PECO Announces Bullhead Track for OO

[Derekstuart]

Martin/ Mike

 

thank you for the information. It seems quite obvious now that I know.

 

Martin: BRT3... I bought a copy as you suggested, though many pages are missing (not stated in the description). I shall buy another copy at some point as it will probably answer all the questions I keep asking here.

 

Thanks again.

[AndyID]

Hi Derek,

 

In long-welded track, only the end sections of a long rail expand and contract. The middle section is prevented from expanding or contracting by being held tight by the Pandrol clips and heavy concrete sleepers. This creates enormous stresses in the rail. To prevent the track buckling under this expansion stress, deep ballasting is needed and the ballast is piled over the ends of the sleepers.

 

Bullhead rail can be welded into longer lengths, and it has been done. But only for two or three 60ft lengths. It can't be welded into very long lengths because the chairs and keys are not capable of holding the rail firm enough to contain the expansion stresses and prevent the rail from buckling.

 

regards,

 

Martin.

 

Hi Martin,

 

The tendency to buckle due to expansion is an irresistible force, and no amount of ballast will prevent it (concrete slab might?). The idea with CWR is to keep most of the rail length in tension over the expected range of temperature. It's a bit like a piano string. It's always in tension but it loses some tension as the temperature increases. (This may sound a bit like semantics, but I think it's an important distinction.)

 

The increased vertical stiffness of "taller" FB rail is important, but the far greater reduction in maintenance cost came from the elimination of bolted rail joints that CWR allowed on major routes. The customers might have thought BR was using CWR to make their journeys more comfortable, but BR was making the change primarily for economic reasons.

 

Andy

[martin_wynne]

The tendency to buckle due to expansion is an irresistible force, and no amount of ballast will prevent it (concrete slab might?). The idea with CWR is to keep most of the rail length in tension over the expected range of temperature. It's a bit like a piano string. It's always in tension but it loses some tension as the temperature increases. (This may sound a bit like semantics, but I think it's an important distinction.)

 

Hi Andy,

 

That's true so long as the rail remains below the equilibrium temperature, but above that it goes into compression. That's why in very hot weather we see speed restrictions and modified timetables announced, to protect against any possibility that traffic vibration will cause the track in compression to buckle. If the rails were always in tension, there would be no need for the piles of ballast over the ends of the sleepers that we see along our fast main lines:

 

linked from: http://www4.radioparadise.com/graphics/tv_img/9598.jpg

http://radioparadise.com

 

 

There is no such thing as an irresistible force -- it just needs a big enough force in the opposite direction.

 

In the UK the CWR rail is installed so that it reaches a stress-free condition between 21 and 27 degC (70-80 degF) rail temperature.

 

regards,

 

Martin.

Edited October 23, 2016 by martin_wynne

[AndyID]

Hi Andy,

 

That's true so long as the rail remains below the equilibrium temperature, but above that it goes into compression. That's why in very hot weather we see speed restrictions and modified timetables announced, to protect against any possibility that traffic vibration will cause the track in compression to buckle. If the rails were always in tension, there would be no need for the piles of ballast over the ends of the sleepers that we see along our fast main lines.

 

deep_ballast.png

 

There is no such thing as an irresistible force -- it just needs a big enough force in the opposite direction.

 

In the UK the CWR rail is installed so that it reaches a stress-free condition between 21 and 27 degC (70-80 degF) rail temperature.

 

regards,

 

Martin.

 

Hi Martin,

 

Given that the the extension due to temperature is defined by well know laws of physics, the buckling force irresistible.

 

Are there other laws?

 

Andrew

[martin_wynne]

Given that the the extension due to temperature is defined by well know laws of physics, the buckling force irresistible.

 

Are there other laws?

 

Hi Andy,

 

There's Hooke's Law, with F negative?

 

wikipedia commons

 

If the buckling force is irresistible, I'm never again travelling by train in Summer.

 

regards,

 

Martin.

Edited October 22, 2016 by martin_wynne

[Joseph_Pestell]

There are expansion joints in long lengths of CWR so heat above the norm should not be too problematic. But I am quite surprised that they set that "normal" temperature quite so high.

[bertiedog]

There are expansion joints in long lengths of CWR so heat above the norm should not be too problematic. But I am quite surprised that they set that "normal" temperature quite so high.

Global warming allowances..................

I am still waiting for Costa Del Brighton...........

 

Stephen

Edited October 22, 2016 by bertiedog

[phil-b259]

There are expansion joints in long lengths of CWR so heat above the norm should not be too problematic. But I am quite surprised that they set that "normal" temperature quite so high.

 

You may be confusing air temperature with surface temperature. On a day with a low air temperature but exposed to strong sunlight, metal surfaces will warm up very quickly and can easily become hotter than on a hot, but overcast day.

 

This is because air (or rather the constituent gasses are very poor) at heat transfer yet metals and fluids are much better at doing so - hence electric heaters have a lousy efficiency score compared to a liquid based (water or oil) heating systems with a boiler and radiators.

[martin_wynne]

There are expansion joints in long lengths of CWR so heat above the norm should not be too problematic. But I am quite surprised that they set that "normal" temperature quite so high.

 

The expansion rail joints ("expansion switches") allow for the normal expansion/contraction in the last 300ft or so of each rail, called the "breathing length".

 

The tensile or compressive forces which exist to prevent the middle portion of the rail from changing length cannot be carried through fishplates from one rail to the next. The rail has to remain un-stressed at rail joints, the stress in the rail gradually diminishing to zero along the breathing length.

 

Also pointwork is unable to handle such forces, so expansion joints are used between pointwork and long lengths of CWR track.

 

regards,

 

Martin.

[The Bigbee Line]

60 pages and counting.  Wow.  I have not read the thread from front to back and may have missed some comments.  There is allegedly some synergy in point work with existing Peco geometry.  The fact that the US outline Code 83 has different crossing angles is handy to make different configurations.  I was wondering if the plain track will have moulded depressions under the sleepers to align third rail?? 

 

I note that newer Peco streamline has a hollow underneath.  Is that to save material cost during construction?  It should make PVA grip better.

 

Can't wait to get a length...

[bertiedog]

The streamline having marks on the underside is not third rail, it is for the Marklin stud strip that Peco make, very little sold or known in the UK. The code 75 that matches the new bullhead track coming soon, has no recess or marks, so I doubt there will be provision on it as the studs would be too tall. Streamline 100 has always taken the strip and recessing there may be to do with saving material.

 

The geometry of the Peco track has more to do with the UK house size than anything else, this was discussed with Mr Pritchard many years ago, and he based the track arrangements on 12x12 rooms and 14x14 as the max. Using the US geometry stretches out the pointwork, and makes the fitting in the space more difficult.

 

All lot of US modellers use the cellars, utility rooms, and they can be 40x30 or more, with many house rooms 20 x 25 or more. Of course you can use shorter geometry to make sharper points, but they are not so easy to use as longer frogged points. Streamline was never made to duplicate the real thing, but to give an average owner a chance to lay out decent track formations that worked for smaller spaces.

 If you want the US geometry then just use the code 83 track, the sleeper spacing is really no worst than the other Peco universal trackwork.

 

Stephen.

['CHARD]

I work amongst plenty of designing cants and a rail creep or two.

Edited October 22, 2016 by 'CHARD

[martin_wynne]

If you want the US geometry then just use the code 83 track, the sleeper spacing is really no worst than the other Peco universal trackwork.

 

Bear in mind that DCC Concepts say they will be introducing bullhead pointwork matching UK prototype geometry (within the limits of 00 gauge). It will need packing to match the height of the Peco bullhead, and uses stainless steel* rail rather than nickel-silver, but otherwise should match.

 

*Am I alone, as they say in the letters columns, in wondering if DCC Concepts have realised they have made a mistake there, and are having problems making the rail parts for their pointwork? I wouldn't be surprised to find nickel-silver offered as an alternative when it finally appears.

 

Martin.

[coachmann]

*Am I alone, as they say in the letters columns, in wondering if DCC Concepts have realised they have made a mistake there, and are having problems making the rail parts for their pointwork? I wouldn't be surprised to find nickel-silver offered as an alternative when it finally appears.

I was thinking along similar lines after using the new DC Concepts track. I have three unopened boxes of the track for sale now I've gone 0 gauge.

[Colin_McLeod]

Hi Martin,

 

Given that the the extension due to temperature is defined by well know laws of physics, the buckling force irresistible.

 

Are there other laws?

 

Andrew

There are very very large forces but there is no such thing as an irresistible force

Even very very large forces can be resisted or even overcome by very very large forces in the opposite direction.

[Mike Storey]

Our colonial cousins who took part in the American Rebellion of 1776 have a lot to answer for........

 

Just to put the record straight, actually no. The USA used the current British standards continuously long after independence. It was the British who changed them eventually, in the 1840's I think, to match a mean or dominant set of measurements adopted across the UK and the remaining and new colonies by that time, for reasons of continuity in trade. 

[Mike Storey]

 

Thank goodness they never ditched the pint!.

 

Stephen

 

But neither did France. The most common way of buying a glass of beer in a bar here, is by asking for a "demi" (a pression), which means "I'll have a half". The origin comes from a half pint, a "pinte" being commonly used in France until, maybe, WW2. But it is not the same measurement as a British pint. Normally a demi is 250 ml Millilitres, or 250 thousandsth of a pint), making a pint 500 ml, or half a litre. The modern interpretation of a British pint equivalent is 563 ml, but I do not know why the small difference exists without further research if I could give a ..... I am sure someone will stump up that one. something to do with Napoleon and his insistence on scientific, empirical measurements I would hazard. Due to the influx of Brits here, primarily those who cannot be bothered to learn any French, or their customary measurements, but have plenty of money to spend at the bar, you can now order a "pint" at many bars, but it won't be a pint as humanity knows it to be. However, by the tenth or twelfth, most tourists don't care.

 

Back to HO/00. "Half 0" is a far more logical statement about the gauge of track and consequent scale (3.5mm/ft, compared to 7mm/ft of 0), and I have not seen mentioned so far in this thread (someone will no doubt point it out) that the origin of 4mm/ft but using H0 track, was a commercial decision based on fitting the smallest available, reasonably priced electric motor into a locomotive able to run on already available H0 track, using the smaller loading gauge of British outline models. Ok, most of you already know that. But, why did that not change when smaller motors became available, which I guess would have been the case by the 1970's? I have researched that and I cannot determine any indisputable reason - Hornby, Tri-ang, Wrenn and Farish were still in flux, and any one of them could have set the future in stone.

 

But we are, as the Hitchhiker's Guide eruditely states, "For a moment, nothing happened. Then, after a second or so, nothing continued to happen", where we..........

[martin_wynne]

But, why did that not change when smaller motors became available, which I guess would have been the case by the 1970's?

 

Hi Mike,

 

The reason is that RTR H0 doesn't work. Only the British were sensible enough to see that.

 

If you have an exact-scale track gauge, you must also have an exact-scale wheel profile. Otherwise you can't fit the wheels inside scale-width splashers, behind scale-width valve gear, inside scale-width bogie sideframes and axleboxes.

 

If you want to use overscale RTR wheels, you need to reduce the track gauge in order to fit them inside a scale-width model. 00 gauge made perfect sense for that reason, and continues to make perfect sense for the same reason.

 

All H0 models are over scale width in the running gear. This would have been especially noticeable on British-outline steam locomotives with splashers and running plates.

 

regards,

 

Martin.

[jamie92208]

Back to HO/00. "Half 0" is a far more logical statement about the gauge of track and consequent scale (3.5mm/ft, compared to 7mm/ft of 0), and I have not seen mentioned so far in this thread (someone will no doubt point it out) that the origin of 4mm/ft but using H0 track, was a commercial decision based on fitting the smallest available, reasonably priced electric motor into a locomotive able to run on already available H0 track, using the smaller loading gauge of British outline models. Ok, most of you already know that. But, why did that not change when smaller motors became available, which I guess would have been the case by the 1970's? I have researched that and I cannot determine any indisputable reason - Hornby, Tri-ang, Wrenn and Farish were still in flux, and any one of them could have set the future in stone.

 

But we are, as the Hitchhiker's Guide eruditely states, "For a moment, nothing happened. Then, after a second or so, nothing continued to happen", where we..........

IIRC there was an attempt by Rivarossi to get british outline HO going in the late 70's with I think a Royal Scot and some LMS coaches.

 

Jamie

Edited October 22, 2016 by jamie92208

[Clive Mortimore]

IIRC there was an attempt by Rivarossi to get british outline HO going in the late 70's with I think a Royal Scot and some LMS coaches.

 

Jamie

And the wonderful Fleischmann Warship and Bulleid coaches, not forgetting Lima's class 33 and 4F (well perhaps we should) and their very good Mk1 and Mk2 coaches.

[AndyID]

And the wonderful Fleischmann Warship and Bulleid coaches, not forgetting Lima's class 33 and 4F (well perhaps we should) and their very good Mk1 and Mk2 coaches.

 

I still have some of the Trix MK1s. Very nice they are too, but they look a bit silly alongside the other equipment. Maybe I could stick them on a siding at the back of the layout for a bit of forced perspective

[AndyID]

Hi Andy,

 

There's Hooke's Law, with F negative?

 

wikipedia commons

 

If the buckling force is irresistible, I'm never again travelling by train in Summer.

 

regards,

 

Martin.

 

Hi Martin,

 

Well yes, "irresistible" is probably a bit strong, but (assuming I didn't muck up the calculation) a force of around 100,000,000,000 newtons is hard to resist. Anyhoo, the general idea is to avoid compression due to expansion by arranging for the rail to be in tension at lower temperatures. Presumably they wouldn't bother stretching the rail if that wasn't the case.

 

Cheers!

Andy

[AndyID]

All H0 models are over scale width in the running gear. This would have been especially noticeable on British-outline steam locomotives with splashers and running plates.

 

 

At the risk of receiving a lot of threatening messages, I find the effect that Martin mentions quite noticeable on H0 European and US steam-outline locomotives. It's also very obvious on the Trix version of the Flying Scotsman.

[Junctionmad]

My goodness , all this excitement, this thread will have a coronary when the actual track appears.

[Junctionmad]

I was thinking along similar lines after using the new DC Concepts track. I have three unopened boxes of the track for sale now I've gone 0 gauge.

I was thinking along similar lines after using the new DC Concepts track. I have three unopened boxes of the track for sale now I've gone 0 gauge.

Omg , and to think all your posts on 00 track are now wasted. Edited October 22, 2016 by Junctionmad