4 have demonstrated by running re-gauged EM profile wheels. It is also one reason, I believe, behind Pendon's decision to stick to EM in preference to P4 for the Vale layout.

 

Jim

[hartleymartin]

Just my personal opinion, but the Proto-Four and Scale-Seven standards seem to be something of an intellectual exercise more than being practical for the average-joe modeller. Sure, the models are beautiful, but I am prepared to sacrifice some scale fidelity for the sake of having something which I know will always work and is a little more forgiving with my occasionally crude working tolerances.

 

The fact is that Scale-Seven (in my case as a 7mm modeller) would mean having to pull apart perfectly good RTR models and my growing collection of model kits, a whole lot of fettling to put in springing/compensation to all my models. Then I face the problem that if I go to a mate's layout, my stock is incompatible with his track.

 

But remember rule #1 of the hobby: "They are YOUR trains, and you do what makes you happy, regardless of what others may say."