Cheating On The Corners (mini-blog)

Let Us Now Praise Unknown Men?

Above is a drawing of an LNER pacific loco (e.g. Flying Scotsman). It shows a side view of a four wheel bogie at the front, followed by ...

... six driving wheels; followed by this ...

... which might be a two-wheeled bogie, usually known as a "pony truck".

But it isn't.

As is clearly obvious from the above picture of a loco under construction, the mainframe is very solid indeed at the back; there is no bogie or pony truck. So how would the wheels get round the corners?

It was Francis James Cartazzi, an engineer with the Great Northern Railway, who had a jackpot idea. It is called a Cartazzi axle; and please don't ask fbb how it works. In very simple terms, it allows the fixed axle to be a bit less fixed and move from side to side and thus cope with the curves of the track.

fbb can find no photos on-line of this genius engineer.

But a normal OO model loco would simply not be able to go round the corners if the back axle section were solid.  "Toy" model railway corners were very sharp!

The solution was easy peasy, make it a pony truck anyway; no one will notice.

See the two wheel "bogie" dangle. So standard was this modelling procedure that fbb always thought that the real 12-inches-to-the-foot A4 actually had a pony truck at the rear!

How ignorant can you get?

But modern collectors of expensive  locomotive models would not tolerate such a bodge. The frame needs to be solid all the way. So on Hornby's model of the LNER "Hush Hush" W1 4-6-4 class loco, the rear 4 wheels  are part of a solid frame.

So, how does it go round corners?

Horny cheats in a different way. Although the boxed model is equipped with prototypical flanged wheels, on pictures of many models those rear four wheels do not have any flanges. You can see the effect below ...

The driving wheels have flanges but the back "4" do not; so they are not constrained by the rails. On sharp curves and viewed from directly above, those wheels would hang out over the rail.

Thus, if you want to use your loco on tight model curves, you buy a set of flangeless wheels as below.

But there's more complexity to this problem. Here is a model of a British Railways standard class 9F 2-10-0.

And the centre driving wheels have no flanges. This helps the model go round the corners. But it's no cheat because here is the centre driving wheel of ....

... the full size 2-10-0 92220 Evening Star, the very last steam loco built by British Railways.

And it has no flanges; which helps it go round the corners!

So even the real locos use a "cheat"!

This now leaves the question of fbb's six wheel coach models and their cornering capabilities.

And there was something quite strange in Paris.

Miss Prince

fbb has been known to make the occasional miss steak in his blagging

The November edition of Railway Modeller popped through the letter box at fbb mansions yesterday.

It contains an advert for Peco Streamline Code 75 OO railway track. It is track for real modellers, whereas much of fbb's assorted but "coarse" rolling stock would not run well on Code 75.  He uses Code 100.

Here is the advert.

And here is the enlargement!

The labels are ALL wrong, misplaced and, just plain silly as displayed!

Whoops!

 Next Route 95 blog : Friday 11th Oct