New Hornby Rocket

[boxbrownie]

2 hours ago, sandwich station said:

 

Father.  

My mistake, I was thinking of his Grand Dad 

[Nearholmer]

MarkSG

 

I don't understand why/how choosing to build a 0-2-2, rather than an 0-4-0 would have significantly altered the overall weight of the machine.

 

Without doing any maths, largely because I'm unsure what the wheels were built from, so can't estimate density, my gut feel is that four mid-sized wheels plus coupling rods would run out not far different in mass from two big wheels, plus two small wheels. Did it alter the mass of framing needed?

 

I'm sure Stephenson had good and logical reasons for choosing to build a 0-2-2 with big front wheels (Was there a speed criterion to be met? Or, maybe he just want to go as fast as possible with the stated load? Or, wanted to simplify, so as to reduce the risk of disabling failures?), I'm simply questioning that weight was the reason, or perhaps looking to understand the source for the statement that it was the reason.

 

Kevin

[Pre Grouping fan]

Luckily managed to order the Limited Edition Pack. It seems everywhere is pretty much sold out of this pack. Annoying that some shops don't remove it from their website once it's sold out like hattons and a few others, just a small note saying unavailable to order or something along them lines.

 

Probably only the smaller shops will have any allocation left now who don't have websites.

[Compound2632]

On 09/01/2020 at 13:09, MarkSG said:

 

What that meant, though, was that although Stephenson's design was technically superior to the other competitors in many respects (only Novelty was, arguably, as advanced as Rocket), his choice of a single driver design - which he stuck with for his later developments for the L&M - was something of an evolutionary dead end as far as locomotive design was concerned. While, taken to its peak, the single driver design later gave us the iconic singles of the late Victorian era - the Stirling Single, the Dean Single, the Caley Single - it was outdated even before they were built.

 

 

But the 2-2-2 was the standard choice for passenger locomotives up to the late 1860s, following in a line of development from Stephenson's Patentee type of 1833. No one, surely, would describe the Jenny Lind type as being in an evolutionary cul-de-sac?

 

7 minutes ago, Nearholmer said:

 

I'm sure Stephenson had good and logical reasons for choosing to build a 0-2-2 with big front wheels (Was there a speed criterion to be met? Or, maybe he just want to go as fast as possible with the stated load? Or, wanted to simplify, so as to reduce the risk of disabling failures?), I'm simply questioning that weight was the reason, or perhaps looking to understand the source for the statement that it was the reason.

 

 

The large, uncoupled wheels would certainly help with speed, for the same reasons they did for the rest of the century: less friction, given the manufacturing tolerances achievable on the coupling rod and axle centres, and reduced piston speed. 

[MarkSG]

16 minutes ago, Nearholmer said:

I don't understand why/how choosing to build a 0-2-2, rather than an 0-4-0 would have significantly altered the overall weight of the machine.

 

Without doing any maths, largely because I'm unsure what the wheels were built from, so can't estimate density, my gut feel is that four mid-sized wheels plus coupling rods would run out not far different in mass from two big wheels, plus two small wheels. Did it alter the mass of framing needed?

 

I'm sure Stephenson had good and logical reasons for choosing to build a 0-2-2 with big front wheels (Was there a speed criterion to be met? Or, maybe he just want to go as fast as possible with the stated load? Or, wanted to simplify, so as to reduce the risk of disabling failures?), I'm simply questioning that weight was the reason, or perhaps looking to understand the source for the statement that it was the reason.

 

The coupling rods themselves would have been additional weight. And wheels also have weight. Given the very stringent overall weight limit, it made sense to dispense with the couplings and have a much smaller - and lighter - set of rear wheels.

 

Bigger wheels certainly do help with speed, and the other contestants also had large wheels, for that reason. Rocket's front wheels weren't significantly different in size to those on the other locos. But Rocket's rear wheels were a lot smaller.

[PaulRhB]

22 minutes ago, Nearholmer said:

 

I don't understand why/how choosing to build a 0-2-2, rather than an 0-4-0 would have significantly altered the overall weight of the machine.

 

 

It was more about weight distribution so I assume they got less slip with the bigger wheels and got the top speed too. If the tests had been about overall haulage in all conditions it might have been different. 
 

[Gibbo675]

21 minutes ago, Nearholmer said:

MarkSG

 

I don't understand why/how choosing to build a 0-2-2, rather than an 0-4-0 would have significantly altered the overall weight of the machine.

 

Without doing any maths, largely because I'm unsure what the wheels were built from, so can't estimate density, my gut feel is that four mid-sized wheels plus coupling rods would run out not far different in mass from two big wheels, plus two small wheels. Did it alter the mass of framing needed?

 

I'm sure Stephenson had good and logical reasons for choosing to build a 0-2-2 with big front wheels (Was there a speed criterion to be met? Or, maybe he just want to go as fast as possible with the stated load? Or, wanted to simplify, so as to reduce the risk of disabling failures?), I'm simply questioning that weight was the reason, or perhaps looking to understand the source for the statement that it was the reason.

 

Kevin

Hi Kevin,

 

Rockets driving wheels were made from wood originally and the trailing wheel under the footplate were cast iron so as a combination may well have been heavier than four wooden wheels. With four coupled wheels it is possible to attain much better traction than a single pair, all I can think is ease of construction and therefore ease of repair in a competition setting may be key reasoning for the wheel arrangement.

 

Gibbo.

 

[Nearholmer]

6 minutes ago, MarkSG said:

The coupling rods themselves would have been additional weight. And wheels also have weight

 

I get that, but I remain unconvinced that the sum of the weights would have been much different if he'd chosen 4x mid-sized driving wheels, yielding a higher tractive effort and a lower top speed.

 

Are you citing from a source, or have you calculated, or are you assuming?

 

Kevin

Edited January 10, 2020 by Nearholmer

[MarkSG]

4 minutes ago, PaulRhB said:

It was more about weight distribution so I assume they got less slip with the bigger wheels and got the top speed too. If the tests had been about overall haulage in all conditions it might have been different.

 

Rocket didn't have bigger front wheels than the other competitors. It had smaller rear wheels! But it did have a much higher axle load on the front, which would have helped with adhesion.

 

Rocket wasn't the fastest loco in the trials, either, that was Novelty. But Rocket was more reliable.

The trials were, in many respects, unrealistic. The rules favoured lightweight, fast locos with only moderate pulling power. Rocket and Novelty were both very much built for the competition, but used very different designs. Rocket's design, though was more suitable as a base to improve for a production model. Novelty, had it won the trials, would have been difficult to scale up to something capable of hauling a full length train.

[MarkSG]

6 minutes ago, Nearholmer said:

 

I get that, but I remain unconvinced that the sum of the weights would have been much different if he'd chosen 4x mid-sized driving wheels, yielding a higher tractive effort and a lower top speed.

 

Are you citing from a source, or have you calculated, or are you assuming?

 

Firstly, it's important to bear in mind that Rocket didn't have bigger front wheels than the other competitors. They all used as large a set of driving wheels that they could, because of the need for speed. It's just that Rocket's design allowed a smaller set of rear wheels. These photos are replicas, obviously, but assuming they're reasonably accurate it's easy to see that the driving wheels are essentially the same same (compare them to the height of the humans). But the small rear wheels of Rocket, as well as keeping the weight down, also made for a more compact, and hence probably more stable design.

 

As for sources, I'm mostly following the citations in the Wikipedia article on the Rainhill Trails.

[PaulRhB]

14 minutes ago, MarkSG said:

 

Rocket didn't have bigger front wheels than the other competitors. It had smaller rear wheels! But it did have a much higher axle load on the front, which would have helped with adhesion.

 

 

Re-read it, “less slip with the bigger wheels” not that they were the biggest wheel there. 
Less axle load on bigger wheels means they tend to be lighter footed on starting. By having more weight on the bigger wheel it helps it grip but limits its adhesion overall, especially in wet conditions. Like others have said Rocket was optimised for the trials not general service. I suspect they were bargaining on getting it going with the trains they knew they had to shift rather than an out and out haulage trial. 

Edited January 10, 2020 by PaulRhB

[boxbrownie]

42 minutes ago, Pre Grouping fan said:

Luckily managed to order the Limited Edition Pack. It seems everywhere is pretty much sold out of this pack. Annoying that some shops don't remove it from their website once it's sold out like hattons and a few others, just a small note saying unavailable to order or something along them lines.

 

Probably only the smaller shops will have any allocation left now who don't have websites.

I am still going to wait until the price becomes “discounted” and if they never make another run (highly unlikely) I’ll still be able to sleep at night 

 

Not going to buy the APT either.......still have an original all boxed and unused 

[boxbrownie]

40 minutes ago, Compound2632 said:

 

 

 

The large, uncoupled wheels would certainly help with speed, for the same reasons they did for the rest of the century: less friction, given the manufacturing tolerances achievable on the coupling rod and axle centres, and reduced piston speed. 

Maybe they had as much trouble quartering coupled wheels as some of my Bachmann Locos?

[PaulRhB]

I suspect Novelty was the most stable as it had a lot of its weight very low down below the axles. 
No doubt with their existing locos they knew all about weight distribution and took the best compromise for the trials. I’ve read that Rocket was designed to put more weight on the leading wheels to give the more impressive acceleration but obviously better distribution of weight helps in hill climbing and overall weight as it’s better at sustained traction. Rocket was a pedigree racehorse and on dry rail it probably worked superbly. I wonder if they had a sanding option if it had rained?

[Nearholmer]

The pictures highlight something that may be as/more important than weight: a medium or large rear driver on Rocket would have put the rear axle in a seriously awkward location in relation to the firebox (which was a new thing, wasn’t it?). Later solved by the ‘long boiler’ concept. Or, am I getting the chronology wrong?

 

I’m coming to think that multiple factors might have eased Stephenson in the direction of a single driven axle.

 

Unless there is a ‘from the horse’s mouth’ explanation.

Edited January 10, 2020 by Nearholmer

[MarkSG]

Incidentally, the BBC "Timewatch" programme did a recreation of the Rainhill Trials using replicas in 2002. The full episode is available on YouTube.
 

 

[Pre Grouping fan]

2 hours ago, boxbrownie said:

I am still going to wait until the price becomes “discounted” and if they never make another run (highly unlikely) I’ll still be able to sleep at night 

 

Not going to buy the APT either.......still have an original all boxed and unused 

I'm sure there will be an NRM limited edition at some point in the next few years.

They wouldn't bother tooling it from scratch if they didn't intend to produce it for years to come. Even though its likely to have covered its costs this run Hornby will want to make the most out of the tooling over time. 

[Nearholmer]

If it’s as good as the photos suggest, they’d be insane not to.

[Hroth]

Perhaps if Hornby do an NRM version of Rocket, they'll also do a model of Sans Pareil for the ultimate Rainhill Trial boxed set, though even in 9 years time I don't think we'll have the technology for a DCC Ready model of Novelty...

[MarkSG]

Novelty had quite a lot of depth below the running board, being a well tank design. I'm pretty sure there would be space in there for a chip.

[GoingUnderground]

2 hours ago, Pre Grouping fan said:

I'm sure there will be an NRM limited edition at some point in the next few years.

They wouldn't bother tooling it from scratch if they didn't intend to produce it for years to come. Even though its likely to have covered its costs this run Hornby will want to make the most out of the tooling over time. 

It's very clever marketing, putting out the 1500 Limited edition models in the Triang Railways packaging, especially as they are priced at a small premium over the standard/NRM version. The Limited Edition seem to be sold out almost everywhere. Will the the special edition come close to covering all the up-front costs of the new models? I wonder what price they'll go for on Ebay once they start being delivered?

 

There's no limit shown on the Hornby website for the NRM version, and I'm sure that they'll rerun it as and when possible, in consultation with the NRM, probably with different coach names. as a Rocket class loco with one of the other names won't have quite the same draw to Joe Public as a loco with the Rocket name. The blurb on the Hornby website implies that the NRM will get a cut of the sale proceeds on the R3810 version.

 

Indeed, future runs could include a choice of loco names on nameplates and having the coaches unnamed and putting  a choice of, say 12 different names on transfers for buyers to apply themselves at home. Rovex/Triang/Hornby Hobbies did sell the EM2/Class 77 in CKD form as R388 back in the 1960s with a choice of names and numbers included in the box, Electra, 27000;  Aurora, 27002; and Pandora, 27006. Worth trying as the additional cost would be minimal.

Edited January 10, 2020 by GoingUnderground

[MarkSG]

I think Hornby would need new tooling to represent any other Rocket class loco, or, indeed, even Rocket itself when in service. All the contemporary drawings show locos with horizontal cylinders (as can been seen on the preserved Rocket). The angled cylinders on Rocket at the trials seem to have been a very short-lived intermediary development phase. The model, and all the replicas, represent the version of Rocket used at the trials. And, at the time, it was a prototype.

[Trains4U]

6 hours ago, Pre Grouping fan said:

Luckily managed to order the Limited Edition Pack. It seems everywhere is pretty much sold out of this pack. Annoying that some shops don't remove it from their website once it's sold out like hattons and a few others, just a small note saying unavailable to order or something along them lines.

 

Probably only the smaller shops will have any allocation left now who don't have websites.

 

Not all shops will have been given their allocation yet (we learned ours yesterday and there are still several days of previews to go) and lots of shops won’t get any at all!

needless to say we have sold out of the centenary pack, with names to spare...

[Butler Henderson]

Seems that the limited pack has the coaches Globe Renown and  Wellington

[JSpencer]

8 minutes ago, Butler Henderson said:

Seems that the limited pack has the coaches Globe Renown and  Wellington

 

I asked about that:

R3809:  Times, Dispatch and Experience (say as the triang ones)

R3810: Globe, Renown and Wellington