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BR 0-4-4 Class M7 Locomotive '30108'
Hornby Railways R2506
Review and DCC decoder installation by Doug Teggin

Prototype info

The London and South Western Railway (LSWR) M7 Class is a class of steam locomotive. Designed by Dugald Drummond, 105 were built between 1897 and 1911. Two, 245/30245 and 53/30053 have been preserved.
[Text and photo source: Wikipedia. Photo below: Richard H Huelin 2002]

Train Vehicle Wheel Rolling stock Mode of transport

They started life as suburban passenger tanks pulling up to 10 heavy wooden coaches but were also used on semi-fast main line workings. After a main line accident in 1898 near Tavistock, they were restricted to lower speeds. The spread of electrification displaced them from much of their suburban work and they moved on to become branchline locomotives in the South West. Along with others, 30051 was fitted with push-pull equipment for branchline work in 1930. Some did banking work on the North Devon lines. As we have seen, some were also used in their later years for empty stock workings at Waterloo. For these duties they could pull long and heavy trains quite competently, despite their age. These included very heavy Pullman stock for the Golden Arrow and the Bournemouth Belle.
[Text source: Pat Hammond]

The 2006 Hornby M7 range
[photo source below:Hornby]

Product Code: R2506
Length: 139mm
Running No. 30108
Livery: Late BR Period 1963

Train Wheel Vehicle Rolling stock Rolling

Product Code: R2505
Length: 139mm
Running No. 30031
Livery: Late BR Period 1961

Train Wheel Rolling stock Vehicle Rolling

Product Code: R2504
Length: 139mm
Running No. 30051
Livery: Early BR black Period 1957

Train Rolling stock Wheel Vehicle Railway

Product Code: R2503
Length: 139mm
Running No. 357
Livery: Maunsell green Period 1932

Train Wheel Rolling stock Vehicle Toy

My Model
Click on the photos of the model below for a larger view.

I was quite keen on the Hornby M7 when it was fist announced. The relatively high price for such a small loco put me off a bit so I didn't get one when they were released. I set up some searches on eBay and wadyou know, one turned up £20 below list last week. It had been run around a shop on a layout, but it shown no signs of a problem.

Train Wheel Vehicle Window Rolling stock

I tested the loco before fitting a decoder to make sure all was alright. The front drivers and rear bogie set this apart from other smaller locos on the layout. It really looks interesting.

The detail is great and the more you look close, the more you find. The cab is highly detailed, but not very accessible as you can only peer in through the side doors.

Train Motor vehicle Window Rolling stock Mode of transport

It has been said elsewhere that this is the finest example of Hornby detaining. This was before the new Britannia was releases. I agree that with the external pipe work, frame and chassis detail make it a fine little loco. The weathering is subtle and effective. A work engine like this shouldn't be pristine if its running on the layout.

Train Wheel Window Vehicle Rolling stock

Train Wheel Vehicle Rolling stock Motor vehicle

As with all these detailed locos, the fiddly bits are fragile. The whistle on my loco had been knocked off and was loose in the box, but as it doesn't touch anything in the box, this must have been done by the previous owner. The brake rod snapped after an hour of holding the loco upside down. I'm getting used to gluing on these extra bits and pieces. A dab of superglue applied with a wooden cocktail stick is best. The whistle is in a prime loco-holding position so it is on the front line of disaster. The rest of the high detailed parts are relatively well protected.

A strange little thing I noticed underneath: the Hornby name under the chassis had been intentionally ground off. Was this done in the factory? If so, why?

Decoder Installation

The model comes apart by first removing two screws holding the body to the chassis. Note: the two screws are different sizes. The thinner one goes in the front. It is found under the front vacuum tank and the second screw is at the rear accessible though the rear bogie. Use a magnetic screwdriver to get them back in. There are two pipes, one on either side to disconnect. These are a bit of a pain as they are painted plastic and too much wriggling and the paint starts to flake.

Inside, the loco has a NEM 652 socket with a blanking plug. I removed the suppression capacitor and then proceeded to fit the decoder to the motor block. After one test I realised that the inside space was so limited that I then decided to remove the NEM socket completely and hard-wire the decoder on short wires.

I had a Lenz LE1014W Ultra-Thin Drive-Select DCC Decoder... It didn't fit above the motor :-(

Wheel Vehicle Automotive tire Motor vehicle Tire

Wheel Vehicle Motor vehicle Tire Train

I had hoped that the decoder would fit above the motor or gearbox. How do you measure these things? Wouldn't it be great if the manufacturer could give you the size of decoder that would fit. They could measure it at the CAD stage. I really doubt that these guys have tried themselves to fit a decoder into a loco like this. An N-scale decoder would fit and John from Bromsgrove fitted a Zimo 620R in his M7 and he says on the forum that a TCS M1 would fit as would NCE Z14SR.

I decided after plenty of head scratching that I'd put it into one of the side tanks. These spaces are filled with metal ballast. After plenty of prying with a cutter and needle-nosed pliers, it came out. Only then did I see that the ballast was being held in by a screw. And only then, I read a post of the forum about this and how you could get to the screw by taking off one of the filler caps from the outside (probably lightly glued on). I chose the wrong side of course. The motor has a bump where the terminals attach on the side I chose. If you do it, undo the right hand side tank (looking from above the loco). My Lenz decoder fits there - just. I still had to round off a corner to prevent the tie-rod from touching. A Lenz Gold wouldn't fit - that's for sure. A spec of super glue on one of the decoder diodes holds the decoder in place on the inside of the tank. This could easily be taken off later if required with a quick twist.

Rectangle Composite material Auto part Fashion accessory Metal

Train Wheel Vehicle Motor vehicle Rolling

Whew! That was a mission. The loco is now given an address and basic configuration is done. 30 seconds later that is done. The loco then went straight onto the rolling road that is connected to my DCC system. It works perfectly.

DCC CV Settings for M7 '30108' Locomotive
Adr3010Long loco
CV212Minimum Speed (V Min at
step 1)
CV316Acceleration delay
CV48Brake Delay (0-255)
Max speed (V high)
CV17203Long address Hi bit
CV18194Long address
Lo bit
CV2955Decoder Configuration
CV29 is set [decimal values in brackets] to allow reverse direction
(I crossed the wires) [1], also to allow 28 or 128 speed steps [2], also to allow DC and DCC operation [4], also to use the user-defined speed table [16], and finally to use the extended long address [32].

The rest of the CV's are left untouched (factory default).

Train Wheel Window Vehicle Rolling stock


This is a very beautiful model. I say that as it is delicate, nicely proportioned, compact and functional and at the same time it is highly detailed and has plenty of interesting features. I particularly like this weathered version as it will be running around my layout pulling small coaches and perhaps some wagons.

The decoder installation was a pain, but perhaps I really should get some smaller decoders. I doubt that the Hornby decoder will fit here. Item #4 of the instructions says: "Location of Decoder". Well I can see where it plugs in, but I can't see where it is meant to go. Come on Hornby, show us where to put the decoder and please think about this step at the design stage of the model.

The little loco runs very smoothly. Very quiet and no rocking around. It has a fascinating movement with it's simple tie-rods on the front drivers and rear trailing bogie. Very pleasant to watch indeed.

I'll update this review when I test the traction of the loco later with a couple of coaches hooked up behind.

- November 2006

All text, photos & graphics ©2006 Doug Teggin - All rights reserved.[/URL]
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