Hornby O1 - how close to an O2

[workev]

Folks,

I am looking to model Grantham and would like to have some O2's. I see Hornby are launching an O1; so my question is how close are the O1 and O2 to each other, could the new model be modified with ease, or should I give up!

Ian

[majormagna]

Sadly, the O1 being released by Hornby is the later Thompson design, the O2 was in fact an earlier Gresley design. The Thompson O1 was incedentally a complete rebuild of the GCR Robinson O4 (ROD) locos.

This means that it would be rather difficult to convert one into the other, as they probably shared few parts. Though I may be wrong about that.

[S.A.C. Martin]

Why not compare the class's entries on the encyclopedia linked to this very forum? (Click the button in the top left)

Thompson O1

Gresley O2

I'd say you'd be hard pressed to make an O2 out of a Thompson O1, they share driving wheel diameter but little else. A few O2s did get a Thompson boiler I seem to recall.

You'd need new bogie wheels, replacement tenders, a source for a Gresley style body, and Gresley cylinders, possibly a different braket for the eccentric crank, . Would that give you a passable O2? It might. An accurate one - not sure, maybe.

I think Graeme King of this parish built one out of a kit at some point, might be worth asking Graeme his thoughts on a cut and shut.

[manna]

G'Day Gents

You will also find the the O1 drove off of the third driver, the O2 drove off the second, me I'm looking at the the O1 chassis might be a goer, for the Gresley O1 later O3, with a few suitable modifications ! as they both drive off the third driver

manna

[workev]

Bugger!

Thanks for the replies, forgot about the Gresley basis of O2s.....

Right, must right a letter to Bachmann

Ian

[Atlantic 3279]

I wondered last night whether I should reply to this one. I think enough has already been said to cast grave doubt on the feasibility of a conversion. A point to add, which simply makes things worse still, is that the Gresley locos, whether O2 (3-cylinder), or proper original O1 (later O3, 2-cylinder), were bigger locos all round than the "Thompson rebuild of Robinson" hybrid. They were bigger than the Stanier 8Fs too, so that chassis is no real advantage either. If you wanted an accurate model it just wouldn't work. The Gresley locos have a significantly longer coupled wheelbase, and a longer boiler to go with it. The Thompson locos kept the Robinson O4 coupled wheelbase, and when the LNER first tried to modernise / "standardise" (a strange phrase in the circumstances) the huge numbers of O4s by fitting the much less numerous O2 boiler, a frame extension was required at the rear. Subsequent rebuilds called for special shortened boilers. Even if you ignore the issue of length, before you could call your Thompson O1 a Gresley "O-something" instead you'd at least need to construct a new curvaceous Gresley running plate, then get a new tender and alter as many other details as necessary to give a convincing disguise.
If you really want the O2 in OO at present, I think it is a case of either build one youself (from scratch, or Nu-Cast, or PDK etched kit, or if very brave from the cheaper ACE Products kit), commission one, or hunt around the auctions with the phrase caveat emptor firmly in mind.