68 replies to this topic

[Ray Bell]

Originally posted by twotempi
To further confuse the issue 1 litre is NOT 1000cc.....

Yes, and doesn't Big Dave love telling people that!

[Marticelli]

A further point worth considering is that we are talking here so far only about calculated swept volume (or if you must, displacement, although I prefer to use that term for shipping in the Archimedean sense). In fact, the discrepancy may have arisen because the claimed swept volume will have been checked after the record runs using the time honoured method of white spirit and a calibrated burette.

As the actual swept volume in the side banks is less than the calculated swept volume, this may explain why a second marginally lower figure was quoted in subsequent references. And be grateful its given in cubic inches or litres, not in gills or another arcane unit of volume measurement...

Marticelli

[Peter Morley]

Only once?
Until one has to go metric the slug is as normal a unit of mass as the pound is a unit of force - or did you use pounds mass and poundals for force?

It was in the 80s when they'd more or less switched to metric (having done most of my schooling in Belgium even pounds and inches were something I'd rarely used) but I do (vaguely) remember coming across poundals and pounds mass as well.

[twotempi]

As a matter of interest with the master rod - slave rods configuration was the effective stroke different on the centre bank of cylinders compared with the two side banks ????

Any ideas ???

Edited by twotempi, 18 September 2012 - 08:40.

[Marticelli]

As a matter of interest with the master rod - slave rods configuration was the effective stroke different on the centre bank of cylinders compared with the two side banks ????

That was the gist of the comment I made in post #17 above... And despite all the bluster about rounding and metric/imperial conversion errors and different values for pi, I actually think this point is the critical one.

Marticelli

[Allan Lupton]

That was the gist of the comment I made in post #17 above... And despite all the bluster about rounding and metric/imperial conversion errors and different values for pi, I actually think this point is the critical one.

Marticelli

Martin, as I pointed out in post no 27:

Whilst I agree with this reasoning, it isn't the answer as the lowest displacement quoted is the one that assumes all three banks have the 5½" stroke.

Value of pi is the most likely variable in pre-electronic calculator days and if you call stating and re-stating that view bluster, fair enough.

[D-Type]

...Ooops - I hope not Duncan. That could be the whole cause of the problem. Maybe 3.1416 might be better....

Sorry - finger trouble. Blame my arthritic fingers but not the FIA (this time)

[D-Type]

A further point worth considering is that we are talking here so far only about calculated swept volume (or if you must, displacement, although I prefer to use that term for shipping in the Archimedean sense). In fact, the discrepancy may have arisen because the claimed swept volume will have been checked after the record runs using the time honoured method of white spirit and a calibrated burette.

As the actual swept volume in the side banks is less than the calculated swept volume, this may explain why a second marginally lower figure was quoted in subsequent references. And be grateful its given in cubic inches or litres, not in gills or another arcane unit of volume measurement...

Marticelli

If you think about it, there was no need to measure the swept volume of the engine accurately. It was clearly in the over 8 litre class and how much over didn't matter.

Different values for pi or a simple arithmetric error will be the reason for the discrepancy.

[Marticelli]

If you think about it, there was no need to measure the swept volume of the engine accurately. It was clearly in the over 8 litre class and how much over didn't matter.

In my youth I worked for the National Engineering Laboratory which had a whole department devoted to Metrology as the science of measuring things was called. And it was about practical measurement of physical things, not about calculations using conversion factors and the like. And strange to relate, accurate calculations were perfectly possible then despite the lack of digital computing; to suggest otherwise is to denigrate the skills of the engineering pioneers.

I would venture to suggest that the first 'capacity' quoted was based on an actual measurement of the engines used, which may have had fractionally larger bores for some reason now lost in the mists of time, the second 'capacity' quoted simply on arithmetic calculation based on the nominal bore and stroke quoted by Napiers of Acton (although interestingly Napiers moved away from Acton to Lincoln during World War 2 to avoid being bombed, and even this might have some part to play in the true explanation of the differing figures).

What I am also now clear about is that the 47,886cc figure is based on a 6 or 7 significant figures value for pi and the generally accepted metric equivalent of 5.5" x 5.125" bore and stroke, so is actually incorrect for the reason I gave in post #17, as only the centre bank of cylinders actually has the full geometric bore and stroke quoted. Sorry if Alan Lupton takes issue with my use of the term bluster, but I can't believe our forebears would be so apparently slapdash.

Don't suppose we shall ever know the true answer as all the contemporary people are no longer with us, and the Napier papers held by the Science Museum appear not to give an adequate explanation, hence this thread...

Marticelli

[f1steveuk]

I would venture that the capacity wasn't checked post record runs, as the Napier Railton was running in the unlimited class, so why would you check it? The differing figures, for the EXACT same two engines actually comes from the governing body via the manufacturer!!

[Marticelli]

There's another anomaly that occurs to me... The car that is the subject of this thread is actually not the Napier Railton, as that had a single Lion engine, and was used latterly by Dunlop for tyre testing and AFAIK is on show at the Brooklands Museum. The car being discussed here is actually the Railton Mobil Special, which AFAIK is currently on show at the new Thinktank Museum in Birmingham, having been moved there from the Birmingham Museum of Science and Industry where it has been for most of its post-LSR life...

Marticelli

[f1steveuk]

Railton Mobil Special,

Marticelli

To be absolutely pedantic about it, it was the Railton Mobil Special only in 1947. Previously it was designed, built, entered, and officially recorded as a Railton. It is only with the passing of time that some have added the engine type and arrived at Napier Railton (no "Special" pre war). So in reality we are talking about the Railton. In much the same way as it's not the "Golden Arrow" it's the 'Irving Napier'

Edited by f1steveuk, 18 September 2012 - 19:19.

[Vitesse2]

And to be even more absolutely pedantic, in 1939 it was called Railton Red Lion.

[GMACKIE]

As there is a bit of 'hair-splitting' here, perhaps someone could tell me if an off-set crankshaft [de Saxe] would make a difference to the swept volume?

[Ray Bell]

It must do, Greg...

Even if only in a hair-splitting way!

Just the same as offset pins in a piston over top of a dead-centre crank will do.

[Lee Nicolle]

While the differences is probably someone doing an estimated calculation from cubic inch to CC taking into account honing the cylinders an extra though for more piston clearance and taking that into account for the measurement may be an answer also. That is probably a fair amount on an engine that big!!

[Marticelli]

I think the most likely explanation is the first figure results from an actual measurement, the second from the simple calculation of 12 x 5.5" x 5.125" bore and stroke...

Marticelli

[Tim Murray]

As others have pointed out, the capacity was fairly irrelevant, both to Napiers and to the AIACR as the car was running in the unlimited class, so would anyone really have gone to the trouble of physically measuring it? My theory is that someone, somewhere, had to fill in the relevant AIACR form which required the listing of the capacity in cubic centimetres. As this information would not have been available ‘off the shelf’ the person involved perhaps did a quick calculation and got it slightly wrong, but the error wasn’t picked up because the actual capacity wasn’t important.

[f1steveuk]

And to be even more absolutely pedantic, in 1939 it was called Railton Red Lion.

Having been through all of Reid Railton's archive, and some of Cobb's, they both refered to it, post war as the Railton Mobil special, but only while the sponsorship money hadn't all been spent ( I think they were contracted to refer to it as such for a set time, but I can't evidence of what this time scale was).

According to the official entry, and the ACF records and certificate,

"1947, Driver, Cobb , place Bonneville USA , average speed flying mile 394.20 mph, gross weight 8082lbs,
entry title Railton Mobil Special, owner Cobb, engine Napier Lion ViiD x2 (2636bhp each), piston, record date 16/9,

constructor Thomson & Taylor/ J Thompson Ltd, designed, R Railton"