Metropolitan F class rear wheel diameter

[IvoryGreen456]

Hi all, I'm currently planning for building a Finecast F Class kit, and was wondering what diameter the rear wheels are.

Cheers, Jacob.

[ThePipersSon]

In the instructions it states 3'9" - 10 spoke.

There is a mention that there is limited clearance if 16mm wheels are used!

 

Tom

[Engineer]

Just been able to look up the Metropolitan Railway 1932 diagram book.  This gives the F Class 062T rear carrying wheel diameter as 3' 6". 

 

Added note:  Now found the drawing with table of sizes and scrapping diameters.  Confirm 3' 6" for the F Class 062T carrying wheels, scrapping diameter 3' 3".

 

The E Class 044T bogie wheel is 3' 9 1/8" diameter, scrapping at 3' 6 1/8", so would be worth care and checking wheel sizes before making a commitment with the model.

Edited July 5, 2021 by Engineer
Additional technical information

[IvoryGreen456]

8 hours ago, Engineer said:

Just been able to look up the Metropolitan Railway 1932 diagram book.  This gives the F Class 062T rear carrying wheel diameter as 3' 6". 

 

Added note:  Now found the drawing with table of sizes and scrapping diameters.  Confirm 3' 6" for the F Class 062T carrying wheels, scrapping diameter 3' 3".

 

The E Class 044T bogie wheel is 3' 9 1/8" diameter, scrapping at 3' 6 1/8", so would be worth care and checking wheel sizes before making a commitment with the model.

Hi, many thanks for that, it's very useful information. Would I be correct in assuming that all four F classes carried 3' 3" wheels before withdrawal then? 

Cheers, Jacob.

[Engineer]

That's a really wise question and I apologise for using terminology that won't necessarily be clear to all.  I'll give the best explanation I can - as a non-specialist on the detail.

 

Wheels for a rail vehicle will have a life of their own, independent of the vehicle life and will very likely be shorter than the vehicle life.  Wheels wear out by use over time, and standards are set for routine checks for correct profile and diameter.  Worn wheels on an axle can be lathe turned to restore their correct profile, which reduces their diameter a little.  This process can be repeated until the restored profile will make the wheel less than its 'scrapping diameter'. 

 

In the context of the wheels used by this loco, there was a separate tyre.  The worn tyre can be removed and scrapped, and a new replacement tyre fitted, giving the wheelset a new lease of life commencing at the given 'new' dimension.

 

So, during the long life of these particular locos, there could be a rear carrying wheelset at 3' 6" new diameter or at 3' 3" 'scrapping diameter or any dimension between, depending on wear and maintenance cycles.  A loco still in use but with little remaining life could still be fitted with a wheelset of 'new' diameter, as the standards for maintenance will enforce replacement of wheels that are at risk of being under size and at an incorrect profile.

 

The range of diameters can be worth knowing when modelling and choosing suitable wheels, particularly when clearances are very tight and there is an option for a slightly smaller wheel.