Gresley V4

There were NOT designed as express locos and increasing wheel size adds weight, not just in the wheel, but in balance weights. A greater coupled wheelbase would be required, with consequent longer frames, longer rods and longer boiler, all adding further weight.

 

Please could you explain that?
If the stroke and motion components are all the same, wouldn't the out of balance forces remain the same?
Indeed if the balance weights are further from the axis wouldn't they be smaller for the same effect?
Not sure about the last, I always have trouble getting my head round the physics of rotating objects.

 

5-8 wheels allow you to have a lower loco with a shorter Wheelbase = a wider route availability - the key attribute of the design
At the time of their design was anything else on The GE section doing 80mph plus or did that happen when they had Brits to do it with ?
Standard 4's have certainly been recorded at speeds into the 70's.... as did 9f's

Todays NR rules for preserved steam lococs mean that having 6ft plus wheels is useful out of proportion to the actual wheel size.

Tornado has been tested and built with 90mph max running in mind
Prince of Wales is being tested and built for the same rotational speed with 83mph max running in mind
The same principles applied to V4 would give a Max design speed of 74mph

In hindsight , given the amount of 80mph plus running the original P2's probably did then having 5ft 8's on them would n't have been much of a handicap and would have enabled a shortened coupled wheelbase/ shorter loco/smaller cylinders (or even higher starting TE) and a better proportioned boiler...
Surprised that Thompson didn't go for 5-8's on the B1 - he gave the L1's small wheels

 

Surprised that Thompson didn't go for 5-8's on the B1 - he gave the L1's small wheels

.......... and look how long they lasted - by all accounts they did not like higher speeds. That said, I'd love to see a new-build one on the NYMR, where I think it would probably be a match for a standard 4 2-6-4T.

 

Didn't say it was good, only that it was consistent; and wasn't that due to skimpy axlebox and a leaky tank design? - but they did have good acceleration! More than a match at preserved line speeds.,

 

I would hope so, the L1 had a TE 7,000lb. ish higher than a Std4 tank.

 

More to locomotive design than just TE though - especially on a line with sustained gradients, the sustained steaming capacity counts for a lot. From what I can see, a 4MT seems to have a bit bigger boiler, particularly a larger grate area.

Tom

 

My post was regarding the above, smaller wheels and noted fast acceleration, not really considering the overall loco design, although you are correct in what you point out.
Andy

 

Motion components would be heavier - not just longer, but possibly also thicker to prevent whip. That said you are possibly right about needing smaller weights.

 

The drawings are available...........

 

You mean for an L1 ?

 

That's what 61624 was referring to.

 

Sadly, I don't think the money is! All thoughts on the NYMR seem to be focused on the Goathland bridge replacements.

 

Think positive!

 

He's positive the money is not available..

 

At least these days with the L1 (and any other class of engine) you can use the computer program to draw the engine wheels/bearings which are driven by the cylinders and run the wheels for say 20,000 miles at 70 mph to see if the bearings are up to it. And if not make them stronger.

 

I don't think I said that the bridge bills would be with us indefinitely so I would never say never!

 

The Thompson L1 would get my vote, support and money though I fear it being suggested by previous non starter schemes might make people even more skeptical of a design which does not have the best reputation, historically.

 

To be honest, I suspect earlier "schemes" (probably giving them 100 times more credence than they deserve) would be neither here nor there - beyond a few diehards on NatPres, I can't imagine anyone remembers them, nor would be put off a credible new project as a result.

The reputation of the originals is probably far more of a problem, even if those historic problems would likely not be an issue, or could be designed out, for a loco aimed at 25mph operation. In Southern circles, I think a Maunsell K class would suffer similarly - probably an excellent design for preserved line use, but even for a loco designed for 25mph running, no-one looks beyond the issue of high-speed unsteadiness that lead to Sevenoaks. The bottom line is that attracting money for a design with a poor reputation will always be an uphill task, even if the reasons for that poor reputation would not be a particular issue for modern usage. At the very least, you'd need a really persuasive salesman to get the necessary early buy-in for a project.

Tom

 

At the end of the day, I'd suggest that whether a scheme succeeds or fails has more to do with those managing it than any other consideration.