Wheel coning and trackholding

[grovenor-2685]

Is there not an issue of wheels changing direction over a switch?

Not quite sure what you mean by 'an issue'. However, the switch area of a turnout is one that often gives the novice trackbuilder some difficulty to get right. There is lots on this topic in the track section so no need to have a parallel discussion here.
Regards
Keith

[Tim V]

The person who can change the name of this thread is I believe - Martin Wynne!

I don't have a problem with this discussion, I'm just waiting for the practical demonstration......

[Alan Turner]

Is there not an issue of wheels changing direction over a switch?

This usualy happens at the crossing not the switch. The problem at the switch, in models, is usualy gauge tightening.

Alan

[LesGros]

The person who can change the name of this thread is I believe - Martin Wynne!

I don't have a problem with this discussion, I'm just waiting for the practical demonstration......

You misunderstand me Tim,

If you look again at my recent post you will see that I am advocating stripping out the posts on wheel coning effects since 5 Jan and putting them under a more descriptive heading. I see no reason to remove, or change the original topic which covers the EM wheel arguments, pro and con, in detail. I believe that the web-master could do that, I note that there is support for that course of action.

regards

[grovenor-2685]

Indeed the administrators can split the topic, even change the title , what is not so obvious is where the new topic should go. Les, any idea on that? Is a new subsection needed?
Keith

[LesGros]

Indeed the administrators can split the topic, even change the title , what is not so obvious is where the new topic should go. Les, any idea on that? Is a new subsection needed?
Keith

I think that "Track and Turnouts" could be an approriate existing sub section, since that is where dynamic problems are observed. Alternatively, if it is thought desirable to open a new section, perhaps the title "Wheel and track Dynamics" would suffice. It could become a natural home for any new topics on the effects of suspension on running characteristics, and also include ideas about diagnosing and resolving dynamic problems.

regards

[Will L]

If we can't scale them then we really are in trouble.

We have been successfully using the P4 standard for over 40 years now, why should there be any doubt.
IMHO, if it doesn't work for you then the problem can be seen in the mirror, make whatever compromise you want but don't suggest that a 40 year old successful standard needs to be changed to suit.

Sorry Keith but I don't think what I wrote means what you think it does. In my mirror I see somebody who can and does make P4 work, and who has no intention of following Mr Goodall's example because it flies in the face of the modelling philosophy that has me working in P4.

I was trying (obviously failing) to point out that the factors that underlie the steering effect of coned wheels are all linear, and hence work for the scale model as they would for the real thing. If you cant scale linear factors, then nothing we do would make any sense. Unlike mass, which both isn't involved in the steering effect and doesn't scale linearly. hence all the issues we have about lack on inertia compared to versions 76 times bigger,


Will

[Terry Bendall]

Not quite what I said, not all pointwork has the rails vertical.

Thanks for the correction Keith.

Terry Bendall

[grovenor-2685]

I think that "Track and Turnouts" could be an approriate existing sub section, since that is where dynamic problems are observed.

I settled for this new subsection under chassis etc. Hope you are happy with it.

Sorry Keith but I don't think what I wrote means what you think it does.

Same here I think, sorry if you thought that aimed at you. I was trying to rub it in a bit that our standard is well proven and works, and those who think otherwise should look in the mirror for the problem, and resolve it in whatever way they see fit.
Regards
Keith

[martin goodall]

..................... Personally I prefer to get on with building a layout and getting it to run successfully.

Terry Bendall

I do so agree Terry.

I also agree. It's what I am currently doing - I have a working layout on which derailments simply don't happen. And it's why I have adopted the approach I have been advocating, rather than worrying about all the engineering theory and higher maths over which some people seem to get so wound up.

Incidentally, I take the point that it is not mass but dynamics which differ, due to our not being able to scale time, and I entirely agree that time ABSOLUTELY CANNOT be scaled. (Einstein made that perfectly clear.)

[Alan Turner]

I don't see how this can apply since the mass of the model is not scaled down from the prototype. As the model engineering fraternity have found with things like steam ports, you cannot scale nature.

The mass is scaled down OK but it's the weight that is not. You see as I said earlier you can't scale time and therefore you can't scale gravity.

If you want to reproduce the dynamic effects on our models you have to run them approximately 8 (8.72 actualy) times faster. So if you wish to reproduce the dynamics of Mallard doing its record breaking run of 126mph then you have to run the model at 1000mph. You then realise what an achievement the actual Mallard run was.

Of course we don’t want to do that because what we are interested in doing is essentially modelling the static dimensions. We must therefore accept that we need to find methods which enable us to allow the model to move and stay on the track. RTR manufacturers do that by employing deeper flanges etc. We do it by introducing non-scale springing and of course weighing up our models with lead (which is an attempt to correct the mass/weight mismatch).

The bottom line is that you can't have linear fidelity and dynamic fidelity at the same time.

Alan

[grovenor-2685]

[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”.]

Not so, most of the posts in this topic were seperated out from the “EM wheels on P4 track” topic in order to discuss this topic seperately. If you must continue discussing the original topic please go back to the original topic and do it there. When I get a few minutes I'll move these two posts back to the original topic.
The two posts that were just above have been moved back to the original topic.
Regards
Keith

[Joe Newman]

On page 12 of the just published Southern Way No. 17 (Noodle Books) is a picture, probably taken in May 1961, of a replacement crossing at North Camp station on the former S.E.&C.R. line from Reading to Guildford.

The picture shows '110A flat bottom rail in inclined baseplates, (where the rails lean towards one anotheron an inclination of 1:20 to match the coning on the wheels) and fastened down with KT clips and bolts.'

As a pre-nationalisation modeller, I thought this might be of interest to others.

Joe Newman

[TonyMont]

Hi Everyone,
I am slightly confused, I understand the coning of wheels, but surely the rails need to be canted too, in order for the centering effect to work, as Joe notes in his post, this as far as I know is not modelled. Is there a gauge available to produce track with canted rails?
Tony

[grovenor-2685]

This was mentioned some way above, the rails do not need to be canted, the coning effect is from the circumference of the wheel tread where it contacts the rail, think of the rail top as having a knife edge, this can contact the wheel anywhere from the flange root to the outside edge. With a new rail inclined (not canted) at 1:20 the contact strip, ie the knife edge will be roughly in the centre of the railhead and as the flange moves closer, prior to flange contact, this will move onto a larger wheel diameter, ie move up the cone. If the rails are not inclined but vertical the contact strip will be close to the gauge corner, but as the wheel moves across the contact point moves to a larger diameter part of the wheel in just the same way.
For bullhead track I don't know of any gauge specifically designed to hold the rails in the inclined position, but if you use the ready made chaired sleeper bases or the functional chairs the inclination is designed in. For flat bottom Colin Craig does offer gauges intended to help hold the rail at the correct inclination.
Regards
Keith
PS. Cant in track is the height of the outside rail above the inside rail on curves, ie the variation of the plane of the track from the horizontal. This has no direct effect on the steering effect of coned wheels but will have an indirect effect dependent on speed.
Inclination of the rails is the angle from the vertical, on uncanted track, of the nominal vertical axis of the rail, in UK practice most rail is inclined inwards at 1:20 with the aim of reducing rail stress and wear as it puts the load bearing area above the axis of the rail.

[TonyMont]

Thanks Keith, for the clarification.
Tony.