7.5in GWR 45xx

[peterhill]

A im thinking about building a 45xx in 7.5in gauge. By scaling up the 3.5in gauge model(firefly), i am thing of using castings from the 7.25in gauge 43xx (cylinders, wheels,etc). As both engines had the same cylinders and wheels.

Peter

[ianmac]

Not sure if this helps but i did ask the a similar question recently.

I liked the look of the jubilee in 3.5 inch......i asked if it was possible to scale up to 7 1/4 and the reply was yes but take care as not all measurements need to be scaled up.

What is said is just an example lets say the plate work was 3 mm when you scale it up it becomes 6.xmm.

i have never attempted to do this but i guess there is some food for thought.

a good exercise for the grey matter.

[Laurie_B]

Sounds like a good idea.I'm thinking about building a 7-1/4" gauge 'Metro' based on Martin Evan's 5" gauge version,using the wheel and cylinder castings,and the same boiler for the 'Dart' design.

As regards a boiler for your 45xx loco,if you are designing your own,or adapting a previously published design,it might well be worth consulting your club boiler inspectors first,as the current boiler regulations do cover design and construction nowadays.
There was an article in Model Engineer a year or so ago,by Peter Rich,which featured drawings for a 7-1/4" gauge 44xx (or 'even smaller prairie'!).The boilers for the 44xx and 45xx classes look very similar.

Also,I think you'll find the driving wheels for the 45xx class were 4'-7 1/2" dia,whereas the drivers for the 43xx were 5'-8",the same as the 'Grange' class.You should find the wheels for the 'Paddington' (7-1/4" gauge 15xx) design the correct size-though somewhat expensive!

[dinmoremanor]

Hi there, Laurie is quite right about the wheel sizes being different, also the cylinders are different, the 45's had cylinders of 17"x24", the Mogul's using 18"x30". If you were to build a large prairie rather than small then the reeves mogul castings would do just the job. There is a chap that goes to the new Echills Wood Railway at Kingsbury water park by the name of John Hancock who has built a 45XX in 7 1/4, he produced his own castings for the wheels and cylinders etc. as far as I am aware. If the 45XX is definately what you want then it may well be worth getting in touch with him and seeing if he is prepared to accept a good few beer vouchers in exchange for some castings!

[dscott]

The boilers on the 44XX and 45XX are identical as I found out when scaling the works drawings for my 4409 design in 5". Both Peter Rich and myself are of the same opinion, that there is only one way with these engines, and that is to build them to scale, with proper extension frames under the cylinders. The 3 1/2" and 5" so called Firefly designs although working well, do not look right, it was designed at the time of big boilers squeesed onto little frames to win an IMLEC or two.

Look at www.churchwardlocos.com where you will find reference to a 7 1/4" 44XX, Use 28XX wheels which will lift the engine the required few inches thus making it a 45XX, reduce the crank to suite the shorter cylinders.

David.

[peterhill]

I see reeves do a 5in 51xx. Just need to scale up from 5in to 7.5in. That way i can use the 43xx parts, if i can afford the shipping to the USA.(plus the castings).

peter
Minnesota USA

[dscott]

Have a look at Jim Vass models, and Model engineers laser which does parts for the 43XX.
Doing a 51XX saves on building a tender, but you still have 3 tanks and a bunker to make.

David.