Ever nearer to scale flange depth in OO

[34theletterbetweenB&D]

This question arises from another thread (which I really musn't take off track more than I am usually wont to do) and it would be interesting to gather inputs from various makers products.

 

I was pleased to see on the Heljan O2 that the pony truck wheel has a very shallow flange; which helps in appearance since this is a small diameter wheel, nominally 2'8" over tyre, represented in the model wheelset as 11.25mm diameter. The small flange depth got my attention enough that I measured it: 0.45mm, scaling one and a third inches. Not seen any complaints yet about it failing to stay on the rails.

 

I have various old kit wheels (mostly under kit wagons) which similarly have flanges in the 0.5mm or slightly under bracket, but don't recall seeing anything this small in RTR OO previously. Any other contenders in the smallest RTR OO flange stakes?

 

[DCB]

Does the 02 really stay on the track?  I am always on the look out for deeper flanges to aid realism as a train staying on the track almost always looks more realistic than one crashing .  When we get correctly formed track sections with the flat tops angled in at 20 degrees and matching tyre profiles which guide the wheels through bends without relying on flange contact then 0.45mm flanges might work but there is no way I can relay my track to cope.  

[Rabs]

Nearly all newer RTR N gauge, RP25 wheels have ~0.5mm flanges.  I'm surprised to hear that they aren't already common in 4mm.  I wonder what makes the manufacturers not use them.

[Horsetan]

Nearly all newer RTR N gauge, RP25 wheels have ~0.5mm flanges.  I'm surprised to hear that they aren't already common in 4mm.  I wonder what makes the manufacturers not use them.

 

Well, you could always adopt P4 flanges.....   ....and maybe the rest 

[Bernard Lamb]

I have never bothered to measure them but PC Models provided wheels in their coach kits yonks ago with near scale flanges.

Bernard

[34theletterbetweenB&D]

Does the 02 really stay on the track?  ...

 Mine's a 100%er for staying on the rails at all times. (Mix of Peco streamline 100 and 75 and SMP, nothing special in precision track laying I promise you.)

 

Nearly all newer RTR N gauge, RP25 wheels have ~0.5mm flanges.  I'm surprised to hear that they aren't already common in 4mm.  I wonder what makes the manufacturers not use them.

 I'd guess at a combination of the existing tooling investment and customer demand, see below.

 

...I am always on the look out for deeper flanges to aid realism as a train staying on the track almost always looks more realistic than one crashing ...

[bertiedog]

Yes, you can reduce the height/depth of the flange, but, and it is a big but, you must work within a set of standards before attempting to alter the finer details.

 

For 16.5mm the best standard, the most researched, the longest accepted standard is the NMRA standard, which works 100% for 00, no problems whatsoever.

 

The DOGA standard copies it for the most part. The UK market suffers to this day by having half hearted acceptance of the standards by commercial makers, usually citing "legacy" problems in not adopting all the dimensions.

 

It is compounded by Peco, in the fact that they alter the point dimensions to make them as universal as possible. However Peco also make 100%NMRA compatible points in code 83.( but visually unsuitable for 4mm),

 

Each standard has to be a package of interrelated dimensions, but oddly the flange size is the odd man out as to depth. If all other dimensions are strictly adhered to, then the depth simply does not matter, as long as the track is well laid and the points are to the right standards.

 

An example is the NMRA standard, running on the Peco code 83, you could reduce the flange to P87 size in height, and the wheels will work over the points. The reason is the thickness of the flange remains standard, and the root curve of the tyre holds the wheels in place on straight track, or the opposite wheel controls it through points. The back to back remains standard exactly.

 

The proto 87 standard does alter things a lot, it remains 16.5, but combines the fine flange with back to back changes and severe changes to the points.

 

However with 00, there is no real standard, and simple reduction of the flange height will work only if the back to back is strictly observed, and the points are also made to DOGA standards, in theory Peco are not suitable to allow wheels with fine flanges and exact back to back to smoothly go through the point.(But it does work)

 

It risks drop in the frog if the wheels are not made with a wide enough tyre, and many commercial types have too little of the tyre overall width devoted to the flange thickness. The outer rim of any wheel supports the wheel over the frog, and thin wheels drop badly on commercial points.

 

However in practise you can reduce the flange height as long as the back to back is spot on or a tiny bit more, than the 14.5mm standard. But it depends on the maker of the wheels, you cannot apply the ideas to all makes, they fiddle to much with the tyre details and the back of the wheel, some times adding a tapered flange, where no taper is really needed, or at least no more than the standards.

 

With HO NMRA I experimented in the late 1970's with exact HO scale flanges, but NMRA thickness, and these wheels worked perfectly on NMRA standard points, but they fail on PECO streamline points, riding the frog too easily. This is not Peco's fault, the wheels were outside what was expected to run on them.

 

I even fitted an Athern Diesel with virtually no flanges, just leaving the curve root to guide it, and it worked fine on good track and NMRA points.

 

But what you cannot do is alter the package of dimensions related to the gauge, each package is just that, a set of dimensions that are interrelated, and must not be used on a pick n' choose basis, unless you are completely knowledgeable about what you are doing.

 

If your using Peco Points, which have the tag universal on them, then it appears tempting to alter things, but the extra tolerances used by Peco work against such alterations, the tolerances are wide, but when altered wheels are used you can more easily overstep the mark, and get very unreliable point operation. Peco are precision made, but are made to take the massive variations of lazy standards of toy and model makers, plus more scale wheels.

 

So if you have good track to NMRA/Doga/Meta standards, then you can reduce the flange to scale, but it must retain the thickness.

Do the same on Peco streamline, and it will tend to derail on the points. (and I am including Tillig HO in that).

 

Stephen

[bertiedog]

Does the 02 really stay on the track?  I am always on the look out for deeper flanges to aid realism as a train staying on the track almost always looks more realistic than one crashing .  When we get correctly formed track sections with the flat tops angled in at 20 degrees and matching tyre profiles which guide the wheels through bends without relying on flange contact then 0.45mm flanges might work but there is no way I can relay my track to cope.  

Well I am afraid a deeper flange is not the solution, it is the track, but please do not take it as you have bad track, just not suitable standards to have smaller flanges. Pizza cutters were useless at keeping the wheels on track, they were designed to stop the drop on the frog. by allowing the flange tip to run on the frog groove bottom, preventing it dropping. This approach is from the Toy trade, not Model Railways.

 

Stephen

[billbedford]

I am always on the look out for deeper flanges to aid realism as a train staying on the track almost always looks more realistic than one crashing .  

 

 

I know what you mean. You just can't get the right 'crumpledness' of crashed full sized trains on a model.

[Pacific231G]

A flange depth of less than 0.5mm does seem unusually shallow, could it be based on RP25 code 88 rather than the more common RP25 code 110. (There isn't a single NMRA standard)

 

Most manufacturers in the European market seem to have used some version of NEM311 for their wheel profiles  but that does cover a range of flange depths from fairly fine to downright coarse (0.6mm-1.2mm) . There is a standard NEM311.1 based on the fine end of those tolerances which is "quasi identical" to RP25-110 but with a flange depth of 0.6 rather than 0.64.

 

This comparison of the two profiles shows very little difference between them.

 

 

 

For its intermediate wheel standard DOGA seems to have adopted the NMRA RP25-110 wheel profile but with differences in the back to back and front to back dimensions.

According to MOROP the slight difference between their NEM311.1 profile and RP25-110 is to avoid derailments of rigid wheelbase vehicles, particularly wagons, owhereas in N. America almost everything apart from steam locos runs on bogies.

 

Some manufacturers have offered a choice between "NEM" and "RP25" but I think that meant the coarser end of the MOROP standardd as opposed to  RP25-110.

 

Absolute flange depth (and tyre width) is surely important or else why would narrow gauge wheels not have those proportionally smaller than on standard gauge wheelsets. 

 

A long time ago I did some modelling based on N. American practice and the thing that did strike me was how much better the RP25 wheelsets I was using performed (on Shinohara and some homebuilt track) compared to anything else I'd used.

I believe that Peco's track standards for code 75 H0 are rather closer to norms than their code 100

[Horsetan]

....Most manufacturers in the European market seem to have used some version of NEM311 for their wheel profiles  but that does cover a range of flange depths from fairly fine to downright coarse (0.6mm-1.2mm) . ....

 

Nowhere better epitomised than by Roco, who never seem exactly sure of which flange depth to use - some of their newer engines are almost RP25-88, but their rolling stock is equipped with the kind of flange depth that was common in the 1970s.