Did this improve performance? Streamlined King + Castle

The T1 s had air assisted power reversing gear.
As The Saggin' Dragon says, Franklin poppet valve gear was fitted to most of the class.
The Q2 s built for freight work were piston valved.
The T1 Franklin valve gear utilised seperate gearboxes in between the frames to operate the valves.
The forward set of cylinders used a horizontal gearbox, in front of the cylinders.
The rear set of cylinders used a vertically mounted gearbox, mounted behind the cylinders.
A tubular linkage ran from the cab control valve, centrally, underneath the boiler, linking up both sets of valve gear at the same time.
I'm fairly sure the regulator was the standard multi valved smokebox regulator, common on many later US built locomotives.

 

Indeed it did.

 

Isn't the cone shaped profile on the tyres supposed to deal with this problem?

Dave

 

The thing is, the only thing that is streamlined is the smokebox door. Without this feature would you consider it to be a streamliner at all?
That's not to say that it isn't an impressive machine though!

Dave

 

The cone was to centralise the wheels within the rails and so avoid the flanges coming into contact with the gauge face. The weight acting on the treads would tend to centralise them even in these circumstances, but in any case would apply to only one pair of wheels, not successive wheelsets of slightly different diameters, where the coupling rods would maintain a common rpm.

 

Umm, no.

The N&W J, like the NSWGR 38, has a tad more streamlining than just the nose. Cast you eyes over the boiler, you may detect a cowling covering everything up. Similarly, the footplate has valancing, cleaning up the sides. One thing that the J has and the 38 hasn't, is a streamlined pilot, covering the front coupling and a streamlined shroud below the smokekbox.

By way if comparison, I've also added a picture of 605, as built during WWII without streamlining.

 

It helps, but consider 3 or more pairs of coupled wheels. It seems to me that with two pairs there might be a dynamic balance where all 4 are at a reasonable point, affected by track variations of course, with 3 pairs its not possible: the centre wheels will always be fighting leading and trailing. Notably Churchward trialled otherwise identical 4-4-2s and 4-6-0s extensively on the road before settling on 4-6-0s. Holcroft, who was there at the time, tells us

Is the tendency on the road for wheel sizes to wear more even or to wear more uneven? Its not something I've picked up, and I can't figure out in my head which is more likely.

 

A streamlined freight loco! As you say not a great success, alongside the firebox was a hot a dirty position for the cylinders and constrained the width of the firebox. The subsequent (unstreamlined) 4-4-6-4s with cylinders ahead of the rear group of coupled wheels were entirely successful.

By the way note the covered brakesman's seat just visible at the back of the tender - reminiscent of the travelling porter's seat on broad gauge tenders at one time.

 

Yes. Leading wheels tend to hit the gauge face of the rail on curves which induces additional wear, but mostly causing the flanges to wear thin. A bogie guides the leading coupled wheels into a curve, so reduces wear to them but at the expense of flange wear to the bogie's leading wheel set. This is why it was common practice to swop the bogie wheels front to rear to even out the flange wear. Today, there is a problem on preserved lines where 50% of the running is tender first. The leading end might have a bogie or pony truck, but not usually the rear end, so flange wear to the trailing wheels is higher than in BR days. You cannot turn just the trailing wheels to restore the flange profile; all coupled wheels must be turned down to the same (nominal) diameter. Hence the SVR's 8F has worn out a set of tyres fitted brand new in 1966.

This has nothing to do with the subject, I have to admit!

 

Duplicate Post deleted

 

I know that that's the intention, but I can't help wondering if in practice there would be a tendency on curves for the loco to ride more to the outside, due to centrifugal force, thus causing the outer wheels to have, in effect, a slightly larger diameter than the inner ones.

Good points, I hadn't thought of that, but how much lateral play is there on the centre wheelset typically? Is there enough to negate this on gentler curves?

Yes, I was also thinking that. Once a wheel, or wheelset, has started to wear more than the others, will it continually slip, even on straight track, due to having a different diameter but the same rotational speed? Will that then cause the differential wear to become even worse? If there is a wheel or wheels continually slipping, then static friction between the wheel and track would be broken. Wouldn't this compromise traction, even on straight track? Could this explain why some locos are said to be prone to slipping?

Pass the paracetamol please

Dave

Edit to say sorry that doesn't have much to do with streamlining

 

According to my understanding (and leaving out a possible quibble about centrifugal force) that is exactly how it works, with the result that most of the time the flanges don't touch the rail head. When they do you get "flange squeal". Within limits, and subject to some ifs and buts, a pair of wheels steers itself along the track.
I take the point that, if wheels on coupled axles have slightly different diameters, at least one set will have to slip very slightly. But how much energy does that waste? Aren't modern diesel-electric locos designed to run with slight "creep" when maximum TE is needed?

 

That's why you have super-elevation, or cant, on curves, i.e. the outside rail is higher than the inside one. The amount of cant is calculated such that at the typical line speed, the tendency of the vehicle to go straight on (and therefore move towards the outside of the curve) is balanced by the fact that it has to gain height to do so and therefore gravity tends to move it back towards the inside of the curve.

A train running at the optimum speed for the radius of curve and level of superelevation will have no flange contact on the curve; if it is running at below optimum speed, it will tend to have contact between the inner rail and flange; if it is travelling faster than optimum, it will tend to have contact between outer rail and flange.

Tom

 

But, isn't the amount of super-elevation restricted to 6 degrees (from memory)? Wouldn't that make the optimum speed quite low in most situations? Sure, it will help, but wouldn't be much use to Guy Martin

Dave

 

I don't know what if any limits there are, but in any case, you can't talk about cant in isolation: it also depends on radius (i.e. the larger the radius, the higher the optimum speed for a given level of cant, or, expressed another way, the smaller the necessary cant to balance a given speed).

I think in practical terms the limiting factor is that you have to allow for a train traversing the curve at very low speed or even being stopped, and therefore you can't have cant that is so steep that it would be uncomfortable / disorientating on a stationary train.

Tom

 

I do know that centrifugal force doesn't really exist, and we should really talk about centripetal force - I was just trying to keep it simple.

I was suggesting that the slippage might compromise traction, not waste energy, although I think this was stated in an earlier post. By the way, what is the "creep" that is designed into diesel locos? Can you give a bit more detail please? Genuine question.

Dave

 

The maximum coefficient of friction between a steel wheel and rail tends to occur if the wheel speed of rotation is ever so slightly higher than the forward speed. The exact amount varies with conditions, but if you push it too far the coefficient drops off considerably and you're into full blown slipping. From about the '80s onwards heavy freight classes have tended to have motor control systems designed to keep the individual wheelsets in this 'creep' regime when trying to exert maximum tractive effort. This is how a class 60 can have a claimed 106500 lb starting tractive effort, giving a factor of adhesion around 2.7, and actually deliver on it.

With a steam locomotive, the power delivery isn't really smooth enough to exploit this effect.

 

Just copied from http://www.railway-technical.com/elec-loco-bloc.shtml
"Creep Control
"A form of electronically monitored acceleration control used very effectively on some modern drive systems which permits a certain degree of wheel slip to develop under maximum power application. A locomotive can develop maximum slow speed tractive effort if its wheels are turning between 5% and 15% faster than actually required by the train speed."