Technical

Here's an interesting one for you!

Whilst servicing one of the club A4 locos I noticed that at sometime during its life the reversing gear unit has been fitted with an alternative set of gears.

In the Hornby spares documentation (which appear to have several part number errors in them) they are listed as Gear Set 1 (larger cog when viewed from nearside) and Gear Set 2 (smaller cog). The only spares that are currently available are the larger Gear Set 1 and just to confuse matters even more as an original Hornby spare this gear set is listed as X-9209 A3'A4 Worm Gear Shaft A.

This is the original Hornby version.

30 teeth on the large cog

15 teeth on the small cog

A ratio of 2:1

This is the modified version

24 teeth on the large cog

12 teeth on the small cog

A ratio of 2:1

So what can I tell you?

• This is a club loco and must have been like this since we bought it . . it was just never noticed.

• We have no idea who did the conversion (so if it was you and you are reading this please get in touch membership@oolivesteam.com

• It appears that the important bit is the ratio . . as long as it it 2:1 then it works like the original.

• Being metal gears operation is slightly noisier than the Hornby version, no bad thing as you at least know the servo motor is responding.

• I spoke to Richard Hallam, the man who invented OO Live Steam and his take is that slightly less, and therefore slightly bigger, teeth will be more robust (he considers the Hornby ones to be a bit in the 'fine' side) and this may well be a good thing.